I bought this 2-relay module: https://www.amazon.de/gp/product/B00E0NTPP4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I'm testing it out using a 5v 1 amp power supply.
If the JD-Vcc jumper is set and I power the relay board via the Vcc and ground pins next to the input pins, everything works fine. When I pull an input pin to ground, the relay actuates.
Anyway, I want to power the relay board through JD-Vcc. Here, I can't get anything to work. I removed the JD-Vcc jumper and connected the power supply's 5v to the JDVcc pin and ground to the ground pin on the separate connector set. If I touch the input pins to ground of the power supply, the relays don't actuate.
I've searched through a few posts her and I can't see what I'm missing. Any clues out there?