[rcheshire (Rowland)]

A little more progress. Managed to fry a mosfet while experimenting with various snippets of code. The digital pin needs to be declared OUTPUT to drive the gate, otherwise, it floats around in no particular on/off state.

The chart shows the performance of the system using a basic time-on time-off milliseconds along the bottom of the chart. The values shown are the analog readings of the temperature sensors. Air temp was about 18.5C the lowest cooling -8.7C. Both temperature sensors were checked against another source for accuracy, within 0.5C. Very quiet, stable method, unlike PWM.

The curve is not unlike that posted elsewhere in the myriad of DSLR cooling threads, and idles down at about 1 - 1.5 amps. To get more cooling I halved the time-off. The limit is about 4 - 5 amps at which point a sharp rise in temperature is indicated. At 4.5a x 13.5v The heat sink/fan combo is somewhere around the 120 watt mark, which is the TEC rating x 2. The system is limited to 6 amps, nominally 12v.

Maxed out at 27.5C differential. Time to get Glen's Argon bag going.

Now to write the code around the curve. It really is walking pace. The mosfet gate is off for a long while so cooling is not an issue.

EDIT: Heat sink 120w - changed in post. 2x the TEC rating to accomodate the power driving the TEC on top of its cooling power.