# Diy coil chrono build instructions



## Veni Vidi Vici (Jan 23, 2011)

Last month, I made a post on this forum in which I gave instructions for inexpensively building a chronograph for measuring arrow speeds, and how to use free software to read the results. Many people took interest in this project, and like other projects on the DIY forum, the input from other members helped the project to evolve into a much more user-friendly tool.

Of particular note,* helsyeah *decided to work on his own software called *COIL CHRONO* for using a DIY Coil Chronograph. He is planning to make this software available, along with instructions and source code, to the members on the archerytalk.com forums. I really want to thank helsyeah for taking on this project and for the enormous amount of time he put into making such a useful and effective program. 

Because this project is so simple to build, almost everyone who has built one so far has come up with their own method using the materials available to them. In order to assist others who would like to build a coil chronograph, I decided to describe another version using inexpensive materials that are readily available. I do not claim that this is the best or cheapest method, but it does work well and provides a standard construction technique.

Attached is a .zip file containing a .pdf of the assembly instructions.

View attachment Assembly_Instructions.zip


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## crazygary (Sep 28, 2009)

amazing thanks for your hard work. think im gonna build me one.


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## Fresno Dan (Dec 9, 2010)

WOW... This is amazing work. I am truly thinking this might be something I can do, and use if I start shooting ASA or IBO. Thanks for your hard work.


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## shinobi3 (Jun 20, 2009)

thanks ...


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## Veni Vidi Vici (Jan 23, 2011)

I received a PM from straddleridge about some testing he has done with his DIY Chrono, and with his permission I am posting it here.



straddleridge said:


> veni vidi vici:
> 
> I thought you might appreciate this. I made a general archery program and to check things I do a lot of shooting and take a lot of data. Of course one of the most important things is speed.
> 
> ...


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## b0w_bender (Apr 30, 2006)

OK dagnabit, now I'm going to have to build me one of these things.

Sweet instruction document really well done great post!


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## bigern26 (Jul 26, 2009)

Ok this is awesome, really awesome thanks for the hard work and sharing the knowledge!!

Do you know if this would work with a gun?


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## droppixel (Nov 5, 2010)

This is great. It really looks like this has been close to perfected and I am going to take a crack at this again. My macbook is on the fritz so I am using a family member's PC laptop lately and this could totally work for me now.

Hopefully if I can get this put together soon, I'll post results and thoughts.


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## edmondsmatt (Dec 17, 2010)

Did not work for me, I used 18AWG dog fence wire. Tried coilchrono and audacity and can not get either one to work. I am just about to the give up and buy a chronograph point.


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## jeremy.b (Dec 7, 2010)

edmondsmatt said:


> Did not work for me, I used 18AWG dog fence wire. Tried coilchrono and audacity and can not get either one to work. I am just about to the give up and buy a chronograph point.


Couple things for you to try:



Do you have access to a multi-meter? If so double-check that you have a complete circuit through the coils (you should either get full continuity, or a fairly low resistance).
Have you tried magnetizing a field tip? I would assume so, but wanted to ask. VVV used a magnet and stroked it along a field point to get it magnetized. I just stuck my field points in the magnetic end of a socketed screw-driver and it worked for me.


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## edmondsmatt (Dec 17, 2010)

I tried dropping a magnet right through the coils, give me a few minutes to snap pictures of what I have already. I also have some small rare earth magnets that I am getting ready to try. Complete circuit is good, my fluke confirms that my soldering skills are still ok.


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## jeremy.b (Dec 7, 2010)

edmondsmatt said:


> I tried dropping a magnet right through the coils, give me a few minutes to snap pictures of what I have already. I also have some small rare earth magnets that I am getting ready to try. Complete circuit is good, my fluke confirms that my soldering skills are still ok.


cool, you may have to throw the magnet through the coils to see a decent pulse (the faster the magnet moves, the higher the peak of the pulse I *think*).


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## edmondsmatt (Dec 17, 2010)

Here is the screen shot of the rare earth magnets free falling through. I might have to get some bigger RE Magnets though if I want to glue them to a point. The ones I have are very tiny (1/16" diameter and 1/31" thick disc) and so they are not very strong. One will not trigger the software, but 100 will.


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## whack&stack (Oct 15, 2007)

ok i saw this awhile back and didnt pay much attention looked too complicated for me and i hate electrical work of any sort(hate tracing problems when you cant see them) but i want a chrono for testing the frankenbow i am making. i am going to give this a try cant wait to see the results. thanks for all your hard work guys.


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## edmondsmatt (Dec 17, 2010)

Ok, got everything lined out with the program and the coils. My problem was actually a self induced problem. If you are going to build a coil chrono, make sure you use a bow that is fast enough for the coils to pick up. I was trying to use a homemade PVC kids bow (94 fps) and had issues with the coils picking the tip up. After changing over to a much faster bow (291.9 fps) the signal came through crystal clear. If anyone is thinking about building one of these "Coil Chrono's" as Nike says "Just Do It." Mine was within 2 fps of the shop before adjusting the coil distance a little bit. Now it is in agreement with two light chronographs.


