Touch Switch

alnajjar1

Hello,

We have a project at our Museum where kids can touch large plastic translucent plexiglas to turn an ultra-bright LED source underneath it. It is a simple interactive to improve little kids gross motor skills.

The plates are 3"x3" 1/4" plexi, and I want to make them act as a switches without any movement. I thought of use a flex sensor but little kids exert very little pressure with there hands. The plan cannot move. Putting a push button next to each plate defeats the purpose of the exhibit. I have used (and seen) capacitive touch switches in the past but not to "charge" such a large plastic surface.

Any idea how to do this reliably? are there any examples of how it is done with a BS2?

Many thanks,

Al

Tumbler

This should work:
http://www.atmel.com/products/touchsolutions/bsw/qtouch.aspx

Crazyrabbit

I just started playing with some IR reflective phototransistor sensors. They are cheao on ebay and have around a 1/2" range..

http://www.ebay.com/itm/140932028945?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

erco

I hate to suggest a non-Parallax chip, but since others are suggesting various other hardware:

The new PicAxes have built-in capacitive touch sensor support. Basically you have a metallic pad (could be a metal plate, foil, almost anything) behind an insulator (no finger contact to the metal) and it returns a reading which varies widely when a hand or finger is near. Here are some of my experiments with a $4 20M2. The three pennies are behind a layer of package tape for insulation:

http://www.youtube.com/watch?v=F8fKZ4A6mto

http://www.youtube.com/watch?v=3e92B8JNNns

Tracy Allen

Since an LED is already involved, it might be possible to use the dual nature of the LED as a photodiode. Here is a thread that has programs for both the BASIC Stamp and for the Propeller.