Ballistics Chronometer

[Ken Geis]

Anyone have any ideas on how to design/build a ballistics chronometer? I'm interested primarily in tracking my handloads for my .22 Hornet Ruger rifle, but it might be handy for my BB gun and even arrows too. I'd like to store the shot data and be able to download it to a pc and do some stats on the results from the range. Phototransistors sound like a good start. But what kind? How might I calibrate the thing, by laser doide maybe? How do you link the sensors to the data stroage device, and make it useful for outdoors on a hot (90 deg F) sunny Florida afternoon in 85% RH? Power requirements?

[josmith]

http://www.oehler-research.com/<p>Check out a real one.

[Ken Geis]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by josmith:
http://www.oehler-research.com/<p>Check out a real one.<hr></blockquote>

[Ken Geis]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by josmith:
http://www.oehler-research.com/<p>Check out a real one.<hr></blockquote><p>Joe,
Thanks for the web site. I looked at it for a little while and it looks like a nice machine. I don't know if I'll spring for one. I'm still interested in the do-it-yourself challenge of making one. Do you own one and which model?
Ken

[josmith]

I don't own one,I hear they work well.<p>I get that you want to build your own. The timing part shouldn't be too hard but the sensors will be a challenge.

[Ken Geis]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by josmith:
I don't own one,I hear they work well.<p>I get that you want to build your own. The timing part shouldn't be too hard but the sensors will be a challenge.<hr></blockquote><p>Joe,
I've read the same from people on other sites who do own one. I may not be able to build one as complete with features, but should be able to get the basic functionality and accuracy from a homebuilt one at a fractuion of the cost. Sensors are 5 bucks apiece, tops. Chips or IC's, displays, etc. may be a different matter. Should be fun though. I have Elect Engineering friends and computer geek friends who can advise me. I've been reading a BB called PIC list for controllers information but have a lot to learn about those yet. Anyway, I'm enjoying the research so far. Thanks for the replies.
Ken

[toejam]

so you want to build one? Ok the first thing you must do is get the projectile to trip a flip flop. I would starte by wiring a jk flip flop to toggle.A good referance to start with would be Forrest Mimm's handbook for engineers availabe through NV.Next I would wire up a photo diode in series with the necessary voltage to allow it to trigger the flip flop.The next part will be tricky. You will have to position the photo diode with a light source focused on it so when the projectile crosses the path between photo diode and light, the flip flop will toggle.Than make another light diode set and place it a foot away from the first.Now you will build a counter described in that hand book and a pulse generator (also there).Now you will have the flip flop enable the counter which is counting the pulses untill it changes state.A little math will do the rest.That handbook should be able to get you through it all.

[Ken Geis]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by toejam:
so you want to build one? Ok the first thing you must do is get the projectile to trip a flip flop. I would starte by wiring a jk flip flop to toggle.A good referance to start with would be Forrest Mimm's handbook for engineers availabe through NV.Next I would wire up a photo diode in series with the necessary voltage to allow it to trigger the flip flop.The next part will be tricky. You will have to position the photo diode with a light source focused on it so when the projectile crosses the path between photo diode and light, the flip flop will toggle.Than make another light diode set and place it a foot away from the first.Now you will build a counter described in that hand book and a pulse generator (also there).Now you will have the flip flop enable the counter which is counting the pulses untill it changes state.A little math will do the rest.That handbook should be able to get you through it all.<hr></blockquote><p>Toejam,<p>Thanks for the advice. I'm getting somewhere with this thing. Called a local electronics distributor who said to call the manufacturer named Fairchild Semiconductors in CAL. The tech explained that photodiodes are about 3 orders of magnitude slower than phototransistors (maybe I have that reversed) so one will be much better than the other for a 4,000 foot per second rifle bullet. Timing needs to be down in the thousandths of a second, and the slower sensors only have rise times of the same magnitude, so I suspect resolution would be better with the faster sensors. Four feet divided by 4,000 feet per second = 1/1,000 s between sensors. I also learned that commercial makes sperate their sensors by about three or four feet. Some of the less expensive models use diffusers to create an even background against which the sensor can see the bullet. It looks like a white strip of plastic under which the bullet passes, above the sensor, held by two wire rods diverging up and out from the sensor. They work best in noon day daylight. For odd angles of sun position, IR emitting light sources and IR sensors are better. What is NV? A jk flip flop? Focusing is not a good idea because the beam needs to be wide enough to discern a tiny 1/4 inch object moving a foot above the sensor in sometimes slightly different positions (depending on my shooting ability). I'm not sure a pulse gen is needed because the voltage or current signal generated from the sensors should be all that is needed as a difference (is that correct?).<p>Ken

[toejam]

ken;
hi, by nv. i meant nuts and volts magazine.A flip flop is a basic memory device that changes state from on or hi to off or low when a pulse is delivered to it . To determine if the bullet is tripping the photo diode or transistor you can wire the sensor with a power source to the input of a flip flop and when the sensor is tripped the flip flop will have changed state which can be indicated by an led connected in series with a resistor to one of the outputs of the flip flop. Once you adjust the emitter sensor combination to insure constsnt tripping on both ends, individually, you can use the outputs to enable the counter till the sensor on the far end is tripped.The frequency of the pulse generator as well as the distance of seperation of the sensors will determine tha accuracy of the device.The engineers handbook has all the circuts needed to construct the device and gives you an easily understandable explanation of how everything i outlined works.I suggested a jk configured as a toggle to simplify the wiring this allows you to wire both sensors in parallel.
tj

[Ken Geis]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by toejam:
ken;
hi, by nv. i meant nuts and volts magazine.A flip flop is a basic memory device that changes state from on or hi to off or low when a pulse is delivered to it . To determine if the bullet is tripping the photo diode or transistor you can wire the sensor with a power source to the input of a flip flop and when the sensor is tripped the flip flop will have changed state which can be indicated by an led connected in series with a resistor to one of the outputs of the flip flop. Once you adjust the emitter sensor combination to insure constsnt tripping on both ends, individually, you can use the outputs to enable the counter till the sensor on the far end is tripped.The frequency of the pulse generator as well as the distance of seperation of the sensors will determine tha accuracy of the device.The engineers handbook has all the circuts needed to construct the device and gives you an easily understandable explanation of how everything i outlined works.I suggested a jk configured as a toggle to simplify the wiring this allows you to wire both sensors in parallel.
tj<hr></blockquote><p>TJ,<p>Thanks agian! I'm going to run your suggestion by one of my computer buddies (Rob, his email is [email protected]). My email is [email protected]. He speaks more of that kind of language, knows a little about pricing chips, and the book reads like a great tool for tinkerers like us.<p>KEG