Isolating and Protecting Your Microcontroller and Motor with Shared Power Supply

[MHR-Love]

Would there be any fear if I supplied both the microcontroller (through a voltage regulator) and the 12V DC motor using a driver connected to the microcontroller from the same 12V source?

Current will be distributed on both the motor and the controller and some other circuits interfaced with it. I think this might cause some current disturbance as DC motors require a considerable amount of current.
I am afraid that the whole circuit will need more current than the one supplied by my AC-DC adapter (400mA).

If I can use the same source, what is the current rating of the new adapter that is suitable for this application?
Thnx

 

[AlephZero]

We can't answer your last question, except by saying the current rating for the adapter should be whatever current your motor needs to operate. See the data sheet for the motor.

Often it is better to have separate supplies for the digital electronics and the analog (and high power) parts of the system, to minimize any problems with the electronics getting a "noisy" power supply with voltage spikes when the motor switches on and off, etc.

 

[jim hardy]

motors with brushes are electrically "noisy" , if you're using one be sure to place bypass capacitors nearby.

 

[schip666!]

Be careful with the "ground"/minus supply wiring. You may need to run a separate ground wire for the processor circuit back to the supply. I use a diode with a good sized filter capacitor in line to the processor's voltage regulator so dips in the power from motor turn-on loads don't drop out the regulator. Reverse biased diodes and bypass capacitors across the motor (or other inductive loads) will help to clamp transients as well.

 

[DragonPetter]

I would put as much isolation and protection between the motor and your microcontroller if they're both supplied by the same 12V. I have blown up my microcontroller voltage regulator and bridge circuits by improperly commutating a motor with high torque ripple before because I did not put sufficient voltage transient protection at the input of my regulator.