How to limit current to a DC motor

Submitted by Ryan Owen on Wed, 04/20/2022 - 01:26

I have a DC motor connected to a 12V 2A power source (an AC adapter). The motor runs as expected, until I add any amount of load, at which point the power supply cuts out and resets. I think this is because the motor is attempting to draw more than the 2 amps that the power supply can provide.

If I connect a 9V and 2 AA batteries in series to get 12V, the motor is able to run with load. Is that just because the batteries limit the current instead of cutting out?

My question is (assuming the above is correct): what is the best way to limit the current that the motor draws so that the power supply can handle it?

My first thought was to add a resistor, but the only resistors I have are only rated for 0.25W. I could order some power resistors, if that's the correct way to go (I've never used those, but they seem simple enough...). Or maybe I just need a power supply that can provide more current?

I don't know how much current the motor would draw if the power supply could provide more; the only information I can find is that it can take 3-12v. If I put my multimeter into the circuit to measure current, it draws around 1.2A at no load. My meter is too slow to read what happens when I add load before the power supply cuts out. With batteries, my mlutimeter shows that it draws <1A even with load.

I'm pretty novice, and this seems like a super basic question; I feel like there is something pretty fundamental that I'm not understanding correctly. Thanks for any help!