# BETTER DIY Chronograph ($1 + some wire)



## Veni Vidi Vici (Jan 23, 2011)

My previous DIY Chronograph thread gave all of the details on the software, so I'm not going to go over it again here. The problem with that method, as I explained on that thread, is determining exactly when to select the point on the soundwave to represent your arrow's launch. The bow makes some noise throughout the entire launch sequence, so picking exactly when the arrow comes off of the string is just a guess.

I started thinking, "What if I could detect the launch without using a microphone?". Here's what I have now.










I took some extra invisible fence wire I had and wound two coils in series. The coils are about 10" in diameter, 16-17 turns each. I mounted them (that's what duct tape is for) to a board and measured the distance between them. Then I took the ends of the wire and attached them to a microphone jack (from the same $1 dollar store mic I used originally).

When an arrow is shot through the coils, the software detects this very precisely. Since the arrow is now passing through two coils spaced apart, I can see each event. Using the audacity software to record the shot and measure the time between the events is what makes this ultra-cheap chrony work.


Here's a screenshot of the initial recording. There are a couple of things to notice. First, the microphone input slider is all the way to the right this time. The coils don't generate much of a signal, so you need everything you can get. Second, after I started recording, I left-clicked on the 0.00 on the left bar multiple times to zoom in as much as possible. I then took the shot and hit stop. The small blip on the graph is the shot. I selected this area and used the Fit Selection in Window button to blow it up. It took a couple of times and I also dragged the window larger, but I ended up with a good view of the two blips that are the arrow passing through each coil.





























After a few times, this is the view I ended up with. If you notice that the second blip is flipped compared to the first blip, that is because I wound my second coil in a different direction than my first coil. This was by accident, and it doesn't effect the end product.

Because the blips feather in and out at each end, I decided that the most consistent place to use as a time selection was the middle of the straight diagonal connecting the high and low humps of each blip. Here's the first selection:














And here's the second selection, along with my spreadsheet showing the results of 5 consecutive tests. Not too bad, huh! :teeth:


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## julle (Mar 1, 2009)

could you give a little more detail about the coils and how you connect them to the microphone jack... maybe some real life pictures. just to make clear.. you made a microphone using just some wire? I would never believe such a thing would work :')


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## Veni Vidi Vici (Jan 23, 2011)

julle said:


> could you give a little more detail about the coils and how you connect them to the microphone jack... maybe some real life pictures. just to make clear.. you made a microphone using just some wire? I would never believe such a thing would work :')












This is what my microphone jack looked like when I cut it apart. I can't solder worth a hoot, so I just twisted my wires around the areas shown and secured with electrical tape.


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## styk (Apr 7, 2010)

What are you shooting through it, aluminum, carbon or other material?


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## tllhunter (Jan 15, 2008)

Can you provide more info and pictures of your wire set up. I don't know what invisible fence wire is. Does it matter what gauge wire you use? Why so many wraps? I assume this is to get a good reading or signal. Does the program record the time as the arrow moves through each coil of wire and the impact of the arrow into your backstop. Thanks for your help. I think I have a good understanding, just looking for confirmation.


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## Veni Vidi Vici (Jan 23, 2011)

tllhunter said:


> Can you provide more info and pictures of your wire set up. I don't know what invisible fence wire is. Does it matter what gauge wire you use? Why so many wraps? I assume this is to get a good reading or signal. Does the program record the time as the arrow moves through each coil of wire and the impact of the arrow into your backstop. Thanks for your help. I think I have a good understanding, just looking for confirmation.


I'll post some pics in a bit. There is really nothing special about the setup, and I haven't tried to optimize it at all. I'd guess the gauge is 16, insulated solid strand. I used it because it is what I have in hand and it seemed stiff enough yo stand up well. The software records anything that it detects as long as you are recording. You have to pick the points off of the wave that represent when the arrow is passing through each coil. It will not detect when you hit the backstop. It is really much more like a real chronograph in this configuration than when using a microphone. Think of it as two metal detectors on the same circuit.


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## MAC 11700 (Feb 22, 2011)

This is a great idea...and one worth doing...Looking forward to seeing more pictures..

Mac


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## Veni Vidi Vici (Jan 23, 2011)

Some more pictures. See, I told ya it aint much to look at 






































The plug drove me nuts this evening. I took my original plug apart for the picture I posted earlier. I had just twisted the wires on, so I figured I'd solder them on now that I knew it worked. Long story short, be absolutely positive that you have a good connection when you plug into your computer. Mine was just "OK". I spent a lot of time trying to figure out why I was couldn't see the important parts of the graph, and it turned out that my slightly looks connector was making the system so noisy that the noise was swamping out the data I was looking for. But it's fixed now and working fine. My last three tests were within 3 fps of each other.


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## Veni Vidi Vici (Jan 23, 2011)

styk said:


> What are you shooting through it, aluminum, carbon or other material?


Sorry I missed your question earlier. I've shot both carbon and aluminum through it, and it worked both ways. I think what it is actually sensing is the steel field point.


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## WYelkhunter (Mar 26, 2006)

Is that wire coated or uncoated?

thanks for all the info


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## tllhunter (Jan 15, 2008)

OK I admit I'm not the sharpest tool in the shed. I still do not understand. If you have essentially built a microphone, then why does it not register the impact of the arrow into the bag target. Is this one of those If an arrow is fired from a bow and there is a chronograph in the way does it make a noise. Kind of like a tree falling in the woods and no one is there does it make any noise.


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## hunt123 (Jan 17, 2009)

This is an awesome DIY!! As long as you have a laptop.  Good job figuring all that out! Can't remember if you posted on your original thread if you checked your results against TAP or some other software? If you don't have the software, PM me and I'll do it for you.


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## Goldbarron (Jun 17, 2010)

It looks to me as if you made your computer into two metal detectors that can sense when the field tip passes through. With that thought If I were to make a cord that would go from a metal detector headphone jack to the computer mic jack and shoot past a 12" coil I should be able to figure feet per second also. Just a thought.


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## Veni Vidi Vici (Jan 23, 2011)

tllhunter said:


> OK I admit I'm not the sharpest tool in the shed. I still do not understand. If you have essentially built a microphone, then why does it not register the impact of the arrow into the bag target. Is this one of those If an arrow is fired from a bow and there is a chronograph in the way does it make a noise. Kind of like a tree falling in the woods and no one is there does it make any noise.


A mic is like a speaker in reverse. Sound vibrates a diaphragm with a coil on it, and when this moves past a magnet the field changes rapidly. What I made doesn't have a diaphragm, so it can't vibrate and capture sound. But if metal or a magnet pass thru it, that changes the field just enough to detect.


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## cbmac (May 24, 2006)

Impressive. Computer technology, physics, ingenuity and ducktape.:jam:

I think you would get a much larger signal if you magnitized the steel field point.


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## donmega (Jan 18, 2011)

tllhunter said:


> OK I admit I'm not the sharpest tool in the shed. I still do not understand. If you have essentially built a microphone, then why does it not register the impact of the arrow into the bag target. Is this one of those If an arrow is fired from a bow and there is a chronograph in the way does it make a noise. Kind of like a tree falling in the woods and no one is there does it make any noise.


By my understanding. By wrapping the wire he is making a COIL. Then when shooting the arrow and the head being a dissimilar metal. It will create a FIELD. Which is picked up as sound or NOISE on the software. Kind of like an electro magnet with the CORE passing through it. 

Why didn't you just cut the mic wires a couple inches back and butt splice or solder it on there, instead of taking apart the jack? Just wondering if it matters.

BTW Great Idea:star:


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## Veni Vidi Vici (Jan 23, 2011)

donmega said:


> Why didn't you just cut the mic wires a couple inches back and butt splice or solder it on there, instead of taking apart the jack? Just wondering if it matters.
> 
> BTW Great Idea:star:


I started out doing that, but the OEM mic wires are a fine diameter stranded wire with some kind of insulating coating on them. I'm a lousy solderer, and I couldn't get a consistent joint on that stuff. If you can solder, I'm sure that would work fine.


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## Veni Vidi Vici (Jan 23, 2011)

cbmac said:


> Impressive. Computer technology, physics, ingenuity and ducktape.:jam:
> 
> I think you would get a much larger signal if you magnitized the steel field point.


You're absolutely right. A magnet definitely gives a stronger signal, and I did try to magnetize a field point. I never got it to be a very strong magnet, and I figured if it would work with just the steel FP then that's one less thing to deal with, right?


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## Veni Vidi Vici (Jan 23, 2011)

hunt123 said:


> This is an awesome DIY!! As long as you have a laptop.  Good job figuring all that out! Can't remember if you posted on your original thread if you checked your results against TAP or some other software? If you don't have the software, PM me and I'll do it for you.


PM sent.


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## naubusan (Mar 23, 2007)

You have two of metal detector coils there. It makes difference how many rounds of wire you have there.
Couple of variants:
http://www.easytreasure.co.uk/bfo.htm
http://detector-sensor.blogspot.com/2009/04/simple-metal-detector.html


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## Veni Vidi Vici (Jan 23, 2011)

WYelkhunter said:


> Is that wire coated or uncoated?
> 
> thanks for all the info


It's coated.


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## jim p (Oct 29, 2003)

I really like this project. If you want more signal out of the coils, you can increase the number of turns of wire or you can decrease the diameter of the coils. It seems that the accuracy of this chrono depends on the precise spacing between the loops of wire. If just one turn of wire could be used for each loop or if the loops could be wound using a flat winding pattern this might help improve the accuracy. Also by spacing the loops as far apart as practical would help to decrease the percentage of error. You could also use some enameled wire as small as a hair wound on a piece of plastic like pvc pipe or even a plastic trash can to help get more turns of wire and at the same time keep the spread of the coil to a minimum.

I may have to go and take a look at your software for this project and see what I can do. I don't have a laptop so if I want to shoot outside I would have to use about 30 feet of shielded microphone cable which might be too noisy to see the signal.

I really like this project. Maybe you can test it with a gun some day. I am thinking that it will detect the bullet as it goes through.


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## revwilder (Apr 11, 2005)

What a great geeky DIY!!! I Love It!!!

I am all over this!

Questions?
1. Is the wire connected between the loops to complete the circuit, or is each loop completely separate connection to the jack?
2. How did you know what was the best spot on the graph to use as a start and stop point for time purposes? In other words why not the peak of the graph and not the side?

Keep up the good work and if you want to start a new Chrono business I'm in.


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## Ju5t H3R3 (Sep 14, 2005)

This would eliminate lighting issues most chrono have
Kn


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## Veni Vidi Vici (Jan 23, 2011)

revwilder said:


> What a great geeky DIY!!! I Love It!!!
> 
> I am all over this!
> 
> ...


Thanks!

1. The loops are connected in series and connected to the jack on the same channel. I've been talking with some electrical engineers where I work this AM, and they noted that I could wire each loop to a different channel (L or R stereo) on the same jack and record them separately. I'm not sure at this point if there is a benefit to this. I guess if I wanted to minimize the distance between the two coils to the point that the signal from the first coil partially overlayed on the second coil's signal, then splitting them into two channels would allow them to be independent and retain their characteristic shapes.

2. When I thought of doing this I had planned on measuring from the start of the first signal to the start of the second signal. In practice, the signal feathers in and out on each end of the blip, but the transition from low to high (or high to low) seemed cleaner, more consistent, and easier to eyeball.

I also got a little bit of a theoretical education from the electrical engineers. In order for this to work, the field points must have at least some small level of residual magnetism. This is not uncommon, but it "may" be possible to have a field point that doesn't have any magnetism. An improved approach would be to design a field point that has a magnet in it, or to permanently magnetize a point. Just rubbing a magnet on it a few strokes before shooting may help it as well. If I built a true metal detector with an energized coil and an oscillator, then the magnetism would not be an issue. But in the spirit of DIY, I wanted to keep this as dirt simple and cheap as possible.

Also, they verified that more turns is better.


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## ZGun4n6 (Jan 11, 2010)

Love this thread... will def have to build one myself. I wonder if you could use a tool magnetizer/demagnetizer on field points to optimize results better than just rubbing against a household magnet. I believe from college physics that the polarity of the magnet and direction you run the tool or field point across the poles has an effect on how well it magnetizes.
great job btw. one of the most interesting DIY on here in a while... would look nice on some of these guy's press/draw board/shooting machine/ (chrono??)....
Z.


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## Veni Vidi Vici (Jan 23, 2011)

*Test results*

*TEST RESULTS*

At lunch today I went to a pro shop and used their chronograph. Then I went home and shot the same arrow through my setup. Here are the results:

SHOP CHRONOGRAPH
268
268
269

Average: 268.33 fps


DIY COIL/AUDACITY CHRONOGRAPH
270.978
270.662
270.563

Average: 270.73 fps

Difference: 2.4 fps ==> 0.9%

Can't complain about that :shade:

One other test note. On the third shot through the DIYC, I did rub a magnet on the fieldpoint for about 10 seconds, and the signal was definitely stronger.


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## PaPaBob (Aug 5, 2006)

Try wrapping a field point with wire from end to end and then touch it a few times to the contacts of a 12V battery. That will really magnitize it and may give you a very strong signal. I do this with screwdrivers all the time.


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## revwilder (Apr 11, 2005)

Veni Vidi Vici said:


> *TEST RESULTS*
> 
> At lunch today I went to a pro shop and used their chronograph. Then I went home and shot the same arrow through my setup. Here are the results:
> 
> ...


That is truly awesome!
Everyone knows that Chrony's are not all made the same, and some folks even have two or three to calibrate between them. 2.4fps is not that big of a deal, and especially <1% difference in the two, I believe it is usable for everyday needs.


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## hunt123 (Jan 17, 2009)

If it proved to be consistently a little high, it would be easy to add a compensating component to the Excel formula.


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## Veni Vidi Vici (Jan 23, 2011)

PaPaBob said:


> Try wrapping a field point with wire from end to end and then touch it a few times to the contacts of a 12V battery. That will really magnitize it and may give you a very strong signal. I do this with screwdrivers all the time.


Thanks, I will try this.


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## jbuhr (Feb 13, 2011)

subscribed!


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## jeremy.b (Dec 7, 2010)

Man I love these kinds of projects!

I wanted to give this a go so I threw together a small scale test yesterday. 

I stripped down a broken computer case fan and used the wiring (30 gauge-ish). 

Using a cardboard tube (again, this is just a test setup) from a roll of wrapping paper I made two, 30 turn coils, only 3 5/8" apart on one end of the tube. I soldered the coils to a spare mic cable I had laying around.

I set the tube vertically, with the coil end of the tube at the bottom and plugged the mic cable into my PC.

I started up Audacity and started just dropping field tips down the tube. Sure enough the tell-tale blips showed up in Audacity!

The field tips only fell @ around 12 FPS, but this goes to show that even at lower speeds this setup will work. On top of that, I'm fairly certain that the faster the object goes through the coils the larger the blips become (basically because you are making a linear generator out of the coils and the field tip running through them, the faster the tip moves the greater the power generation)

I'm on to making a full scale version this week and ordered up 800 ft of 36 gauge motor wire to build the coils out of (only $8-9 on Ebay).

So I need something to wrap the coils around, ideally making the coils only 1/8" to 1/4" wide. My wife suggested using the inside ring from a cross-stitch ring. I had the thought of cutting the tops off of large planting pots. At this point I throw this out to all you fine folks, what else could I use to wrap the coils around?


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## gnv (Jun 16, 2010)

a short scrap from plastic culvert would work to support your coils, you can find sizes from 8 inch to 24 inch


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## hunt123 (Jan 17, 2009)

Gallon paint bucket? Bottom of a drywall bucket for something bigger. Your planting pot would work also but you don't have to cut the top off. Just wrap the wire then slide the coils off and tape them.


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## 05_sprcrw (Aug 18, 2009)

Great work I am subscribing like others have hinted at I am pretty sure the coiled wire has a low current running through it that generates a magnetic field and the arrow is actually disrupting this field and this is what you are detecting on the software. I think it is a great idea and I am planning on making one of these for myself definitely would get rid of the lighting issues with some chronographs.


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## hunt123 (Jan 17, 2009)

helsyeah said:


> Man I love these kinds of projects!
> 
> I wanted to give this a go so I threw together a small scale test yesterday.
> 
> ...


Interesting that two coils 3 5/8" apart worked well. AND they were still wrapped around the tube? So maybe that means the distance between coils can be anything as long as it's fixed and the magnetic disruption will penetrate a nominal thickness of cardboard. Perhaps the tip should be as strongly magnetized as possible to produce the best waveform.


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## Veni Vidi Vici (Jan 23, 2011)

hunt123 said:


> Interesting that two coils 3 5/8" apart worked well. AND they were still wrapped around the tube? So maybe that means the distance between coils can be anything as long as it's fixed and the magnetic disruption will penetrate a nominal thickness of cardboard. Perhaps the tip should be as strongly magnetized as possible to produce the best waveform.


I would suspect that there is some practical limit to how close together you can place the coils. If you reach a point that the signals from each coil start to overlap, it may become difficult to identify where to select your start and stop times.


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## Veni Vidi Vici (Jan 23, 2011)

I've written a a PDF document that covers how to build, operate, and interpret this system. (Thanks for the review support, hunt123!) As soon as I can upload it to a host I will post a download link.


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## Veni Vidi Vici (Jan 23, 2011)

helsyeah said:


> Man I love these kinds of projects!
> 
> I wanted to give this a go so I threw together a small scale test yesterday.
> 
> ...


Glad to see you are playing with this. You could make a spool by sandwiching a 10" diameter circle of 1/4" plywood between two 12" diameter circles.


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## 05_sprcrw (Aug 18, 2009)

Well in spirit of this awesome post and in preparation for me building one I created an excel spread sheet that will take 5 times you put in (from the time graph) with the arrow weight and give you speed calculations, average KE, and Average Momentum. 









I also setup a bow specs section so that you can give print outs to people if you want. 

* please note that I have it setup so that the coils should be 1 foot apart for correct calibration if not you will have to edit the speed fields distance portion*


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## 05_sprcrw (Aug 18, 2009)

Veni Vidi Vici said:


> I've written a a PDF document that covers how to build, operate, and interpret this system. (Thanks for the review support, hunt123!) As soon as I can upload it to a host I will post a download link.


You can also send it to a zip folder and upload it directly here I just did that with an excel program I wrote for this.


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## jeremy.b (Dec 7, 2010)

hunt123 said:


> ...*and the magnetic disruption will penetrate a nominal thickness of cardboard*...


Actually, if this is truly operating as a linear generator ANY non-magnetic material can be used to support the coils, cardboard, wood, aluminum etc.



hunt123 said:


> ...Perhaps the tip should be as strongly magnetized as possible to produce the best waveform....


