James Lewis shares his experience in debugging SONOFF AC relay with a thermal camera:
The clever solution seemed to be clever, at least for a few minutes. Suddenly the light turned off. I thought maybe there was a timeout for the manual button. Annoying, but workable. The lamp remained off for about another 2 minutes when I started to smell that unmistakeable burning plastic odor. Touching the case of the SONOFF identified the culprit immediately.
Great. So I have an AC mains switch that isn’t working, but I do not want to go poking my multimeter into it. What do I do?
Turns out, that SONOFF module was defective. I wanted to debug it, but I did not want to measure anything while connected to AC. Here’s how I used a thermal camera to debug my SONOFF.
See the full post on Bald Engineer blog.