Control of peltier device by adjustable power supply

In order to better control the cooling effect of the 12 volt peltier device and avoid possible thermal shock to the CCD chip by too rapid of a cool down or warm up, I purchased an adjustable power supply as shown below:

Adjustable Power Supply - $19.25 new on ebay

The power supply has selectable voltages of 3, 4.5, 6, 7.5, 9 and 12 volts DC, all at 2.0 amps. The procedure I use is to start cooling at 4.5 volts, switch to 6 volts after about three minutes and switch to 7.5 volts after about another three minutes. I have found that a maximum cooling of 35 degrees fahranheit below ambient is acheived for my converted greyscale quickcam with a single stage peltier when operating at 7.5 volts. Higher voltages provide slightly lower temperatures initially (about two degrees F) but then the CCD temperature begins to climb about 10 degrees F. After an observing session I reduce the voltage in a like manner to ease warmup of the CCD chip and leave the fan running after voltage goes to 0V.

For field use I plan to use the adjustable power supply with a 12V DC to 120V AC converter and a 12V marine battery. I have not tried this yet but I expect it will work okay.

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