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by lloydjatkinson
3283 days ago
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Anything involving collapsing magnetic fields, eg solenoids, relays, motors, absolutely simply has to have a flyback diode. So your suggestion is actually introducing a second magnetic field, so now you've doubled the chances of blowing up your Pi and or the MOSFET. Whether you're using a transistor/MOSFET directly with a motor or instead with relay + motor you need the flyback diode. |
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No. You haven't fixed the original problem, but your motor is now isolated from the rest of the circuit.
You've just now have a relay with an inductive element instead of a motor. Ultimately, you haven't solved anything (unless you are using an AC motor, and you don't have a triac or something else solid state to control the motor). You still need the flyback diode.
But you haven't doubled your problem by introducing a relay, merely moved the issue to another part.
Now - in regards to the mosfet - many mosfets (not all!) have a built in protection diode between the source and drain. Check your datasheet for details (including what kind of back-feed voltage/current can be handled by them - some may need an added diode with better ratings in detail).
EDIT: Also - some relays have built-in protection diodes (or can be ordered as such) as well (again, check the datasheet). You see this more on relays for automotive applications (ie - standard BOSCH style relays) than ordinary bare PCB relays.