Re: [CAD_CAM_EDM_DRO] Re: Is this servo usable for position control?

grantfair2001 wrote:

> --- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> > grantfair2001 wrote:
> >
> > > I have 3 Japan Servo DC servomotors . . . If I count the tach
> pulses can I
> > > use this to establish positions reliably? And control this
> > > position with the 24 volts DC supply?
> >
> > If the tach only has one channel, then you can't determine which way
> the
> > motor is going. If that is so, it is not suitable for positioning
> use. Are
> > these
> > brush motors or brushless DC. If 2-wire brushless DC, then itwill
> only turn
> >
> > one direction, so that is also useless for positioning
>
> Well, it's a two wire DC motor. I see no sign of brushes on the
> external housing, but it looks as if access to the inside is intended
> at one end. But the black lead goes to ground on the control PCB, so
> clearly, there was no plan to reverse it with the existing control
> electronics. Is there an easy way to determine if it has brushes?

Hmmm, not so easy. You might try using a DVM in ohmmeter mode
across the wires. if you get very low readings (10 Ohms or less)
with both polarities, it is almost certainly a brush motor. If you get
high reading one or both ways, then it is a brushless DC motor, and
cannot be reversed (without changing circuit wiring inside the motor).

Jon