Hopefully someone might have a lead/idea on this, hopefully someone has come across this while working on EM switches, etc.

I'm looking for some sort of sensor that will measure the relative force of an object hitting a wall.  Here's the background.  I'd like to build something similar to this:

http://bounceonair.com/TopShot_hockey.htm

I'd like to start with just one panel, and having a simple contact isn't a problem, i.e. you hit it and the light goes out.  In addition to that however, I'd like to some sort of meter to display the force of the shot.  The reasoning is that I would like to make it more fun for the kids as well as a teaching aide.  You can tell them until you're blue in the face that one way will work better than the other, but unless they see the results it's an uphill battle.  At least with my kids.

I'm not looking for something that will measure the exact force, just an amount of force relative to the next impact.

Any thoughts? Thanks.

Given that force is a funciton of mass & speed, with a constant mass, you could just measure the speed.  (easier said than done) but if it were a mass travelling on a constant path (like the surface of a shuffle board) then you could use two optical beam sensors to measure the speed between one sensor and the next.  Just an idea.

Now, how about a scale that has a Min/Max function?  If it could operate vertically and it was sensitive enough (and could take the force being exerted) you could measure the maximum "weight" of the impact?

You might be able to use a piezo sensor. My brother made some electronic drums using piezos scavenged from something at the dollar store (greeting card?). The sensor is placed under the center of the drum head with piece of foam between. Striking near the center of the drum or with more force produces a higher "volume" signal from the sensor. Seems like it might be suitable for your application.

I had thought of the scale option as well, a simple spring scale would do I think, the problem is that it or things like it would just record the max as you point out.  If you want to see the individual results, you'd have to reset it all the time.  The key thing here is that it has to be easy/fun for the kids.

I've looked a bit more and I think that an accelerometer is the way to go, the question is how to interface to it.  I'll look more, but I think hacking a Wii remote may be the way to go.  I've also found some info on connecting them to a PIC, which would be neat/portable, but I'm also ok with a USB interface a dedicating a PC to it.  Sadly, they are cheaper than any other displays....

Tiny, I'm not sure that the piezo would work in this case as they operate based off of deflection.  Hmm, wait, maybe if they were mounted perpendicular to the surface....

Either piezos or an accelerometer, I think the question now is finding an appropriate A-D board to connect it to the PC.  I think I've come to the conclusion that I could make it more interesting if it was on a PC.