I am building a laser projector using a red DVD diode, a blue diode from the casio projector, and a green module. Because I want to be able to run as long as possible without turning the projector off I decided to use a TEC for every laser in the system. The TEC will electrically isolate the red diode and green module as well so they will serve another purpose. The TEC will also stabilize the green module, hopefully enough that I will be able to run it with full analog modulation without it changing modes or any other weird things! Also, the red diode decreases in wavelength the cooler it is run making it appear brighter which will help even the color balance out nicely.
I need some kind of controller for my TECs, I can't direct drive them as condensation would likely be a problem. Also, as I mentioned above, each diode/module has a temperature it will work best at, for example the green module will most likely work best at around 25c, the red diode would be best as cold as possible, and the blue diode should be held stable at 15-20c. The base of my projector is going to be the "hot" side of the TECs as well so I can't go too crazy as I would have no way to get rid of the heat from the TECs.
Is there a simple solution for an adjustable temperature dependent TEC driver? From my limited experience with electronics I thought about a transistor and a thermistor but I do not know if this setup would be stable enough for my project. Does anyone have any insight or experience with something like this?
Here are pictures of my progress so far...
This is the setup, all three lasers going foward to flexible mirror / dichromatic filter stands. http://img594.imageshack.us/img594/3327/wholepo.jpg
This is one laser assembly, the TEC (30x30mm) is sandwiched between the base and the top block. The top block was machined to a specific depth to keep the laser perfectly level with the mirrors of the galvos. The mounting bolts are sleeved with nylon bushings to keep the laser unit thermally and electrically isolated. http://img853.imageshack.us/img853/3087/tecj.jpg
Currently I have no laser drivers with any modulation so there is no "blanking" which makes things look like a garbled mess. I did manage to draw and scan a simple smiley face though!http://img853.imageshack.us/img853/4645/facef.jpg
Thank you for looking and sharing!