Re: [CAD_CAM_EDM_DRO] Re: moving Bridgeport steppers with Gecko drivers - help!

theokspindoctor wrote:

>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.
>

It is half-winding. Since you leave the other winding terminals
disconnected,
it can't be parallel.

> 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.
>
>

You must have had the phasing of the two coils reversed, nullifying the
inductance. That exposes a weakness of the Gecko, it can't handle a
short or near short.

>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?
>
>

Exactly right. Now, I'm not saying you can move a Bridgeport machine at
144 IPM with Gecko 201 drives and size 34 motors! Why do you have the 2:1
belt reduction? This is almost always counterproductive with stepper
motors.

>Do you have a 1000 oz/in motor as used in the Bridgeport with your
>Gecko driver?
>
>

I don't use steppers on my Bridgeport. I have servos on that. (I also
don't
want to haul a Bridgeport to a 2-day show!) The steppers were on a 150 Lb
minimill that I took to NAMES for the 2003 show.

Jon