I'm working on transmitting audio through light using amplitude modulation of an LED, received by a solar panel connected directly to an active speaker. Something like this:
I only have rudimentary understanding of analog electronics (I work mostly with software), so I'm wondering which transformer that should be used. The schematics I find online are all for a 9v or 3v circuit, but since I need a strong light, my LED is 7W 12V. Is an 8 ohm to 1k ohm the correct one? What's the equations for audio transformers and voltage? I only seem to find voltage converter circuits and equations when searching for this online.
The circuit contains parts I already own (LED and solar cell), but I'm happy to order other types if need be.
Here are a couple of projects using this technique:
http://www.instructables.com/id/HOW-TO-Send-AudioYour-Voice-Over-a-Beam-of-Light/?ALLSTEPS (photoresitor instead of solar cell)
http://asd.gsfc.nasa.gov/blueshift/index.php/2013/01/22/try-it-at-home-turning-sound-into-light-2/ (No transformer)