So, if you look at my post about Node-RED experiments and my portable powered breadboard, you’ll notice that the “power” LED isn’t lit on my home-made portable breadboard. I could have just wired the LED to the +5 of the power supply, but if the supply died then all lights would be out, including the “power” LED, which wouldn’t really be much help in diagnosing the problem. I found this circuit https://www.eeweb.com/extreme-circuits/mains-operated-led-circuit-schematic that uses the capacitive reactance at 60Hz to bring the current to the LED to about 10mA. Here’s the circuit. (I used two 0.1mF at 400WV for C1 and C2)