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## Veni Vidi Vici (Jan 23, 2011)

Thanks for the update, Matt. I'm glad it worked so well for you, and it's great that you are passing your lessons on to benefit others.


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## Gfunk (Jul 26, 2009)

Wow that is alot of hard work done, thanks for sharing this info. gotta love AT.


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## Veni Vidi Vici (Jan 23, 2011)

OK, so it's now just over a year since I posted this. Has anyone else built one of these, and how is it working for you? If you haven't built one, summer is the perfect time to get your DIY on and give it a shot


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## figo40 (Jun 1, 2012)

Tried to download the software but the link appears to be broken??


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## Veni Vidi Vici (Jan 23, 2011)

figo40 said:


> Tried to download the software but the link appears to be broken??


Try sending AT member helsyeah a PM. He wrote the software and may not know that the download link is broken. If that doesn't work, I might be able to find the setup file and e-mail it to you.


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## klean1 (Jan 14, 2012)

lots of free hosts out there, just host it an link it up! 

Sent via My Mobile Time Sucker


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## Veni Vidi Vici (Jan 23, 2011)

I believe this is the latest version of the Coil Chrono software setup file. I hope it works for you guys.


View attachment CoilChrono_Latest.zip


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## figo40 (Jun 1, 2012)

Thanks for the link!


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## h3lman (Jan 9, 2010)

First off thanks for the information. I'm looking forward to having a go at making one of these. I went out in search of copper magnet wire today and went to a workshop that rewires electrical motors. He gave me three near empty spools of wire. By the looks of it just one will be enough to do the job as it has well over 100 loops of the 4 inch spool. Small quantities such as this appear to be too small for rewinding a motor so this gent was happy for me to take it away. No charge !!


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## brandonlw (Feb 23, 2011)

marking for later


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## LowTrunkOzz (Apr 5, 2008)

So I got mine all built and tested and it works great so now it's time to tear it down and pretty it up some! My question, though, is if anyone savvy in androids java language has or is willing to write this program as an android app. I'm thinking wiring this up to a bluetooth headset would be the cats pajamas, but I'm not fluent in java....anyone?

nate


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## isaacdahl (Feb 27, 2010)

what a great idea. looks like its not too difficult. any idea on what the resistance should be for each coil? i have some guitar pickup wire i'm thinking of using but it's 42 gauge. also do you need more resistance the bigger the tube? i don't want to worry about missing!


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## edmondsmatt (Dec 17, 2010)

isaacdahl said:


> what a great idea. looks like its not too difficult. any idea on what the resistance should be for each coil? i have some guitar pickup wire i'm thinking of using but it's 42 gauge. also do you need more resistance the bigger the tube? i don't want to worry about missing!


There is no resistance value needed. if you go bigger on your support tube, make adjustments to the number of coils (add for bigger) you wind on. How this works is the change in magnetic flux as the ferrous point passes through the coils of wire triggers the audio recording portion of the application. The change in magnetic flux creates a small current on the wires. Two coils gives you two spikes in magnetic flux, the time measurement is taken from the peaks or crossing points of these two spikes. The distance between the coils is then used with the time to calculate the speed.


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## vern-the-brute (May 31, 2011)

do you still need to use the audacity program with helsyeahs program? and are there instructions with it?


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## Veni Vidi Vici (Jan 23, 2011)

No, you don't need Audacity, and yes there are instructions for Coil Chrono. Go to the COIL CHRONO link in the first post. Helsyeah gives good instructions there, and a few posts down in his thread he provided those instructions in .pdf format.


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## Huntinsker (Feb 9, 2012)

This is pretty sweet and I'll definately have to make one. Thanks for the info!


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## Texoma (Jul 1, 2006)

Thanks for posting this. Just got back from town and was able to find everything but the 1/8 plug.
I will find it online.


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## Veni Vidi Vici (Jan 23, 2011)

Hope you guys post some pics, results, and any lessons learned here after you get yours done.


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## Moler (Mar 25, 2012)

Gonna have a go a building one of these soon..... thanks for posting....


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## Antihunter (May 5, 2005)

There is an app for the Iphone called "Sports Speed Gun" that is suppose to provide arrow speed.I have not tried it just thought I would post it up in case someone wants to give it a try.Not sure how it triggers the start and end end point of the timing.


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## dw'struth (Mar 14, 2008)

Antihunter said:


> There is an app for the Iphone called "Sports Speed Gun" that is suppose to provide arrow speed.I have not tried it just thought I would post it up in case someone wants to give it a try.Not sure how it triggers the start and end end point of the timing.


Well.....there is also a range finding app, but it is pretty much a joke IMO.


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## Mig (Nov 26, 2008)

I just used audacity alone. I just zoom in to the wave lengths and select the peaks of both, which would tell you the exact time it was created. Find the difference and do the math to find fps. It took a minute but my chrono showed 1fps slower then the chrono at the shop. can't find my arrow tip with the magnet i put in it.


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## Antihunter (May 5, 2005)

dw'struth said:


> Well.....there is also a range finding app, but it is pretty much a joke IMO.


Just why I haven't bought it....


