LM317T Voltage Regulator with Pass Transistor

I built this in my spare time in an afternoon. I had an old DVD writer that I dismantled to pull the laser diode out of (you can find other videos on Youtube showing how to dismantle the DVD writer). I had bought a couple of 10mW laser modules for $6.95 each a year ago and hadn't made use of them yet. They were perfect for this as they had their own heatsink already and a nice focusing lens and the same diode package as the DVD writer so just popped the 10mW one out and press fitted the replacement diode in. Rough estimate of 300 mW based on 300 mA and 3V for the laser which is 900mW total power and assuming 30% efficiency. Believe red laser diodes have around 50% efficiency but this is an old unit. Will test it with a photometer I have at the office later. Takes less then 2 seconds to burn through a plastic CD case. The aluminum case works as a heat sink for both the laser diode assembly and the LM317T driver. If doing it this way be sure the LM317T is electrically insulated from the metal case with silicon or mica transistor spacers as the tab on the 317 is the output and the case of the diode is at ground, else you will short it out.



http://www.youtube.com/watch?v=nUF_eH6JjUw&hl=en