LEDs as light sensors
Forrest Mims is somewhat famous for using LEDs as light sensors. I wanted to try this myself:
It seems to work reasonably well with a transimpedance amplifier and a 100M feedback resistor. I was using the LED from a torch (as it was the only clear LED I had to hand). The response time was surprisingly slow. I kind of wonder if the torch LED module has a decoupling cap in it (and also a current limiting resistor) so I’ll try this experiment again when I have some proper LEDs…
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