Mach Discussion > General Mach Discussion

GEC Gemini DC drive question

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Graham Waterworth:
Thanks Ian DXF is not a problem.

Graham.

jwhitley:
Graham,

Is this a Gemini drive by any chance? It's from a Boxford 260VMC I picked up a couple of weeks ago. I've replaced the stepper drivers and installed a PC in the mill and all works well with Mach3. Now I need to find out how I'm going to control the spindle - ideally without having to replace anything else.

Many thanks if you can help...



By the way, based on my own experience to date, if you buy a Boxford machine, don't count on ANY kind of help from Boxford themselves, regardless if you're willing to pay for that help or not. If you're not an education site, they don't want to know - full stop.

Graham Waterworth:
that is a gem, all you need is a PWM to 10V board to drive it.

Its not so much Boxford will not help, they can't due to the tie in with the L.E.A.

Graham.

jwhitley:
Thanks Graham,

I've put the original Boxford electronics back together to see if I can find out what's going on. With the spindle off I get +8.4v across pins 2 & 3 (pin 2 as -ve small black wire and pin 3 as +ve thick red wire). When the spindle is running the voltage varies from -12v (ie a potential difference of -20v from not running) to around -20v - a range of about 8v - so I'm guessing the 0-10v range of control is in relation to another voltage supplied to the board? (as I'm getting +8v at idle)???

My understanding of electronics is rusty at best... I can see the a contactor is energised in two different ways depending on whether the spindle runs CW or CCW.

Do you by chance have a schematic of the Gemini? This might help me understand what's going on a little better.

Many thanks,
Chris

jwhitley:
Have got a partial schemtatic from a TCL 125 which uses the same DC motor, Gemini drive and Yaskawa reversing contactor. Seems pin3 isn't GND, which is why I'm getting strange results (thanks Roy).

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