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## Jake Leibke (Jun 8, 2012)

Is there a software program available for a Mac?


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## jerzy-joe (May 23, 2010)

Sounds good


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## Texoma (Jul 1, 2006)

Here are pics of mine.This was a fun build. Thanks again for putting this together for us!


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## dac (Jun 27, 2003)

I made one awhile back and the only problem I have is, I will get a couple readings I feel are accurate then I will start to get err readings or numbers that I know are not correct either way high or way low. I don't know if this has to do with the point not being magnetized enough or what, so when I get some time I will get back to working the bugs out. But it is a cool little project and I appreciate those that took the time to put this together and shared it with the rest of us.


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## beerman6 (Nov 12, 2011)

Do you guys have a PDF build file I can not get the zip file to open on my phone


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## ChadBrailer (Mar 6, 2009)

what do u plug the speaker jack into? sorry for the dumb question into the Audio port or what?


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## sb220 (Jul 20, 2009)

Antihunter said:


> There is an app for the Iphone called "Sports Speed Gun" that is suppose to provide arrow speed.I have not tried it just thought I would post it up in case someone wants to give it a try.Not sure how it triggers the start and end end point of the timing.


Check this out http://www.archerytalk.com/vb/showthread.php?t=1770199


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## Veni Vidi Vici (Jan 23, 2011)

That seems like a cool app. I just downloaded it and will try it out when I get back from vacation.

Sound waves are what I originally set out to measure when I started this project last year. But I wanted "muzzle velocity" instead of an average, and I also found that echoes made it unreliable to use indoors. That's why I took the approach I did with the coils of wire and magnet. The coils can be placed close to the bow to give a better idea of muzzle velocity, and the electronics are unaffected by background noise, echoes, or even light as a standard chrono is.

That said, I'm not knocking this app at all. It is much easier to just pull out my phone and get a velocity if the conditions are right for using it. I will keep both of these tools in my toolbox.


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## dac (Jun 27, 2003)

ChadBrailer said:


> what do u plug the speaker jack into? sorry for the dumb question into the Audio port or what?


The microphone port.


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## vern-the-brute (May 31, 2011)

Well, I built the chrono(i was 10 wraps short on each 8inch tube with 29guage wire, making it only 40per tube hope it still works) and loaded the latest program but when i start it and plug it in I get no audio input choices. Sometimes it does for only a split second and then it pops up an error saying that that program has quit working. any suggestion?


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## Veni Vidi Vici (Jan 23, 2011)

Maybe someone else will have run into this, but I have not seen this issue. If no one else has the answer, I suggest sending helsyeah a PM and see if he has any ideas.

Maybe you could try installing Audacity and see if you can record a shot with your chrono using that. That could at least ensure your system is functioning, and maybe it would give helsyeah some valuable information ...?


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## gavin83 (Jun 25, 2012)

so i can set the coils at any distance i want and how many coil wraps do i need for 15 inch diameter cheers


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## beerman6 (Nov 12, 2011)

Does anyone know if chrono and software will work on a kindle fire?


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## LowTrunkOzz (Apr 5, 2008)

vern-the-brute said:


> Well, I built the chrono(i was 10 wraps short on each 8inch tube with 29guage wire, making it only 40per tube hope it still works) and loaded the latest program but when i start it and plug it in I get no audio input choices. Sometimes it does for only a split second and then it pops up an error saying that that program has quit working. any suggestion?


I had this problem at first, also. I had to plug the jack in to my computer first, choose what I wanted it to be (line in, audio out) and then start the CoilChrono program. 

nate


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## SDHockin (Aug 30, 2011)

I built one yesterday, it's not working correctly though, I'm getting readings all over the place, 20 fps all the way up to 4500 fps. it will read in the hundreds even when nothing has passed thru it! Anyone with suggestions? continuity is fine, screws in mic plug are isolated, I'm at a loss! 
Thanks Shawn


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## vern-the-brute (May 31, 2011)

LowTrunkOzz said:


> I had this problem at first, also. I had to plug the jack in to my computer first, choose what I wanted it to be (line in, audio out) and then start the CoilChrono program.
> 
> nate


pardon my ignorance but where do i choose the line in, audio out? (i'm using windows 7 by the way).
thanks, Vern


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## Veni Vidi Vici (Jan 23, 2011)

SDHockin said:


> I built one yesterday, it's not working correctly though, I'm getting readings all over the place, 20 fps all the way up to 4500 fps. it will read in the hundreds even when nothing has passed thru it! Anyone with suggestions? continuity is fine, screws in mic plug are isolated, I'm at a loss!
> Thanks Shawn


Have you gone through all of the trigger adjustment instructions helsyeah provided in his Coil Chrono post?


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## Veni Vidi Vici (Jan 23, 2011)

vern-the-brute said:


> pardon my ignorance but where do i choose the line in, audio out? (i'm using windows 7 by the way).
> thanks, Vern


He probably means, right-click on the volume icon in your sys-tray. Select "Recording Devices". Then select the "External Mic" option. Here's a pic of the window I'm talking about. In this pic, though, the internal mic is selected (see check mark) because I didn't have an external mic hooked up when I grabbed the image.


