SouthWestern Industries Prototrak servo drive replacement with A-M-C 12A8

Todd, Many, many thanks!! "Ok, according to how it connected to the 7i77 the encoder is differential without index.
My question: " Does this mean the encoders are differential or single ended wiring?

Edit:
The encoders provide a "back EMF" type/form of feedback for velocity control.

So differential encoders have additional set of Complimentary or “mirror image” signals to reduce "electrical noise".

Encoders with "index" often have an additional channel, referred to as index channel. This channel outputs one pulse per revolution, and is typically an extremely narrow pulse equal to about one-quarter of the width of an A or B channel pulse, but it can be wider. The encoder index can be used for homing (absolute position reference) and for commutation alignment.

many thanks!!


Edit: I welcomed all help. Attached is a diagram (please disregard the top image, I used marker to darken up lines in bot scan) with the leads for encoder (single ended US Digital) going the way I think they should be going. The original encoder was propriety, I had no info, now using "single ended encoders", I am seeking a 2nd opinion on diagram, please. This is USDigital part numbers:

EM1-2-500-N
www.usdigital.com/products/encoders/incr.../modules/EM1-2-500-N

HUBDISK-2-500-500-NE
encoder wheel:
www.usdigital.com/products/encoders/incr...HUBDISK-2-500-500-NE

CA-LC5-W4-NC-1
Cable&Connector
www.usdigital.com/products/accessories/cables/CA-LC5-W4-NC-1

many thanks, all help warmly welcomed.

That looks like it would be correct for connecting a single ended encoder. (Don't forget the enable wiring which you don't have on those drawings.)

Don't forget to change the jumpers on the 7i77 for single ended encoder inputs. (see the 7i77 manual for details) There is a separate jumper for each input line on each encoder for the 7i77. (that would be 3 jumpers per encoder A,B, and Index.)

But I'm not sure that the single ended vs differential pair signals was source of your problem.

Todd, Many thanks. I have jumpers in the left location as per the 7i77 drawing. The enable wiring, how does one decide? I have studied the manual for the 12a8 and 7i77 and 5i25, what am I looking for, or is this something more involved, that requires many years of hands on? Is it possible on the 12a5 driver #4 pin (+REF IN) go to TB5 location 2 (ENAO+) & 12a8 driver #5 pin (-REF IN) go to TB5 location 1 (ENAO-), from looking at the pictures this may have been the way it was wired with the original encoders? If now that single ended encoders are used does this mean or require the enable wiring as you have suggested? I am just thinking about the way the 12a8 were 1st used.

many thanks!

Edit: This encoder is used as, back EMF as a form of feedback for velocity control?

many thanks.

Many thanks to all that make this forum so helpful, I am so grateful. Attached is a pic of latest hal scope of x axis. I have started with the P, I & D setting from prior setup that worked. See name of file for detail settings. I have several drives, but only 2 have green LED and do not have "run away" as soon as e stop is released. The pic is of x axis and this axis works as per commands, arrow keys.

The drive in y axis will not respond to arrow keys, but DRO shows motion & velocity shows the feed rate that is selected, but no motor motion.

I believe the drive in the x axis is working and needs more tuning. The only difference in the tuning of this drive and the original 12a8 is that I did not have data sheet on motor and POT 2 (I think is the one to adjust max current) so the tuning may not be exactly the same.

The drives that I have that I don't think will work; 1 of them has Red LED; 2 of them make the motor run away as soon as e-stop is released.

Any help warmly welcomed. I plan to buy 12a8 (or something close) drive from ebay.

Many thanks

Did you read my response on your other post? I marked up your analog drive connections. The ones shown here look correct.
Is it possible that one of your drives are still miswired?

Many thanks to Todd, OT-CNC, the forum members and the moderator piasdom for all the help and guidance. I have a (new to me, from ebay) AMC power supply PS2x300, and 25A8 drives.

Set up: SW1-1, 2 & 4 are off; SW1-3 is on; POT 1 is full CCW (current mode) and POT2 after the 14 turns CCW; turn 6 3/4 to 6.8 turn CW to not exceed motor data 6.25 Amp. (see attachment). I am not completely shore of this setting, could use a 2nd opinion. Attached is 25a8 data sheet, see page 6 and 8, I think.

All help warmly welcomed!
many thanks

The 25A8 uses tach feedback. You can't use the encoder on them according to the attached pdf. Did you abandon the other drives? I'm losing track of what direction you're going in. Someone else will have to help you with other feedback options with this as I only have set up with tach or encoders.
What feedback to the drive are you now planning on using? I assume you are still using the encoder mounted to the motor for feedback to linuxcnc?

Regarding your amp setting question, you need to know the continuous amp and peak amp values of your motor. The attached doc shows rated 6.25 amp and a graph that peaks under 14 amp? I would check with SW to see if that reflects continuous and peak values. Then adjust the pot accordingly. The 12A8 will be closer out of the box than reducing a 25A8. Again, check with AMC but if I read correctly, on the 25A8 you would need to reduce the current by 1/2 or more with pot 2 if your motor is 6.25a continuous and 12a peak as an example.

OT-CNC, Many thanks! I offer my sincere apology for the confusion, the new digital drives I simply after 90 days lost confidence. The inability to decide on a wiring diagram after that length of time made me decide to return the drives. I am going to find some 12a8 as to go back to the original set up, until now I was not aware the 25a8 were not going to work. The encoders are on back of motor, I was thinking "back EMF" (I think, this is what was used originally) as feedback to drive.The motors are 6.25 amp continuous and 12a peak as you stated. The AMC power supply has options, see attached .pdf, page 2, I believe.many thanksEdit: OT-CNC, I have read the .pdf you refer to "The 25A8 uses tach feedback. You can't use the encoder on them according to the attached pdf.". I am unable to find the part that says the 12a8 is different than the 25a8 for feedback. Is there a different document I need to read? Just want to clearly understand.Edit: add current diagram

The 12A8 is the same family as your 25A8. If you want to read in encoders the BE series (I'm using BE25A20) discontinued product can do so. It's a brushless drive that can do brushed motors as well. If you're looking at fleabay, check to make sure there is a P3 encoder connector present, labeled channel A and channel B.
The 25A20 should be able to do the same as what the 12A8 did. Is it possible that the original motors had tachometers fitted for feedback to the drives?

OT-CNC, Many thanks for the help. I see your P3 requirement (on the BE25A20) and I greatly appreciate your help. If you read the following post (I am not suggesting you do, it is long) the diagram I have posted works with a good drive. I have several 12a8a and 1 good one (so far) in addition to the 25a8s (these need the J1 (resistor location) replaced, and these are on order).

Edit: Motors have encoders only.

This post date (describes TB5 to driver connection) is about the diagram and set up of original conversion: 01 Apr 2017 17:43 - 02 Apr 2017 13:31 #90721 This is link to the entire post: forum.linuxcnc.org/12-milling/32294-prot...5i25-cards?start=170

I believe the 25a8s will work if the J1 is all thats needed and provided POT 2 is adjusted proper. I may go back to use the Prototrak power supply, I am not shore of the max/peak amp of the AMC power supply when using the 48vdc 6 amp option.

Many thanks