Again, with the assumption that this is a linear generator the stronger the magnet (as well probably moving it faster) *should* create a much more pronounced wave.

I'll have to ask my wife about this though, her grad school project is to create a linear generator much like what we have here, so she should know alot more about how this all is really working.


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## jeremy.b (Dec 7, 2010)

05_sprcrw said:


> You can also send it to a zip folder and upload it directly here I just did that with an excel program I wrote for this.


The one thing we REALLY need is a program that can detect the wave as it occurs and automatically does the math on the fly and shows the speed.

I've already taken a look at using a VBA program in excel, but it's not really suited for this kind of thing.

A full blown data acquisition software (like labview or matlab) would be the best bet, but I'm not aware of any that are open source/free.


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## revwilder (Apr 11, 2005)

05_sprcrw said:


> Well in spirit of this awesome post and in preparation for me building one I created an excel spread sheet that will take 5 times you put in (from the time graph) with the arrow weight and give you speed calculations, average KE, and Average Momentum.
> 
> View attachment 1045779
> 
> ...


BEST DIY EVER!!!!

You are saying with your program that the coils only need to be 1 foot apart and still should work nicely as a chronograph?
Another Question? I still need the exact spot on where to start and stop the time on the graph?


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## 05_sprcrw (Aug 18, 2009)

Yes I did 1 foot spacing so I could make the program velocity = Distance/ Time So in my formula to keep things simple and not have to do a bunch of conversions I had it be 1 foot apart so now however long that sound blip you get is will be the time it takes to travel 1 foot. 

As for where you measure as long as you measure to the same point it will be the same. Again you will only be so precise with a click on the graph so depending on how accurate you are there, that is how accurate the calculations will be. There is no other way for it to be off because it acts purely on fields being interrupted. 

This is way over simplified but make sure that you have coils traveling in the same direction so you get the same blip both times then pick a spot that is easily found on both and the time between those two points is what you would use. 











revwilder said:


> BEST DIY EVER!!!!
> 
> You are saying with your program that the coils only need to be 1 foot apart and still should work nicely as a chronograph?
> Another Question? I still need the exact spot on where to start and stop the time on the graph?


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## Veni Vidi Vici (Jan 23, 2011)

*Instructions for building and using the chronograph*

*INSTRUCTIONS FOR BUILDING AND USING THE CHRONOGRAPH*


Here are the instructions I wrote. My intent is to show how simple it CAN be. Once you build one, you will probably have lots of ideas on how to improve it. Please share your ideas and pictures.

View attachment DIY_CHRONOGRAPH_INSTRUCTIONS.zip


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## Veni Vidi Vici (Jan 23, 2011)

@05_sprcrw: Just noticed your sig. *82#, 550 GR!!!!!! *Holy cow, you tryin' to kill 'em TWICE!????:eek2: That's quite a setup! :icon_salut:


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## 05_sprcrw (Aug 18, 2009)

Veni Vidi Vici said:


> @05_sprcrw: Just noticed your sig. *82#, 550 GR!!!!!! *Holy cow, you tryin' to kill 'em TWICE!????:eek2: That's quite a setup! :icon_salut:


I have some spots that I hunt very close to bedding areas, I like to shoulder nuke them when in these spots this just makes sure I get through both shoulders.


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## Veni Vidi Vici (Jan 23, 2011)

helsyeah said:


> The one thing we REALLY need is a program that can detect the wave as it occurs and automatically does the math on the fly and shows the speed.
> 
> I've already taken a look at using a VBA program in excel, but it's not really suited for this kind of thing.
> 
> A full blown data acquisition software (like labview or matlab) would be the best bet, but I'm not aware of any that are open source/free.



Audacity is open source and I believe it can accept add-on filters and effects. If some motiviated programmer could develop a filter that could run within Audacity while it is recording this could very well be possible.


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## jeremy.b (Dec 7, 2010)

Veni Vidi Vici said:


> Audacity is open source and I believe it can accept add-on filters and effects. If some motiviated programmer could develop a filter that could run within Audacity while it is recording this could very well be possible.


I started looking into this as well. From what I could gather all of the filters and such are for AFTER doing the recording, not necessarily real time DURING the recording process.

I'm not skunked yet, I'll write a custom program if i have to in order to get this to just spit out velocities.

Edit: I did run across a interesting little program called Spectrum Lab that is free ware and does have live triggers for input. The only thing I don't really understand is how to get it to trigger on our little blips of input the coils give.


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## 05_sprcrw (Aug 18, 2009)

helsyeah said:


> I started looking into this as well. From what I could gather all of the filters and such are for AFTER doing the recording, not necessarily real time DURING the recording process.
> 
> I'm not skunked yet, I'll write a custom program if i have to in order to get this to just spit out velocities.
> 
> Edit: I did run across a interesting little program called Spectrum Lab that is free ware and does have live triggers for input. The only thing I don't really understand is how to get it to trigger on our little blips of input the coils give.


If you do figure it out please let us know with the combined knowledge of everyone here we could really be on to something, unfortunately I don't know much about programing side of things myself.


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## 3Fletch (Apr 5, 2009)

Great thread.... I would guess the further the distance the coils are appart the more accurate your speed calculations would be. If you were off 1/8" at 12" on your measurement on the coils VS 1/8" at 48" the error would be 4 times less on the 48" distance. 

Kudos for working on this project. It is really simple once you get the theory behind it.


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## Seanr900 (Aug 22, 2009)

starting my build now! hope to post results by tomorrow about this time 

great diy thanks for sharing it VVV.


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## Veni Vidi Vici (Jan 23, 2011)

I built a new one tonight. Two coils, 50 turns each, wound around a clear 10" diameter plastic pipe that is 24" long. 50 turns of wire tends to spread out a bit, so rather than measure the distance between the coils, I decided to back calculate the distance based on my now known arrow speed. I ran several tests and calculated the effective coil distance each time by picking the first peak, and then again by picking the midpoint of the transition line. I found that I got slightly more consistent results by picking the midpoint. Here's a graph of my results.












Here are some pics of my setup. I used a quick release mount for my tripod to mount the pipe. The other thing I tried was magnetizing a field point by the battery method. I got little to no induced magnetism this way, but the wire got really hot really quick! :mg: I ended up stroking the FP with a magnet like I did before.


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## naubusan (Mar 23, 2007)

You don't need electricity for magnetizing. Just rub a normal magnet along the field point in one direction a few times.


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## Veni Vidi Vici (Jan 23, 2011)

naubusan said:


> You don't need electricity for magnetizing. Just rub a normal magnet along the field point in one direction a few times.


Yes, that's where this started, but it was suggested that trying the electrical method might produce a stronger magnet.


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## naubusan (Mar 23, 2007)

Sorry, readed badly your earlier post.....


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## naubusan (Mar 23, 2007)

Found one interesting page for similar project. Instead of coils this guy is using phototransistors. http://www.inpharmix.com/jps/Jims_chrono.html
But He had interesting software also called Wav2txt. http://www.inpharmix.com/jps/wav2txt.html

Interesting project, but I cannot test anything but software because broke my ankle, and laptop is only project for a while...


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## naubusan (Mar 23, 2007)

Not sure if this works straight with coils, but I guess it's quite near that kind of sowtware we're looking for SoftChrono

It didn't work for me straight because I'm running x64 Win7. 
Error was missing msstdfmt.dll.
Fix for that:
Download msstdfmt.dll and put it into windows folder, and then run Command prompt with admin rights and give command regsvr32 C:\Windows\msstdfmt.dll.
(system32 path is ok too, just change path on registration)


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## naubusan (Mar 23, 2007)

After little testing with laptop mic and handclapping SoftChrono works!
I just hope that that little signal from coil is enough for the program...
At least is something to start..

Hope this helps, because operated ankle keeps me on sofa just dreaming about shooting. And best of all, I just got new destroyer 340 at monday!

Maybe keeping the coil as narrow as possible gives better signals, just a thought. Like this. I think wire can be wrapped between cardboard discs or something like that to keep it narrow.


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## naubusan (Mar 23, 2007)

If the signal from coils isn't enough, I think that soft chrono works if you put two sheets of paper with mic between them and shoot through papers. Cheaper than wire ;D

Like:

paper---0.5ft---mic---0.5ft---paper

edit: this might be best solution because softchrono have mic distance locked to be exactly middle between shot and impact. If that could be set to zero, then you could use softchrono straight with coils.


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## buckslayerII (Nov 5, 2004)

helsyeah said:


> I started looking into this as well. From what I could gather all of the filters and such are for AFTER doing the recording, not necessarily real time DURING the recording process.
> 
> I'm not skunked yet, I'll write a custom program if i have to in order to get this to just spit out velocities.
> 
> Edit: I did run across a interesting little program called Spectrum Lab that is free ware and does have live triggers for input. The only thing I don't really understand is how to get it to trigger on our little blips of input the coils give.


Could you have 3 coils and use the first one as a trigger to start your software recording?

On the narrow coil topic - some of the larger diameter pvc pipe have wall thicknesses in the 3/8-1/2" range. You could turn grooves in that to contain the wire if you had access to a lathe, which it sounds like some of you should/do.

Also - what gauge wire are you using in your 2nd build VVV? Maybe it's a perspective thing, but it looks large.


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## jeremy.b (Dec 7, 2010)

buckslayerII said:


> Could you have 3 coils and use the first one as a trigger to start your software recording?...


Actually, I'm pretty sure the right program can hold a "buffer" of signal from the mic and as long as the program can catch the spike of signal from the coils it should then have no problem recording the exact amount of signal to catch the full wave form.

I'm actually building my own program using AutoIt that I *hope* will allow us to do the calculations on the fly. As soon as I have a workable copy going I'll post it up here for other folks to play with.


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## Veni Vidi Vici (Jan 23, 2011)

buckslayerII said:


> On the narrow coil topic - some of the larger diameter pvc pipe have wall thicknesses in the 3/8-1/2" range. You could turn grooves in that to contain the wire if you had access to a lathe, which it sounds like some of you should/do.


That's a good idea.




buckslayerII said:


> Also - what gauge wire are you using in your 2nd build VVV? Maybe it's a perspective thing, but it looks large.


My guess is 18ga. It came from a 500 ft coil of stranded wire for an invisible dog fence. When we moved to my current house, the previous owners already had the wire buried but they took the control box. So I had this spool of wire available.


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## Veni Vidi Vici (Jan 23, 2011)

naubusan said:


> If the signal from coils isn't enough, I think that soft chrono works if you put two sheets of paper with mic between them and shoot through papers. Cheaper than wire ;D
> 
> Like:
> 
> ...


Good find, naubusan. I will try to play with SoftChrono tonight. My concern with using an actual mike is that the start of the sound of the shot from a bow does not coincide with the actual time that the arrow is released from the string. Also, the shot from the bow and any echoing in the room may mask the sounds of the arrow passing through two sheets of paper. Or it might just work! There are lots of things to experiment with.


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## Veni Vidi Vici (Jan 23, 2011)

Here's an example of what I got when I tried this before with a microphone. The problem is that there is no distinct signal that represents when the arrow is released from the string (as opposed to the sound of a spud gun firing). The target impact is easy to detect (second oval). I knew my bow was shooting around 270 fps, so I picked a start point that gave me the right answer. As you can see, the necessary start point doesn't coincide with anything unique on the sound signature. As the graph shows, the bow starts making some sound the instant the string is released. This sound stays low for awhile, then increases towards the end of the shot. The arrow actually comes off the string before the sound really ramps up. This makes sense to me, as the bow will be louder once it no longer has an arrow to put its energy into.


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## naubusan (Mar 23, 2007)

Veni Vidi Vici said:


> Good find, naubusan. I will try to play with SoftChrono tonight. My concern with using an actual mike is that the start of the sound of the shot from a bow does not coincide with the actual time that the arrow is released from the string. Also, the shot from the bow and any echoing in the room may mask the sounds of the arrow passing through two sheets of paper. Or it might just work! There are lots of things to experiment with.


I think echoing is easily solved by mic volume settings.
But thats true that starting point for the calculating time will be very hard to find with bow, thats why I suggested two pieces of paper. softchrono was quite easy to calibrate. And there comes instructions inside the zip file.


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## naubusan (Mar 23, 2007)

Did some more investigations about softchrono.
It seems that it doesn't take mic distance on formula, it just shows you how far mic should be. http://talonairgun.com/forum/viewtopic.php?p=16785#16785
If you can use two mics it cannot count sound travel time to mic. This is great news, because then you can use coils straight if you can get strong enough signal from them. -> signal amplifier...


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## Veni Vidi Vici (Jan 23, 2011)

naubusan said:


> Did some more investigations about softchrono.
> It seems that it doesn't take mic distance on formula, it just shows you how far mic should be. http://talonairgun.com/forum/viewtopic.php?p=16785#16785
> If you can use two mics it cannot count sound travel time to mic. This is great news, because then you can use coils straight if you can get strong enough signal from them. -> signal amplifier...


IT WORKS, NAUBUSAN!!!!!! I'll post some screenshots in a bit, but Softchrono was able to detect and trigger on the coil signals. I could see the signals if I shot in the middle of my coils, but the signal was so low that it kept triggering on the baseline noise. So I tried shooting off center, much closer to the coil, and I got great results! Pics to follow .....


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## Veni Vidi Vici (Jan 23, 2011)

Here's the signal I saw when my shot was centered through my coil:











After adjusting my settings to this:










I got the following 5 shots in a row:
























































On the odd 277 fps shot (Shot 007), I actually shot so close to my coils that a vane hit the chrono tube and the arrow hit the backstop at an angle. That probably had some influence on the signals (which is why an average and throwing out obvious bad data is the right thing to do).

So since I have two other methods (commercial chrono and DIY coil+Audacity) that say my speed is 270, it's hard to argue that SoftChrono isn't working just as well!  Great find, naubusan! :icon_salut:


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## naubusan (Mar 23, 2007)

Great! It looks pretty accurate too according your results.
Did you try different mic levels and mic boost do they affect on curve from coils?


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## Veni Vidi Vici (Jan 23, 2011)

naubusan said:


> Great! It looks pretty accurate too according your results.
> Did you try different mic levels and mic boost do they affect on curve from coils?


Yes, I did. The best I got while shooting in the center region was 257-261. As soon as I moved closer to the coil, the numbers came into agreement with the other two devices I've tried. I need more signal if I want SoftChrono to work right. I have not been successful inducing much magnetizm to a field point. The little bit from rubbing a magnet on it is enough if I want to keep using Audacity, but a stronger signal is needed for SoftChrono's triggers to work.


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## naubusan (Mar 23, 2007)

Ok. Have to think how to amplify signal today. Thinking doesn't hurt.. :teeth:


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## axeforce6 (Sep 15, 2010)

This is so neat. Lol. Someone deserves a sticky!!


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## 05_sprcrw (Aug 18, 2009)

Great job naubusan and Veni :thumbs_up. Like naubusan said would a signal amplifier work?


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## tackscall (Jul 26, 2004)

Would Cat 3 cable work? Ive got lots of that laying around. Otherwise my dog is probably going to get hit by a car this weekend


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## JJudd (Jul 27, 2006)

Would magnetizing both the tip and the coil wire increase the signal strength? I think this would increase the electrical impulse, but i am not an electrical engineer so dont really know for sure. Hell i would probably electrocute myself trying this, lol.


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## 05_sprcrw (Aug 18, 2009)

I think when I go to make mine I will have to make a custom field point by cutting it down and jb welding a magnet to the base of the fp tough part will be matching weight.


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## naubusan (Mar 23, 2007)

http://www.kolumbus.fi/pami1/miscprojs/metaldet.html simple metal detector coil design. Notice Faraday shield.


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## psu111376 (Aug 4, 2009)

This is a great idea. I would like to offer some thoughts to help people with their optimization ideas. Again this is just to help people move in the right direction.

The principle behind the idea is the use of electric current/magnetic field, which are directly linked to one another (a change in one changes the other and vise verse). 

An electric current in the wire loop(s) produces a magnetic field that extends 90 degrees from said electric current.

Making a loop or loops with the wire form a magnetic field that extends from the the wire to the center of the loop. 

Changing the magnetic field (in this case shooting a steel tipped arrow through the loop as stated previously) will change the electric current in the wire which is then detected by the computer/software. 

Singal can be increased in a couple of ways: 

More loops creates a larger magnetic field. This has been realized in previous posts. A trick here...the magnetic field is produced by current...more current more magnetic field. The thicker the wire the more current it can carry, but the computer outputs is small (in relative terms) and the limiting factor.... moral of this is use the smallest diameter (largest gauge) wire you an find and wrap so it stacks as much as possible (grooved pvc is a great idea, or put that duct tape to use...two pieces 1/4" apart to make a valley). This will concentrate the magnetic field in a smaller area.

A smaller diameter loop will also concentrate the magnetic field...again discovered a couple post above by shooting closer to the loop. The magnetic field is strongest at the origin.

A stronger magnetized field tip will also increase the change in the field as discussed previously.....using an electromagnet (wrap tip in a coil and attach to a 12V battery) is a great idea.

Lastly increase the current in the wire...this I don't know how you could "safely" do. I have some ideas, but I am not going to use my lap top as the test subject in fear of frying the mic. 

Hope this helps with all the optimization ideas.


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## Panzer 4 (May 22, 2009)

This is a really cool thread, and project.

It is a shame I am not in town, with my work bench. There are several detector circuits on the net. I want to try a few of them, and see the simplest affective way to amplify the siganls from the coils. I should be able to generate two pulses, that can be adjusted for magnitude, to use for the triggering in the circuit.

What is beating me, at present, is getting the two programs to work on this laptop. I need to circumvent some of the IT goodies.

It is nice to see some people giving thier input, time, and talents on this. Thanks to all for posting.


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## Veni Vidi Vici (Jan 23, 2011)

tackscall said:


> Would Cat 3 cable work? Ive got lots of that laying around. Otherwise my dog is probably going to get hit by a car this weekend


Since it's insulated it should work. Let's hope so for your dog's sake!:laugh:


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## Panzer 4 (May 22, 2009)

Actually, Audacity is functional, SoftChrono is being a bit pesky.


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## Veni Vidi Vici (Jan 23, 2011)

@psu111376: Thanks for summarizing all of the optimization tips in one clear post.

Regarding magnetizing a tip with a 12V battery, I have not had any luck doing this. The FP was induction heated very quickly and the wires got very hot, but no significant magnetism resulted (could not lift one end of a paperclip).

