Re: Question tuning G320 servoamp --> Figured it out!

Hello all,
After some debugging I managed to figure out my problem.

I was correctly driving the optos with 5V (from a seperate supply
referenced to the parallel port's idea of ground). The motor was
still jittering and the instantaneous error test point of the Gecko
Servo driver was indicating very little error. A closer look on my
DSO at the pulses coming into the controller made it look as if
Master5 was actually sending out a mess of pulses, stopping for a
while, sending out a mess more, etc. etc.

A couple minutes scratching my head and spelunking around Master5 I
decide to isolate the Parallel port from the Gecko and see if it is
still putting out odd pulses (perhaps not able to sink enough current
to flash the optos). It is at this point that I just happen to
notice that my parallel port output is only 3.3V. Duh. Laptop.
Duh. I knew this was the case and just didn't think about what would
happen if I tried to drive an open collector type opto isolator with
a 0-3.3V cmos driver : 5V-3.3V = 1.7V which is roughly the forward
bias voltage of a weakly lit LED. In other words fairly random pulse
transmission. Too much electronics late at night....

The whole thing works smooth as silk on my desktop system even
without the load of the leadscrews or table. I'm tempted to wire the
common optoside up to 3.3V and use it as is with my laptop. since I
don't really have an easy to use handy 3.3V supply I will have to
wait until tomorrow. Thankfully this means I'll be putting in level-
shifting opencollector drivers and doing it at least partially right.

Thanks for all the suggestions and help.

PS whoever recommended the PMDX board, that thing looks really cool.
If I wasn't so impatient to make some chips I would definitely go for
that thing instead of rolling my own.



-Erik Reikes

> Erik Reikes wrote:
>
> > Hello all,
> > I turned on my G320's last night and was playing around

optimizing

> > the settings. I'm not sure that I have a concise question, but I
> > thought I'd share what I'm seeing so that others who might have

had

> > the same symptoms might comment.
> >
> > Some background : I am using some leeson 1/8HP DC motors with
> > USDigital 100cpr encoders. It will hook up with a 2-1 reduction

to a

> > 10tpi leadscrew on my 3-1 machine. So, there are 8000 counts per
> > inch which in theory will get me roughly 60ipm with Master5. The
> > power supply is a Camtronics.
> >

....