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Help with servos and drives.
« on: January 22, 2010, 01:32:05 PM »
OK, I'm comfortable with steppers having built a half dozen machines but now want to make the leap to Servos.  I'm building a large gantry mill (6' X 10').

I've got a couple of G&L centurion drives and some Aerotech BA series drives as well.  I've got pinout diagrams and manuals for the drives but just don't know where to start.

I'm pretty much clueless as how to interface the drives with mach

Any basic help would be much appreciated!

Offline Hood

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Re: Help with servos and drives.
« Reply #1 on: January 22, 2010, 01:34:07 PM »
I can probably help withthe Giddings and Lewis drives as I use the DSA variants of these drives.
What models do you have?
Do you have the motors for them?

Hood
Re: Help with servos and drives.
« Reply #2 on: January 22, 2010, 01:58:13 PM »
Thanks so much!

I've got  Centurion micro DSA drives.  I've got a collection of various motors and will get others if needed.  I've got some Mitsubishi AC servo motors and also some Aerotech brushless DC servo motors.

Not sure what is compatible with the G&L drives..

Offline Hood

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Re: Help with servos and drives.
« Reply #3 on: January 22, 2010, 02:10:37 PM »
If they are brushless motors they will work fine with the drives as long as the encoders are compatible. What I mean by that is the encoders must have hall outputs on them so that the drive can determine the commutation for startup, once running they are not required. You can set the drives up to self sense and thus you will not need the commutation signals on the encoders but the downside to that is everytime you power up the drive the motor will rotate slowly for a small amount to sense the commutation. This probably wouldnt be an issue on a spindle but could be on an axis. If however the drives are left with power to them they will not need to do the sensing. Still best to have the right encoders though.
You can fit encoders to these motors and lining them up is fairly straightforward if you have a scope but even if you dont the drive has a means to offset the signals but I prefer to do it correctly.
 The proper type encoders are not cheap and I have found in the past it is much cheaper to get a smaller motor off eBay that has the correct type encoder and just pull the encoder and put it on the bigger motors. Few things you need to know about that however is that the pole pairs are the same and also you really need the shaft size where the encoder mounts to be the same although you could make extension shafts or sleeves if its not.

Wiring up the motors to the drives are fairly straightforward, the drives can accept single ended outputs for Step/Dir but I prefer to use the Differential inputs. As the signals from Mach are single ended you need to make up a small circuit and use a line driver to turn them into differential outputs but as said its not needed but preferred to help with noise immunity.

Hood
Re: Help with servos and drives.
« Reply #4 on: January 22, 2010, 03:40:28 PM »
Starting to make sense to me..

Here's a pic showing the pin assignment for the motor.

Maybe you can tell me what pins on the motor go to what pins on the drive?

Thanks again for your help here!

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Re: Help with servos and drives.
« Reply #5 on: January 22, 2010, 04:05:36 PM »
I am not sure if you can use that encoder or not. I have similar setup on the spindle of my mill with the Sine Cosine encoder but it is an intelligent encoder and has the info for drive setup in it and it is an Allen Bradley motor (same as G&L)
 I will have a look later to see if I think it will work but at the moment I am thinking if it will work it will need to be connected in a similar way to the MPL motors, cant remember if G&L call them MPL  but its similar.
 What drive model do you have?

Hood
Re: Help with servos and drives.
« Reply #6 on: January 22, 2010, 04:13:58 PM »
model DSA 030-230

Thanks

Offline Hood

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Re: Help with servos and drives.
« Reply #7 on: January 22, 2010, 05:22:14 PM »
Nice drive, I use them on my mill and lathe :)
Not had a chance to look yet but will try later or tomorrow but I am thinking the intelligent encoders have 9V so that might not work for you.
Hood
Re: Help with servos and drives.
« Reply #8 on: January 22, 2010, 07:11:42 PM »
I pulled apart some Mitsubishi servos that looked as though the had gone bad due to bearing failure. I've got 5 or 6 of them so I'll look into what type of encoders are on them.  Good advice to find encoders on smaller less expensive motors!

Thanks again,

Offline Hood

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Re: Help with servos and drives.
« Reply #9 on: January 22, 2010, 07:31:35 PM »
Just looked at the motor config utility in the drive setup software and seems you can set up a Sine/Cosine encoder and use Hall Inputs for startup commutation so chances are your encoder would work fine.
You would need to make a custom motor profile and then load that into the drive via serial, do you have the DSAPro software?
Hood