And I agree with you about needing to "safely" evaluate any amplification techniques. I don't want anyone to fry their mic inputs. In fact, a self-imposed requirement on my own design is doing this without building any circuits or powering anything. If that means that I can't get the signal high enough to use SoftChrono, then I'll just stick with Audacity and be happy about it. I should have a field point with a rare earth magnet installed in it ready today or tomorrow for testing, but that will probably be as far as I take this. It will be interesting to see what others on here will come up with, and I'm hoping people will start posting pictures and results soon


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## fishinbuff (Sep 8, 2010)

I built one last night, but when I use audacity or softchrono, I am getting too much noise to detect any disturbance. Any idea what this is from or how to solve this?


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## tackscall (Jul 26, 2004)

Veni Vidi Vici said:


> Since it's insulated it should work. Let's hope so for your dog's sake!:laugh:


Maybe i'll hook the laptop up to the invisible fence and see how fast the dog is going


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## revwilder (Apr 11, 2005)

tackscall said:


> Maybe i'll hook the laptop up to the invisible fence and see how fast the dog is going


You know the rule, we have to have pictures! It is required. LOL!


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## naubusan (Mar 23, 2007)

http://cgi.ebay.com/USB-2-0-Mic-Spe...661?pt=LH_DefaultDomain_0&hash=item230af4ebc5

Cheap usb soundcard so you wont fry your laptop...

Different soundcards have different specs. Soundblaster gives 5V out of mic line but my hp gives only 2.8V and 0.34 mA so I think that coil doesn't work with all soundcards. If someone have that cheap under 10$ usb soundcard and is nice enough to test it if it works.
Here is nice info about mics and soundcards. At bottom of that page is also simple microphone preamplifier schematic.

More info about powering mics is here.


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## naubusan (Mar 23, 2007)

Veni Vidi Vici said:


> Regarding magnetizing a tip with a 12V battery, I have not had any luck doing this. The FP was induction heated very quickly and the wires got very hot, but no significant magnetism resulted (could not lift one end of a paperclip).


How much bigger signal plain magnet gives dropped through coils compared to field tip?

And have someone really tested softcrhrono as its ment to be used, with plain mic between you and the target?


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## Jumpboots101 (Oct 20, 2010)

I give you an A for effort! But this "cheapo" method has alot of drawbacks and time consumption is a huge factor. I think it's way more benefitial to just get a crony F1 from walmart for $70.


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## psu111376 (Aug 4, 2009)

I hadn't tried to magnetize a field point (the electromagnet seemed good in theory), but I do see how the short stubby nature of the field point would prove to be difficult. Just can't get enough of a field around the point. 

Hobby shops often have rare earth magnets (some of them are feak'n stong). You might be able to magnetize a field point with them, or even an old stereo speaker have some strong e-magnets. Heat was mentioned before will aid and time....leave it next to the mag for a couple days (I know, not instant gratification).

My worries about attaching a magnet to a field point is that, upon impact with the target it would ruin it? Not to say it can't be done (I have not even tried), just an initial worry.

Oh, just a note as well; remember you guys, you don't need the signal of a rock concert....all you need (each setup will be different with this) is the signal to noise ratio to be high enough to see it in the software. So, more turns may just be the answer for your individual system. Try the easy stuff first....more turns, smaller diameter loop, etc


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## Veni Vidi Vici (Jan 23, 2011)

psu111376 said:


> Hobby shops often have rare earth magnets (some of them are feak'n stong). You might be able to magnetize a field point with them, or even an old stereo speaker have some strong e-magnets. Heat was mentioned before will aid and time....leave it next to the mag for a couple days (I know, not instant gratification).


The magnet I'm going to use is rated for 3.2 pounds of pull. The "few strokes of a magnet on a field point" version improves detectability but won't even pick up one end of a paper clip. It will be interesting to see how much better the stronger magnet works.



psu111376 said:


> My worries about attaching a magnet to a field point is that, upon impact with the target it would ruin it? Not to say it can't be done (I have not even tried), just an initial worry.


I'm drilling a pocket into the tip of the FP and putting the magnet in there, so it will be protected from impact. I'll probably lose 7-8 grains of tip weight, so I'll make that up with a washer between the FP and the insert.



psu111376 said:


> Oh, just a note as well; remember you guys, you don't need the signal of a rock concert....all you need (each setup will be different with this) is the signal to noise ratio to be high enough to see it in the software. So, more turns may just be the answer for your individual system. Try the easy stuff first....more turns, smaller diameter loop, etc


I wouldn't want to go smaller than 8-10" for a free-standing version. You can't really use your sights to aim that close, so unless someone is behind you helping you line up you could have contact. However, if someone wanted to make one that attached to the stabilizer mount and moved with the bow, you should be able to get the coil diameter down to 4" or so. These coils would need to be far enough forward to ensure that the arrow is completely off the string before the tip passes through the first coil, so the bow might be kind of annoying to shoot.


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## Veni Vidi Vici (Jan 23, 2011)

Jumpboots101 said:


> I give you an A for effort! But this "cheapo" method has alot of drawbacks and time consumption is a huge factor. I think it's way more benefitial to just get a crony F1 from walmart for $70.


I won't argue with you there. For most folks it's not a money issue, and most people at home would only use this occasionally. I just wanted to see if I could come up with something "MacGyver style" with things I had available. My first one was made up of dog fence wire, a 4' piece of shoe molding, electrical tape, duct tape, and a microphone jack. I literally laughed out loud when I compared my results to a real chronograph and saw how good they were with a rig like that! :laugh:


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## Veni Vidi Vici (Jan 23, 2011)

fishinbuff said:


> I built one last night, but when I use audacity or softchrono, I am getting too much noise to detect any disturbance. Any idea what this is from or how to solve this?


Did you try to magnetize your field point?

Also, make sure you zoom in (mouse click in the left margin) as far as you can. And drag the bottom edge of the recorded track window down to magnify the vertical scale. The blip is not large, but when you find it you will recognize it. 

Are all of your connections good? Does the mic plug seat into the jack solidly? The first plug I tried was a loose fit, and just bumping the wires would wiggle it enough to see significant noise.

Are you near any electrical equipment?

What is your coil diameter and how many turns do you have per coil?

I think Audacity is a better tool to use while you are troubleshooting. It lets you zoom in on the plot much closer. There is one thing I can think of that you could try in SoftChrono for troubleshooting, however. On the settings page, set your muzzle trigger value and your target trigger value to 2. Click on START. Does it automatically trigger and stop recording? If so, increase the trigger values a bit at a time until you find the lowest value that will not cause the software to trigger on noise. My setup triggers on noise up to 3, but doesn't trigger at 3.5. If you have to go much higher than that, that is another indication that your noise level is too high and you should check all of the issues listed above.


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## rdmwc (Sep 21, 2010)

What about machining a field point out of iron and then magnetic it? If I had a grains scale, I would make one up real quick. Or here is a thought. Make the coils tall slender oval... our arrows need more space up and down than side to side. That would put the arrow closer to coils


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## jeremy.b (Dec 7, 2010)

There's been alot of talk about seen the waves outside of the noise, why dont we just remove the noise?

I checked out the frequency spectrum in Audacity and saw that there is a lot of noise above 1000 Hz (kHz??) that should be safe to remove. So I applied a Low-pass filter at 1000 Hz and bam, most of the noise in the wave dissappeared:

Before (zoom in to see the noise better)







After









Now I mentioned that I'm working on writing a program to do this all on the fly, which I've had some success doing.

Below is what I've built so far:









It successfully triggers on the waves, and I've also started building in the Low-pass filter so the noise is even lower.

The last two pieces of the puzzle are to also add some amplification (for those faint peaks) and then to actually find the tops of the peaks in relation to time to do the FPS calculations.

The amplification is pretty easy to do, it's the peaks that have given me issue, but I'll get it whipped sooner or later .


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## rdmwc (Sep 21, 2010)

here is another idea for the softchrono software. build 2 doughnut shaped boxes, place a microphone ( such as an earbud used as a microphone) in each box plug the 2 microphones into a splitter and plug the splitter into the computer. when the arrow passes through the hollow doughnut shaped box, causes vibrations in the box..... think it would work?


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## droppixel (Nov 5, 2010)

Forgot I have a spool of cable in my garage from when I had my fence put in. Going to look to put one of these together as soon as I can. Need to find a lead to hook the wires into.


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## Veni Vidi Vici (Jan 23, 2011)

*@helsyeah:* I've been having my most consistent luck picking points by selecting the midpoint of the steep change from up to down (or down to up, depending on which way you wound your coils). What I do is put a piece of paper on the screen so that it is even with the data before and after the shot (Points A & B below). Then I pick my first and second times where the curves intersect the paper at C and D. I have tried trying to find the point where the curve first lifts off of the baseline, peaks, valleys, etc., and this seems to be the most consistent method. Since you are trying to write a program to do this, you may want to try to implement a similar techique instead of finding the peaks. The logic would be:

After the signal  deviates from the baseline (B) by a defined threshold, find then next point after it crosses the baseline. Then find the baseline again, wait again for a deviation, and find the next point at which it crosses the baseline. Actually, once you cross the baseline, you probably should look at that point and the point before it crossed the baseline and interpolate to find the actual crossing point.

t=((B-y0)/(y1-y0))*(t1-t0)+t0

Where

B=average y value of the baseline data
t=interpolated time at which the baseline is crossed
(t0,y0)= point coordinates just before the baseline is crossed
(t1,y1)= point coordinates just after the baseline is crossed



This screenshot is from my first build where I didn't wind my coils in the same direction, but the algorithm described above would work regardless of which direction one or both coils are wound.


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## revwilder (Apr 11, 2005)

Veni Vidi Vici said:


> *@helsyeah:* I've been having my most consistent luck picking points by selecting the midpoint of the steep change from up to down (or down to up, depending on which way you wound your coils). What I do is put a piece of paper on the screen so that it is even with the data before and after the shot (Points A & B below). Then I pick my first and second times where the curves intersect the paper at C and D. I have tried trying to find the point where the curve first lifts off of the baseline, peaks, valleys, etc., and this seems to be the most consistent method. Since you are trying to write a program to do this, you may want to try to implement a similar techique instead of finding the peaks. The logic would be:
> 
> After the signal  deviates from the baseline (B) by a defined threshold, find then next point after it crosses the baseline. Then find the baseline again, wait again for a deviation, and find the next point at which it crosses the baseline. Actually, once you cross the baseline, you probably should look at that point and the point before it crossed the baseline and interpolate to find the actual crossing point.
> 
> ...


Of Course! :doh: That is what I have been saying all along...Lol

Seriously, you guys are even bigger nerds than I ever dreamed of.


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## 05_sprcrw (Aug 18, 2009)

Great work guys I wish I could help out more with this project.


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## Veni Vidi Vici (Jan 23, 2011)

revwilder said:


> Of Course! :doh: That is what I have been saying all along...Lol
> 
> Seriously, you guys are even bigger nerds than I ever dreamed of.




LOL Guilty as charged! At least being a nerd pays well.


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## tllhunter (Jan 15, 2008)

Is there a consensus on which gauge wire works best, stranded or solid wire, coated or uncoated, lay the wires in each individual coil side by side or stack them on top of each other.


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## Veni Vidi Vici (Jan 23, 2011)

tllhunter said:


> Is there a consensus on which gauge wire works best, stranded or solid wire, coated or uncoated, lay the wires in each individual coil side by side or stack them on top of each other.


I don't know about gauge, but the wire definitely needs to be coated. The varnished wire you see on motors is fine (I think it's actually called magnet wire), but if the wire is truly uninsulated the coil will just be a short and won't act as a coil.

I think you want the coil as narrow as possible, so stacking the wires would be best. I really like a previous poster's idea of cutting a groove in a piece of large diameter heavy-walled PVC pipe and laying the wire in that.


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## droppixel (Nov 5, 2010)

I was just going to ask if the coated vs. uncoated would work better - fail - read the rest of the above and think I got my answer.


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## jeremy.b (Dec 7, 2010)

One step closer...

I was finally able to get my program to apply a specified ammount of amplification to the recorded signal AND calculate the cross-over points for the times. 

VVV, your comments were perfectly on the money as far as how to go about doing the calculations, thank you.

Here's how it currently looks:









On the sample that I recorded yesterday I was able to get it to accurately calculate the speeds, so now all I have to do is the live testing when I get home.


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## 05_sprcrw (Aug 18, 2009)

Sweet, now to throw one last loop in the mix guys what about using a lighted nock to increase the magnetic field disruption? The only problem is then your algorithms would be off because you would have 4 disturbances instead of 2.


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## Veni Vidi Vici (Jan 23, 2011)

05_sprcrw said:


> Sweet, now to throw one last loop in the mix guys what about using a lighted nock to increase the magnetic field disruption? The only problem is then your algorithms would be off because you would have 4 disturbances instead of 2.


It's funny that you bring that up. I actually tried that last night using an Easton Tracer, and I couldn't detect anything.

I have my field point with the magnet installed in it now, and I'll be testing it this evening.


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## Veni Vidi Vici (Jan 23, 2011)

*@helsyeah:* I want in on the beta testing for your software


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## Veni Vidi Vici (Jan 23, 2011)

Here are my results from the field tip with a magnet installed inside it.


First, some background .....

When I did my first tests with my original coils, it took rubbing a magnet on the field tip to give enough of a signal to see above the background noise. I also had to zoom in the y axis scale to the maximum zoom, and then stretch the window vertically. Here's an example of that:











So today I drilled out a 125 grain field point and installed a rare earth magnet measuring 1/4" diameter x 1/4" long. I then added a few washers to get the weight back up to a total of 126 grains. My goal was to get a strong enough signal to reliably trigger the SoftChrono detection algorithm.

Here are my settings in SoftChrono and the Windows 7 external mic settings:











Here is the first shot I recorded with the embedded magnet and SoftChrono:











Here are the results of a 10 shot series in SoftChrono (min was 268, max was 270, average was 270):











Here is another shot using the same field point recorded in Audacity. The signal spike was clearly visible without zooming in the y axis at all .... a HUGE improvement (compare this to the first picture in this post):











Here is the signal after one "Fit Selection to Window" and still no y axis zoom:











After going through my manual process of picking points, I got a calculated speed of 269.9 fps.

So everything is in agreement now! :rock:

Chrono at pro-shop: 268-269 fps
Audacity and manual analysis without magnet: 270.5 fps
Audacity and manual analysis with magnet: 269.9 fps
SoftChron with magnet: 269 fps

So after all of this, I think I can safely conclude that my setup is shooting 269-270 fps! :jksign:

So ..... my final setup is 2 coils in series, 10" diameter, 50 turns per coil, 18 gauge insulated wire, coils spaced ~ 2 feet apart, 1/4" diameter x 1/4" long rare earth magnet installed in a field point. I think I'm done tweaking this thing at this point.


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## revwilder (Apr 11, 2005)

Can we make it affordable, portable and marketable? Seriously a $25-50 Chrono with software that is just as accurate as anything else out there. It is possible.


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## Veni Vidi Vici (Jan 23, 2011)

revwilder said:


> Can we make it affordable, portable and marketable? Seriously a $25-50 Chrono with software that is just as accurate as anything else out there. It is possible.


I thought about this before I posted anything, but decided to just give back to the archery community. I've learned a bunch from the people who post on forums like this, and for a number of reasons I would rather just share the idea. Most of the concept was already out there; my only addition was the use of coils instead of a mic. It's been fun seeing the interest others have taken in this project, and I respect the skills they brought to the table.


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## 05_sprcrw (Aug 18, 2009)

Great job VVV I will have to start making some magnetic field points in a couple sizes.


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## cbmac (May 24, 2006)

Super thread VVV. this is the AT hobbiest community at its best.


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## Veni Vidi Vici (Jan 23, 2011)

05_sprcrw said:


> Great job VVV I will have to start making some magnetic field points in a couple sizes.


I'm pretty sure the magnet I have is from McMaster-Carr, #58605K75 http://www.mcmaster.com/#rare-earth-magnets/=bsv6n0

The 125 grain FP I put it in measures 5/16" OD, so drilling it out for the 1/4" diameter magnet removed almost all of the tapered tip. Based on the signal improvement I got, you could probably get away with two 1/8" diameter x 1/8" long magnets.

I ended up stacking three #10 lock washers between the tip and the arrow insert, plus supergluing one to the front of the now blunt tip in order to get the weight back up. I couldn't put more than three behind the tip because the threads wouldn't engage.


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## straddleridge (Apr 28, 2010)

I have to say you guys have done an outstanding job. About 45 years ago I worked at McDonnel Aircraft Corp. and we used a similar setup to measure gas flow rates through a glass tube with 2 plastic grooved rings containing series wound cables at a predetermined distance. The glass tube contained a fiber piston sealed by a mercury ring that caused the same waveform as it passed through the rings.  We used the waveform to trigger a timer. You picked the right place on the waveform - the crossover. As I recall the coils used enamel insulation and were probabley about 22 gauge. 

Now here is a suggestion. We used what is called a "Carrier Amplifier". From an electronics store get an IC oscillator at about 15 KHZ. run the 15 KHZ through the coils and put a current limiting resistor in series with the coils so the oscillator doesn't think it is a short circuit. Then make a detector with a diode and a resistor at the computers microphone input. This may give you an output as large as the peak to peak voltage of the oscillator.

I use a radarchron so I have never even seen a chronograph - but sometime in the near future I am going to try an build one of these.

great job guys - I would have never thought of it.


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## tllhunter (Jan 15, 2008)

One more stupid question. Are you using copper wire, aluminum or other type of wire.


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## edmondsmatt (Dec 17, 2010)

Maybe these would be worth purchasing, http://www.doubletakearchery.com/air-rest/inserts.htm I have been thinking about an easy way to add a magnet and this is the best I have come up with short of drilling and epoxy.


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## Veni Vidi Vici (Jan 23, 2011)

tllhunter said:


> One more stupid question. Are you using copper wire, aluminum or other type of wire.


I used copper.


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## Veni Vidi Vici (Jan 23, 2011)

edmondsmatt said:


> Maybe these would be worth purchasing, http://www.doubletakearchery.com/air-rest/inserts.htm I have been thinking about an easy way to add a magnet and this is the best I have come up with short of drilling and epoxy.


Unless you were going to use these in all of your arrows, they would change your weight. But many people could drop back one size in FP weight and make up for most of the difference.


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## jeremy.b (Dec 7, 2010)

After MUCH wrestling with audio reading API's and such, SUCCESS! 









I'm still polishing the tool (I'll add lines for the calculation threshholds and couple other things) before I start handing it out, but its at least functional.


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## Don Schultz (Jul 5, 2002)

*no microphone*

It's not a microphone. It's 2 induction coils. Nicely done!


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## Veni Vidi Vici (Jan 23, 2011)

@helsyeah: Nice! What are the two bars with the green on the left ends?

Also, once you are putting the finishing touches on it, it would be slick if you had a graphic that looked like a virtual chronograph


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## naubusan (Mar 23, 2007)

Nice job helsyeah.
Is it too late to add KE calculator in it?


