Electronic Targets - DIY?

[magicniner]

Another crazy idea of mine

I had a thought that it would be possible to use an old Palm PDA (like a Palm VX - about £10 off the bay of e) as an electronic target. You'd need someway of reducing the pellet power to that of a stylus tap. I'm not sure of that bit but some kind of absorbant material. A small bit of Palm software would be needed to translate the tap position to serial code for the serial port (not USB!) that these old Palms have. You then link the serial port to a laptop (old cheap one again) near you to use as the scorer and display. Again some software needs to be written here.

I have images in my head of many shot up Palm PDAs whilst trying to select an appropriate pellet absorbing material. Mind you you could use an iPhone or iPad

Has anyone used the currently available professional electronic targets and how do they sense the pellet strike position?

Are they worthwhile?

Thanks for your thoughts.

Re. your Palm idea -
How about a matrix of say 50mm long 3mm round steel rods with 10mm long 4mm square ends passing through a plate with 3mm clearance holes at 4mm grid centers. The flat area made up by your square sections will be the target surface.
With springs between the heads and the plate you can limit movement, use a second plate with the same pattern of round holes but half the depth filled with O ring cord and the rod ends able to just hit the cord - the other end of the cord touching your touch screen
I accept no responsibility for any frustration/insanity/self harm resulting from attempts to implement any wild ideas I may throw out.
Regards,
Nick

[Adam77K]

How about a matrix of 2 mm square plates, each row and column carrying a slightly different voltage, but having some hard insulating substance between that can resist a pellet strike. A pellet strike would very briefly make a circuit between adjacent plates. The voltage would be proportional to the distance along along the x and y axes, and the position of a strike could be plotted from the voltage recorded across the plates hit.

Baked, or half-baked?

[Synthasy2000]

Thanks for all your answers, it's certainly food for thought.

Matrices seem quite intricate to engineer and I was looking to take short cuts here for price and laziness reasons

For just fun gunning you could make a target of metal concentric rings matching a 10m air pistol target with microswitches underneath. There's no way I could fabricate something like this as my metal working skills is basic at best. But I think this can be cheaply done with the right tools. There maybe something on the market like this already.

I thought about tiny little computer keyboards like on mobile phones/blackberries too but I was hoping to get to a professional 0.02mm hit resolution. This can be achieve with 2000 DPI resolution and graphic tablets do have this. However, graphic tablets always seem to require a special stylus to "complete the circuit" so a pellet strike would not register.

I've also thought about using laptop touchpads to register hits. You need to put the software driver in absolute rather than relative mode so you get a direct X/Y readout (absolute) as opposed to where it last left off (relative). All laptop drivers are in realtive mode so you can move the cursor from one end of the screen to the other using several wipes across the touchpad. This is no use for this application.

I just think you can make and sell an electronic target the equivalent of the professional systems for about a third of the price (£300 to £500) with certain caveats. This might make these targets within in reach of more clubs.

I know the systems I am proposing would only be suitable for 6ft/lbs or less or maybe with a change of impact absorber 12ft/lbs rifles. Bullets would be out of the question which is where the acoustic detection method is king. But ruling that out means a cheaper method can used.

[magicniner]

The reason I suggested a matrix is that any re-useable sheet material which would modify impact would throw pellets back nearly as fast as they came in and would spread any pressure applied, a steel matrix would absorb energy and transmit movement to a limited area.
I suspect you underestimate your capability and the functionality of hand and basic power tools, I feel sure you could make the circular target you describe without machine tools, before I began to build up a machine shop I stitch drilled, hacksawed and filed to shape inlet and exhaust manifold plates and many other relatively complex parts, have a go, I'm sure you'll be pleasantly surprised
Laptop touchpads use a matrix of crossed wires embedded in polymer and respond to the presence of a field modifier (the water in your skin) and not pressure, try using one with a plastic rod - it won't sense it.

[Synthasy2000]

any re-useable sheet material which would modify impact would throw pellets back nearly as fast as they came in and would spread any pressure applied

Excellent point #1 made here. I know I was looking for an almost magic material here like a metal mesh. Rubber was not going to be used but I'm sure the material exists but NASA probabably doesn't want to release it!

Laptop touchpads use a matrix of crossed wires embedded in polymer and respond to the presence of a field modifier (the water in your skin) and not pressure, try using one with a plastic rod - it won't sense it.

Excellent point #2 made here. You have to dip your pellets in water first! No wait

Touchpads out then.

Right, now I'm investigating linear photodiode arrays and going optical. One array in the X-axis and one array in the Y-axis should do it. The current linear CCD arrays I've looked at are a little too slow though to notice a pellet crossing their path.

From my Government Approved "back of fag packet" calculations (tm) worst case, a 5mm long pellet travelling at 800 ft/sec (12 ft/lbs) will take about 20us to cross a linear sensor. So I need to sample that sensors at a 50kHz line rate. If there are 512 sensors in the line then I need a 25.6MHz pixel rate.

You can get sensors matching that rate but you don't get many - a 512 pixel array only covers 1/4 inch of target. There are larger arrays up to 2048 giving over an inch but the line rate drops proportionally to 20kHz. The figures are out but not that much out.

I think optical sensing is the way to go. More robust for a start although more expensive.

[Toecutter]

Why not just use or make a projector & project a target onto a white background/wall etc
Toecutter.

[magicniner]

Why not just use or make a projector & project a target onto a white background/wall etc
Toecutter.

Now there's an idea,
follow through & tell us how we're deciding what we hit?
Regards,
Nick