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I'm designing a circuit which includes a fan being controlled and I've seen on a few websites that I should include a protection diode across the fan (as shown in the diagram below).
However, after searching and trying to think about it, I can't see what the purpose of the diode is? If it's in that direction it's not allowing any current to travel down that branch of the circuit anyway as it will always be reverse biased?
Does anybody know/can explain if this is necessary/correct to use a diode in this way for a fan/motor circuit?