I changed my oil usage monitoring system last weekend.
I wanted to change from a sound based system where the pi listened for the burner to a visual system.
I connected a 2w G4 bulb to the terminals feeding 30v to the oil pump solenoid – it worked but it was stopping the burner firing up cleanly*
I the realised I had a relay that was switched by a 3-32v input, so I put that on the same terminals and connected the other (power) side of the relay to a gpio pin and ground on the pi.
The boiler firing closes the relay and the pi senses this and fires off a message to IFTTT which adds a row to the spreadsheet recording all the burns.
Same happens when the boiler stops.
Much nicer, simpler code that shouldn’t fall over and I now get actual burn times accurate to within 4 seconds.
The burner would fire but then stop immediately, then try again once or twice before finally firing properly.
<span style=”font-size: 0.8rem;”>I can only assume the extra 2w load was stopping the solenoid working properly. Which surprised me.</span>