Electronic Targets - DIY?

[Synthasy2000]

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.

[jax13]

you would probably be better with a small 12v motor and battery and just make a switch return type that you see in the films on the police shooting ranges.

you'd need a length of suitable wire / cord, a pulley for each and, motor, battery, something to attach a target to.

thats gotta be cheaper and easier than breaking a load of old palms!!!

[Synthasy2000]

...how do they sense the pellet strike position?.

(poor form replying to myself again )

I've read from here http://www.thehighroad.org/showthread.php?t=76580

"All the different types I have seen or heard of use microphones that record the sound of the passing bullet. Impact is then triangulated based on the time it takes the sound to reach the different microphones, usually three or four. There are also microphones at the firing line recording the sound of the shot itself, so that the computer can keep count of how many shots are fired by each shooter, so that any misses or shots fired at the wrong target can be correctly recorded."

So that's one way!

[Synthasy2000]

thats gotta be cheaper and easier than breaking a load of old palms!!!

Where's the fun in that!

With electronic targets it can do the scoring for you and do fractional scores too with instant feedback.

Plus I'm an electronics geek, this appeals to me - there I've said it

[Rutty]

"All the different types I have seen or heard of use microphones that record the sound of the passing bullet. Impact is then triangulated based on the time it takes the sound to reach the different microphones, usually three or four. There are also microphones at the firing line recording the sound of the shot itself, so that the computer can keep count of how many shots are fired by each shooter, so that any misses or shots fired at the wrong target can be correctly recorded."

That's how most of the 1st and 2nd generation systems work, the shot position is calculated by hyperbolic fixing, not as is sometimes claimed by directional plotting. There are new systems coming on the market that employ various forms of optical technology that are said (by the manufacturers) to be more accurate and reliable. All the 10mtr and 50mtr sytems have one thing in common and that is that you shoot at a "black hole" so there is no problem with the sun on the target as can occur with paper.

When I last investigated, the cost of installing a single lane was between £1000-£1500 depending on the system and the bells and whistles you required. With multiple lanes and judicious planning you could probably get the cost down a bit lower. If the price appears high it is because of the accuracy, reliability and consistency that is required of these systems. If you needed a simple Hit/Miss system it could probably be knocked up quite cheaply.

Rutty

[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

[Garry]

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

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.

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

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

Time for a lie down now.

[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!

[barnesr]

Why not use the original palm/laptop set-up but with an airsoft pistol firing the plastic 6mm bbs??

In fact I'm going to try shooting at my key board to see what I can write in word!