I am doing a project using the output of a Raspberry Pi GPIO pin (3.3V) to power a 12V remote control.

If the two are on different circuits, can I use a transistor to switch on the 12V circuit or do I need to use an optocoupler?

I'm presuming the 3.3V would go into the base and the 12V would be across the optocoupler.

I'm totally new to electronics and have been trying to understand various guides and tutorials and can't work this out.


1 Answer 1


If the two circuits need to be isolated, then an optocoupler, relay, or optical relay would be preferable. This should prevent ground loops or other dangerous interactions.

A relay may require more current than the gpio can supply, but then again I haven't used them as often as opto's.

  • \$\begingroup\$ perhaps they can use a simple transistor to source current into the relay using the GPIO signal? That was far better than hoping you dont pop a GPIO pin, or a whole port. And they should ALWAYS use a 1k resistor (for DC signals) in series from their GPIO pin, to limit the max current to 3.3mA coming out.. that's my theory anyway \$\endgroup\$
    – KyranF
    Jun 13, 2014 at 4:25
  • \$\begingroup\$ @KyranF Why would I need to limit the current to 3.3mA? \$\endgroup\$ Jun 13, 2014 at 15:26
  • \$\begingroup\$ Because more than 3.3mA will damage the port...3.3v (system voltage ) and 1k res will limit to 3.3mA. However the voltage drop of the parts being driven may require a lower value ressistor . \$\endgroup\$
    – Spoon
    Jun 15, 2014 at 10:36

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