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## 09Dreamseason (Feb 11, 2010)

helsyeah said:


> After MUCH wrestling with audio reading API's and such, SUCCESS!
> 
> View attachment 1049579
> 
> ...


Will this be a plug in for us to use Audacity?


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## 09Dreamseason (Feb 11, 2010)

Jumpboots101 said:


> I give you an A for effort! But this "cheapo" method has alot of drawbacks and time consumption is a huge factor. I think it's way more benefitial to just get a crony F1 from walmart for $70.


where in WalMart is this sold at?


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## 05_sprcrw (Aug 18, 2009)

helsyeah said:


> After MUCH wrestling with audio reading API's and such, SUCCESS!
> 
> View attachment 1049579
> 
> ...


Great work if you need the math behind calculating the ke and the momentum its in an equation in the Excel sheet I put up earlier on in Page 2 of this thread it would save you some time if you want it.


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## rdmwc (Sep 21, 2010)

I just built mine, but something isn't right. When I wired the microphone plug, I may have wired it incorrectly though. But my results were odd. When I click the start button the line singles but doesn't read my field point with the magnet in it.. so I change the settings for muzzle volume and such to below 5 and click start and it triggers itself and says its 1137.00 fps. When I didn't drop anything through it..? Any help?


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## naubusan (Mar 23, 2007)

Guess it triggers from background noise..
Check with audacity if you can get signal at all.
If audacity shows you proper signal then just adjust softchrono.


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> I just built mine, but something isn't right. When I wired the microphone plug, I may have wired it incorrectly though. But my results were odd. When I click the start button the line singles but doesn't read my field point with the magnet in it.. so I change the settings for muzzle volume and such to below 5 and click start and it triggers itself and says its 1137.00 fps. When I didn't drop anything through it..? Any help?


Can you check the resistance of your coil? I would expect just a couple of ohms. Also, have you verified that the jack on your pc works? From what I've seen, with an actual magnet you should get a very strong signal. And naubusan is right... You are triggering on noise.


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## rdmwc (Sep 21, 2010)

I will do that after work and report back. Thanks!


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## jeremy.b (Dec 7, 2010)

Veni Vidi Vici said:


> @helsyeah: Nice! What are the two bars with the green on the left ends?
> 
> Also, once you are putting the finishing touches on it, it would be slick if you had a graphic that looked like a virtual chronograph


The two bars show the current input volume levels (approximately).

As far as the virtual chronograph goes, interesting, but I'm more worried about functionality at this point still .



naubusan said:


> Nice job helsyeah.
> Is it too late to add KE calculator in it?





05_sprcrw said:


> Great work if you need the math behind calculating the ke and the momentum its in an equation in the Excel sheet I put up earlier on in Page 2 of this thread it would save you some time if you want it.


Great idea, I can certainly add a field for arrow weight that will then do the KE and momentum calcs.



09Dreamseason said:


> Will this be a plug in for us to use Audacity?


Nope, this is a stand-alone tool built with a scripting language called AutoIT using a sound API (programming library basically) called BASS.

Also, this is reading data from an un-amplified audio input (but does have a low and high-pass set of filters on the input to remove as much noise as possible). 

Translation: The tiny blips that VVV was seeing when he first started this project WILL be detected by this program, assuming they peak higher than the noise that the coils are picking up. Which in turn means that it may not be necessary to create special field points with magnets and such (unless your setup isn't seeing the peaks from the noise).

Hopefully I can get this puppy polished enough to let you all take a crack at it by the middle of next week.


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## hunt123 (Jan 17, 2009)

09Dreamseason said:


> where in WalMart is this sold at?


Online only.


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## rdmwc (Sep 21, 2010)

I just checked the plug on the laptop and its working. I checked the resistance of the coils by touching the multimeter leads to my wired plug, and it reads about 15 ohms. I'm not sure why this isn't working. Could it be I soldered both solder soldered connections together ( left and right channel)?


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> I just checked the plug on the laptop and its working. I checked the resistance of the coils by touching the multimeter leads to my wired plug, and it reads about 15 ohms. I'm not sure why this isn't working. Could it be I soldered both solder soldered connections together ( left and right channel)?


This is how mine is wired:











What gauge wire and how many turns are you using? My coils only measure just under 3 ohms total using 100 total 10" diameter turns of 18 ga copper.


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## rdmwc (Sep 21, 2010)

Ok, I downloaded audacity and I'm clearly getting a signal. The orientation of my magnet isn't good. I had made a field point out of iron and drill the tip and inserted the same magnet and not it works in softchrono but when I lightly toss other through it tells me it was going almost 1200 fps.


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## rdmwc (Sep 21, 2010)

I just used some magnet wire I had around. One coil is 20 turns of 22ga. And the other is 20 turns of 30ga. The multimeter I used isn't mine, it was on the 1.5 ohms mark but the switch was on RX10


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## rdmwc (Sep 21, 2010)




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## Veni Vidi Vici (Jan 23, 2011)

So it is working now in softchrono? Are you getting a reasonable speed? Do you know your actual speed for comparison? BTW I like your use of arrows for supports! Can you post some screenshots from audacity and softchrono? Also, have you calculated your speed from times in audacity? 15 ohms still seems high. I would expect maybe half of that based on this calculator. http://www.cirris.com/testing/resistance/wire.html. What don't you like about your magnet's orientation? Sorry about all of the questions, but you might be going thru some things others can learn from.


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## rdmwc (Sep 21, 2010)

well, i have just been dropping the field point through. i started getting what i think were reasonable speeds (1-2 fps) but once and a while it would jump to around 1100 now i cant get it to stay under 500 unless i change the frequency to the lowest setting. i have also found that it will trigger after going through just one coil ( i put the point on my arrow and slid it through by hand and it would trigger after the first coil!). kinda frustrating. lol thanx!


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## rdmwc (Sep 21, 2010)

im not sure how to do the screenshot thing. well the first tip i experimented with i took a 100 grain field point and drilled a hole through it, sideways (90* from the shaft of the arrow) and inserted the magnet. my magnet is 1/8" diamer and is same length as the width of my arrow. i will look up how to calculate the speads in audacity and post some.


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## Veni Vidi Vici (Jan 23, 2011)

You can play with some of the auto analyze settings in softchrono and see if that helps with the triggering. As for screenshots, AT allows you to upload pics to an album. You should be able to hit shift-print screen (or ctrl, alt, fn, etc.) to capture a screenshot. Then paste it into Paint or something and save it. After all that, you can upload it to an album, get the image URL or BB code, and paste it into your post. Ez peezy!


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## Veni Vidi Vici (Jan 23, 2011)

Make sure you set your min and max speeds to something that bounds the range you expect to see. That should keep you from getting 1100.


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## rdmwc (Sep 21, 2010)

if i happen to have my coils wound opposite of eachother, would it cause this? because in audacity it appears that my coils are opposite. one goes up then down, then next goes down then up.


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## Veni Vidi Vici (Jan 23, 2011)

I don't think so. In softchrono, it looks like it can trigger on either an increase or a decrease from zero. Since you used two different wires for each coil, you can swap the leads connecting the two coils and that will swap the coil direction. I hope you can get a decent answer with audacity so we can verify that you're having an issue with softchrono and not your hardware.


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## Veni Vidi Vici (Jan 23, 2011)

If you can't get the screenshot to work, you can just take a picture of your screen and post it like you did for your chronograph image above.


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## naubusan (Mar 23, 2007)

Or you can use this free simple tool to take screenshots.
http://lightscreen.sourceforge.net/

with it you can take shots only on active window, and it saves it straight as jpg.


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## Silver Pine (Dec 9, 2005)

Great DIY project. 

Just a few random thoughts - 

Would the steel blades (more iron content?) on an old broadhead hold a higher induced magnetism than a field tip? Instead of adding a magnet? 

Wrapping steel wire around a closed expandable broadhead should also have a higher magnetism. 

Winding the "start" coil clockwise and the "stop" coil counter-clockwise produces reversed (mirrored) signals and also identifies which coil triggered and in what order. I don't know if that would be important or not. 

The coils of wire should be round. The shape is important in order to create an electrical field inside the coil and produce the strongest possible field. Any other shape would produce a weaker field or non-existent field. 

I seem to remember that the insulated wire should be laid side by side while wrapping, without overlapping the wire, to form a short cylinder. Both coils should have an equal number of wraps and be the same gauge wire. The first winding of the "start" coil should be the same distance from the first winding of the "stop" coil as the last winding of the "start" coil is from the last winding of the "stop" coil, 1', 2', 3' etc.

Twist the wires running from the coils to the tip and ring connections on the plug to reduce noise and outside signal interferrence. 

The DC current from the "mic" jack passing thru the loop and back to the jack, creates the magnetic field. The stronger the current, the stronger the field will be. Passing a magnet thru the magnetic field of the coil(s) will produce an electrical spike. Passing it back and forth 60 times per second will produce 60 cycle electricity. 

:cocktail:


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## rdmwc (Sep 21, 2010)

I will work on getting the screenshots after work today. lastnight I adjusted the velocity range to 1-5 and then slid my arrow through. it kept yielding a spear if 1.1 to 1.6 consistently. could one of you guys that has a working softchrono try the same test with the velocity set to 1-1200 and see what you get for readings? also Veni, you said you think soft chrono will trigger on an up or down spike... this actually makes sense why mine is messing up. one of my spikes will be a nice soft blip and the other will be a huge spike above and below the base line... I wonder if that single aggressive spike up and down was triggering the tart and stop?e..


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## Veni Vidi Vici (Jan 23, 2011)

If you look at this shot, you can see a little more about how softchrono uses the settings to find the trigger points.

In this picture, the muzzle trigger and the target trigger were both set at 100. These lines are shown in blue at the top and bottom of the graph. You can see that the first time the graph crosses a trigger line, SC marks that as the muzzle trigger. In this case, the graph was going down when it triggered.

Looking at the top, you see a small red tick mark that says Max measured Velocity 300 fps. There is a similar tickmark at the bottom further to the right that says Min measured velocity 200 fps. (These marks are mirrored at the top and bottom of the window but are not labeled.) These numbers come from the settings. After SC identifies what it thinks is the muzzle trigger, it calculates when it should expect to see the target trigger (between 300 and 200 fps) and ignores everything until enough time has passed that 300 fps could be a possibility. It then looks for the next time that the trigger is crossed, either up or down. In this case, since the coils are wound the same way, it again triggered on a down and marked the impact trigger point.

This delay (i.e. not looking for a signal until it expects to see one) is why it didn't trigger on the three times the graph crossed the trigger thresholds betweeen the muzzle trigger and the impact trigger.

If you are using softchrono, you probably should have your coils wound the same direction, and making them round would probably help, too, as suggested above. If the signal through your coils is identical, then SC would do fine. But if the signal is not identical, then SC might trigger a little early or late. The manual method with audacity of finding the times associated with the crossover from high to low (or low to high) will work even if the coils are wound opposite directions .... that's how my very first setup was accidentally wound.


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## Veni Vidi Vici (Jan 23, 2011)

@rdmwc: Have you tried shooting an arrow through it yet and measuring that? Since all of my testing has been done that way, and since it will be more consistent than sliding an arrow through, it might be easier to compare your screenshots if they are of an actual shot.


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## rdmwc (Sep 21, 2010)

I will try tonight


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## rdmwc (Sep 21, 2010)

Well, I shot through it and sure enough it was triggering on the up and down side of the first coil. I adjusted the settings and now works like a charm... will still have to shoot through a professional chrono to check accuracy.


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> Well, I shot through it and sure enough it was triggering on the up and down side of the first coil. I adjusted the settings and now works like a charm... will still have to shoot through a professional chrono to check accuracy.


Are your coils still wired opposite or did you change that? What kind of numbers are you getting? If you do shoot through a real chrono and get slightly different numbers, you can adjust your target distance to correct this. You can also use the Cal. Offset field to adjust it, but I'm assuming that adds or subtracts a fixed amount. I think the more accurate way to fix it is to change the distance. That should make a slope correction which would be more accurate at any speed, while the offset will only truly be correct close to your speed.


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## rdmwc (Sep 21, 2010)

According to the analysis in sc they are wired backwards. I will be switching that coil around before the weekend.


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## rdmwc (Sep 21, 2010)

MY bow is awaiting new limbs, but I just bought my girlfriend a parker sidekick xp 40-50# I think she is about 40# shooting my arrow through it ( about 450 grain) 24" draw and the sc average was 158.4 fps. Which I think should be possibly a little low by 20 fps.... guessing, but it was shot through a whisker bisket.


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## varmintvaporize (Feb 9, 2010)

Great DIY project!
I would like to add some food for thought. Use 3 coils instead of just 2, then you would have a "Proof Channel" like the Oehler 3 screen chronographs. This should also make it easier to find an exact center of each bump in the signals.


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## Veni Vidi Vici (Jan 23, 2011)

varmintvaporize said:


> Great DIY project!
> I would like to add some food for thought. Use 3 coils instead of just 2, then you would have a "Proof Channel" like the Oehler 3 screen chronographs. This should also make it easier to find an exact center of each bump in the signals.


Interesting idea. I wasn't familiar with the Oehlers.

Thinking this through

a) Oehler seems to be trying to handle readings in difficult lighting situations. Lighting is not an issue with the coils.
b) The software (are you listening, helsyeah?  ) would have to support three coils.
c) I'm concerned that if the software is using the same algorithm to find times between coils 1 and 2 as it uses for 2 and 3, and since the coils are in series and being measured on a single input channel, then the proof reading may not be truly independent. Maybe if the points used for 2 and 3 were selected on different parts of the curves ... ?
d) Since lighting is not an issue with the coils, maybe the simplest way to proof it is just to shoot several shots.

Can you explain why it would be easier to find the centers of the signals with a third coil?


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> MY bow is awaiting new limbs, but I just bought my girlfriend a parker sidekick xp 40-50# I think she is about 40# shooting my arrow through it ( about 450 grain) 24" draw and the sc average was 158.4 fps. Which I think should be possibly a little low by 20 fps.... guessing, but it was shot through a whisker bisket.


Using this speed calculator and info from the Parker site about the sidekick, it's calculating a speed of 145 fps. To use the calculator, I put in Parker's specs of 60#, 28", 300 grain arrow and adjusted the IBO speed until it gave Parker's claim of 270fps. Once I had that, I put in your specs of 40#, 450gr, 24" and it gave 145 fps. The calculator starts by assuming the IBO speed is at 70# and 30" draw, then reduces the speed as necessary. I would bet that it is a little low when it has to go so far, so your 158 fps may be closer to reality. I would doubt that it should be 178 fps, though.


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## jeremy.b (Dec 7, 2010)

Veni Vidi Vici said:


> Interesting idea. I wasn't familiar with the Oehlers.
> 
> Thinking this through
> 
> ...


Another thought to this is that the close the coils get together (physical distance) the closer the signals get together, which in turn will magnify calculation errors due to distance measurement errors, non-uniform waves, etc. Three coils, in general, will probably be closer together than two coils.

Also, by adding a 3rd coil you may indeed have three signals to read from, but the math does get more difficult to rationalize what is what and where the time triggers really fall.


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## 09Dreamseason (Feb 11, 2010)

guys I'm lost!! I made my coils and wired them to a jack to put into my mic jack on my laptop. When I start Audacity I can see that it's picking up noise, however, I can't differentiate from the soundwave created where my arrow is passing through them! Are there specific parameters that I must set the program up with to see the soundwaves? Is there a filter setting where I can adjust the background noise out of it like a static zero? 

What I did was take a cardboard box that is long and pretty tall and wide. I cut out a 12 inch hole at either end putting my holes 30" apart from each other. I put my coils at each opening so I have essentially created a tunnel out of the box with a coil at each end and wired in series like in the OP's original post.

It's my understanding that once I get this figured out I will be able to figure out the speed from soundwave of Coil 1 to soundwave of Coil 2 and use the 30" distance between the coils to figure out FPS using the Math problem V=D/T

I just need some help figuring out Audacity now..........


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## rdmwc (Sep 21, 2010)

What are the dimensions of your coils? If they are too large you will have to put a magnet in your field point. I could. Help you if you were using softcchrono program.


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## Veni Vidi Vici (Jan 23, 2011)

@09Dreamseason: rdmwc is right. You can get a signal that is just above the background noise level by rubbing a magnet on your fieldpoint, but it will work MUCH better if you can put a real magnet in the fieldpoint. I drilled a .256 diameter hole in the end of a fieldpoint deep enough to install a 1/4" dia x 1/4" long rare earth magnet, which I glued in place. This gives me a huge signal and makes the noise irrelevant. Look at post #111 for an example of how much improvement a real magnet makes.

As far as Audacity goes, you shouldn't need to run a filter. If you only have a weakly magnetized fieldpoint, you will have to zoom in as much as possible to see the waveform. Left-clicking on the vertical scale on the left of the plot zooms in and recenters it. Do this until it won't zoom in any more. Hopefully you will see a tiny blip above the noise at the time of the shot. The first pic of post 111 shows this. Now highlight the blip by dragging over it and click on "Fit Selection to Window". Repeat this until the blip fills about 2/3 of the plot. Now grab the bottom edge of the plot window and drag it down to stretch the vertical even more.

Truthfully, your best bet is to get a real magnet and use softchrono (or whatever helsyeah comes up with). From what I've seen, this combo should work great.


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## 09Dreamseason (Feb 11, 2010)

I just downloaded softchrono.........now what?


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## 09Dreamseason (Feb 11, 2010)

so I set it up and I'm getting readings.........but I'm not sure if I'm doing it right! What are you putting for Min/Max Velocity and Muzzle/Impact Volume?


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## mwitty111 (Dec 2, 2008)

Wow... between this thread and the smoker thread (which I read right before this one), I'm totally blow away. This is awesome.


-Witty


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## rdmwc (Sep 21, 2010)

On the bow I tested, I set the range from 100 to 250 fps because I knew it was somewhere between there since its a low poundage beginner bow. For the volume, I started at 6... but then looked at the zoomed in analysis screen and used that to find the.values I needed. Which are 62 and 70. That all depends on your coils and your field point. You will want to find values that will hit same point on both spikes.


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> I just downloaded softchrono.........now what?


Do you have a magnet in your fieldpoint? If not, you can rub a magnet on your fp several times in one direction. In SC, enter the distance, your speed range (200-350?), and set your triggers both to 2. Hit start. It will probably trigger on the noise. Bump the triggers up 1 at a time until it will run without triggering on the noise. NOW start it and shoot thru the coils. If it triggers, look at the results (the plot and the speed output) and see if they make sense. If it doesn't trigger, try shooting closer to your coils (not thru the center) BUT BE CAREFUL NOT TO GET TOO CLOSE!!! That might be enough to give you a small signal that SC can detect and analyze. The next step from here is installing a magnet in your fp.

