Electronics > Beginners

First Tinkering Project

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Colfaxmingo:
I think you should be operating your receiver like a Class A amplifier.

You want it conducting all the time and modulate it so that it swings between the rails but doesn't distort.

selkathguy:

--- Quote from: SeanB on January 07, 2013, 06:18:13 am ---You might want to try using a IR LED as both transmitter and receiver photodiodes. No visible light though, but they do switch fast.

--- End quote ---
Bingo.  Infrared diodes.  Thank you.  Changed the code a tiny bit and had to lower the TX output voltage (thank you LM317) didn't touch anything else with the circuit.  Didn't change the R/C characteristics or anything.

Yellow: Transmitter Diode voltage
Blue: Receiver ADC input.
Compare this with the image a couple posts above...

selkathguy:
Didn't quite like that startup on the transmitter, it was causing the IR diode to have a <40% duty cycle which was messing with recovery at the receiver.  So I removed the electrolytic from the LM317's adjust -> output, and the regulator no longer suffers the significant startup time and the duty cycle has returned to 50%.



Furthermore, the receiver now reports less than 0.2% error in recovery.  Problem is I've now lost the benefit of range that the laser had.  Hmm.

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