[rcheshire (Rowland)]

The Eagle circuit is a plate of spaghetti and perhaps it would be wise to draw each sub-circuit first. Time, I guess.

There is a way to handle switching the TEC during manual temperature setting, with software. So, rather than use a hardware switch, I will use the MOSFET and delay cooling a few seconds with each button push. If your not pushing buttons then you must be cooling - if the thing has power. Otherwise, off is off at the power point.

For the Arduino people, I'm pretty sure MSTimer2 will do it, counting the seconds between button pushes, without using delay. A bit like the ubiquitous LED blink sketch.

EDIT: Using a single LED as an on temperature indicator and reset indication for manual setting and dispensing with the OLED would trim this down to a very small unit. The OLED is a bit of a gimmick. Electronic indicating and alerting systems is for aeroplanes and people who are unsure of what a blinking red light means?