Please post some screenshots of anything you have questions about.


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## Veni Vidi Vici (Jan 23, 2011)

@rdmwc: sounds like you've really figured it out now


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## rdmwc (Sep 21, 2010)

Veni, thank you for all your help!!!


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## Veni Vidi Vici (Jan 23, 2011)

No problem!  I think it's great that you're helping answer some questions now, too.


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## sharkbone (Dec 5, 2010)

Hi to All,

This is one the best DIY threads on the fourm.

First as far as background noise and unreadable signals are concerned, make sure your built in mic is off and the external mic is on and the volume is all the way up, this will save you hours of fustration (TRUST ME) :BangHead:

I have been following this since the begining and last weekend I decided I had to build one, and it works ( after fixing the problem mention above ).

I used 2 storage type bowls that I got from the dollar store and give me an 8 1/2" diameter ring. Then I used 100' 16ga stranded wire from the automotive section of a local store and I used 18 wraps for each coil. I have my coils 2' apart right now but I think I am going to increase this to 30" as I seem to get alot of variation in my readings sometimes, especially if the arrow is off centre. Right now I fire 8 shots and then discard the high and low reading and use the average, I don't have access to a real crono to test the accuracy of my system yet.

I found some ball bearing sized rare earth magnets and drilled a 13/64 blind hole and epoxied on in my fp. Then used wire to bring back to 125gns. If the pictures work you hopfully will be able to see the magnet.

I even managed to put an old laptop to use and give a new purpose. I can also use a microphone and audacity to see if those little tweaks are actually helping with noise or is it in my head.

Thanks for the great idea and all the work you guys have done so far and I can't wait to see how this develops. I wish I could contribute, But I'm a carpenter and know pretty much squat about electronics. Having said that I hope the pics turn out.


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## droppixel (Nov 5, 2010)

Gave this a go tonight, might have to go back and re-read some things. Mine wasn't picking up any waves... I'll have to double check my wire connections, I didn't solder but I had really good copper, to copper connection in the wire. Does it matter which connection is at which point on the input jack?


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## 09Dreamseason (Feb 11, 2010)

Veni Vidi Vici said:


> Do you have a magnet in your fieldpoint? If not, you can rub a magnet on your fp several times in one direction. In SC, enter the distance, your speed range (200-350?), and set your triggers both to 2. Hit start. It will probably trigger on the noise. Bump the triggers up 1 at a time until it will run without triggering on the noise. NOW start it and shoot thru the coils. If it triggers, look at the results (the plot and the speed output) and see if they make sense. If it doesn't trigger, try shooting closer to your coils (not thru the center) BUT BE CAREFUL NOT TO GET TOO CLOSE!!! That might be enough to give you a small signal that SC can detect and analyze. The next step from here is installing a magnet in your fp.
> 
> Please post some screenshots of anything you have questions about.


I don't see where to adjust the triggers.........I have played with the analysis and figured my muzzle/impact settings and I'm not needing a magnet to get a reading at all! Not sure how to do screen shots either.


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## varmintvaporize (Feb 9, 2010)

Veni Vidi Vici said:


> Interesting idea. I wasn't familiar with the Oehlers.
> 
> Thinking this through
> 
> ...



In your pictures of the pulse-bumps there is a fairly wide up and down line. You were using the what appeared to be the center of the upward line in both the 1st and 2nd coil to make your measurement from. 
If you had 3 coils the time between #1 & #2 should be exactly the same as the time between #2 & #3 and exactly twice as much time between #1 & #3. Thus making it much more accurate.
Oehler 3 screen chronographs (model 35 & 43) process all 3 of these measurments, and that is why they are so popular with firearms shooters and ballistic labs.
Maybe overkill, but food for thought!


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## naubusan (Mar 23, 2007)

09Dreamseason said:


> I don't see where to adjust the triggers.........I have played with the analysis and figured my muzzle/impact settings and I'm not needing a magnet to get a reading at all! Not sure how to do screen shots either.


You can use Lightscreen to take screenshots. It's really simple.
http://lightscreen.sourceforge.net/


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> I don't see where to adjust the triggers.........I have played with the analysis and figured my muzzle/impact settings and I'm not needing a magnet to get a reading at all! Not sure how to do screen shots either.


On the settings screen, the triggers are called "Muzzle Volume" and "Impact Volume" and they have a range of 0-127. You can also drag the trigger lines around on the analyze screen.


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## Veni Vidi Vici (Jan 23, 2011)

sharkbone said:


> I have been following this since the begining and last weekend I decided I had to build one, and it works ( after fixing the problem mention above ).


Great job, sharkbone!

Did you purchase your magnets or did you scavenge them out of something?


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## EmCommer (Apr 11, 2011)

Someone should make an app for that; meaning a phone app. I could see mounting this on a tripod and just hanging the phone from the tripod facing the shooter.

My new bow shows up tomorrow and I plan on making something like this soon. Great DIY project.

Brian


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## EmCommer (Apr 11, 2011)

helsyeah said:


> After MUCH wrestling with audio reading API's and such, SUCCESS!
> 
> View attachment 1049579
> 
> ...



Are you getting close? 

It might be worthwhile to put additional note fields and logging in to easily organize multiple arrow and bow configurations for future reference. Just a thought. Maybe that's a seperate logging app.


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## 09Dreamseason (Feb 11, 2010)

I'm still having problems even with softchrono..........I click on calibration shot and then I dont do anything and it shows a reading!! I'm getting so many different inconsistencies that it isn't even fun anymore. I taped a magnet to my arrow to see if it triggers anything and I'm getting nothing different......

I'll be interested in the tool that helsyeah puts together so I can try that out! This is definately NOT an easy DIY!!!


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## 09Dreamseason (Feb 11, 2010)

Veni Vidi Vici said:


> So ..... my final setup is 2 coils in series, 10" diameter, 50 turns per coil, 18 gauge insulated wire, coils spaced ~ 2 feet apart, 1/4" diameter x 1/4" long rare earth magnet installed in a field point. I think I'm done tweaking this thing at this point.


So we're looking at needing 18 gauge insulated wire, 50 turns per coil(does this mean 50 10" circles?), 10" diameter, 2 coils in series around 2 feet apart(you originally said it needed to be longer than your arrow?), and the 1/4" x 1/4" rare earth magnet installed in the field point(where do we purchase these at and at what cost?)........

I'm going to start all over again with my coils as I'm thinking the 12" coils I used and only using 10 complete circles isn't enough at this point.........

Can you make a complete list of meterials and estimated cost you have involved?

How many feet of wire used and cost:
Rare Earth magnet cost:


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## droppixel (Nov 5, 2010)

Going to adjust my wire connections tonight and hopefully give this another run. I don't know that I will be able to run SoftChrono (mac user) but my crossover might fire it up, otherwise I'll stick to the regular calculation. Friend of mine just picked up a chrono so if I get this working properly I can compare the results.

Thinking about tightening my coils up, currently a little under 10" - I wrapped them around a paint can.


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## rdmwc (Sep 21, 2010)

Dream season, I used magnet wire ( enamel coated copper wire). It can be purchased from radio shack or online for under $10. My coils are around 10" diameter with 20 full circles each, wrapped as tightly together as possible. My coils are exactly 12 inches apart. The magnet wire from radio shack comes in a kit, 3 different gauge spool. I have one coil of 30 gauge wire and one that's 22gauge. Both of which comes in that kit. As far as the magnet, I'm not sure other than online. Should be less than $5. I just got done making a fieldpoint out of iron with a magnet inserted in the end. Weighs out at 102 grains. I will take some pictures of my setup tonight. Only cost me some time... oh, if its triggering without shooting, the trigger/muzzle volumes may be too low. I think I had similar problems as you starting out. Thanx again Veni!


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> So we're looking at needing 18 gauge insulated wire, 50 turns per coil(does this mean 50 10" circles?), 10" diameter, 2 coils in series around 2 feet apart(you originally said it needed to be longer than your arrow?), and the 1/4" x 1/4" rare earth magnet installed in the field point(where do we purchase these at and at what cost?)........
> 
> I'm going to start all over again with my coils as I'm thinking the 12" coils I used and only using 10 complete circles isn't enough at this point.........
> 
> ...


I'm sorry you are having so much trouble with this. It was easy to throw together, but the details are scattered throughout this thread.

Here is the list of materials I used for my first version:

•	4 ft piece of scrap shoe molding
•	~100 ft of 16 gauge insulated wire (I had this already from my invisible dog fence). You could get 125 ft of 16 ga magnet wire from McMaster-Carr for $20.62 (#7588K21), but I would probably get 792 ft of 24 ga magnet wire for $22.11 (#7588K77)
•	1 rare earth magnet, ¼” diameter x ¼” long, McMaster-Carr #58605K75 (I had this already, but they are $3.30 each). I believe you could substitute one or two 1/8” diameter x 1/8” long magnets and still get a good signal, but I haven’t tried this.)
•	Field point
•	#10 lock washers or wire (used to adjust the weight of the fieldpoint back to the correct weight after adding the magnet).
•	PC accessory microphone. Mine was a combination ear bud/microphone from Dollar Tree for $1. You only need this for the plug. A headphone plug would work as well, but you may need to solder the tip and ring electrical contacts together as I showed in a previous post.
•	Tape, solder, etc.

My total cost was truly $1 because I had some of the materials. If you were building this from scratch, it would run you about $35. As rdmwc said, Radio Shack may have wire cheaper.


Initially, I thought that the entire arrow would contribute to the signal, which is why I recommended spacing the coils further apart than the length of the arrow; I wanted the entire arrow to clear the first coil before entering the second coil. Now that I understand the principles a little better, I realize that only the magnet has to be clear of each coil. Since the magnet is essentially the field point, this means the coils can be spaced closer together. I settled on 2 feet between coils. If you go too close, then any error you have in measuring the spacing will have a bigger impact on your measurement accuracy (1/8” is a bigger percentage of 24” than it is 48”).


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## 09Dreamseason (Feb 11, 2010)

VVV, how many turns do you have in each coil?


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## 09Dreamseason (Feb 11, 2010)

rdmwc said:


> Dream season, I used magnet wire ( enamel coated copper wire). It can be purchased from radio shack or online for under $10. My coils are around 10" diameter with 20 full circles each, wrapped as tightly together as possible. My coils are exactly 12 inches apart. The magnet wire from radio shack comes in a kit, 3 different gauge spool. I have one coil of 30 gauge wire and one that's 22gauge. Both of which comes in that kit. As far as the magnet, I'm not sure other than online. Should be less than $5. I just got done making a fieldpoint out of iron with a magnet inserted in the end. Weighs out at 102 grains. I will take some pictures of my setup tonight. Only cost me some time... oh, if its triggering without shooting, the trigger/muzzle volumes may be too low. I think I had similar problems as you starting out. Thanx again Veni!


This was going to be my next try was the coated magnet wire but did you use different qauge sizes because the kit didn't come with enough wire?


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## rdmwc (Sep 21, 2010)

Yes, the spool I started with was partially used... so I had to make the other out of the other gauge spool.


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> VVV, how many turns do you have in each coil?


My original setup had 16 turns in each coil, with 10" diameter coils. My second setup had 50 turns (again, 10" diameter) of 18 ga wire that I already had. The more turns you can do, the better.


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## Nockhuntin88 (Dec 31, 2010)

I don't know if this was mentioned yet, but using some smaller uninsulated copper wire for your windings might work a little bit better to help on the sensativity of the system. Just a thought. Great idea by the way.


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## sharkbone (Dec 5, 2010)

I got the magnets for my field point from a store in the mall that sells scientific type toys and stuff, they are called Bucky balls. They usually come as big cube but this was too expensive, luckily they sold them individually for .29. I got 10 for $3.00.


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## 09Dreamseason (Feb 11, 2010)

I just redid my entire coil assy with 6" coils and 15 turns of 16 gauge wire this time 24" from center of coil to center of coil............I'm still getting the same results! I wrapped the coils side by side over a 6" plastic tube and taped it down with duct tape. I twisted the wires coming to/from the coils together and connected them to my connector. When I plug it into my laptop it makes a nice humming sound over the speaker. This humming is obviously making some background noise as it creates quite a soundwave on its own...........If I unplug it I get no noise and no soundwave on the program. I don't know where to go from here........I'm frustrated and ready to go spend $100 on a chrono!!!


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## Don Schultz (Jul 5, 2002)

09Dream...
You are likely getting a 60 cycle hum from lighting, or wiring where you are working on the chrony.


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## 09Dreamseason (Feb 11, 2010)

Don Schultz said:


> 09Dream...
> You are likely getting a 60 cycle hum from lighting, or wiring where you are working on the chrony.


will Flourescent lighting do this?


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## Veni Vidi Vici (Jan 23, 2011)

@09Dreamseason: I've asked you to please post some screenshots. I'd like to see screenshots of your SC settings, your SC analyze screen, and an Audacity screenshot. Also, did you see sharkbone's post about the internal mic? I don't mind helping, but you've got to help us help you. Don Schultz' comment is a good one, and yes fluorescent lighting is very prone to this.


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## Veni Vidi Vici (Jan 23, 2011)

Nockhuntin88 said:


> I don't know if this was mentioned yet, but using some smaller uninsulated copper wire for your windings might work a little bit better to help on the sensativity of the system. Just a thought. Great idea by the way.


Uninsulated wires will not work for a coil.


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## Nockhuntin88 (Dec 31, 2010)

Veni Vidi Vici said:


> Uninsulated wires will not work for a coil.


okay, just wonderin. Why is that?


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## Veni Vidi Vici (Jan 23, 2011)

Nockhuntin88 said:


> okay, just wonderin. Why is that?


The current will take the path of least resistance and not flow around the coil. It will just flow straight from where the wire starts the coil to where it ends the coil.


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## 09Dreamseason (Feb 11, 2010)

Veni Vidi Vici said:


> @09Dreamseason: I've asked you to please post some screenshots. I'd like to see screenshots of your SC settings, your SC analyze screen, and an Audacity screenshot. Also, did you see sharkbone's post about the internal mic? I don't mind helping, but you've got to help us help you. Don Schultz' comment is a good one, and yes fluorescent lighting is very prone to this.


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

I just did these with my lights turned off...........I don't have a built in mic in my Sony Vaio. I have my coils plugged into my Mic jack.......and I have the microphone settings turned to 1/2.


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## Veni Vidi Vici (Jan 23, 2011)

Thanks, 09DS 

Were these recordings of a shot, or just of the coils? Did you use a real magnet or just a magnet-rubbed FP? If you didn't use a real magnet, then it looks like the noise you are seeing is completely swamping out your signal. When I used a magnet-rubbed FP, I had to zoom Audacity in so the vertical scale was -0.05 to +0.05 just to see the blip, and when I found it, it was still greater than the noise. Your Audacity picture shows that you haven't zoomed in at all vertically, so all of that noise is much stronger than the signal a magnet-rubbed FP can produce.

On your settings:

Your hardware device should be set to External Mic, if that is an option. When you installed SoftChrono, there is a copy of the software manual in the folder where the program is located. Please refer to the instructions in that manual for your mic setup. You might have the right option already, but without seeing all of the options that come up for your computer I can't say for sure.

Your distance says 8 feet, but you said your coils are 2 feet apart?

Your triggers might be OK, but if you shot an arrow through your coils when you recorded the SoftChrono reading, then it didn't register. This might be because your hardware device setting wasn't on External Mic. But if you don't have a magnet in your FP yet, then it might be due to lack of signal strength.

I marked up your analyze screen to make a few points.

First, Don Schultz was on the money  I put a dot over every 5th peak, and there were 90 peaks. Over the 1.5 second recording interval, that would be 60 peaks in one second .... i.e. 60 Hz. If your lights were off, then there is some other 60 Hz noise source.

Second, the blue arrows show which peaks in the zoom window are shown in the total waveform window. Whatever area is highlighted in gray in the top window (total waveform window) is displayed zoomed in the zoom window.

Third, your triggers are currently set to 50. For the noise level shown, you could probably get away with 23-25. The green lines show that the noise amplitude is about half of what your triggers are set for.

So, please try this:

Set your hardware device to External Mic if you can.
Set your distance to 2 feet.
Do you have a magnet? Can you try recording and pass your magnet by a coil? What does the signal do when you try that?


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## Veni Vidi Vici (Jan 23, 2011)

Here's a shot of my signal using a fieldpoint rubbed by a magnet. You can see that even though I was zoomed in all the way, my noise and signal were still much smaller than the noise you currently have. We've got to figure out what is causing your noise issues and eliminate that before we can even tell if you are getting a signal. It may be hidden in there somewhere, or there might be some other issue.


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## droppixel (Nov 5, 2010)

Having to give up on this for a few days otherwise I will obsess and go crazy... Still not getting anything on mine. Going to come back to it and redo my coils and have a buddy help me solder my connections. Need to try to track down one of the magnets just to see if that helps or a stronger magnet to rub my FP on or go the battery route.


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## Veni Vidi Vici (Jan 23, 2011)

@droppixel: Get a magnet you can install in a fp. It will give a great signal, and I never had any luck with the battery trick.


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## 09Dreamseason (Feb 11, 2010)

I've gotten some of the noise dialed down now........but even passing a magnet through in my hand isn't showing anything that I see as different! I'm going to sleep on this for the night and revisit it tomorrow........


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## naubusan (Mar 23, 2007)

Check your connections with multimeter if possible. Shortcut can also be a reason for 60Hz humm.


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## jeremy.b (Dec 7, 2010)

09Dreamseason said:


> I've gotten some of the noise dialed down now........but even passing a magnet through in my hand isn't showing anything that I see as different! I'm going to sleep on this for the night and revisit it tomorrow........


When you are testing by hand you need to have a fair amount of speed on the magnet. 

In my small scale test setup I have to literally throw the field point through my coils to get any kind of signal.

The faster the object moves the larger the signal should be.


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## 09Dreamseason (Feb 11, 2010)

naubusan said:


> Check your connections with multimeter if possible. Shortcut can also be a reason for 60Hz humm.


when I check this what setting should I do on the multimeter and where do I test from? Thanks......


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## 09Dreamseason (Feb 11, 2010)

helsyeah said:


> When you are testing by hand you need to have a fair amount of speed on the magnet.
> 
> In my small scale test setup I have to literally throw the field point through my coils to get any kind of signal.
> 
> The faster the object moves the larger the signal should be.


I think I need to get this 60hz humm to go away........I've tried it in 3 different places in the house and with the lights off and I'm still getting this humm. I've turned the mic down and turned the external speakers off but I don't find an internal mic of any kind on my Vaio. When I turn the mic down to 1 or 2 I don't get as much noise on the soundwave and it seems a little more manageable. 