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## Veni Vidi Vici (Jan 23, 2011)

Veni Vidi Vici said:


> Have you gone through all of the trigger adjustment instructions helsyeah provided in his Coil Chrono post?


@SDHokin: I had another thought. Are you sure you plugged it into the microphone input jack, and not a headphone jack? Mine are right next to each other and the little labels are difficult to see, so I've done that a few times. Also, you might want to try downloading and installing Audacity for trouble shooting purposes. That will let you post screenshots of the entire waveform.


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## SDHockin (Aug 30, 2011)

Thanks Veni, I checked to be sure I was in the right port a couple time's, I reloaded the chrono and will try after work tonight, I'll see if that works.


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## LowTrunkOzz (Apr 5, 2008)

Veni Vidi Vici said:


> He probably means, right-click on the volume icon in your sys-tray. Select "Recording Devices". Then select the "External Mic" option. Here's a pic of the window I'm talking about. In this pic, though, the internal mic is selected (see check mark) because I didn't have an external mic hooked up when I grabbed the image.


Yup! That's exactly what I meant...sorry Vern, I'm usually on my phone on here and shorten everything up...let me know if VVV's post helps...

nate


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## isaacdahl (Feb 27, 2010)

Thanks, but i'm afraid i've already checked that. when i'm on that window it shows the external mike picture and when i wave a magnet by one of my coils the little graph lights up like its receiving a signal. just for the fun of it i loaded the program on my old desk top computer running window xp. though i havent hooked up the chrono to it(because that jacks in the back), the program pops up fine and even shows the select audio device and input choices. this is more than my laptop does.(at least until i plug it in and then only briefly till the "program has stopped working" thing pops up.) I did try to run it through the audacity program and was able to make some disturbance on the graph
Vern (or Isaac)


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## edmondsmatt (Dec 17, 2010)

isaacdahl said:


> Thanks, but i'm afraid i've already checked that. when i'm on that window it shows the external mike picture and when i wave a magnet by one of my coils the little graph lights up like its receiving a signal. just for the fun of it i loaded the program on my old desk top computer running window xp. though i havent hooked up the chrono to it(because that jacks in the back), the program pops up fine and even shows the select audio device and input choices. this is more than my laptop does.(at least until i plug it in and then only briefly till the "program has stopped working" thing pops up.) I did try to run it through the audacity program and was able to make some disturbance on the graph
> Vern (or Isaac)


Try rght clicking on the program and running it either as admin or go to properties and select the compatibility tab and run as compatible with Windows XP to see if that will help.


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## isaacdahl (Feb 27, 2010)

I might be getting somewhere. i tried clicking the run as compatible with window xp and now i get the select audio device but nothing in the select audio input,but at least there's no "program stopped running" message.


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## Ronin Conan (Jul 4, 2011)

Just curious what all you chaps are using to hold the coils? I built one using 90mm diameter pvc pipe, and while it works fine, it's just not big enough to comfortably shoot an arrow through. I can't find the snap coupling things that were recommended, nor can I seem to find anything else that would be appropriately sized. Any suggestions?


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## Veni Vidi Vici (Jan 23, 2011)

Some people have used 8" concrete forms.


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## h3lman (Jan 9, 2010)

Here's my Coil Chrono... a Detergent container. The coils are only 10.75" apart but it works... which shocked me. I got the wire free from an electrical motor winder so my total cost was $1.85 for the plug.


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## Veni Vidi Vici (Jan 23, 2011)

Very cool build! I wonder why your peaks are so different for the first and second coils? Could be that the field inside the square shape isn't even, and if you shot at an angle it went through a weaker region first, then a stronger region. Or it could be that you were a little too close, and the arrow wasn't completely off the string yet when the tip went through the first coil. What are your thoughts on this? Have you shot through a standard Chrono with this setup? How does the speed compare? Do the amplitudes of each coil always look like this?


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## h3lman (Jan 9, 2010)

I was hoping someone would pick up on that. I shot from a fairly close distance to the chrono but long enough that the arrow would have completely left the string. I was stabiliser distance away from it and my stab is around 36". I don't have access to a real chronograph the only other thing I have is Archer's Advantage which estimates the speed should be around 235fps so I figure its pretty close.

I guess there is always the possibility that I have a few more loops on one side of the chrono than the other. After 20 + years working shifts I think I'm starting to loose a few too many brain cells to even keep count accurately. Would having an uneven number of coils produce such a wave form ?

Oh another thing... the exit end of the tub is slightly narrower than the entry


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## h3lman (Jan 9, 2010)

Correction to the above. I had a couple of settings wrong in archer's advantage. After correcting it the estimate for arrow speed is 257.60fps and thats pretty damn close for a $1.85 Chronograph don't you think ?


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## Veni Vidi Vici (Jan 23, 2011)

Yes, a different number of turns would have an effect. But based on your AA results things look good. Your crossover points are definitely getting picked up correctly. If you get a chance to shoot through a real Chrono, you can then adjust your distance value in Coil Chrono so that the results match. That will be your "effective coil distance", and you will have essentially calibrated your system.

