Re: moving Bridgeport steppers with Gecko drivers - help!

Jon, I was confused by the comment that a sowftware-only solution
would not work. I am also using a stepper board motion controller
that is sending the step and dir commands to the Gecko driver
board. It is supposed to be effective, but the setup is apparently
not so straight forward. From reivewing a previous post you made
earlier in the month, the half winding mode at 7 amps is the
preferred connection, which is what I think I have done.

However, there is still the question of whether the 470 uF capacitor
is necessary across the power connection. Mariss writes that this
is required when the power supply is more than a 18 inches away or
uses a fuse, both of which are true for my setup. I assume that is
the length of the wire from the power supply to the Gecko drive. He
says this is necessary because the drive draws supply current in
20khz pulses and needs "flywheel" for proper function.



thanks!

Keith Clark

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "theokspindoctor"
<mail@t...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>

wrote:

> > theokspindoctor wrote:
> >
> > >I am in the painful process of retrofitting a Boss 6 Series 1
> > >Bridgeport mill using the original stepper motors and new Gecko
> 201
> > >drivers with a Galil stepper board and CNC Lite controlling
> software
> > >from Cam Soft Inc.
> > >
> > >At this point I can move the motors at a slow speed the

distance

> I
> > >specify in diagnostic mode and am able to write G code programs
> to
> > >get proper movement. However I cannot seem to change the
> feedrate
> > >and the rapids are very slow.
> > >
> > >The motors are wired according to Les Newel's suggestions

(thanks

> > >Les!) in half winding mode using only 2 of the 3 phases on the
> Gecko
> > >drivers.
> > >
> > What 3 phases? The Gecko 201 is a 2-phase bipolar driver. You
> must mean
> > only using 2 of the 3 wires of each phase of the MOTOR. That is
> correct.
> >
> > > Am using a 340Kohm resistor although Les recommended no
> > >resistor. The resistor limits the amperage to about 6 amps, I
> think.
> > >
> > >Does it matter that the motors are 200 steps per revolution and
> the
> > >Gecko drives 2000 steps per rev?
> > >
> > >
> > The Gecko is a x10 microstepping driver. With a 200 full-step

per

> rev
> > motor, then you need 2000 step pulses to get a full revolution.
> >
> > >It seems that I cannot jog, but can move pitifully with G code
> > >programming.
> > >
> > >Any suggestions?
> > >
> > >The tech help at Cam Soft has not been able to solve the

problem

> and
> > >Mariss at GEcko Drives is on vacation until next week.
> > >
> > >
> > Is the problem that nothing you do on the software gets a faster
> > movement, or
> > does the motor clatter and lose sync? If it is a case of the
> software,
> > has the
> > setup of the software been told it takes 2000 steps/rev? I

don't

> know
> > CNC Lite, so I can't go much farther than that.
> >
> > I will mention that I am running a stepper-driven machine with
> Gecko 201A
> > drives and my Universal Stepper Controller at 48,000 (micro)

steps

> per
> > second,
> > which works out to 1440 RPM. You pretty much can't do that with

a

> > software-only
> > solution.
> >
> > Jon
>
> Thanks Jon,
>
> I have 8 wire motors with 4 "coils". They are wired with 2 of the
> coils not connected and 2 of the coils connected to the Gecko

drive.

> The ones connected are "across" from each other I think. The

wires

> go to the 4 connectors on the Gecko drive labelled phase a b c and
> d. This is probably a half winding or parallel wiring I think.

We

> have the 340kOhm resistors across the current set terminals but do
> not have the capacitor Mariss describes across the power.
>
> Also, when I tried to wire the motor using the 8 wire parallel

setup

> described in the white paper from Gecko it burned out the drive.
>
> What does 1440 rpm equate to in terms of movement of the axis. I
> have a 2:1 gearing with a 5 pitch lead screw. 10 rotations of the
> motor will move the axis 1 inch?? considering these specs? 1440

rpm

> would then be 144 inches per minute?
>
> Do you have a 1000 oz/in motor as used in the Bridgeport with your
> Gecko driver?
>
> Thanks!
>
> Keith Clark