sensing high speed movement

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smurff

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Hi all,

I am an avid airgun user and I am bored of shooting the average paper printed targets. So I was thinging of making some games. E.g. speed shoot metal targets that knock down and I could time them with a PIC etc.

But I would like to create the paperless target. So I had an idea of creating a bank or lasers from laser pens to some LDRs and then sense when one is broke by a pellet and then recording which one was broke etc. One set for vertical and one for horizontal. the problem is that a pellet is so small I am not sure I could have so many LDRs together to make sure I collect the 3mm pallet as it passes.

Anyway I am stuck and would like to see if you guys had any ideas?
Thanks for your time
Danny
 
That's gonna be a heckuva problem. It's a matter of sensor resolution. The only things I can think of that would work is a linear CCD that can be salvaged from a digital copy machine, but it won't be easy to use. It's not a trivial project, and you will do ALOT of reasearch before you have a working project.
 
Hi BrownOut,

Thanks for the reply. Yes I thought so too. Its not easy but I got married the other week and now I need a hobbie otherwise I will have to talk to the wife

Then how about a bank of small LDRs, one light shining on them in a box, the PIC takes a calibration reading. Then fire the pellet and see which of the LDRs resistance changes. It may not be accurate but I wonder how good it will be?

Cheers
Danny
 

resolution is a big problem... while you could use a simple camera, the volume of data far exceeds the capacity of ANY PIC.

an "inexpensive" HD sensor ($30), can capture full res (2592H x 1944V) at 14 frames/second for a 98MHz PIXEL rate.

what you are proposing would require an FPGA to read the target coordinates and relate just the coordinates to the PIC. at least you can probably arrange for it to be simple math as opposed the the project I am working on: **broken link removed**
 
Atually, there has been nothing of the sort proposed. I said a linear CCD, not a full 2-D array. After more thought, I realize the event just happens too fast to be capured. I see no solution for optical target sensing.
 
Neat idea, don't give up yet. It just needs some thought.
 
BrownOut said:
Atually, there has been nothing of the sort proposed. I said a linear CCD, not a full 2-D array. After more thought, I realize the event just happens too fast to be capured. I see no solution for optical target sensing.
Click to expand...

i see now. i misunderstood the question.

for the sake of argument for a 1000ft/s velocity and a 1/4" sphere the arrays would have to be read 100,000 times per second to be marginal.
 
So how do you think it works? Maybe it could be expanded for "MORE POWER".
 
ronv said:
So how do you think it works? Maybe it could be expanded for "MORE POWER".
Click to expand...

piezo sensors along the edges would do it. latch on to the first one to respond gives the strike location on a given edge. if you are really clever and have a lossy target material the first to respond would be the location and the peak output could register a distance.
 
I was thinking about a contact membrane. But it would need to be both flexible and tough. Don't know what material would work though. Perhaps some of the new "memory" materials????
 
Last edited:
How about the piezo idea with 4 or 5 metal rings around a bulls eye put together with say silicone (as a damper) holding them together. Each ring with its own piezo.
 
ronv said:
How about the piezo idea with 4 or 5 metal rings around a bulls eye put together with say silicone (as a damper) holding them together. Each ring with its own piezo.
Click to expand...

silicone gap would have to be less than half the diameter of the pellet and would still take a beating. at that point you could however simply use a small piezo pickup and sense the impulse created from the hit.
 
Ubergeek63 said:
i see now. i misunderstood the question.

for the sake of argument for a 1000ft/s velocity and a 1/4" sphere the arrays would have to be read 100,000 times per second to be marginal.
Click to expand...
The readout may not have to be that fast. There is a way to read out the CCD at a more normal rate (say 50-100 times/s or even slower depending upon the sensitivity you need).

A CCD detector well will store the image it has captured for some significant period of time until it is read out. Suppose you illuminate the bullet area from the same side as the CCD with a string of narrow angle LEDs so that it can detect the reflected light from a bullet passing through. So you would periodically read out the CCD to see if and where is has detected the reflection from the bullet (you don't really care exactly when). The peak detected signal would be the location of the bullet on the linear CCD.

The difficulty would be protecting the CCD from significant stray ambient light so it wouldn't saturate the CCD well while it is waiting to see the bullet.
 
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