Re: Any old encoder or how to make an inexpensive servo motor

Thanks for all the answers. It doesn't look like there's much that
would be useful in the gearmotor.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "k1hop" <russ@p...> wrote:
> hi... I have a bit of experience playing with these Globe
> Gearmotors. You can remove the gearhead held by the three pins by
> punching the pins INWARD enough to remove the head. Then, once
> removed, you can force the pins back out for reassembly/use.
>
> The brake and Hall-effect sensor CAN be removed in fine condition
and
> reused. You need to shim under the rear-end assembly pieces with
the
> armature hanging free (say in a lose vise) and hammer (I use an
old
> centerpunch) on the end of the shaft. A few hard taps and it
comes
> off undamaged. Be careful to support the armature so it doesn't
fall
> from the vise when the "backend" stuff comes free. Be careful not
to
> damage the brushes or rotor pieces in the process.
>
> These parts are pressed on TIGHT, but can be removed successfully
if
> you are careful but not afraid to use some force!
>
> Russ
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@y...>
> wrote:
> > Hello,
> >
> > I can tell you that that specific "encoder" will not work as a
> servo
> > feedback type. It is a hall effect single pulse per rev; more of
a
> > tach actually. FWIW, The brake is easily removable. The gearbox
on
> > the end of the motor itself is held on by three spiral pins,
which
> > sould need to be drilled out to remove the gearbox. The gearbox
has
> > excessive backlash for use with CNC.
> >
> > Hope this helps,
> >
> > Ballendo
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>
> wrote:
> > >
> > >
> > > etfrench wrote:
> > >
> > > >Will any encoder work for creating a servo motor from a PMDC
> motor?
> > > >
> > > >or
> > > >
> > > >Will the encoder on this gear motor
> > > >(http://www.surpluscenter.com/item.asp?
> > > >UID=2003120116311635&catname=&qty=1&item=5-1440) work with
the
> > motor
> > > >suggested by Mariss Freimanis
> > (http://www.surpluscenter.com/item.asp?
> > > >UID=2003070308293941&item=10-1931&catname=electric)?
> > > >
> > > >
> > > Maybe. Don't be completely sure you can get the encoder off
the
> > motor
> > > in such condition that it can be reused. They don't really say
> that
> > the
> > > encoder can be removed in working condition, just that the
> > brake/encoder
> > > is removable.
> > >
> > > Second, they don't say anywhere that the $24.95 motor is a
servo
> > motor!
> > > It may well work fine for servo positioning use, but
apparently
> was
> > a
> > > treadmill motor. It could have a lot torque or velocity
ripple, or
> > > magnetic cogging, which will interfere somewhat with smooth
> motion
> > at
> > > low speeds.
> > >
> > > >p.s. How do you calculate the oz/in for just the motor from
the
> > > >following?
> > > >
> > > >SPECIFICATIONS
> > > >• RPM primary 25
> > > >secondary 4.5
> > > >• Voltage 12 DC
> > > >• Amps 130 mA no load
> > > >• Torque primary 33 in. lbs.
> > > >secondary 125 in. lbs.
> > > >• Ratio 620:1
> > > >• Rotation reversible
> > > >• Duty continuous
> > > >
> > > >
> > > >
> > > Pretty tough. I'm guessing the 620:1 is from the 4.5 RPM
rating
> > point, so
> > > the motor RPM is 2790. If you get 125 In-Lb at 4.5 RPM, then
the
> > motor is
> > > delivering 125/620 In-Lb = 0.202 In-Lb or 3.23 In-Oz. Not a
> > tremendous
> > > motor,
> > > for sure. Actually, a 620:1 gearbox is pretty lossy, so the
motor
> > could be
> > > twice that.