How to measure stall (max) current from DC motor?

Other Hardware Motors, Mechanics, Power and CNC
1

I have a 5V DC motor but I don't have the datasheet because the motor was just given to me, what I do know is that it came from a drill. I need to know how much current this motor can draw so I can use a proper voltage regulator (and H-bridge).

The internet said that you can just measure the current with a multimeter while forcing the motor to not spin and that must be the max current your motor can draw. Is that correct?

Bonus question if you dont mind: Can I attach the "metal head" from the voltage regulator to my drone metal structure to act like a dissipator? But the whole structure becomes grounded, is that a problem?

2

guarda-chuva:
I have a 5V DC motor but I don't have the datasheet because the motor was just given to me, what I do know is that it came from a drill. I need to know how much current this motor can draw so I can use a proper voltage regulator (and H-bridge).

The internet said that you can just measure the current with a multimeter while forcing the motor to not spin and that must be the max current your motor can draw. Is that correct?

Bonus question if you dont mind: Can I attach the "metal head" from the voltage regulator to my drone metal structure to act like a dissipator? But the whole structure becomes grounded, is that a problem?

Answer to first question: measure the lowest resistance of the motor leads while rotating the motor by hand. Use Ohm's law to compute the current.
Answer to the second question is impossible because you failed to tell us the ID of the voltage regulator nor how it is currently mounted.
Paul

3

The internet said that you can just measure the current with a multimeter while forcing the motor to not spin

"The internet" does not seem to know that this is a good way to destroy a brushed DC motor.

4

Temperature will have an effect on your readings as well. Measuring it with the shaft stalled is the Locked Rotor value, not max power rating. You need to know the load and RPM it is rated at. I would suggest getting a motor you can get data on although It may be possible to get data from the OEM of the drill.

5

I would use a lab supply, and set it to a current limit that the motor can comfortably handle, say 1Amp.
Then measure the voltage with a DMM on the motor terminals, with a locked rotor (several positions).
You then can compute the stall current at operating voltage.

Yes, you can attach the tab of a voltage regulator to a metal case, if nothing else electrical is attached to it.
But if you need to cool a (linear) voltage regulator, then maybe you should use a buck converter.
Leo..

6

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.