DIY Chronograph

[luke213]

This is a continuation of the thread here: http://miairsoft.proboards.com/thread/50895/diy-chronograph

Well guys working prototype;) And I'm thrilled with the results so far. Please do note this is the try after the photoresistors using photodiodes since the previous attempt didn't work I decided to build this quick and dirty rather than nicely. The only thing I really did right was solder all the connections etc;) Otherwise it's a piece of pipe with a couple holes drilled into it, and two pieces of wood;)



But it works and not only that the results are pretty dang close to what I suspected they should be for guns. I tested 15 or so guns across it, and for the most part I'm seeing consistent results and about what I expected. IE My CA M15A4 that I've just gone through and fixed things on running with an m120 spring is shooting 403+- 5. My M14 was a little bit of a surprise since it's running very close to 450fps with some drops here and there I'd say +-10fps right now. Which makes some sense though it's an m120 spring it's a full cylinder with a long barrel so the BB has a fair amount of time to accelerate. My Sniper rifle is coming in at 470 with an M150 Spring in there, which could be a bit low for that spring being a TM gun but I may not have a perfect air seal on the hopup there, as well it's the stock short gspec barrel which is likely to go up some in FPS because of joule creep occurring. GBB's all fell in the range of 280-320 which with the cold temps in my shop right now makes pretty good sense to me. My CYMA AEP ran right in the 210fps range which again makes some sense to where it should be. My stubby M4 came in dang close to 350fps which is what it's quoted factory speeds are. My G36 fell a little lower than expected but I'm not sure the spring in it, felt like an m120 but could have been less.

So photodiodes and matching IR LED's will make a diy chrono, I'll include more info and picture once I build a pretty version of this;)

Take care!

Luke

[kjones734]

Looks pretty good, Glad to hear that you got your working correctly. I forgot to take pictures of mine before I turned it into my teacher. I will get some pics of it when next semester starts in 2 weeks and post them. Mine worked pretty good too. I would say it was +-5 fps.

[luke213]

Well I'm not sure enough that any of my guns are that consistent. So the +-reading I gave is how much I varied without wild shots where I hit the wall of the tubing and lost 100fps;) That said I got pretty consistent results with some guns my g36 was pretty stable in the 360's for allot of shots but I don't know the accuracy but I can't imagine it's any better but it seems good enough.

I'd love to see your setup I'm planning more prototypes along with a more compact version and a battery holder and switch getting fancy.

Take care!

Luke

[kjones734]

The way I made mine for class is not the way I would make it for myself. For class I made it kinda like a exploded view so everyone could see how it worked. I also used a lot of hardware that I wouldnt use but I was required to make it using digital logic for class.

[luke213]

Understandable this one is functional but it's not what I'd call durable as it stands with exposed wiring etc etc. So my next one will be allot more robust and built to take more of a beating and last;) This one will likely become my shop chrono that will stay in here but I'll still do some wire routing and whatnot to make it durable to a degree with a battery holder, switch and likely just panels covering it in a box form. But at least the proof of concept works;)

Luke

[luke213]

Another update, need some time to do further testing. I'll say results are consistent if not accurate. I borrowed another chrono and it's conflicting with the results from my DIY. I don't 100% trust the results though because there are some weird things that don't make allot of sense. So I'm waiting till I can borrow another fancier chrono to compare the three and see if I can't get things dialed in as close as possible.

Really though this project if for no other reason has been a great diagnostic tool when rebuilding and changing guns since I can chrono before and after a change to insure what results changed. So more info coming soon in the next few weeks likely with some more in depth results and maybe a video of the function of it.

Take care!

Luke

[Snarf]

When you think the design is finalized, could you write a little how to guide, or at least a parts list? I'm pretty interested in building one myself.

[luke213]

Sure planned on doing that when I build the next version which will be prettier version more of a final version.

[zephurah]

I made one myself. I found out the hard way that you need to buy the IR LED's online. Most stores overprice their LED by alot. Another tip, make sure to drill the holes after you have glued on your support pieces with a really long drill bit.