Today I built a laser pen solar panel audio transmitter thing – using these two sets of instructions – for the most part:
- http://www.wikihow.com/Transmit-Audio-With-a-Laser-Pen
- http://www.instructables.com/id/How-to-Send-Sound-using-a-Laser/
It works great, but I should have used a battery case instead of soldering the batteries together.
Built it into a Sparkfun box:
The next step is to experiment with filters – like an aquarium for example.