Re: [CAD_CAM_EDM_DRO] Re: Encoder for stepping motor

Digikey also sells the detent type encoders. They aren't as robust as
optical units but are much less expensive. They would do what you want but the
optical would be a more reliable option. I agree, it is just too involved
using a stepper as an encoder and still not as good as using the real thing.

Randy A.


In a message dated 1/14/2008 3:29:27 P.M. Eastern Standard Time,
gjo@... writes:

Thanks Tom
To use the stepper motor as an encoder is beyond my skill so I will
follow your recommendation and buy a real rotary optical encoder.
Gaute

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@...> wrote:
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "poppey_au" <gjo@> wrote:
> >
> > Hi
> > I'm in the planning phase (got most of the parts) to upgrade my
X3
> > mill to CNC. I'm basically following the instructions given in
MEW
> > article. Before I start putting the parts together I would like
to be
> > able to manually control it via an encoder and make a control
box. A
> > colleague of mine came with a Sanyo Denki stepping motor Type 103-
770-
> > 6 8 wire. The motor is mounted on a bracket and equipped with a
55 mm
> > plastic hand wheel. He claims it has been used to manual control
a CNC
> > machine. The motor wires are terminated 2 by 2 on a terminal plug
(4
> > off) and together with a wire that goes to a 9 ways computer
> > connector. 3 of the computer connectors wires are terminated
together
> > with 3 wire cable that has been cut off.
> > Could this work as an encoder? Moreover, how should it be
terminated?
> > Gaute
> >
>
> Making an encoder out of a stepper works but takes electronics since
> the voltage out is proportional to RPM. You can get anything from a
> 100 millivolts at slow RPM to 10V at high rpm. In addition the
> quadrature signal is developed from two coils and it's possible to
> generate one signal and if it's slow enough the phase gets messed up
> and you get a direction reversal signal.
>
> The coil becomes a voltage generator and loading it will decrease
the
> volts at low RPM. You circuit has to be tolerant of a wide range of
> input and only output logic correct TTL levels (5V max).
>
> We designed and sold a hand controller for MACH (MPG-02) that used a
> small stepper as the encoder. It worked but it took a lot of design
> and testing.
>
> You could probably program up a PIC to recognize the signals and
make
> sure the low speed pulses don't get out of phase BUT at that point
you
> might as well do you pulsing from the PIC based on the position of
an
> analog signal.
>
> My advice (having been there) is just buy a real rotary optical
> encoder (Grayhill makes some with Detents). It's setup to do
exactly
> what you want....
>
>
> TOM CAUDLE
> www.CandCNC.com
>




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