Re: [CAD_CAM_EDM_DRO] run two geckos from same pins

carlcnc wrote:

>
> I am sure someone is doing this already.
> i am building a table with twin screw drive on X.
> Will I have to do anything special to facilitate running two
> gecko210s with the same step and dir. pins from parallel port?

Hi Carl:

That shouldn't be a problem. You might need a buffer
(an extra TTL gate to amplify the S&D signals) if the
parallel port signal is weak.

Also you mention G210's which are of course stepper.
For kicks one day I connected two 3.5 Amp steppers in
series (set resistor for 3.5 amp), then in parallel
(set resistor for 7 amp) to one G201. They seemed to
work fine on the bench (thus saving one controller:
ie 1 Gecko stepper controller for 2 stepper motors).

But since it wasn't connected to a machine, nor under
any load, I don't know if they were losing steps relative
to each other. They just had tape on their shafts and
seemed to move in unison.

I would suggest an experiment: put two facing each
other with a loose flat ribbon connecting their shafts
(to decouple them from each other). Then run a torture
test (IMSRV's trough for example), and see if the
ribbon remains untwisted (ie a success). Then do
it again, adding some load to one or both shafts,
and see if they stay in sync.

This trick will never work with DC servo (G3xx)
controllers of course.

Back to your XXYZ cnc router, it would be great to
to run a timing belt across both X axes (even though
you have 2 motors with 1 or 2 controllers), just to
keep them both honest (because steppers are <usually>
open loop systems).


Doug Fortune
http://www.cncKITS.com