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Poor Man's Electronic Chronograph

July 31 2011 at 5:42 PM
Dimitrios Michailidis  (Login Dimitris76)
YF

Ok after a few requests I sat down and made a schematic of my DIY chronograph.

[IMG][linked image][/IMG]

As you can see it's very easy to build it and most of the stuff needed are usually available at any home.

I used a piece of heavy plastic tube - the broomstick of an old broom that lost most of it's bristles long ago... happy.gif - two small 10x4x4cm wooden blocks.

Then you need a power drill and a 5mm bit to drill a hole through the wood and across the pipe's center. A wood screw inserted from the top keeps the wooden blocks on the pipe.

Two pairs of IR LEDs/Phototransistors are inserted in the holes, opposite each other.

I have used this IR LED
http://www.datasheetcatalog.org/datasheet/siemens/LD271HL.pdf

And this matching IR Phototransistor
https://www1.elfa.se/data1/wwwroot/assets/datasheets/ryL-7113P3C_data_e.pdf

both working at 950nm wavelength, but any matching (in wavelength) pair will do the job.

The IR LEDs are working on 1.2 Volts and can be either run in parallel from a single 1.2 Volt NiMH AA battery, or - like I did - use a higher voltage source and drop down the voltage with an in-line resistor.
I figured out that since this contraption is going to be used always next to a computer, I might as well "steal" some power from the USB port. In that case you need a 25 Ohm resistor - any wattage will do.
Observe the LEDs polarity. The kathode (shorter leg) goes always on the negative pole, the anode (longer one) on the positive.

Then you take a 3.5 stereo plug (I used one and the cable from an old cheap headphone set) and wire the two phototransistors in series with the tip of the plug going to the collector of the first transistor and the ground (barrel) of the plug to the emitter of the second (see schematic). The ring pole in the middle of the plug is not used.

This is the prototype (before cutting the excess tube)
[IMG][linked image][/IMG]

And here is next to the laptop running the SoftChrono software
[IMG][linked image][/IMG]

The software can be downloaded for free here:
https://docs.google.com/file/d/0B8POq9lplo4YeFZHTkcwaF9sQlU/edit?usp=sharing

or here:

http://talonairgun.com/forum/viewforum.php?f=16

This project - as everything else - has advantages and disadvantages:

CONS
-You have to waste about 30 mins of your life to build it.

PROS
-It's working like a charm.
-It's cheap! The parts/components don't cost more than a buck and the software is free.
-Unlike the commercial chronos is self-contained and is not influenced by external factors like, fluorescent lamps, AC flickering, clouds, sun, rain, etc... You don't need to build light boxes.
-Since all the data is collected by the computer and displayed on the screen, they are easily saved, analysed, compared, and manipulated in any possible way. Unlike commercial chronos that need extra accessories in order to be interfaced to PCs.

TIPS:
-You can source the IR LED/Phototransistors for nothing from old TV-sets,VCRs,CD-players etc that used IR remotes. They are matching and free!
-If you can't/don't feel like soldering you can use a Terminal strip like thhttp://www.radioshack.com/product/index.jsp?productId=2103232&CAWELAID=107595253 for all the connections.
-The distance between the sensors (length of the pipe)is not important as it's a value that can be adjusted later in the software. Shorter pipe, more compact chrono - longer pipe, more accurate. Approximately 1.5 feet long is a good start.
-USE AN IRON PIPE instead of plastic IF YOU INTEND TO USE THIS CHRONOGRAPH WITH HIGH POWERED AIRGUNS.
-USE A SUITABLE BACKSTOP AT ALL TIMES!
-Keep the laptop away from the pellet's flight path.
-MAKE SURE YOU SHOOT STRAIGHT IN THE PIPE. You can even place the gun's barrel in it.

DISCLAIMER:
-This chronograph is not built or tested for use with firearms. The products of gun powder combustion might foul the sensors or not, but I consider very dangerous to shoot a firearm in a metal pipe.
-This information is provided as it is for experimentation. Use common sense and observe all the rules when using power tools, airguns, guns, and/or working with electricity. I shall not be held responsible for any damage, injury or death caused during the construction or any direct or indirect implications of using this chronograph.

[IMG][linked image][/IMG]

ENJOY!

Dimitrios


    
This message has been edited by Dimitris76 on May 13, 2013 6:58 AM


 
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AuthorReply

Mike
(Login 17hornet)
YC

Very Cool!!

July 31 2011, 6:01 PM 

Nice setup... I think it's a really good idea!
Mike

" Ever have one of those mornings where it hardly seems worth the effort to chew through the leather restraints? "

 
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Marauder23
(Login tbln930)

That's Great. Does the shock wave bother it since you have

July 31 2011, 6:17 PM 

to hold the barrel up tp the pipe? Can you make the pipe diameter thicker w/o negative affects? Say 2" or so.

 
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Dimitrios Michailidis
(Login Dimitris76)
YF

Yes you can BUT

July 31 2011, 6:30 PM 

the larger the pipe diameter the harder will be to align the barrel to it.

Don't forget that the pellet needs to cut both light beams in order to register velocity. The light beam is only 5mm wide across the pipe's diameter though, so the pellet might fly by the side and miss it.

Dimitrios

 
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Dimitrios
(Login Dimitris76)
YF

The shock wave is not a problem

July 31 2011, 7:03 PM 

since it's invisible to the IR sensor.
But even if you use CO2 guns that expel a small cloud of condensated gas during discharge, you can adjust the sensitivity levels a little lower.

