[757labs] Piezo Glass Thumpin'

[telmnstr at 757.org]

AJ, Enferex, Skhisma and I were watching some Alex Jones flick and talking 
about stuff. An idea came up. There are some examples of similar tricks, 
but not really used in this manner.

The idea is this.

Attach a few Piezo sensors to the back of the front window, then project 
on a rear projection surface. Use microcontroller to track light taps on 
the glass, use the time to figure out where, and wala, cheapest 
controllable display evar.

Looking at something like these which cost $14 for 8 of them:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120550367693

But the issue is, it might be, that there is a circuit in the box with the 
sensor that halts output unless a high threshold is hit. Or perhaps it's 
tuned to a specific frequency.

It's also quite possible to use the raw component I imagine.

People use the piezo transducers to build their own drum triggers 
(electronic drum pads). According to random web page, a popular one:
Radio Shack Piezo Transducer (273-073A).

Thoughts? Any guesses if this will work? Don't want people hitting the 
glass too hard. Would be sweet if it could detect a gentle tap.

I assume it will false.