Cardboard Bullet sensing target

Thread Starter

alden_45

Joined Jun 23, 2017
2
Several companies are coming out with cardboard/foam targets that can sense when they are shot by metallic ammunition, and in what section. They are using conductive layers on the targets.

I tried using aluminum foil as my layers (as a switch essentially) and the GPIO on a raspberry pi, but the bullet travels through too quickly. E0514E00-23FF-40BE-B238-4C0D6E8D7ED1.png32C87556-61B5-467A-A759-032C063D85E0.jpegEA8AC347-BAE4-4CA4-9EF2-E0B7820F32F0.jpeg

Any ideas on how they are making this work?
 

Externet

Joined Nov 29, 2005
1,531
A piezoelectric disc glued to the cardboard will surely produce a spike for every hit. Until the bullet hits the disc. But can be placed at a far corner.
 

visionofast

Joined Oct 17, 2018
71
very short spike is known as impulse in circuit theory and you can convert it to a durable pulse by an integrator circuit.
usually an RC circuit will do the trick.also known as debouncing circuit.
 

Hymie

Joined Mar 30, 2018
849
If the short time connection (due to the pellet penetration) between the two conductive planes in the target take pin 2 of a mono-stable 555 timer circuit low – I think this would work.

The timer time period could be set to say 5 seconds, giving an indication of which target area has been hit, after which it would be automatically re-set ready for the next hit – with a separate 555 timer circuit attached to each desired target area.

The timer circuits could be attached to the target areas via crock-clips; once the target area was shot to pieces, the timer module could be easily attached to a fresh home-made target. Such a circuit could be powered from a 9V battery making it ideal for outdoor use.
 

shortbus

Joined Sep 30, 2009
7,857
I tried using aluminum foil as my layers (as a switch essentially
If it was standard household aluminum foil it probably isn't strong enough to stay in contact with the bullet as it passes through. Something a little thicker would be needed. Something that extrudes before punching through. Something like aluminum roof flashing.
 

Hymie

Joined Mar 30, 2018
849
Some experimentation might be required to determine the optimum separation distance between the two conductive layers and the physical nature of the conductive substrate (as shortbus recommends/notes).

Besides the projectile successfully triggering the detection circuit – the target assembly should be such that the two conductive layers are not permanently short circuited as a result of the projectile passing through (although I suspect that this is what renders the commercial units inoperative after 100+ shots).

By my calculation; a bullet 25mm in length travelling at 1000m/s would take 25μs to travel its length – plenty of time to trigger a 555 timer.
 
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