Dimitrios

 
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Marauder23
(Login tbln930)

I get a missing DLL error on WIndows 7. MSSTDFMT.DLL brand new laptop

July 31 2011, 6:25 PM 



    
This message has been edited by tbln930 on Jul 31, 2011 6:40 PM


 
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Dimitrios Michailidis
(Login Dimitris76)
YF

I didn't have this problem in one computer

July 31 2011, 6:35 PM 

and had it on another one.

Just download the .dll file, place it in c:\windows\system32 and then run Command Prompt as Adminitrator and type "regsvr32 msstdfmt.dll".

Dimitrios

 
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Marauder23
(Login tbln930)

WIth Windows 7 that must be distributed with app or must be downloaded

July 31 2011, 7:27 PM 

Since it is an old VB 6 runtime dll.

The Visual Basic 6.0 IDE is no longer supported as of April 8, 2008

http://msdn.microsoft.com/en-us/vbasic/ms788708


    
This message has been edited by tbln930 on Jul 31, 2011 8:00 PM


 
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NOVAir
(Login fe7565)
YF

Before install, go to "properties" and change compatibility to WinXP. Next...

August 1 2011, 12:30 AM 

Before install, go to "properties" and change compatibility to WinXP. Next "Run as Administrator" the .exe file. It runs on Win 7 Ultimate fine.

 
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robny
(Login robnewyork)
YF

very impressed!

July 31 2011, 7:36 PM 

so its easy to set the program for the distance between sensors?but tough to align the pellet flight path with 2 5mm sensor paths.

 
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David S.
(Login DavidS-Elite10)

Re: Poor Man's Electronic Chronograph

July 31 2011, 8:54 PM 

Hello Dimitrios,

Now that is very ingenious indeed and sounds great to me if I had a portable computer to use!

 
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Bruce Dodson
(Login BDodson)
YF

Post of the month?

August 1 2011, 12:06 AM 

This is cool and if not post of the month at least should be posted up top as a future reference.

Bruce Dodson
AireTex Compressors
(214)402-5574 Mobile
(817)633-5505 Office
www.airetex.com

 
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NOVAir
(Login fe7565)
YF

Ultimately, just make an adapter that allows the tube to slide over the end of the barrel

August 1 2011, 12:20 AM 

Excellent! Ultimately, just make an adapter that allows the tube to slide over the end of the barrel so it keeps the pellet path straight and makes the chrono portable.

Is the software capable of reading 1 foot distances between the IR leds? If yes, this could be a super-sized Combro.

 
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Dimitrios
(Login Dimitris76)
YF

You can use the muzzle's LDC threads

August 1 2011, 3:59 AM 

and attach it as a silencer.

That will ensure correct alignment everytime and you can even move it easily between guns.

Dimitrios


 
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Dimitrios
(Login Dimitris76)
YF

I don't think it's that critical

August 1 2011, 4:19 AM 

how large or short the sensor separation is. I started with 1.5 feet and shooting my relatively slow guns through I get an enormous separation between the two peaks on the graph. I could easily make it only 0.5 feet long instead without suffering loss of resolution.Now if you are shooting firearms @ 4000fps through it (not recomended) you might want to extend it to 1.5-2 feet long.

My advice is not to cut down the pipe from the start. Make multiple holes and experiment with gradually shorter sensor spacing and THEN when you are happy with the measuring accuracy, trim the extra length.

NOVAir

Yes the software accepts any decimal value in feet or meters.

Dimitrios



    
This message has been edited by Dimitris76 on Aug 1, 2011 4:27 AM


 
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Jim
(Login Jim027)
YF

Thanks Dimitrios

August 1 2011, 8:06 AM 

This is great info.I have built a few devices using these IF diodes and photo transistors and for those that do not want to get them from salvaged parts they can be bought in matched sets at Radio Shack.
Jim

 
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boo
(Login boohoo9)
AR&P

cool, neat idea !

August 1 2011, 10:42 AM 

You should start manufacturing these low cost chronographs and selling them.
I bet they would sell like hot cakes.

boo

 
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Dimitrios
(Login Dimitris76)
YF

Well... I guess it's too late now

August 1 2011, 2:04 PM 

everybody knows how to make one himeself.

Plus, I have a day job that will generate much more money, if I decide to work overtime!

Dimitrios

 
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Vasco
(Login vfrod)
YF

Re: Well... I guess it's too late now

August 1 2011, 2:32 PM 

Hi Dimitri:

Congratulations, that's a very clever design!
What do you think about using several IR led and Phototransistor, side by side, to enlarge the capture area, not using a tube but other kind of support/frame. If possible you should get a more conventional chrono.

Best regards,

Vasco

 
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Dimitrios
(Login Dimitris76)
YF

You can increase the number of Phototransistors

August 1 2011, 4:28 PM 

that are placed opposite the IR LED.
All the phototransistors should be daisy-chained in-series and the LED pushed further in it's hole in order to light them all simultaneously.

Imagine having the LED at 12 o'clock and 3 phototransistors at 5,6 and 7 o'clock around the pipe's circumference. (or LED at 9 and phototransistors at 2,3 and 4 o'clock, placing the wooden blocks like in the photo above...).

Dimitrios

 
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