When the weather is too cold I can’t etch because the etching fluid freezes. So I made a heated etching tank, the heating element is recycled from an old washing machine. It consisted of 2 heating elements, a large 2Kw and a smaller 1Kw, I cut the 2Kw off so it would fit in my tank (and 3Kw would be too much). 1Kw is still a lot off power so I put a dimmer on it. To regulate the temperature I made a temperature controller with a pic16f676. The temperature sensor is a LM35 with heat shrink around it. The display is a 2x7segment display (Datasheet).
The hex file for the pic can be found here: Link.
The pcb (PDF):