Re: Encoder for stepping motor

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
>