GEC Gemini Speed Controller - Info required

[melee]

Hi,

I need information on the GEC Gemini Speed Controller, quite commonly used in combination with a Lenze DC spindle motor on the 1980s - 1990s Boxford lathes and others.

I have found mentions on the forum, but no specifics.

What I ideally need is a schematic, manual, wiring diagram etc.

Failing that, a description of the connections and what they do.
I am trying to identify what pins on the board take the 0-10v  signal for speed control and generally anything else about the board

Mine appears to be a CPM8804 (or T162-40001 if that is wrong)
It has a numbered 12 connection screw block at one end and a 4 screw one labeled F+ F- Aux 1 Aux 2 plus 4 connection posts L1 L2/N A+ A- at the other end.

Any information gratefully received

regards

Melee

[SimonD]

Have you managed to get any information on the Gemini speed controller?

My machine is connected thus...

L1 = Live Also connected to Aux1
L2/N = Neutral Also connected to Aux2
A+ & A- = Motor windings

1 = n/c
2 = 0v DC
3 = 0-10v DC speed signal
4,5,6 = n/c
7,8,10 = Earth
9 = ??

Pin 9 appears to be some kind of "enable" but I don't know what to connect it to.

Thanks
Simon

[melee]

Thanks Simon

Thats great

I will check later, but there are certainly only 2 paired connections onto the 12 screw board, so the rest are probably just going to GND.

I haven't figured out how the polarity is reversed for running CCW yet, need to trace the rest of the redundant wiring.

Thanks again

Melee

[SimonD]

On all my Boxford machines the motor is reversed by going through either a mechanically interlocked contactor or a relay.
Basically all it does is take the A+ and A- wires and switch them to the other way around on the motor.

P.S. n/c is "not connected" in the above, not normally closed.

I would appreciate any info on your pin 9, everything is ready to fire up the spindle on mine except I can't get the thing to move!

Thanks
Simon

[melee]

Hi

Had a look and mine is wired differently, so this may assist you.

Since the original posting I tracked down and identified some further wiring from the original Fanuc controller, so I am quite happy that the 0-10v speed control signal should be on a screened wire which actually looks like co-axial cable.

On that basis my pin outs are
1 unused
2 core of screened cable - so 0-10v
3 connecting loop to 9
4 unused
5 unused
6 unused
7 Screening of screened cable and linked to 8
8 link to 10
9 link to 3
10 loop to main ground connection
(even though is on green/yellow cable and signed earth, this is the - V ground run from the rectifier bridge and not earth as such)
11 unused
12 unused

There is a 2 pole Yakasa contactor connected to the motor outputs, so that is CW and CCW sorted hopefully.

I am not able to run mine up until I can test the main transformer, which is showing signs of having overheated.

Hopefully this will answer your pin 9 question, let me know how you get on

regards

Melee

[SimonD]

I am running out of 3 amp fuses fast!
However I connect it up it blows the main fuse. I know it does work as I have had it spin the motor but as soon as I switched it off, it blew the fuse again.

Thanks
Simon

[SimonD]

I stripped everything back and started again trying your wiring and I have got it working of sorts...

1 - not connected
2 - 0-10v
3 - 9
4 - not connected
5 - not connected
6 - not connected
7 - 8 - 0v
8 - 10 - 7
9 - 3
10 - 8 - Earth

However the speed control is over a much smaller voltage than expected, I expected max speed to be at something like 8v as this is what is was origionally.
Max speed is now something like 3.5-4v I haven't actually found the max as it sounds too fast and I bottled it.

Any ideas?

Thanks
Simon

[melee]

Glad you got it working

The 0 - 10v was a guess, because that is the standard sort of range.
I know that the 160 TCL was more like 0 - 8v

Because I do not have the running controller from the old set up, I cannot measure what the signal voltage was.

The only thought that occurs is regards Pin 9

Is that connected to Pin 3 as an Enable or is in fact it a link which enables you to change the signal voltage?
It would be quite handy to use 0-5v as a signal on some controllers, because that is the range most commonly available driving the circuits.

What happens if you remove the link between 3 and 9 ?

regards

Melee

[SimonD]

Melee

If you remove the link between 3 and 9 then it stops running and I can't get it to run again. All it does now is make the transformer buzz and then blow the fuse. If you start the spindle by hand then it can kind of keep it going but it is not happy! I will let the electronics lose all their charge for a bit and try again but I am not holding out much hope for it

Simon

[melee]

OK - just a thought!  Don't blow any more fuses.

My thought was that which terminal 3 (or 9) linked to (or whether it did at all) might determine the voltage level required, akin to different taps onto a potentiometer.

If you are running from Mach to get the voltage level, you can reduce the step signals, thus reducing the converted voltage from your speed board, by 'de-tuning the motor' in the configuration set up.

I did this with my 160 to keep the max speed within range, because my speed board gave out 10V and was only adjustable within 10% of that.

I don't have the exact figures to hand, but my steppers were 200 steps per revolution so I started with that figure for the spindle motor tuning.
If for instance you tell Mach that it only takes 100 steps per revolution, the output at any given dialed up speed should be halved.

There is probably a point at which this does not work, but it worked fine to trim my max speed to 3000 rpm from an exciting 3800 rpm when I started.

The other alternative is a resistor to drop the voltage itself.

Melee