I have been doing this for years (on automotive projects) but the need finally arose to clarify:
When using a SPDT 12V relay (with internal flyback diode), should I isolate the ground trigger when using a micro-controller?
I suppose I could drag everything out and measure current when switching (I am thinking there is none), but I am charging a battery that will likely not complete tonight.
Should I use an optocoupler, or can I simply feed the ground in one pin and trigger output on another?
Oh yeah, Arduino UNO is the target controller.
Maybe I should also clarify the relay wiring:
(will be replacing switch with Arduino)
Note that the previous description was incorrect. Please see diagram drawn from circuit.