In short I'm building a relay controller and want to limit the current going to specific relays.

My power source is 12V DC @ 20A.

For one relay I want to limit the current to 10A and another to 2.5A. I'd also like to have minimal voltage drop, say ± 0.5V, but if this is unreasonable I understand.

If anyone would please help me I would be grateful. To keep things simple, I'd only need to be shown how to do this once and can figure it out for the other relays.

Thank you.

  • \$\begingroup\$ Voltage and current are tied together. It's not possible to limit current without also changing the voltage across whatever the relay is switching. \$\endgroup\$
    – Hearth
    Feb 5, 2019 at 4:02

1 Answer 1


You haven't said why you want to limit the current. If you want to prevent accidents you can simply insert a 10A and 2.5A fuse or circuit breaker in series with the relay. If you need to give your load a constant current you'll need something more complicated.


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