Im looking at buying a 0-30V 0-5A variable regulated power supply to play around with dc motors ranging from 3v to 12v and varying amps. I plan to connect them directly without using mosfets, transistors or switches of any kind, just looking to vary the speed of them for use with 3D printed models.

My question is, can I do this successfully without needing a fly-back/snubber diode or without overloading the capacitors in the power supply? Im only new to electronics and have read a lot about needing fly-back diodes when dealing with mosfets and inductive loads but cant seem to get a good answer when it comes to directly using nothing but a dc motor.

Thanks in advance.

Just looked into powering the dc motors more and I was reading that a short circuit protected power supply wont work with DC motors, is this true? because every power supply i can find has that built into it.


1 Answer 1


you can directly used the motor with variable power supply because it has built in protection. Snubber circuit and fly-back diodes are used to control back emf of motor.

  • \$\begingroup\$ I have read that but was not to sure, so theres no need for anything else? and also what would cause reverse polarity with a dc motor? \$\endgroup\$
    – PyNuts
    Jun 13, 2017 at 7:44
  • \$\begingroup\$ Would it still be ok to use the motor with a switch, just a simple switch not any sort of mosfet? \$\endgroup\$
    – PyNuts
    Jun 13, 2017 at 9:37
  • \$\begingroup\$ Absolutely; a modern, good-quality DC power supply is designed to take all sorts of abuse from highly inductive and highly capacitive loads — and I think you've correctly identified that when you're switching motors on and off, that's when you have the most issues to worry about. This is because inductors really don't like it when you change the amount of current flowing through them (like a switch tends to do) \$\endgroup\$ Jun 14, 2017 at 6:22
  • \$\begingroup\$ So dont use a switch? sorry im new to all this. I understand what back emf is now and reversed polarity. Also ive heard a dc motor acts like a short circuit before it starts, the psu im looking at buying is short circuit protected so im hoping that will not be an issue? \$\endgroup\$
    – PyNuts
    Jun 14, 2017 at 6:35

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