The narrower exit should result in a stronger signal for equivalent number of turns, so that helps explain your signal.


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## SDHockin (Aug 30, 2011)

Still no luck! reloaded the program, rewired, retried, No luck, Still reads a value even though nothing has passed thru it, anyone have anymore suggestions?


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## Veni Vidi Vici (Jan 23, 2011)

SDHockin: Any chance you are near a source of electrical interference? Fluorescent lights, invisible dog fence...?


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## SDHockin (Aug 30, 2011)

Fluorescent light,s in the shop I work at, They are actually High pressure sodium, But they are 22 feet above the floor, Still causing an interference maybe? 
Shooting in my office thinking wire to the chrono was too long, with lights off too!(during the day of course)!Thanks,


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## Veni Vidi Vici (Jan 23, 2011)

SDHockin said:


> Fluorescent light,s in the shop I work at, They are actually High pressure sodium, But they are 22 feet above the floor, Still causing an interference maybe?
> Shooting in my office thinking wire to the chrono was too long, with lights off too!(during the day of course)!Thanks,


I notice you have the "Set Thresholds from Current Recorded File" box checked. The quick start instructions here http://www.archerytalk.com/vb/showthread.php?t=1485256 say to leave it unchecked. Have you tried this? Looks like your thresholds are being set to trip on system noise. The first 3 steps in the quick start guide are where the software grabs a short sample of your system's noise and sets the the thresholds.

If you want to record a shot using audacity, I'd be happy to take a look at it.


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## Veni Vidi Vici (Jan 23, 2011)

Looking at your graph again, you are definitely triggering on noise. Change your threshold percentage to positive 40 and select Set Thresholds again. With no shot, you want the red lines on the graph to be above and below all of the system noise. 

I think going through the quick start guide should fix it for you as well.


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## SDHockin (Aug 30, 2011)

Thanks, I'll try again tonight.


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## vern-the-brute (May 31, 2011)

i finally got a chance to try mine. first i tried to magnetize my field point by rubbing it with a magnet, never could get it to pick up any thing but it did move a compass so i thought it might be good enough. after adjusting the settings on the program i got two good shots that seemed reasonable(i haven't shot it through a "real" one). when my son tried his bow the graph seemed upside down and after repeated shots from both our bows kept getting different reading and errors.any ideas?


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## Veni Vidi Vici (Jan 23, 2011)

Sounds like you rubbed it with a magnet again but with the magnet poles reversed. That would make the graph upside down from the previous time. Also, impacts can cause the magnetism to be removed. Try marking your magnet so you always hold it the same way, and always stroke it on the field point from nock to tip. Do this every few shots and see what happens.

It doesn't matter if the graph gets turned upside down; the software doesn't care. But if you are not rubbing consistently, you may be magnetizing then de-magnetizing the field point.


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## clutchjunkie (May 25, 2012)

So, has anyone done this using an arduino or other microcontroller? Seeing this gives me some ideas, I am thinking of going portable and maybe even bow mounted. Also, is there a reason for going with coils instead of light or I/r sensors?


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## beerman6 (Nov 12, 2011)

Hi all got a quick question, I USED ONLY;40 WRAPs aroound a 8" concrete forming tube will this still work


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## Veni Vidi Vici (Jan 23, 2011)

beerman6 said:


> Hi all got a quick question, I USED ONLY;40 WRAPs aroound a 8" concrete forming tube will this still work


Yes it should.


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## Veni Vidi Vici (Jan 23, 2011)

clutchjunkie said:


> So, has anyone done this using an arduino or other microcontroller? Seeing this gives me some ideas, I am thinking of going portable and maybe even bow mounted. Also, is there a reason for going with coils instead of light or I/r sensors?


I went with a coil because of the materials I had on hand and because I could use Audacity to read the wave. Of course, the coils get away from the lighting issues present in standard Chrono as well.


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## vern-the-brute (May 31, 2011)

an idea occurred to me today, tell me what you think. from what I know(just a little) an electric guitar pickup is a magnet with a coil wrapped around it and the strings vibrating over the pole pieces make the signal. would it work to make the the chrono the same way? i'm thinking maybe using coffee cans or cookie tins wrapped with coils and a magnet attached to each. this way the field point wouldn't need to be magnetized. they even make hum canceling pickups (humbuckers) which is two single coil pickups each wound the opposite direction with each one magnetized with poles opposite. I'd try it but i want to make sure i'm not overlooking or misunderstanding something.


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## Veni Vidi Vici (Jan 23, 2011)

vern-the-brute said:


> an idea occurred to me today, tell me what you think. from what I know(just a little) an electric guitar pickup is a magnet with a coil wrapped around it and the strings vibrating over the pole pieces make the signal. would it work to make the the chrono the same way? i'm thinking maybe using coffee cans or cookie tins wrapped with coils and a magnet attached to each. this way the field point wouldn't need to be magnetized. they even make hum canceling pickups (humbuckers) which is two single coil pickups each wound the opposite direction with each one magnetized with poles opposite. I'd try it but i want to make sure i'm not overlooking or misunderstanding something.


