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Topic: Extend Pulse from Op-Amp/Photodiode combo? (Read 14624 times) previous topic - next topic

jremington


polymorph

Well, the ATTiny's input resistance is -very- high. You may be able to drive it directly with the photodiode.

Seems backwards... You haven't told me yet if you have the scope on AC or DC coupling. It seems like the photodiode should be keeping the Op Amp input LOW as long as the LED is shining on it, and go HIGH when the coin passes.

Try this: Photodiode cathode to ground, anode to ATTiny input. 100k potentiometer across it wired as a variable resistor. Check with the scope to see what is happening.

Another way to try: 100k pot from 5V to ground. Photodiode cathode to pot wiper arm, anode to ATTiny input. 1M resistor in parallel with photodiode.
Steve Greenfield AE7HD
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