The other question I have now is my settings on SC........I reset my target distance to 2' since my coils are 2' apart, assuming this is the correct setting, but I'm not sure on what frequency I should have it set on....it defaults on 96000 but Audacity defaults on 44100. I've set SC on 44100 also but I have no idea what this does! My other question is Pellet Mass.........I'm assuming this doesn't matter unless we're trying to figure out the Energy part so it shouldn't effect my soundwave, correct?


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> I think I need to get this 60hz humm to go away........I've tried it in 3 different places in the house and with the lights off and I'm still getting this humm. I've turned the mic down and turned the external speakers off but I don't find an internal mic of any kind on my Vaio. When I turn the mic down to 1 or 2 I don't get as much noise on the soundwave and it seems a little more manageable.
> 
> The other question I have now is my settings on SC........I reset my target distance to 2' since my coils are 2' apart, assuming this is the correct setting, but I'm not sure on what frequency I should have it set on....it defaults on 96000 but Audacity defaults on 44100. I've set SC on 44100 also but I have no idea what this does! My other question is Pellet Mass.........I'm assuming this doesn't matter unless we're trying to figure out the Energy part so it shouldn't effect my soundwave, correct?


96000 worked for me. And you are right, pellet mass only matters if you want KE and it won't affect the signal.

Here's a screenshot of the settings I used when I tested with the magnet installed in the FP.











Here's the signal I got with those settings and the magnet.


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## droppixel (Nov 5, 2010)

Think I may have discovered my problem... I'm on a macbook pro and there is a difference between the Line-in jack that this computer has and a Microphone-in jack. I guess for the Line-in, I will need some sort of power adapter to power the "microphone" otherwise it won't pick anything up.

Does anyone know if a USB connection would work with this sort of setup? I have plenty of spare cables that I could chop up and use...

Just another fricking way Apple can suck money out of their users...


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## Veni Vidi Vici (Jan 23, 2011)

droppixel said:


> Think I may have discovered my problem... I'm on a macbook pro and there is a difference between the Line-in jack that this computer has and a Microphone-in jack. I guess for the Line-in, I will need some sort of power adapter to power the "microphone" otherwise it won't pick anything up.
> 
> Does anyone know if a USB connection would work with this sort of setup? I have plenty of spare cables that I could chop up and use...
> 
> Just another fricking way Apple can suck money out of their users...


I'm getting waaay out of my area here, but I "think" you can use a preamp or mixer to bring a standard microphone up to line-level. From Wikipedia on line level, "Line level in traditional signal pathsAcoustic sounds (such as voices or musical instruments) are often recorded with transducers (microphones and pickups) that produce weak electrical signals. These signals must be amplified to line level, where they are more easily manipulated by other devices such as mixing consoles and tape recorders. Such amplification is performed by a device known as a preamplifier or "preamp". After manipulation at line level, signals are then typically sent to a device known as a power amplifier, where they are amplified to levels that can drive headphones or loudspeakers, which convert the signals back into sounds that can be heard through the air."


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## EmCommer (Apr 11, 2011)

For relatively cheap (I think $10-15) you can get a USB sound dongle. It is a usb device that acts as a sound card and has its own speaker and mic jacks. Another option if you know anyone who can do basic electronics is build a small power supply that uses two AAA batteries to put 3v on the line. That should be plenty as I think the mic jacks themselves range from about 2.5v to 5v. This power supply could be built with about $5 worth of parts from an electronics out or Radio Shack (Radio Shack might be a little more expensive).

Someone also mentioned using uninsulated wire and got the right response, that uninsulated wire will not make a coil. To clarify a little, you can get wire specifically made for making coils that has a very thin lacquer coating on it as an insulator. The closer your wire is while still insulated the more efficient your coil will be. Using regular insulated single conductor wire makes for a horribly inefficient coil. 

Brian


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## sharkbone (Dec 5, 2010)

I am outta my league here too, but what about trying a usb sound card?


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## sharkbone (Dec 5, 2010)

Somebody beat me by a second.


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## rdmwc (Sep 21, 2010)

Well, I received my new limbs and cams, re-assembled my warthog! I shot it through my chrono and wasn't real pleased with the results. I am hoping my chrono is a little off. I have not had time to take it to a shop and have it chrono yet. Veni could you possibly run the numbers like you did with my girlfriends bow? Martin warthog 70# 31" draw and about a 450 grain arrow. The ibo is 350 my chrono averaged it at 299.8 fps. 
@ dream season. Is your laptop on the charger when you are running the test? Just wondering if your getting feedback from the charging unit/cord. I know my truck stereo does if I have my mp3 plugged in the aid and have it charging. Just a thought.
Keep up the good work guys! Stay positive


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## Veni Vidi Vici (Jan 23, 2011)

@rdmwc: I had to use a different calculator because the one I usually use won't work on my iPod, but it says you should get around 320 fps. Are your coils still backwards? Have you compared audacity to SC? And as always, ya got any pictures?


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## 09Dreamseason (Feb 11, 2010)

rdmwc said:


> @ dream season. Is your laptop on the charger when you are running the test? Just wondering if your getting feedback from the charging unit/cord. I know my truck stereo does if I have my mp3 plugged in the aid and have it charging. Just a thought.
> Keep up the good work guys! Stay positive


yes it is!!! I'll try again when I get home with it unplugged and we'll see what it does......


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## rdmwc (Sep 21, 2010)

Veni, yes, my coils are still backwards. I will fix them this weekend. Thanks for calculating that, I thought it should be around there. I will also get you some pictures. Also, I have not checked it in audacity I don't know the formula.


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## droppixel (Nov 5, 2010)

What I am thinking about doing is rigging my coil up to a usb line to treat it like a usb mic. If that doesn't work, I will look into the converter dongle - I just have to find one that isn't going to be too expensive because this would be the only thing I would be using it for. There are a few out there that I have seen in the $30+ range...would like to avoid that if possible.

Appreciate the feedback so far.


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> Veni, yes, my coils are still backwards. I will fix them this weekend. Thanks for calculating that, I thought it should be around there. I will also get you some pictures. Also, I have not checked it in audacity I don't know the formula.


Select the signal and use "Fit Selection to Window" to stretch the width of it until it is about as wide as the picture below. Then drag the bottom edge of the window down until it is about as tall as the picture shows. Lay a piece of paper across the signal as shown, making sure that you are catching the baseline data before and after the signal. Click your mouse where the signal crosses at C, then look in the bottom left and write that time down. Click your mouse where the signal crosses at D and write the new time down.

The formula is DISTANCE divided by 12, divided by (D-C). See what you get that way.


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## rdmwc (Sep 21, 2010)

Here are some screen shots. It won't let me post the settings screen.


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## rdmwc (Sep 21, 2010)

In audacity, I get start 11.501 end 11.505 my distance in 1 foot. So formula. 
12/12 / .004 1/.004 250


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## rdmwc (Sep 21, 2010)

wow my numbers are all over! lol the calculator says 320 audacity calculations say 250 and sf say 300 i am going to the shop this weekend to get a number.


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## killerloop (Mar 16, 2008)

jim p said:


> I really like this project. If you want more signal out of the coils, you can increase the number of turns of wire or you can decrease the diameter of the coils. It seems that the accuracy of this chrono depends on the precise spacing between the loops of wire. If just one turn of wire could be used for each loop or if the loops could be wound using a flat winding pattern this might help improve the accuracy. Also by spacing the loops as far apart as practical would help to decrease the percentage of error. You could also use some enameled wire as small as a hair wound on a piece of plastic like pvc pipe or even a plastic trash can to help get more turns of wire and at the same time keep the spread of the coil to a minimum.
> 
> I may have to go and take a look at your software for this project and see what I can do. I don't have a laptop so if I want to shoot outside I would have to use about 30 feet of shielded microphone cable which might be too noisy to see the signal.
> 
> I really like this project. Maybe you can test it with a gun some day. I am thinking that it will detect the bullet as it goes through.



the same concept on a speedometer, like winding of the wire, seems there is a magical number in the speedo world,, so says peterbilt


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## Veni Vidi Vici (Jan 23, 2011)

You are definitely getting a strong, clear signal now. I'm guessing that reversing the coil and maybe spacing them further apart may help. If you notice on the A,B,C,D shot I posted, although my coils are wound like yours are, they are 1 foot further apart and the signal has a chance to come back down to zero in between blips. Since your first signal is being overlaid with the second signal, it may be throwing the shape off enough for the second trigger point to be off. The difference between 320 fps and 302 fps is only 0.2 milliseconds with your setup. So try 2 feet apart and reversing your second coil and see where you are at. You are sooo close!


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## rdmwc (Sep 21, 2010)

I will look for a longer 2x4 lol. Thanx! 
@ ds. You get results? I hope un plugging your laptop works for you man!


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## 09Dreamseason (Feb 11, 2010)

it was my power supply!!!










now to figure out where to measure from.........


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## 09Dreamseason (Feb 11, 2010)

but now SC isn't picking anything up!!


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## Veni Vidi Vici (Jan 23, 2011)

@09DS: *rdmwc rocks!*  Great call, rdmwc!

Scroll up a few posts #223 to where I have the picture with ABCD on it. Stretch your window vertically so it fills the screen better, then follow those instructions. Use the distance in inches for your calculation.

Also, do you know why your two signals are different shapes/sizes? Do you have more turns on one than the other, or maybe did you shoot through at an angle so you got a stronger signal on the second coil? SoftChrono might have trouble if the signals are not a little more balanced.


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> but now SC isn't picking anything up!!


Screenshots, buddy, screenshots  especially your settings and the analyze screen.

And do you already know what your speed is supposed to be from a real chronograph? If not, what are your specs (Bow, IBO speed, Draw Weight, Draw Length, Arrow Weight, and what's on your string?)

Oh, are you using a magnet in your FP now, or just rubbing the magnet on the FP?


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

I'm thinking I'm getting close.......I'm just rubbing a magnet across my fieldpoint


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## 09Dreamseason (Feb 11, 2010)

how do I zoom in and expand the soundwave on SC?


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> how do I zoom in and expand the soundwave on SC?


You can't zoom in vertically. You can only stretch it horizontally. You see how there are two graphs on the analyze screen? The one on the top shows the entire 1.5 second interval that was recorded. There is a blue box highlighting the area that SC thinks is your signal. The area inside that box is shown in the big main window. You can click on that blue box. If you click in the middle of it, you will get a four-arrow cursor and you can move the box left and right. If you click on the left or right edge of the box, you will get a two-arrow cursor and you can drag the edges to make the box wider. You can also use the A, D or W,S keys. W drags the right edge further to the right, S drags the right edge further to the left. A and D move the entire box left or right.

You are definitely getting close. The problem is that your signal is just not very strong. You are probably at the point where installing a magnet in your fieldpoint will make all the difference.

I'm impressed by your persistence, 09DS. You may have had the most struggles (that 60 cycle hum was a puzzler!) but you're definitely working through them. Keep at it!


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## 09Dreamseason (Feb 11, 2010)

So it looks like I have .007857 as my difference between the 2 waves per D-C. I should have 2 feet divided by 12= 6 for my distance or 24 inches divided by 12=2 for my distance.....

If I do the 2 divided by .007857 I get 254.55
If I do the 6 divided by .007857 I get 763.65

there is no way I'm getting either of those correct!

I chrono'd my bow last year shooting a 411gr arrow at 72lbs and achieved 311fps
I'm now shooting a 374gr arrow at 72lbs.........I should be faster


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## 09Dreamseason (Feb 11, 2010)

I did the math again using different cross points on the soundwave and a different piece of paper on the screen and came up with 255.75

the blips on my screen are definately my arrow going through the coils...........but the math just isn't adding up


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> I did the math again using different cross points on the soundwave and a different piece of paper on the screen and came up with 255.75
> 
> the blips on my screen are definately my arrow going through the coils...........but the math just isn't adding up


I agree, I scaled off the screenshot you posted and got 259, so we are doing it the same way. And I agree that the blips are realistic. At this point, other than checking your distance between the coils and making sure that is accurate, I'm not sure what to tell you. I actually do think your signal is strong enough for Audacity to work just fine. I'll have to think about it .....


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## Veni Vidi Vici (Jan 23, 2011)

@09DS: I am really puzzled by your results. I just went and shot a magnetized FP through my setup several times. I recorded in Audacity, picked the points, and calculated my speed. I came up with a 5 shot group ranging from 268.9 - 270.7 fps. These numbers match everything else I have tried: real chronograph, magnetized FP, magnet-installed FP, Audacity, SoftChrono. All of these were shot with 125 grain points. Just now I switched to a 100 grain point and the speed went up to 277 .... which is right at what I expected.

Your signal is actually cleaner than mine. Your first coil's signal looks a little different than your second coil's, but I don't think that would make a difference.

All signs point to your measurement being accurate, but that doesn't jibe with the speed you said your bow is shooting. Your measurement is way off of what you say the bow shoots. Even if your distance between coils was a little off, that wouldn't account for this error.

All I can suggest is to shoot through a real chrono to verify your speed, and double check your coil distance. I can't see anything that you are doing wrong, and I don't think it's possible for your GX to only shoot 260 fps without a really heavy arrow, so other than those suggestions I'm at a loss. If you want to go through the effort to install a magnet in a fieldpoint and see what you get, then fine, but right now I think your magnetized FP should be enough based on the screenshots you've posted.


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## 09Dreamseason (Feb 11, 2010)

I'm going to take a picture of my coils and a tape measure in place to show distance just to varify........


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

so I'm showing how I'm measuring from the center of the coil to the center of the coil, the 6" diameter coils wrapped around a piece of plastic tubing, and how I twisted the 2 wires together going to my connector!

Hope this helps a little


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## 09Dreamseason (Feb 11, 2010)

the 6" plastic is from a Windshield Washer Fluid bottle that I cut the top and bottom off of and then cut in half..........

my bow information:

http://tune.pse-archery.com/BowDetail.aspx?Year=2009&Model=0805GX


it shows 334-342 IBO

my bow is currently 72lbs and 28" draw


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## 09Dreamseason (Feb 11, 2010)

If I use this calculator:

http://backcountrybowhunting.com/articles/calc/

and plug in:
342 for IBO
72 lbs for draw weight
28" for draw length
374gr for arrow weight
20gr for added string weight

it gives me 313 fps!!

If I plug in the 411 grains my other arrows weighed last year......it shows 302 fps. The shop chrono we used gave us 311fps so the online calculator is a little off but not by much.......I should be over 300fps easy!!


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## 09Dreamseason (Feb 11, 2010)

so I just came up with an idea...........I'm standing too close to my chrono when I shoot!! My arrow hasn't left the bow completely yet while it's going through the first coil....I need to back up and shoot from further back! Standby.......


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## Veni Vidi Vici (Jan 23, 2011)

09Dreamseason said:


> so I just came up with an idea...........I'm standing too close to my chrono when I shoot!! My arrow hasn't left the bow completely yet while it's going through the first coil....I need to back up and shoot from further back! Standby.......


I hope that's it! That would also explain why your first signal is lower than the second ....


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## 09Dreamseason (Feb 11, 2010)

so........












my first soundwave is almost identical to my second soundwave now and when I do the math now I'm getting 288 fps........


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## Veni Vidi Vici (Jan 23, 2011)

Better .... Any chance you are brushing a vane on a coil? It's definitely sensing your fp and the fact that both the signal went up and the speed increased makes me think it is responding appropriately. There has to be something else we are missing. I don't think the problem is in the software or the coils anymore.


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## 09Dreamseason (Feb 11, 2010)

another shot










I started another one for second shot and got 287.6 fps


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## 09Dreamseason (Feb 11, 2010)

Veni Vidi Vici said:


> Better .... Any chance you are brushing a vane on a coil?


I'm not hitting anything....it's accurate shot after shot now right at 288fps. I need to verify with a real chrono and then see if I can get SC going now.......


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## Veni Vidi Vici (Jan 23, 2011)

You used a different arrow, or remagnetized your fieldpoint for that second picture, didn't you? See how the signal changed from down/up to up/down? Unless you swapped your coil leads, then it's because your North and South poles are different this time. You either held your magnet a different way or you stroked the FP the opposite direction. It's really pretty cool how much information you can glean out of these simple signals.

I'm glad you are getting good clean data and consistent results now.

Here are the settings I used with SC and a magnetized FP like you have, and an example of the plot I was getting.











This one is when I was centered in my coil (my coils are larger than yours, so yours might have a stronger signal).












This one is when I shot off-center, very close to the coil.












4 might not be the best value for you to use for your triggers. You need to find the value that keeps it from triggering on noise, but catches your signal. Just start low, then bump it up one point at a time until it quits triggering on noise. Once you see consistent results in SC, you can forget about Audacity unless you need it for troubleshooting.


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

I changed my distance to 1.75 thinking that the plastic for the coils is causing my field to actually be closer! I'm going to do one more with it set at 2 feet in the settings and see if it's closer to the 288 from Audacity.


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

so I'm going to do some multiple shot groups and see what my average comes to........I think I have it figured out now


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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)




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## 09Dreamseason (Feb 11, 2010)

I won't post any more shots!!! :darkbeer:

I adjusted my distance back to 1.75 feet to make up for the plastic rings causing my field to be larger and closer together than I measured the coils from center to center. I'm consistently getting around 298-299 now with SC. I also found my note card from when I had these new strings put on and I had taken out a turn on my limbs so I put that back into it....which is why I'm around the 298-299 mark!!

I will go back through Audacity now that I've added a turn to my limbs and recheck my soundwaves there!!!

Thanks again VVV for this OUTSTANDING DIY.........I had trouble with the 60hz hum and stuck with it and I'm pretty happy with it. I'm going to get it pulled at the shop with their scale now too and see what weight I'm actually drawing now and test our DIY chrono against theirs.

:shade:


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## Veni Vidi Vici (Jan 23, 2011)

@09DS:

I'm glad things are working better for you. I'm a little concerned with the muzzle trigger of 1 and the impact trigger of 0 .... it seems like this will be prone to triggering on noise and a setting of 0 doesn't really make much sense to me. However, if it is working consistently for you it "might" be OK. I'd still recommend installing a magnet in a fieldpoint that you can keep around just for use with the chrono. With a real magnet, you should be able to set your triggers around 80 - 100 and set them equal to each other.

About adjusting your distance ... I don't have a problem with doing that, but it should be based on something. Once you shoot through a real chrono and know your speed that way, you can adjust your coil distance until SC matches. That would be determining your effective coil distance .... nothing wrong with that. It's basically calibrating your coils against another "standard". If you eventually do a real magnet, you might find that you will need to set your effective distance again. That didn't happen in my case .... I get the same results whether using a magnetized FP or a real magnet. But in your case, the triggers at 1 and 0 concern me as not necessarily "real", so I think you might come up with a different effective distance with a better magnet. Just make sure you shoot your magnet tip through a real chrono, then tweak your distance in SC to match.