I think this would work. However, the arrow may have to pass very close to the pickup ....? The theory of having a piece of ferrous metal moving over a coil with a magnet in it to produce a signal is solid, though.


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## SDHockin (Aug 30, 2011)

I just tried again with no results, tried audacity also(I think I'm using it right?(no signals), anyway, I started playing with the mic connector and started getting "spikes" on the read-out, possibility of a bad port? I'll look into it tomorrow maybe.
Shawn


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## Fury90flier (Jun 27, 2012)

Didn't read everything so maybe it's been done...

I read where you can't use regular field points that they must be magnetized. Why...not enough signal, right? Why not add a simply opamp to the circuit? Any reason that won't work?


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## Veni Vidi Vici (Jan 23, 2011)

I'm really not very good with electronics, but I believe this detection method is based on Faraday's Law and that it is the movement of the magnet's field through the wire turns that generates the voltage that is being detected.

Magnetizing a field point is easy, though. The best signal is achieved if you can install a magnet in the field point, but simply rubbing a magnet on a field point will induce enough magnetism to be detectable.


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## Fury90flier (Jun 27, 2012)

Looks like I've got a project to work on. I'm going to try magnetizing the tip as I don't have any method of machining the point other than a dremel tool. Maybe gluing will work.

Can the coil be large diameter?


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## Veni Vidi Vici (Jan 23, 2011)

The larger the coil is the less sensitive it will be. 6" - 8" seems like a good balance between sensitivity and usability.

It shouldn't take much magnetization to do the job. Just make sure you always hold the magnet on the same orientation when you stroke the FP. I explained how I do this in the build instructions.


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## Fury90flier (Jun 27, 2012)

Ok, that's three projects. 1 for the chrono as is the the modifications of an amp and another for charging the coil. If I do then it should pickup any thing that passes through...basically the same method a metal detector works.

On magnetizing the tip, I've got a magnetizer for screwdrivers and stuff.


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## Veni Vidi Vici (Jan 23, 2011)

I can't get my original assembly instructions from my OP to download anymore, so I'm going to try to attach them here again.

View attachment Assembly_Instructions.zip


And just for good measure, here is helsyeah's COILCHRONO software.

View attachment CoilChrono_Latest.zip


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## clbrown23 (Jan 6, 2010)

I was wondering how accurate people have been seeing these compared to some bought chronos before you have calibrated them? Thanks


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## Veni Vidi Vici (Jan 23, 2011)

clbrown23 said:


> I was wondering how accurate people have been seeing these compared to some bought chronos before you have calibrated them? Thanks


Check out my post here: http://www.archerytalk.com/vb/showthread.php?t=1485253&p=1061022433#post1061022433

That's comparing to a Radar Chron, which works on an entirely different effect. I've had similar good results when comparing to a standard chrono. If you measure the distance between the coils carefully you should be within just a couple feet per second.

As an example, for a bow shooting 275 fps, if the distance between the coils is exactly 30", then the time between pulses will be .0090909 sec. If the coils were actually 1/4" closer together, the speed would be 29.75/.0090909 = 3272.5 ips which is 272.7 fps, a difference of only 2.3 fps. 2.3/275 = 0.008, or 0.8% error.


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## Fury90flier (Jun 27, 2012)

has anyone tried to charge the coils so you don't have to drill the ponts and add a magnet?


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## Veni Vidi Vici (Jan 23, 2011)

Fury90flier said:


> has anyone tried to charge the coils so you don't have to drill the ponts and add a magnet?


Not that I know of, but all you really need to do is rub the point with a magnet.


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## Fury90flier (Jun 27, 2012)

if that's all, then I've been way over thinking this...I've got a magnitizer for screwdrivers--that should work fine.


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## clbrown23 (Jan 6, 2010)

ok Veni thanks, I saw that post you're refering to earlier I just wasn't sure if those speeds were after you compared it to a radar chrono and then adjusted the distance between your coils. Thanks for the reply I don't have any chrono so I was wondering how much I could fully rely on what this one will read. Sounds close enough for me tho. Thanks again


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## straddleridge (Apr 28, 2010)

clbrown23:

Veni posted a pm I sent him (he asked for my permission). I shot the arrows through my diy chronometer while the radar chron was attached to my bow. The readings are from the same shot in all cases.


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## clbrown23 (Jan 6, 2010)

Alright thanks straddle, was the distance between your coils still the original 30 inches when you were doing this comparison then?


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## straddleridge (Apr 28, 2010)

clbrown23

I made mine a little different. My coils are 6" in diameter and 36 inches apart. As I recall I used 50 turns of 22 gauge wire on each end from a kit of wire I bought from radio shack. By the way I can get a reading without magnetizing the tip.


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## clbrown23 (Jan 6, 2010)

geez that's pretty nice, I guess I will try it and if mine doesnt work I will build one more like yours
thanks


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## elkbow69 (May 7, 2010)

bump any updates?????????????


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## Fury90flier (Jun 27, 2012)

I wasn't able to get mine to work...

