With supersonic rounds, you can pick up on the shockwave as the bullet passes a microphone array. Air gun pellets aren't going fast enough so I used the impact sound._Shorty wrote: ↑Sat Nov 30, 2019 12:16 amVery interesting read! I was wondering yesterday how it was that nobody had come up with a reasonably-priced target system yet, given how cheap technology has become in recent years. Did you ever try the system you'd come up with with .22LR rounds? Or just pellets? I know Jeff, the guy that writes the OnTarget software in the video you posted at the top of the page. A problem with using paper impact sounds is obviously the paper could be gone for the next shot. A steel plate obviously gets around that problem. Some commercially available targets solve that with a rubber roll that you have to replace now and then. I see there are also laser targets available now, but I'm not sure how those function. I'd really like to know which targets Eley uses at their ammo test ranges, as it sounds like they're using something similar to the scanner idea.
Yes, you could damp the plate, I just used a really thick plate I had to hand, 1/2 inch I think._Shorty wrote: ↑Sat Nov 30, 2019 11:49 pmYeah, I shoot subsonic target rounds in 22LR, so the supersonic method wouldn't be of any use in that case. How thick of a plate did you find was sufficient for pellets in order to stop the ringing? I imagine a sheet of Dynamat from a car audio supplier would also help in that regard. Stick it to the back of the steel. They're designed to stop the sheet metal in a car from resonating and adding/altering the sound you hear from the stereo.
As for ultrasonic sampling, I imagine you could also run into limitations of the microphones, depending on what you use.
That's similar to what I tried to do, the detector is easy, it's the scanner bar out of a flatbed scanner. In order to cast a shadow that is directly in line with the bullet, the light beams all have to be exactly parallel (colimated). Thats the tricky bit._Shorty wrote: ↑Mon Dec 02, 2019 3:38 amhttps://www.meyton.info/en/measuring-pr ... index.html
Too bad the small one is 4700 Euros, haha. Interesting concept, though.
I just wonderd what materials would transport sound slower than air and found that sound in rubber apparently has a speed of only 60m/s . Now I imagine getting a clear signal from material like rubber will become the problem - but if that would be solvable, you might come down the required resolution? Maybe other materials with sound speeds much lower than air exist?richardtheboffin wrote: ↑Sun Apr 28, 2019 5:20 pmAs the pellets are subsonic, I was detecting the impact with the plate. Initial experiments with piezo's on the plate is not much use as sound travels fast in the steel.
A pellet travelling at 200m/s takes 25us to impact from first initial touch to completly squashed flat. The sound wave comes out during that 25us.
Possibly. I guess if the sensor is down the end of a tube so it can only 'see' directly ahead, it will only detect pellets directly in line with it. Not sure how consistent the shadow being cast will be, when the pellet is near the light source. It would obviously be better the closer it is to the detector._Shorty wrote: ↑Fri Dec 13, 2019 7:03 pmThat’s why they used a replaceable roll of rubber.
I’ve been thinking about those Meyton targets. I don’t think they’re using lasers or any collimated light source at all. I’m betting they’re simply recessed LEDs so you get a cone of light that only reaches a certain number of the sensors on the other side. Their beams figures likely relate simply to the number of photocells they’re using. I don’t think it is the number of light sources.