GPIO pin from MKR1000 is rated 3.3v 7mA I need a relay which has the sale coil rating. So far I have not been able to find one. What I have seen is that as the coil voltage goes down, the coil current goes up. Normally 3v coil volt relays operate at 50mA. Can you suggest a relay which will work in my situation?


1 Answer 1


A "GOIP" isn't an established term, so I assume that you actually mean GPIO (General Purpose Input/Output).

Relays which will work at less than 7 mA, 3.3 V are exceedingly rare. For example, the parametrized search of digikey.com could only find one relay which can be directly driven by that GPIO pin, a 4$ reed relay in a SIL package.

It makes much more sense to drive a "normal" relay with a transistor, and it's not like you have to add a million parts: you just need a NPN bipolar junction transistor (Q1) and a current limiting resistor for the base (R1). The diode D1 is mandatory in any case for absorbing the voltage transient generated by the relay coil when you switch the relay off.

  • \$\begingroup\$ Thanks for the cool answer. I fixed my spelling in the question. \$\endgroup\$
    – Kashif
    Commented Sep 22, 2016 at 12:39
  • \$\begingroup\$ I have an Omron G5Q-DC5V relay coil rated at 5VDC / 40mA, you think it will work with your suggested circuit/components? \$\endgroup\$
    – Kashif
    Commented Sep 22, 2016 at 13:00
  • \$\begingroup\$ Sure, the 2n3904 is rated for 200mA. The Relay doesn't have to be a 5V one either, you could use a 12 V or 24 V relay if you wanted to (after increasing the relay supply voltage to match). \$\endgroup\$
    – jms
    Commented Sep 22, 2016 at 13:06

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