Electronic – sensing light and outputing voltage suitable for audio


I have an idea for a project where I use a pc fan to make an oscillator. The oscillation is created by the cycle of light/dark falling on a light sensor as the blades of the fan rotate.

My initial research points to the use of the photodiode in combination with a op-amp to provide a suitable line audio output. My question is: What are the critical parameters for the circuit?

Here is the datasheet for the photodiode i'm prototyping: http://www.jaycar.co.nz/products_uploaded/ZD1948.pdf


Best Answer

If you just use a 555 timer you won't need to amplify it, you can plug it directly into a line level input (microphone in on computer, aux in on hifi etc). By putting the photocell on the bottom of the fan and a light source above the fan you could get some interesting results. The speed of the fan would create an oscillation, also the 'brightness' (pitch of harmonic content) of the oscillator could be adjusted by changing the intensity of the overhead light source. Amos is right, you could use a very similar circuit to the one in my Posc, I'll draw up an example just give me a mo....