Newsgroups: comp.robotics
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From: nagle@netcom.com (John Nagle)
Subject: Re: Stepper Motors to drive mobile robot?
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Date: Thu, 3 Aug 1995 16:09:04 GMT
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Saleem Mukhtar (sm8t+@andrew.cmu.edu) wrote:
> I managed to get two identical stepper motors from a dot matrix printer
> which had been trashed and they seem to be working. I am planning to use
> them to drive a differential drive mobile robot. Would connecting the
> shaft directly to the wheel work?

      That will work.  The main drawbacks are:

1)  Stepping motors are power hogs.  They use much more power than a
    DC motor to achieve the same output torque, at least if you don't
    want them to skip steps.  They continue to draw high power at
    slow speeds, all the way down to zero.  This is a pain for a
    battery-powered device.

2)  You need a stepper-driver IC to drive them, and maybe power MOSFETS
    for the bigger ones.  But the circuits are simple.

3)  Don't expect the shaft and bearings of a dot-matrix printer motor to 
    support the weight of the vehicle.  They can can drive the wheels
    directly, but they probably can't support them.  They're not
    designed for side loads.  You need some sort of wheel bearing.

					John Nagle

