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?


You need to connect power to both JD and Vcc. By removing the jumper you are only powering one side.

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  • \$\begingroup\$ Thanks, evildemonic! That's exactly it. It's working now. And do I need to connect ground on the input connector set? \$\endgroup\$ – user9374448 Sep 9 at 14:20
  • 1
    \$\begingroup\$ The ground should be common across both sides, so no. You could verify this with an ohm meter. \$\endgroup\$ – evildemonic Sep 9 at 14:22

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