The reason is totally user related-- trying to make an amplified version...either amplify the coil or amplify the signals...when I get more time, I'll make it work.


I'd like to see one that can be used on a smart phone.


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## inverted (Jan 2, 2014)

Hi all,

I've just finished building one and after it's all done I've realized I've made an error.

I wound coils in different directions.

I haven't got the chance to test it jet so I wanted to ask will it be usable as is or will I have to rewind one side to match the other?

Thank you!

Best regards,
W


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## 1dwn4up (Jan 22, 2013)

Tag


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## Veni Vidi Vici (Jan 23, 2011)

It should work fine with helsyeah's software. I think he only looks for where the signals cross the baseline, regardless of whether they are going up or down.


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## charlsand (Jan 29, 2014)

I just finished this (two different builds) and I'm getting what seams like a lot of "background noise" every time I run it. Does anyone have any ideas on a way to clear that up? All my connections are soldered, the coils are wound snug, the plug is even gold plated. The only thing I changed was the overall length, from 30 to 24.


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## Veni Vidi Vici (Jan 23, 2011)

The only noise issue I ran into was caused by testing it within about 10 feet of where the wire for my in ground dog fence was run. I was testing it in the basement and it took me awhile to realize that the fence wire ran along the nearest wall.


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## charlsand (Jan 29, 2014)

I've tested it in multiple areas. Most recently inside and EM safe room at work (we use it when calibrating some equipment) and it doesnt make a difference. I am using a solid core wire for my lead into the plug, would that make a difference?


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## Veni Vidi Vici (Jan 23, 2011)

No idea. Both of the ones I made were solid core. If you figure it out, please post the solution here.


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## redneck-archery (Jan 8, 2014)

Veni Vidi Vici said:


> I can't get my original assembly instructions from my OP to download anymore, so I'm going to try to attach them here again.
> 
> View attachment 1628091
> 
> ...


what in the world do I have to have on my computer to open these files ? I have tried everything. any help would be greatly app.


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## redbone311 (Sep 6, 2010)

brandonlw said:


> marking for later


ditto


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## Veni Vidi Vici (Jan 23, 2011)

*******-archery said:


> what in the world do I have to have on my computer to open these files ? I have tried everything. any help would be greatly app.


All you need to do is extract the zip file and then run the .exe file. If you are using Windows, just right click on the downloaded .zip file and select Extract All.


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## blazinsoles (Jul 23, 2013)

Subscribed


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## flinginairos (Jan 3, 2006)

What an awesome idea!! I never even thought about making a chrono but after reading this I am gonna do it. I work with electronics and soldering every day so it shouldn't take long at all to put together. I'll post back when I get a chance to do it!


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## V-TRAIN (Feb 27, 2009)

tag


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## Dierte (Nov 18, 2007)

I'm going to give this a whirl this week. Looks like a decent set up.


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## inverted (Jan 2, 2014)

Hi all,

it worked with coils wounded in different ways, spikes were opposite one to another but nothing wrong with the signal and it worked.
But, I've rewinded one side anyway.

So far, I've tested it with 3 different type of arrows.
Easton A/C/C - everything fine
Easton xx75 - everything fine

Easton Carbon One - I get a funny looking signal (forgot to make a screenshot) and impossible to measure anything

Any reason why this particular arrow wouldn't work?

Thank you!


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## camohunter24736 (Oct 15, 2007)

tag for later


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## GrayTech (Jan 29, 2013)

inverted said:


> Hi all,
> 
> it worked with coils wounded in different ways, spikes were opposite one to another but nothing wrong with the signal and it worked.
> But, I've rewinded one side anyway.
> ...


Is the point on these smaller/ lighter? Or could the arrows be flexing more so they are not going through the coils as flat?


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## inverted (Jan 2, 2014)

GrayTech said:


> Is the point on these smaller/ lighter? Or could the arrows be flexing more so they are not going through the coils as flat?


tip is a bit narrower but not lighter (120gn), and it is magnetic so i did magnetized it properly

can't be sure about flexing tough.

Best regards!


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## Glenn58 (Mar 25, 2013)

charlsand said:


> I just finished this (two different builds) and I'm getting what seams like a lot of "background noise" every time I run it. Does anyone have any ideas on a way to clear that up? All my connections are soldered, the coils are wound snug, the plug is even gold plated. The only thing I changed was the overall length, from 30 to 24.


Your wire attached to the magnet wire leads should be twisted pair. In the instructions he mentions using cat5 wire which is twisted...it helps to cancel any stray noise pickup.


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## Outsider (Aug 16, 2011)

Can I make it using any diameter tube?


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## Outsider (Aug 16, 2011)

Also did anyone tried using different gauge wire? I have A LOT of this wires at work but not 30 GA


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## S.Alder (Aug 4, 2012)

Marking for later. I am building one.


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## Fury90flier (Jun 27, 2012)

Pysiek said:


> Also did anyone tried using different gauge wire? I have A LOT of this wires at work but not 30 GA


I'm not sure if it's in this thread or the others but there have been people that used other gauge wire. From what I remember, the thinner the better- very little signal going through- think the resistence is too much for a clear signal....maybe adding a preamp to the line...(mic amp)


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## Outsider (Aug 16, 2011)

I have pretty thin wires. Thanks for the info will try them out and see how it turns out.


