I've been working on creating a laser harp, following the posts made by 'Genesis' here:
His beam detector circuit works with a photodiode sensing the reflected light from a laser beam - basically when the performers hand breaks a beam, it is reflected back at the diode. His detector is here:
...and the timing on his laser blanking signal is shown here:
(The blanking turns the laser on and off, and is the lower trace on the scope - based on what I see I would say the frequency of the laser modulation is about 500Hz).
I get to talk to the guy once in a while, and during our last conversation he said that the detector circuit is tuned to the laser modulation, and so can reject daylight quite well. Does anyone know how this is achieved?
I would guess that it's the caps in the opamp feedback - but how are the values calculated?