For years our heating timer was sitting on the wall being not particularly useful. It was so awkward to reprogram new times into it that it had come to a point where it had a basic program on it and was mostly manually controlled by switching it on for 1/2/3 hours at a time. Finally i had enough of it and with some spare time on my hands i set about adding some remote control functionality to it. The first plan was to gain control over the “+hrs” button we were used to using and then see what was possible. In preparation i ordered an arduino ethernet shield but i wasn’t sure what i was going to do with it.

A popular method of controlling a switch with a microcontroller is to replace it with a transistor. As i didn’t want to interfere with the normal operation of the switch i traced back the pads on the switch to two vias on the PCB which allowed me to solder some thin wires in to attach the transistor to. To test i brought out GND and the base wire and reassembled. Running some simple code to toggle the switch let me cycle through the times and turn it off as expected.