Gas station without pumps

2017 November 18

Checking out the new gearmotors

Filed under: Robotics — gasstationwithoutpumps @ 09:07
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Last night I did some quick checks of the new 210 rpm and 300rpm motors (one of each).  The new 210rpm motor seems to be substantially the same as the ones that came with the wheels, but the 300rpm motor is indeed faster.  I assumed that the difference in speed would come from a difference in the gear box (same motor but different gear ratio), but instead it seems to come from a different motor on the same gearbox.  The 300rpm motors have a lower DC resistance and so take more current at the same voltage.  That shifts the speed-vs-torque line upward, giving more free-running speed and more stall torque.  The cost, of course, is that they take more current to provide the extra torque.

It may be worthwhile for me to use these beefier motors in my robot, since I can PWM to lower speeds, and the torque-per-amp seems to be about the same for the two motors (assuming that the gearhead efficiency is the same).  One of these days I’ll have to build myself a stand for testing running torque and stall torque on my motors and characterize them properly—but probably not until after mechatronics is done, as the details of the motors are not on the critical path for completion.

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