So the USB connection to my osPID is super unreliable. When it connects it grabs values for a few seconds and then the graph flatlines and the numbers on the left don’t update. I’ve noticed that sometimes when the relay fires the USB light blinks. It seems like the noise from the contactor opening and closing is playing merry hell with the osPID’s USB comms. I’m not driving all the current for the furnace through the osPID’s relay, rather I’m using the relay to drive a big contactor in the furnace which was previously used by its old control circuitry.
I’m running the osPID with a 12v transformer wall wart, powered from the same AC supply used by the contactor. Has anyone had any success with isolation filtering on the DC input side? I suspect it’s spiking quite a lot.