Do It Yourself Free Space Optics

Parts

Adafruit
- Teensy 3.1, 25mA out $19.95
- Laser Diode - 5mW 650nm Red, 2.8 - 5.2V DC, 25mA max current draw $ 5.95
- Analog light sensor. Vin to 2.3-6VDC, Output up to 3v $3.95