Need help picking a Fuse for WLED-wemos-shield

I purchased all of the parts for my 5x new WLED-wemos-sheilds in order to run a couple of different projects. All of my projects will be 12V based.

  1. I am planning on using a 20A PSU for one project to run a couple (2-3) strands of WS2815 (600-900 LEDs)
  2. I am planning on running a 30A PSU to power all 10x WS2811 50LED strings (500 LEDs in total), my justification for the 30A PSU for less LEDs was that it is over a longer distance.

I have several questions:

  1. What size fuse should I use for these two separate projects?
  2. Do I need to run all of the power via the WLED-wemos-shield or can I tap into the PSU directly to provide power injections for strips in which case I shouldn’t need that big of a fuse for the first set of strips that might be powered by the WLED-wemos-shield?
  3. I suspect that if I inject power directly from the PSU, the downstream strands that are power injected directly from the PSU won’t be able to take advantage of the “Relay for power saving feature” feature of the shield, correct?

Thank you

Whats the max current the relais is recommended? I’d say 10A ?
So there is no way to run the power over the relais.
I would use the relais to switch a second relais automotive standard (30A or 40A), like this one:

The fuse has to match the maximum current of your cable, NOT the consumption of the strip.
It depends on the gauge thickness of the wire and the length.

Kind regards,


Some people say you should use ~5A fuses at each injection point.

Max current for standard relay 10A. But there is a direct replacement proposed by user WebOskar which is 20A. So fuse rating can be 10A for 10A relay and max 20A for 20A relay. Otherwise you have to use external relay to switch currents more than 20Amps.

That 20A relay is 5V is there a 12V version?

What about just a little fantasy by yourself?

The relay above is named SRA-05VDC-CL , what if I just enter SRA-12VDC-CL in Google…? :shushing_face:

If you planning to use on board relay so it’s a 5V relay circuit. Even if you using 12V power supply. In case you want use external relay it’s up to you which one you choose.

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