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## S.Alder (Aug 4, 2012)

Following


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## Chrispret (Sep 4, 2013)

I posted a solution to the requirement for magnetized FPs in the other Coil Chrono thread here:
http://www.archerytalk.com/vb/showthread.php?t=1462291&page=14&p=1071317804#post1071317804


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## fgignac (Aug 21, 2014)

Tag


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## Bowpro-295 (Jul 30, 2013)

Tagged till I get home


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## bonecollector66 (Mar 2, 2011)

tag


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## b0w_bender (Apr 30, 2006)

I have magnets in the bottom of my target quiver to keep the arrows from falling out. One of the things that I noticed was that over time my field points became magnetized I expect that woulds help with the coils picking up the head without changing the weight by adding a magnet.


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## NoDeerInIowa (Mar 5, 2012)

b0w_bender said:


> I have magnets in the bottom of my target quiver to keep the arrows from falling out. One of the things that I noticed was that over time my field points became magnetized I expect that woulds help with the coils picking up the head without changing the weight by adding a magnet.


When I built mine, I didn't need to add magnets to the arrows at all. I also found that Easton's titanium coated points will not read.


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## Chrispret (Sep 4, 2013)

I hear you, there is lots of noise in my basement from flourescent lights, the furnace fan etc. Even with a magnetized FP mine doesn't work reliably.

With the magnets in the coils it works every time.


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## randolph_ar (Sep 24, 2013)

Here is my version of it. I was original going to build it with coils but went with the guitar pickups instead. I wired it up the same as the OP. I had an issue with my laptop though. Apparently you need to have separate Mic in and Audio out jacks, my laptop has them combined in a 4 conductor jack. I found a USB powered sound card off of Amazon for pretty cheap. I tested it out tonight and got it to work sometimes, still have some bugs to get figured out. But here are some pictures. I have never shot the bow through a "real" chronograph so I have no way to actually calibrate it, but it is pretty dang close to what OT2 predicts. 

Guitar Pickups









USB Sound Card









Screen Shots


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## Chrispret (Sep 4, 2013)

With the 4 conductor jack the mic is typically the one closest to the jack body and the other wire goes to ground, usually the tip.


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## idw (Feb 4, 2015)

Thanks for the software and ideas, I used 100mm tube, 480mm space, with 20wraps of wire. I use a mobile recording interface so instead of magnetize the my field points I just turned on phantom power and charged the coils.


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## flinginairos (Jan 3, 2006)

I made one from guitar pickups and it works sporadically. For some reason my arrows with normal field points read all over the place but when I add the screw in weight to the back of the insert it reads much better but the speeds are always faster which makes no sense lol. Maybe the bigger mass of metal at the tip is picking up correctly? I'm getting good wav peaks on the readings so not sure what the deal is.


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## camar068 (Feb 12, 2015)

I saw a few links for the program and instructions but they are .php files. I was about to ask for updated links, but on a whim I changed the .php to .zip and alls well now. Not sure if it's a Windows technical preview or what, lol moving on.

Thanks Guys


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## flinginairos (Jan 3, 2006)

Just an FYI, I bought a Caldwell Chrono and compared it to the DIY coil chrono I made and they read exactly the same. Pretty cool! I will stick with the Caldwell since it's easier to use but the DIY one works too!


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## camar068 (Feb 12, 2015)

Has anyone tried using a Bluetooth transmitter instead of the cable? Someone mentioned using a phone to do this instead of a pc. Has anyone tried anything with a phone yet?

Update: I thought it was Bluetooth receivers I have, it turns out they are transmitters. I'll give a shot when I build mine and let you all know.


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## Rapt_up (Mar 18, 2013)

Hi All,

Found this thread and the relate donand just read through this. Its a great idea. And some thoughts as an electrical and mechanicanl engineer.

The more turns you put in the coil the stronger the signal, this helps counteract the lost of signal from a larger diameter coil. Thinner wire (within reason) benefits because you can get more turns in the coil without taking up more space, because again the larger the space taken up in the coil the lower the field effect.

Finally for the folks who have stray triggers and random effects the setting of the low and high pass filters is important to eliminate a lot of the noise without loss of the signal. They are what cleans up the signal so it looks like a nice line with pulses rather than a messy line that floats and wanders and is jagged all over the place.

Finally, if you have the option to power the coils then any conductive item passing through the field that creates should generate a pulse.


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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/UCS18jS5XvEecqNsb7OWvSmg)
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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## Veni Vidi Vici (Jan 23, 2011)

Well done, @barbox .

If I may make one comment. In some of the videos, I think you may have been standing a little too close to the chrono. You need to be far enough away that the arrow has completely left the string when the tip passes through the first coil. Otherwise the arrow is still being accelerated by the bow when the first peak occurs and your reported speed will be lower than the true speed.


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## Veni Vidi Vici (Jan 23, 2011)

TTT since I've had people sending me PM about this lately.


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