Re: [CAD_CAM_EDM_DRO] Re: Has anyone made their own servos from DC Motors?

Hi Glen,

When used as a servo, the positioning is dependent on the resolution of
the encoder not the number of magnets in the motor. Drives are capable
of holding the motor in any position. Ideally the motor should have
little 'cogging' or lumpiness when you turn it. True servos have
virtually none. The drive has to work to counteract this lumpiness which
translates into a slight unevenness when moving slowly. A good test is
to connect the motor to a 1.5V battery. If it turns smoothly in both
directions it is likely to work quite well as a servo.

One way to improve the situation is to increase the number of lines on
the encoder. The more lines on the encoder, the more quickly and
accurately the drive can compensate for unevenness. You may have to use
a drive with pulse multiplying with higher resolution encoders.

Most scooter motors tend to be short and fat. The ideal shape for a
servo is long and thin as this reduces inertia.

Les

roboticscnc wrote:

>
>Hi group.
>I picked up a couple of 24 volt motors for electric scooters. One is 6
>amps and the other is 16 amps.
>The main concern I have is that the resolution of the magnets is very
>large and this dictates the number of positions the motor will stop at
>per revolution. I don't know if servos are like this or better. Maybe
>the problem won't be there once they are geared down.
>Has anyone used this type of motor as a servo ?
>Regards,
>Glen
>
>
>

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