RE: [CAD_CAM_EDM_DRO] Gecko servos

Here is the preliminary report on the Gecko servo drives. I have not run
them on an actually machine yet, but I have so far driven bare motors them
using a PIC and EMC.

First an EMC item:
EMC using steppermod on a Pentium MMX 200 chokes when set to an input scale
of 40,000. I tried freqmod with an input scale of 16,000 and could not stop
follow errors above 80 ipm. The good news is that steppermod with a scale of
16,000 (this would be for 400 line encoders with a 2:1 drive reduction and 5
tpi screws) works solid at 180 ipm!

What is even better is that the Gecko servo drives seem to work just fine at
180 ipm with this setup. I tested by connecting one of the smaller
Electronic Goldmine 24 volt motors with encoder (or as they call them with
tach) to the Gecko driver and used a 36 volt power supply (I know it is a
little much on the voltage, but it was handy). I did get the driver to fault
if I did a reverse of direction at 180 ipm. This sort of surprised me as I
expected EMC to apply the acceleration to both the stop and start, but this
did not appear to be true.

I can't wait to try this setup out on my machine. The steps work out to be
.0000625" apart which is a bunch better than the .00025" I have with the
steppers. If I can get the machine to do rapids at 90 ipm and reduce the
stair stepping on long tapers I will feel the time and money to switch will
be well invested.

BTW, I talked with Mariss on the phone and he was very interesting to talk
with. He has been designing motor drives all his professional life and
certainly seems to know how to herd electrons around a board.

Tim
[Denver, CO]

PS, in reply to the below question using EMC I would venture a guess that a
Pentium Classic 166 or better would be able to deliver the 50 ipm you are
looking for with the Gecko servo drives.

> -----Original Message-----
> From: Alvaro Fogassa [mailto:fogassa@...]
> Sent: Thursday, July 13, 2000 10:39 PM
> To: CAD_CAM_EDM_DRO@egroups.com
> Subject: [CAD_CAM_EDM_DRO] Gecko servos
>
>
> Hi All!
> Ok! I could figure out the pins on the pcb for the harris
> chipset,A,B,+ but the ground,after playing with it for while I've
> gave up!,got more important things to do.Anyway thank's a lot!
> Now,i've a 1/2 stepper system on my minimill and a 5mm pitch
> Aprox.0.200" lead ballscrew and i've being thinking about upgrade it
> to the GECKO servo driver.
> What's the specs. for the Gecko servo driver?
> and what would be the performace using a 0.200" lead ballscrew
> what about computer power?(486,586,P2)necessary for let's say
> 50"/min.using the same lead screws and 500 cpi encoder X 4?
>
> I'm just trying to compare to what I've now and if it worth the
> money to buy a new set of servo motors, and drivers.