Let's Make Robots!

Using LED's as touch sensors awsome video!

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Here's a brief post on Make website that gives a little of how it works, some timing anyway. Looks like 2 IO, one on each side of the LED, alternately switched forward biased (lit) for a ms, then reverse (off) for a ms, then read the cathode (input). Here's video showing something similar.
I can't give you a schematic or anything but basically a LED is a photodiode, as far as I know this was done with a pic processor. I'm waiting on parts so I can have a go at it.
how does this work....this looks really cool btw!
In the case of a 4 by 1 matrix of LED's, imagine lighting the first and third diode while sampling the voltage developed across the second and fourth. And then doing it the other way around, alternating really fast.