LED as a Light Sensor and more....

Recently got interested in the use of a normal LED as a light sensor. Its amazing, but there seems to be some conspiracy on the part of the electronics professionals, in keeping this interesting and wonderful physical phenomenon, hidden from public. Or is it ignorance?

Just take a normal voltmeter (or a digital multimeter) and connect the two terminals of any (say red) LED to the voltmeter. Cover the LED with your hands and note the voltage on the voltmeter. It should read close to 0. Now expose this LED to bright light. What do you observe?


The only book that talks about this is by Forrest Mims.

We just published a Design Idea in EDN on this topic.

The natural extension to the idea of LED as a touch sensor, is to use commonly available 5x7 or 8x8 LED matrix displays as a touch panel. We have been toying with this idea for some time now and have made some interesting progress. Its not very straight forward, but we are getting there...



Dhananjay Gadre