I'll say it again .... I'm really impressed at how you stuck with this! Your struggles, and the lessons you learned and shared as you overcame them, will help others in the future. Please keep posting updates as you experiment with this.


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## rdmwc (Sep 21, 2010)

Great job DS!! I'm glad it worked out for you!! This is a great DIY! 

Well a buddy of mine just. And over and brought his bow. He just had it chrono at a shop at 227 fps. He shot it through my DIYC and came up with 222.8 consistently. So it seems to be somewhat accurate. This disturbs me. My bow calculated from audacity at 250. Online calculated at 320 and at said about 300...


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## Veni Vidi Vici (Jan 23, 2011)

@rdmwc: are you sure you aren't standing too close to the chrono like 09DS was? His arrow was starting through the first coil before it had left the string.


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## adrian5800 (Oct 18, 2009)

Veni
Congrats on an awesome job with this.
I made up one today - 5" coils of 50 turns of enameled copper wire 0.4mm connected to the laptop with cat 5 cable. I realised cartel triple points aren't ferrous! I was getting no signal at all, until I tried my nanos. Here's a screenshot









It's a pretty strong signal. Here's the results from Softchrono









Here's my settings









I'm thinking the enameled wire is creating a stronger magnetic field - so adding a magnet or magnetising the points is unnecessary.

*EDIT* the cartel points must be austenitic and not martensitic. (depends on how much nickel is in the alloy making it magnetic or not) Thanks Wikipedia!

Pics to follow tomorrow of the coils :darkbeer:

Cheers

Adrian


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## Veni Vidi Vici (Jan 23, 2011)

Great job, Adrian! My guess is that it is the smaller coils you made (5" vs. my 10" coils) that is giving you the biggest increase in signal strength, but by using enameled wire you are also able to pack your turns closer together which should help. Looking forward to pictures.

How does the speed compare to what you expected?


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## Veni Vidi Vici (Jan 23, 2011)

Adrian, based on what I've found on AT about your bow setup, your measured speed agrees with this calculator.


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## rdmwc (Sep 21, 2010)

Just got back from the archery shop, I'm very frustrated. They checked my draw weight, 75#! 31" draw, weighted my arrow at 441 grains and chronoed it at an average of 293 fps so my chrono is pretty close. But my issue is with my bow! That calculator said I should be at 327 fps


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## droppixel (Nov 5, 2010)

Still not getting anything on mine, spliced in a usb cable and didn't get a difference. One thing I never asked but assumed, are the 2 coils one continuous piece of cable or do you have separate lines that meet up at the plug in?

I'm going to revisit this in the future when if I pick up one of the converted boxes for my line in. Also will be redoing my coils either way. Feel like they are sloppy and that could be part of the problem. With the coils is it best to have the cable in a row? Or if it is stacked on top of one another is that bad?


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## Veni Vidi Vici (Jan 23, 2011)

rdmwc said:


> Just got back from the archery shop, I'm very frustrated. They checked my draw weight, 75#! 31" draw, weighted my arrow at 441 grains and chronoed it at an average of 293 fps so my chrono is pretty close. But my issue is with my bow! That calculator said I should be at 327 fps


That is very strange. Something definitely seems wrong. There's no way your speed should be that low. As far as your chrono goes, did you find a longer 2x4 and redo it with the coils wound the same direction yet?


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## Veni Vidi Vici (Jan 23, 2011)

droppixel said:


> Still not getting anything on mine, spliced in a usb cable and didn't get a difference. One thing I never asked but assumed, are the 2 coils one continuous piece of cable or do you have separate lines that meet up at the plug in?
> 
> I'm going to revisit this in the future when if I pick up one of the converted boxes for my line in. Also will be redoing my coils either way. Feel like they are sloppy and that could be part of the problem. With the coils is it best to have the cable in a row? Or if it is stacked on top of one another is that bad?


My coils are in series, i.e. one continuous piece. I think my microphone input is only mono, so I only have one channel to work with.

As for coil winding, I'm not sure what the right answer is. My coils are 50 turns made by 5 passes of 10 turns each. After the first two passes, things got pretty sloppy. The pictures 09DS posted of his looked like all of his coils are next to each other, which makes for a wide coil and will make it more difficult to find the true center point of the coil. However, his signal is much cleaner than mine. If you have access to a real chrono, once you get your speed from that you can tweak your coil distance in softchrono or in your manual calculations until your numbers match. That will determine your "effective" coil distance, and is essentially calibrating your system. That is actually what I did on my second setup. Since I already knew my speed, once I determined my setup was working correctly I just entered my effective coil distance and am using that from now on.

Please post back once you get things together. You appear to be the lone soldier with a Mac right now, so others might be able to learn from your input.


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## rdmwc (Sep 21, 2010)

No, I will have to go buy one. But for the time being , I'm going to use is and do some tweaking to see if I can squeeze out some more speed. I'm so aggravated at this! That's 40 fps!


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## adrian5800 (Oct 18, 2009)

Veni
Yeah the speed is what I expected of my setup, I haven't chrono'd it but I use accurate sights software and that calculated around 270fps. Here's some photos


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## droppixel (Nov 5, 2010)

Veni Vidi Vici said:


> Please post back once you get things together. You appear to be the lone soldier with a Mac right now, so others might be able to learn from your input.


That is the plan. My usb experiment failed, so I am going to go back to the mic jack and solder the wire in place when I can. For that does it matter which of the wires is soldered to a certain position on the jack? I am assuming your first coil wire would go to the front and the second to the rear.

Also, for those that know anything about the line-in adapter business I am probably going to have to try, do you think this would do the trick? Trying to find the cheapest route possible for this to function.
USB Audio Adapter

It is a USB device that has a split for headphones or mic input. Since I have seen that the iMic or something of that nature is what the Macbook Pro needs to run an external mic, I assume this is similar in fashion.


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## 09Dreamseason (Feb 11, 2010)

Nice looking setup Adrian......

I'm going to take my coils off of the box and attach them to a piece of conduit so that I can attach it to a tripod now as well.......this will make it a little more mobile instead of stacked boxes in my basement!


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## Veni Vidi Vici (Jan 23, 2011)

@droppixel: This is how mine was setup for mono input. I'm strictly guessing, but if you try to use 2 channels (one for each coil) I would guess that one coil would go to one of the "red" contacts and the other lead would go to the black. The other coil would go to the other "red" and again to the black. And you would not want the two "reds" to be shorted together.


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## Veni Vidi Vici (Jan 23, 2011)

@rdmwc: I tried installing a magnet oriented 90 deg to the shaft like you described yours, and it didn't work well at all. I get a signal, but each coil blip is more like a shallow down, a big up, and then a shallow down before returning to zero. The amplitude of the signal is also not good. On my original fieldpoint, I drilled it from the tip and inserted the magnet that way. It is related to Faraday's Law, I believe. So I would recommend that you either try a) redoing your fieldpoint so the magnet is inserted from the tip, or b) rub the tip with a magnet. You have to rub in one direction only, and you should mark your magnet so you always hold it the same way. If you flip the magnet or if you rub the opposite direction you will demagnetize the tip. I marked one end of my magnet "Nock" so I point it towards the nock and stroke it towards the tip.


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## 09Dreamseason (Feb 11, 2010)

I shot through a neighbor's chrono tonight and it averaged at 315fps..........I'm going to the shop tomorrow, not that it's really any different, but I'm just going to test against it again! Once I figure out what it is, I'll adjust my SC accordingly.

I shot through audacity here tonight and I'm getting 305fps so I'm within 10fps from my buddy's chrono at this point. Knowing that Audacity uses the actual soundwaves and I have to manually do the math makes me wonder if I should first adjust the distance between my coils to match Audacity to the real chronograph's speed and then adjust the SC specs accordingly. This will make both programs spot on.


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## Veni Vidi Vici (Jan 23, 2011)

@09DS: I use the same distance in SC and in my manual calcs from Audacity. I think that once you get a better FP with a magnet, SC and Audacity will agree using the same distance. I'm sure you're feeling much better about the 315, though lol! Based on the .006654 seconds you posted somewhere, your effective coil distance is 0.006654 x 315 = 2.09601 feet. Use that with a better magnet and I bet you'll get good consistency. It probably won't work with your current magnetized FP and SC trigger settings of 1 and 0, though. Make sure you use higher trigger settings when you get a better magnet ...... something like 80 - 100 would probably work.


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## droppixel (Nov 5, 2010)

Veni Vidi Vici said:


> @droppixel: This is how mine was setup for mono input. I'm strictly guessing, but if you try to use 2 channels (one for each coil) I would guess that one coil would go to one of the "red" contacts and the other lead would go to the black. The other coil would go to the other "red" and again to the black. And you would not want the two "reds" to be shorted together.


Just so I got this straight, your 2 wires here are all one continuous piece? Meaning you should only have 2 ends, you started with one wire, wrapped - extended to the second coil, wrapped and the tail of that is the end? Is the Red from the first coil and the Black from the second? This could very well be my problem because I had put the lead from the first coil on the black as marked in the image and the tail end from the second coil to the Red. Appreciate everyones feedback on all of this, this is definitely turning out to be one of the coolest DIY threads I have seen thus far.


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## 09Dreamseason (Feb 11, 2010)

droppixel said:


> Just so I got this straight, your 2 wires here are all one continuous piece? Meaning you should only have 2 ends, you started with one wire, wrapped - extended to the second coil, wrapped and the tail of that is the end? Is the Red from the first coil and the Black from the second? This could very well be my problem because I had put the lead from the first coil on the black as marked in the image and the tail end from the second coil to the Red. Appreciate everyones feedback on all of this, this is definitely turning out to be one of the coolest DIY threads I have seen thus far.


Yes..........this is one continuous piece of wire. It doesn't matter which lead goes where on the mic jack. This closed system creates the field in each coil sitting static. It automatically shows a soundwave in the order of disturbance no matter how it's wired.


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## 09Dreamseason (Feb 11, 2010)

I had a leftover piece of carpet transition that was 4 feet long so I cut it down to 30" and taped my coils to it at 24" center of coil to center of coil again. This aluminum transition is very lightweight and yet sturdy enough to hold everything nicely. I even drilled and tapped a hole in the center for my tripod to screw into so that I can take it all apart and transport it with me..........


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## jgreg (Aug 3, 2006)

Great job
Jim


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## Veni Vidi Vici (Jan 23, 2011)

@09DS: I see you like to pose your chrony in front of exercise equipment, too lol!


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## 09Dreamseason (Feb 11, 2010)

Veni Vidi Vici said:


> @09DS: I see you like to pose your chrony in front of exercise equipment, too lol!




you might see it as exercise I equipment........I just see it as pre-season work!! lol


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## 09Dreamseason (Feb 11, 2010)

since I got my spin cycle though, the kids are the only ones that use my nordictrack.......


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## Veni Vidi Vici (Jan 23, 2011)

Got another data point today. I took a heavier arrow (524 grains vs. 396) and shot it with the same bow through my coil chrono and a pro-shop's chrono. My coils averaged 236.3 fps, and the pro-shop's chrono averaged 234.4 fps. Again, this is less than a 1% difference between the two devices :banana:


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## naubusan (Mar 23, 2007)

And might be that your chrono is better calibrated than proshops one...

Great job Veni! :thumbs_up


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## MasterCATZ (Feb 17, 2009)

Definatly going to do this on the weekend 

why not just put a magnet in the Shaft ? fridge magnet .. or my fav .. old dead HDD magnet ( most power fuLL ones I know off  )


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## MasterCATZ (Feb 17, 2009)

Is their a way to Edit posts ?? 

O well just a few Questions 

#1 whats better Thinner or Thicker wire 
#2 whats better Narrow ?? or wider coils I have 2" ( 60mm tube ) and 4" ( 100 mm tubing ) I would like to use ( I have a Shooter so its dead straight ) or is 10" best ? 
#3 what would the maximum amount of Turns be ? somewwhere here said the more the better 

but how many turns is going to be to many turns 

ie if its a 1m long tube you wouldn't cover one half with 1 coil 50 cm long then the other half with the 2nd coil 50cm long wouln't you ? 

or if you do use 50cm long worth of coils how does one determin the Distance between coils >?

#4 whats the ideal distance between coils 

#5 why sould this kill the soundcard ?? the input jack can take a pretty good beating 
I have backed up Answering machine messages ect just by re wiring into PC's input 


on another note any one thought of just shooting through the guts of an old speaker >? 

with all the Flood damage i am sure theirs gota be a heap of dead speakers out their ... 
from memory those old electric organs had masive speaker coils


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## 09Dreamseason (Feb 11, 2010)

MasterCATZ said:


> Definatly going to do this on the weekend
> 
> why not just put a magnet in the Shaft ? fridge magnet .. or my fav .. old dead HDD magnet ( most power fuLL ones I know off  )


putting a magnet into the shaft is going to change your overall weight.............the purpose of this DIY is to figure out your setup at your current weight, draw weight, and draw length


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## Mig (Nov 26, 2008)

I couldn't get softchrono to work but with audacity, it works very well. I haven't shot out of an actual chrono lately so I'm not sure how close my it is. I'm going to order ball bearing magnets to insert into the tips. is k&jmagnetics.com a good place to order from?


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## Veni Vidi Vici (Jan 23, 2011)

See my replies in *bold.*




MasterCATZ said:


> #1 whats better Thinner or Thicker wire *I would guess thinner is better because it will allow you to make your coils narrower.*
> #2 whats better Narrow ?? or wider coils I have 2" ( 60mm tube ) and 4" ( 100 mm tubing ) I would like to use ( I have a Shooter so its dead straight ) or is 10" best ? *When I said narrower above, I'm talking about the length of the coil, not the diameter. But I think you are asking about whether a large diameter or a smaller diameter is better, right? My coils are 10" diameter. I chose that size because I had a piece of pipe I wanted to use, and I thought it would be a good size to shoot through SAFELY. 2" or 4" diameter is definitely too small IMO. 6" is the smallest I would go, and I still think that is risky if you don't have someone behind you to help line you up. That said, for the same number of turns the smaller diameter will be more sensitive. 09DS's coils appear to be more sensitive than mine and his diameter is smaller. If you are in the 6" to 8" range, you will probably have no trouble detecting a field point that you've rubbed with a magnet, which means you won't need to install a magnet in your arrow.*
> 
> 
> ...


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## Veni Vidi Vici (Jan 23, 2011)

Mig said:


> I couldn't get softchrono to work but with audacity, it works very well. I haven't shot out of an actual chrono lately so I'm not sure how close my it is. I'm going to order ball bearing magnets to insert into the tips. is k&jmagnetics.com a good place to order from?


If you can post a screen shot of what you are getting in Audacity and in SoftChrono, we might be able to help you out.

As for ordering magnets, I don't know about that place either way. I know rdmwc used ball magnets, but I would use a cylindrical magnet. It is important for the north and south poles to run the same direction as the arrow. With a cylindrical magnet, the poles are on the ends, so if you just drill a hole in from the end of the tip and stck the magnet in you'll be in good shape. I'm not sure how the poles run on a ball magnet or how you would figure that out, so if you install the magnet wrong you might struggle to get a good signal. Mcmaster-Carr has rare earth disk magnets, and while I used 1/4" diameter x 1/4" long magnets, I would bet that one or two 1/8" dia x 1/8" long magnets would do the trick. I also found a 10 pack of 1/4" x 1/8"magnets at a local Harbor Freight. Another source for a magnet is one of those telescoping retrieval tools you can get at Autozone or Lowes. The ones I looked at had 1/4" magnets.


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## Veni Vidi Vici (Jan 23, 2011)

I just went back and looked, and it was actually sharkbone that used the ball magnets. Sorry if this confused anyone ...


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## Veni Vidi Vici (Jan 23, 2011)

Here's a source for magnets: http://www.mcmaster.com/#rare-earth-magnets/=byrd5n

Also as far as using ball magnets goes, after thinking about it you should be able to identify the N and S poles by putting a few of the magnets together. They will stick together from pole to pole. You could then take a Sharpie and mark the magnets. Install the marked magnet so that the N and S poles are in line with the length of the FP. I haven't tried this, but it should work. I did the cylindrical magnet as shown below.


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## MasterCATZ (Feb 17, 2009)

ok then I will make something around 1.5m long then ( at least it can easily fit in trailer / stand near a door somewhere ) 

anyone else get soft chrono working in win7 / 2008 ?? i just keep getting this 


---------------------------
SoftChrono
---------------------------
Run-time error '380':

Invalid property value
---------------------------
OK 
---------------------------


and with the Pic abouve RAW magnets are extreamly fragile hope you made a Tip to protect it with or else you will have magnet dust everywhere soon  

in the end i ended up using a lighter Tip and installed magnet inside shaft keeping the arrow weight the same 

how ever i also drilled out a bludger and jammed magnets in that also

just a shame its a Public Holiday , hoping dad's still got some speaker wire handy from when he used to hand make them  

apart from that i'll be hunting down any Toy with an electric motor in it 

tho I did see an install their that looks like it is CAT 5 cable how did that go ? I have oodles of that laying about


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## Veni Vidi Vici (Jan 23, 2011)

MasterCATZ said:


> ok then I will make something around 1.5m long then ( at least it can easily fit in trailer / stand near a door somewhere )
> 
> anyone else get soft chrono working in win7 / 2008 ?? i just keep getting this
> 
> ...


See naubusan's post #60 . That might help.

It worked for me with Win 7 64-bit with no issues.


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## Mig (Nov 26, 2008)

I would order them from mcmaster but I'm looking for 3/16 diameter ball bearing magnets. K&J seems to be a legit site after looking at it some more. Plus I like playing around with magnets and they have more of a variety that I would like to order. I also installed softchrono on my windows 7 64 bit with no issues at all. I'll try again later tonight and post some screenshots.


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## MasterCATZ (Feb 17, 2009)

Na msstdfmt.dll was my First Hurdle 

it is meant to be an Microsoft Visual Basic issue 
msmask32.ocx ActiveXControl was meant to fix it but still nothing 

well if Win 7 64 Can run it then this thing sure as hell should .. fresh install 1 week old with R2 Sp1


unless i am using an older version 

SoftChrono_beta1 was all i could find 
File Version 1.0.0.46


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## MasterCATZ (Feb 17, 2009)

*sigh* i guess edit is only available for a few minutes 

other places on the web says to put the file in the syswow64 folder

but I just get this error now 

[Window Title]
RegSvr32

[Content]
The module "msstdfmt.dll" may not compatible with the version of Windows that you're running. Check if the module is compatible with an x86 (32-bit) or x64 (64-bit) version of regsvr32.exe.

