Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

20.4:1 Metal Gearmotor 25D Pole Number


I’m currently trying to simulate and controll the ‘20.4:1 Metal Gearmotor 25Dx65L mm HP 12V with 48 CPR Encoder’ (Pololu Item 4843) by using an Arduino Uno and the ‘Dual TB9051FTG Motor Driver Shield for Arduino’ (Pololu Item 2520).

The issue is that I’m measuring spikes in the current, that occure 3 times per motor revolution (61.2 times per shaft revolution). I’d now like to check wether those are commutation spikes or something else.

Therefore I am looking for information on the number of rotor poles, stator poles and commutation segments or a graphic of the internal structure of the motor if available.



Our 25D gearmotors use three armature windings, three commutator segments, and two permanent magnets for the stator (one north pole magnet and one south pole magnet). We do not have a graphics showing the internal structures of our specific motors, but in case it helps our brushed DC motors match the general layout of this generic graphic of a 3-pole DC motor from this blog post by Precision Microdrives

- Patrick