Electronic Targets - DIY?

[Synthasy2000]

I've been trying to come up with ideas for this today, so here's my contribution

Thanks GarryP

It might be possible with a keyboard membrane type arrangement behind some concentric metal circles which are heavy enough not to rebound the pellet. Getting a suitably arranged membrane might be a problem though.

I came up with something similar but this really only tells you you hit a 9 ring or and 8 ring somewhere but not where "exactly".

Another idea is circles again, with piezo transducers on the back of them to trigger a hit signal.

More reliable\consistant than membrane switches or micro switches but hard I think to obtain suitable transducers?. I haven't looked at piezo transducers and I only know of the large coin sized disc ones. It may be difficult to isolate which ring has been hit.

Also, this again severely quantizes the pellet strike position. A hit that clips the 7 and 8 ring is given the positional equivalent as a pellet that strikes the 8 and almost the 9 ring. Yes, this is what happens in scoring but you won't get the sort of postional feedback of your shot.

Or a single plate with 4 piezos or strain guages on the back, and measuring the voltages to triangulate where the pellet hit.

This is the best yet and I considered it. You are either looking for time differences in the received signals to give the pellet position or perhaps the differences in the signal amplitude.

If the time difference method is used, like the current system of microphones and pellets in air, then there are problems too. The speed of sound in steel is about 6000m/s compared to 343m/s for sound in air.

The worst sensing case is a pellet hitting the plate sending waves to the sensors that are different to only 0.02mm. This is the current level of resolution I believe for electronic targets in NSRA use today. I'd need timing resolution of no more than 3ns. That's 300MHz sampling which is very high. I could use less precision and get the sampling rate down but then it would be better to use the 17 times slower speed of sound in air where 0.02mm needs a sampling rate of 18MHz which is doable. But then I'd need sensitive microphones now and not cheap piezos.

If the signal amplitude method is used where the further the sensor is from the pellet hit the more attenuated the signal is and vice versa. Also it assumes that the sensors would give the same output for the same input for all 4 sensors. This would require delicate calibration and I feel that the attenuation of the signal over target sized proportions is very slight so lots of gain will be needed to highlight the differences leading to noise and then uncertainty i.e. error!

Time for a lie down now.

You've earned it and your contribution was gratefully received.

Paper really does have a LOT going for it!