[OK]


half tempted to install a big dll pack


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## 09Dreamseason (Feb 11, 2010)

When I downloaded Softchrono I manually chose each file once I unzipped it and saved them to my desktop...........you may need to open it further after the download!


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## naubusan (Mar 23, 2007)

MasterCATZ said:


> *sigh* i guess edit is only available for a few minutes
> 
> other places on the web says to put the file in the syswow64 folder
> 
> ...


Did you put it onto syswow64 folder?

Try to follow instructions on post 60 and put it onto windows folder and run regsvr with *admin rights* from there. And register dll.
softchrono is 32 bit app.


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## Bean Burrito (Apr 20, 2011)

I haven't read all the pages, so I don't know if anyones covered this, but I'll explain this in terms of physics.

Your coils of wire have a small electric charge (I believe) carried through them while they are pluged into the laptop. It's a minute charge, but enough. Any current travelling through a wire creates an electric field around the wire. Wire coiled into a loop will result in the force being concentrated predominately in the middle of the loop. I won't describe the motor and generator effects too precisely, but:

Magnetic field + motion = induced electronic current

Your two coils are exerting a weak magnetic field concentrated in the center of the loops. Any conductive object (It does NOT need to be ferromagnetic i.e. iron) passed through this magnetic field will have an electric voltage induced in it (if the wire passed through is part of a non closed system i.e. it's a single strand, a voltage will be induced, if it's part of a circuit or complete loop a voltage and current will be induced).

The weak magnetic field, with the conductor passing through it induces a small electrical voltage in the conductor- your arrow. (It's worth noting here, your arrow will need a reasonable amount of conductive mass, even if it's only a field point). This electrical voltage in the arrow creates a magnetic field around it. As the coils of wire are moving (relative to the arrow) an electrical current is now induced in the coils of wire. The higher the speed of the conductor, the higher the voltage (i.e. a faster projectile will have a higher peak in audacity). The more loops/winds, the higher the current/signal. Due to the speed of the projectile, the voltage in the coils will be slightly higher than the original, causing the "noise" you see in audacity.

As it's fairly simple physics, you can apply some basic equations involving fields and electricity to see the effect of modifying parameters:

Force (newtons) = B(magnetic field strength in teslas)I(current in amperes)l(length of conductor in m)
So, a larger value for the length of conductor (i.e. your coils, and the number of) will increase the force, and eventually result in a stronger signal.

Electric field strength: voltage/distance
So, decreasing the distance from the arrow to the coils, i.e. reducing the coil diameter will increase the strength of the electric field, resulting in a stronger signal.

Also,
As force = BIl
We can assuming that increasing the force (here, we'll talk about this in terms of the speed of the projectile) will increase either the values for B, I, or l. As B and l are constant, this will increase I, the current in amperes, thus producing a stronger signal. i.e. a higher speed projectile will have a stronger signal strength.

Then, we can simply measure the distance between the two peaks on the audacity plot. This is your t value in seconds (time). The distance between the center of your two coils is your value for d or s (distance or displacement, if you're assigning it as a vector). Then your equation is simple:

speed = distance/time

so,

speed (f.p.s.) = distance (in feet)/time (in seconds)
speed (m/s) = distance (in meters)/time (in seconds).

use the highest peak on the audacity plot to get your value for time.

For energy of the arrow:
E (energy in joules) = 1/2 the mass(in kilograms, remember to convert grns-kg)*v(meters per second)^2

This will give you the kinetic energy of your arrow at x distance from your bow (however far away you shoot at it from).

This can then be used to give a rough estimate of your bows efficiency with that particular setup (assuming you know the work of drawing the bow):
(Kinetic energy of arrow/work taken to draw bow)*100= Efficiency of bow in %
Work taken to draw bow-kinetic energy of bow= residual energy left in bow

Your residual energy left in your bow is going to cause your vibration, noise etc. A bow operating at 100% efficiency would create no noise, heat, or vibration- however this is impossible. However, the less residual energy left, the less vibration and noise.

Hopefully this answers any technical questions anyone had. I'm going to work on one of these chronographs soon.


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## Veni Vidi Vici (Jan 23, 2011)

Hi, BB, and thanks for joining in on the discussion.

To clarify a couple of things.

From my testing, it is actually better to detect the crossover points of the signals rather than the peaks.

You can calculate the KE using the well known equation KE = Weight * velocity^2 divided by 450240, which allows you to input weight in grains and velocity in fps.

Any baseline current passing through the coils is due to the way voltage must be measured, but as you noted it is very small. Even a conductor of large mass moving slowly through the coils was undetectable on my setup (I tried a hammer). However, if the baseline noise levels are low enough, an unmagnetized fieldpoint may create a small signal in some setups because it is moving very fast through the field. Any level of magnification applied to the arrow greatly increases the signal.


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## 09 Bengal (Aug 1, 2010)

Just to put my .02 worth in. You can get a small magnet to give a reading without shooting it through the coils by slaping it together with another magnet. I couldn't get a reading at all with just a magnet running thru the coils. Then I got a larger magnet it wouldn't read anything also, but when I slapped it with my hand it registered on audacity ??? Can any of you electronics geeks explain this to me??? Is this magnetic fluctuation the reason why we are able to get a reading from the coils ?? I know BB said it was actually the coils magnetic field reading the magnet, but why does it not work with just a large magnet up next to it ?? Thanx for this great DIY!! I'm getting mine tuned in.. at least I was before this storm hit....


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## Veni Vidi Vici (Jan 23, 2011)

Are you sure your computer was reading the external mic and not just still hearing the noise of the slap with the built-in internal mike?

The coil senses a *change* .... so if you hold a magnet against the coils, after the initial change of having the magnet enter the field, it will go back to no change. It takes motion of the magnet for this to work, and if you have a weak magnet, it takes a high speed. A stronger magnet can be detected at a lower speed.


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## bowhntng4evr (Dec 18, 2009)

That's some great ingenuity.


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## 09Dreamseason (Feb 11, 2010)

These are my readings now with a magnet installed in the fieldpoint!!! BIG difference..........


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## straddleridge (Apr 28, 2010)

I had a lot or trouble making this thing work - don't know why but it is working properly now. In an earlier post I mentioned I have a radarchron instead of a normal chronograph. The following audacity screen shot and picture are from the same shot. That is I shot through the coils with the radarchron attached to the bow.

The radarchron displays speed in 2 stages - first is hundreds and the picture is the 2nd stage - 25 - 225 fps.

my DIY has 6" coils of 30 awg magnet wire 35 1/2 inches apart with 50 turns per coil. It is from the Radio Shack kit that an earlier poster used. The time is .013 seconds or a speed of 227.6 fps. I tried this several other shots (5 total) and I got 0.0130 seconds all 5 times. My radarchron varied between 225 and 226 fps. The arrow had a 125 grain saunders combo tip unmagnitized.


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## Veni Vidi Vici (Jan 23, 2011)

@09DS: Now that's more like it, huh? :banana:

@straddleridge: That's a great signal for an unmagnetized FP. If you havent tried softchrono yet, you should. I think you signal is strong enough for SC to work with it, and it will eliminate the calculations. And that is great agreement with your radarchron! I'm glad you stuck with it


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## 09 Bengal (Aug 1, 2010)

VVV I was smart enough to think on those lines and I did clap my hands in the coils and next to the internal mike. No Readings... I have a digital noise level meter I downloaded and I'm getting the same readings there ?? I clap my hands together in the coils, nothing, I snap 2 small magnets together and get about a 20db reading, 2 large magnets gets me about 100db ???


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## Veni Vidi Vici (Jan 23, 2011)

@09 Bengal: The only other thing I can think of is that the orientation of your magnets matters. The N and S poles of the magnet need to be running through your coils parallel to the axis of the coils. Other than that, I'm really not sure what the effect is that you are seeing. Have you had any luck getting your arrows to read yet?


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## 09Dreamseason (Feb 11, 2010)

@09 Bengal: I wasn't getting any pickup by just running a magnet through either, but as soon as I shot an arrow through that had been rubbed by the magnet it popped up. Now with the magnet inside of my fieldpoint it's 50 times stronger! I don't think anyone has had more troubles putting this together......but now that I've gotten all of the "bugs" figured out I have to say this is easy to do and hard to mess up. I was trying too hard and not paying attention to the small details.


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## 09 Bengal (Aug 1, 2010)

Yes, I have been getting readings with the magnet in my fieldpoint, just nothing to consistant ?? I had my boy shoot his thru and he got great readings and consistant readings. I'm trying to set up softchrono now to shoot as it was meant to without the coils ?? I'd like to get a better idea of what to look for in FPS to compare the results.


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## Veni Vidi Vici (Jan 23, 2011)

This archery calculator http://backcountrybowhunting.com/articles/calc/ should get you close. Also, please post some screen shots from audacity and softchrono. We might be able to help with your setup.


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## 09 Bengal (Aug 1, 2010)

Something must be wrong with the calculator ??? It said me arrow speed should be -10928 fps??? - 7451 mph ???? LOL I guess that means I would shoot myself ??? I'll try it again later.. I've checked it once before on that site and it came out to around 298 fps. The readings i've gotten on audacity ranged from 249 to 279 ?? The readings I just got shooting it 30 ft gave me a 267.89 & 268.76 Audacity gave me 2 readings of 270 & 275 I'm guessing my bows shooting about 272 fps ?? When I get a chance i'll take it to Gander mntn and test it for accuracy...


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## Veni Vidi Vici (Jan 23, 2011)

If you post some screenshots from Audacity and SoftChrono, we can probably help you figure out what is real.


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## MasterCATZ (Feb 17, 2009)

well I built mine from CAT 5 cable ( had pre seperated cable from using for survalance system just had to untwist the pair'd cables ) 

I used what was either a vinal roll or carpet roll tube 

its 4" Diamenter and plenty for my use ( have a bow shooter simular to another DIY thread thats on here attched to my bow press ) 

what I used was some cerial carboard box wraped around the tube and then wound the wire around that ( that way i could slide the coils to fine tune them ) 


pretty much taped carboard wraped around tube 

taped on the wire start 

and just started spinning the Tub that way both ends got wound at the same time 

GF spinned the Tube and I used my thumb to guide the wire on tightly 

used 20m long wire ( did not count the winds ) 

taped the wire on nice and tight 


then just made the connection to connect to Laptop 

( draged out an old 32 bit oS'd laptop to solve my softcrono issue )


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## Veni Vidi Vici (Jan 23, 2011)

@MasterCATZ: So if I understand correctly, you wound both coils at the same time. So one of the coils is wrapped CW and the other is CCW? If so, then SoftChrono may have a problem with that. Coils wrapped in opposite directions will produce signals that are mirror images of each other. If the first coil goes down, then up, the second coil would go up, then down. If your bow is shooting pretty fast, the (in this example), the first coils may start to go down but not make it to zero before the second coil makes the signal go back up again. This can make the impact trigger point occur in an inconsistent portion of the curve. Backwards coils will still work in Audacity if you are measuring from the crossover points of each signal. It may not trip SC up at all, but there is a chance that it will. Let us know how this works, or if I've misunderstood and both your coils are wound in the same direction let me know that, too.


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## MasterCATZ (Feb 17, 2009)

same direction the tube only rolled one way .... 


ie Left side was wound Right - Left Right side was wound Right to Left 

Tube Rolled ^^^^^^^^

L Coil End ( Thumb Side ) <<<<< Coil Start Tube ^^^^^^^ Roll Coil End ( Thumb Side ) <<<<< Coil Start R


also allowed for both ends to be the same with out counting ( tho its around 50 Turns think Circumfernce was 37cm x 20m cable ) 

Distance between Coils are 1m ( or 2 ~3 feet depending on where its tuned to ) the only issue now is making a stand thats stable 

also building in a mono / stero switch soon ( currently both coils seperate )


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## adrian5800 (Oct 18, 2009)

Bean Burrito said:


> Magnetic field + motion = induced electronic current
> 
> Your two coils are exerting a weak magnetic field concentrated in the center of the loops. Any conductive object (It does NOT need to be ferromagnetic i.e. iron) passed through this magnetic field will have an electric voltage induced in it (if the wire passed through is part of a non closed system i.e. it's a single strand, a voltage will be induced, if it's part of a circuit or complete loop a voltage and current will be induced).
> 
> The weak magnetic field, with the conductor passing through it induces a small electrical voltage in the conductor- your arrow.


BB 
I don't want to contradict what you have said and you seem to be much more educated in physics that I am but in practice it doesn't seem to work that way. I understood that for this effect of disrupting the magnetic field it had to be a magnetoferrous object not just a conductor. Here's a screenshot of two waveforms shot - the first with (I presume) a martensitic stainless steel target point and the second one with a austenitic stainless steel target point. See how the second one doesn't create even a ripple? Both are shown without any zoom at all.

l








Veni - please note I haven't zoomed in on these at all - and without a magnet inserted in the point. You may want to revisit your coils and make them from enameled copper wire and shield the cable to your sound card 


Ades


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## Veni Vidi Vici (Jan 23, 2011)

@adrian5800: You are getting a great signal. Did you rub the FP with a magnet? I think the biggest factor may not be the enameled wire but that your coil is half the diameter of mine. If magnetic fields work like many other phenomena, then the field strength is probably a squared function with distance, meaning your 5" coils would be four times as sensitive as my 10" coils.


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## adrian5800 (Oct 18, 2009)

Veni
No I didn't rub the point with a magnet and you are probably right the smaller coils have a more concentrated magnetic field within them. Enamelled wire will give a stronger field as well because the coils of wire are much closer together than using plastic insulated wire. 

I can't beleive I wrote _magnetoferrous_... :mg:


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## Veni Vidi Vici (Jan 23, 2011)

adrian5800 said:


> I can't beleive I wrote _magnetoferrous_... :mg:


If ever there was a thread to write that in, this is it


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## rdmwc (Sep 21, 2010)

I love this thing! Been doing a lot of tweaking with my warthog and running it through the chrono. With my new arrows I'm averaging 347fps! Great DIY!


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## jeremy.b (Dec 7, 2010)

I wanted to drop in again and tease you all with an update on the program I've been working on to work with these chronographs. It'll look something like this:









So far it's been working well on my setup (36 AWG wrapped on a 8" cardboard concrete form tube).

With any luck (and some more testing ) the program should be pretty close to put out for you guys to play with.


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## 09Dreamseason (Feb 11, 2010)

helsyeah said:


> So far it's been working well on my setup (36 AWG wrapped on a 8" cardboard concrete form tube).
> 
> With any luck (and some more testing ) the program should be pretty close to put out for you guys to play with.


I'm still waiting patiently!!

and can you post a picture of how you're using the concrete form tube?


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## jeremy.b (Dec 7, 2010)

Yup, i'll do a whole build list and write up for everyone before long.

I will probably test some noise reduction ideas that I want to try first though, but my noise levels are already pretty low, so maybe they'll help someone else.


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## Veni Vidi Vici (Jan 23, 2011)

I can confirm that helsyeah's software is pretty sweet!  While SoftChrono is fine, his software is able to take advantage of the fact that we know what the signal we are analyzing is supposed to look like. That information allows him to be more discriminating in noise reduction and selecting the timing points.


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## 09 Bengal (Aug 1, 2010)

Hey rdmwc, have you had that bow chrono'd to see how close the readings are to your homemade one ?? 347 is only 3 fps less then IBO speeed ??


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## Veni Vidi Vici (Jan 23, 2011)

adrian5800 said:


> Veni
> No I didn't rub the point with a magnet and you are probably right the smaller coils have a more concentrated magnetic field within them. Enamelled wire will give a stronger field as well because the coils of wire are much closer together than using plastic insulated wire.
> 
> I can't beleive I wrote _magnetoferrous_... :mg:


All of my fieldpoints must be austenitic. I made a second chrono using 50 turns of enameled wire and a 6.75" coil diameter, and all I get is the tiniest blips above the baseline noise ( which is pretty low now).


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## booone0 (Nov 30, 2013)

Finished mine today. I'm sending my bow out for new strings, change in draw weight and length, so I wanted baseline info.

I drilled out a small game head and glued in a rare earth magnet. It worked really well and gave an awesome signal!








Here is the audacity reading, zoomed in. This is shooting a magnet. I barely got a discernable waveform using a field tip rubbed with a magnet.








I used the spreadsheet, with a few modifications, because I'm on a mac and can't use CoilChrono.








The magnetized tip I used.


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## booone0 (Nov 30, 2013)

Last pic...my setup.

I found a cable that had two RCA plugs on one end and a 3.5mm audio on the other. I soldered the tips of the RCA cables together, then connected those to one end of the coil circuit. The other end went to the ground connecter on the end of one of the RCA plugs (on these, the silver collar is ground on both plugs)

I used 50 wraps on each end, using 40ga enameled wire, around the 8" dia. concrete tube. 46" distance between centers of the coils.

One tip: you can burn the enamel off the wire for making connections. Then lightly sand to get the residue off for a clean connection. Sanding it alone takes way too long.

Thanks for the great idea. This worked well, and cost me around $12.


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## Chrispret (Sep 4, 2013)

*Amazing signal with non magnetized FPs*

I built one over the weekend and loved how well it works, but I hated the fact that I can't shoot any old arrow, the tip had to be magnetized. So I've been scratching around for ideas. I think I found the solution.

This is what my coil chrono looks like.








If I shoot a non-magnetized FP through it I get noise, noise and more noise. No signal.








So I thought about it some, looked at the Guitar pickup version and got thinking. After looking at Metal detectors, permanently magnetizing FPs and lots of options I had an idea. Why not shoot the normal FP through a magnetic field? So I put some old speaker magnets I had lying around inside each coil like this.








The impact was incredible, where I previously got a decent signal using a magnetized FP, I now got a signal that is at least 10x stronger with a normal FP (readings in the 0.1 range vs 0.01)! I'm sure smaller magnets will do the trick, these are simply what I had lying around.








It even works ok with the Coil Chrono software, although I think a bit of work is required to make the detection work reliably.








I'm happy and had to share.


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## barbox (Oct 23, 2014)

Hi, here is my chrono, tested with BelaKbows (http://belakbows.wix.com/belakbows , Youtube Channel: https://www.youtube.com/channel/UCS1...EecqNsb7OWvSmg)
We got some really good results.
https://www.youtube.com/watch?v=ZYKuJGRina0
https://www.youtube.com/watch?v=PAVP_5o6KXA
https://www.youtube.com/watch?v=e1CqaoHVv9w
https://www.youtube.com/watch?v=A39h9x9BQhA
https://www.youtube.com/watch?v=08SoraDjUok

You can also find us on Facebook - BelaKbows


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