Set up using AMC AB15A100 drives, brushed DC motor Prototrak Plus with Encoders

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15 Apr 2022 15:54 #240321 by new2linux
I have read this at post #9 at this link: www.cnczone.com/forums/servo-motors-driv...a20-torque-mode.html

This describes that AMC drivers require a way to inhibit the drive. Does this apply to my application?

Many thanks, for all help is warmly welcomed.



"Re: Setting up AMC BE25A20 in torque mode?

I am currently working on a retrofit using the Mesa 7i92, 7i77, and AMC 30A8 drives in torque mode which should be very similar to your setup. I don't know if you have seen them, but AMC has multiple manuals on their site that provide details on how to setup the drives in torque mode, adjust offsets, and such. Go to their website and search for your model:

www.a-m-c.com/products/?page=product&id=25A20

This will give you the datasheet for your specific model. On the above page, if you click on the reserved and discontinued items link, there will be a link to the classic analog drives HW manual which has a bunch of good information on setting up the drives. A direct link is here:

www.a-m-c.com/wp-content/upl...alog_Panel.pdf

PCW_MESA is correct in that the inhibit line left open enables the drive by default (it has an internal pull-up to +5VDC). I wanted the drive to be disabled by default and and didn't want to modify the drive's circuit board so I am using a normally closed solid state relay to pull the inhibit line to ground at power up or any other time when either the E-Stop is triggered or the drive enable switch isn't turned on. I also use another NC SSR for the fault line feedback to the 7i77 since I'm using 24VDC for field IO and the AMC drive uses a 5VDC TTL output. I can provide a hand drawn schematic for my interface board if you are interested. It uses 6 x CPC1333G ICs (4 pin DIP NC SPST SSR) and 6 resistors for current limiting."

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28 Apr 2022 13:22 #241479 by new2linux
Many thanks andypugh for your help! This is you offering the diagram describing "DC servos with tachometers. A +/- 10V analogue control signal into the drive" (12 Dec 2016 09:55 #83938 the link:
forum.linuxcnc.org/12-milling/31949-deck...4ma-retrofit?start=0)
Could I start with this diagram and where the tachometers attach, replace with encoder input??
The diagram is at this link, I will try to attach pic: forum.linuxcnc.org/media/kunena/attachments/723/Deckel_p115.pdf
Attachments:

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28 Apr 2022 22:09 #241576 by andypugh

Could I start with this diagram and where the tachometers attach, replace with encoder input??

Probably not. 

Old analogue drives with tachometers used a very simple scheme where the control voltage and the tachometer voltage were compared and the motor voltage set accordingly.  Encoders don't output a voltage proportional to speed, so more interfacing is needed. 

Now, if the drives are already conffigured to close an internal velocity loop from the encoder pulses, then what you describe will work. 

But, is it? 
 
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29 Apr 2022 16:38 #241649 by new2linux
andypugh, Many, many thanks!! I have read this response several times,

"are already configured to close an internal velocity loop from the encoder pulses,"

I can/will research this more if necessary, if this will lead to success.

Or if there is a way to use the P1 Connector; location: Pin 8 Current Monitor (Note in AMC AB15A100 Drive manual, says: analogue output signal proportional to actual current output). Is this a potential workaround or part of a successful approach?

Many thanks!! All help is warmly welcomed.

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01 May 2022 23:07 #241818 by andypugh
If the drives only mention that current is proportional to input voltage then they are torque-mode drives, and the encoders go straight to LinuxCNC, not to the drives.

This is fairly common, both my servo machines work that way.
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04 May 2022 19:10 - 13 Jun 2022 18:23 #241996 by new2linux
Many, many thanks, andypugh, I have read your reply:I have just got off phone with news: I am working with AMC support engineer a question has come up about when booting up LinuxCnc it appears as if I had forgotten to power up the power supply for the AMC drives

Edit: the proper wiring diagram, dated 6/2022 attached.
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Last edit: 13 Jun 2022 18:23 by new2linux. Reason: new info; attach diagram; add equation for POT2 Edit: Proper wiring diagram attached dated 6/2022

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06 May 2022 16:18 #242152 by new2linux
Many thanks to the forum moderators, members and others that make this forum so informative.
As per suggestion to include pic of the error screenshot attached.

 

Many thanks!!
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06 May 2022 19:35 #242167 by andypugh
5i25.0.7i77.0.1.analogoutout0-scalemax not found

This might indicate that the 7i77 field power supply (which runs a small processor on the 7i77 ) might not be connected.

This is (typically) the 24V supply used for limit switches etc, which it is quite reasonable to not expect to need yet. (It doesn't have to be 24V, anywhere from 5 to 30 is OK)
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06 May 2022 19:59 - 06 May 2022 20:43 #242170 by new2linux
Many thanks, andypugh!!

I will be checking the 2 small transformers for voltage over the weekend.

Many thanks for your time.

Edit: There are 2 transformers, 1 is 5.6 v DC; the other 1 is burnt out, it was 24 v DC, went to TB-2. I plan to try the other 5.6 v DC transformer to both TB-1 & TB-2.

Many thanks, I am very greatful for the help!!
Last edit: 06 May 2022 20:43 by new2linux. Reason: note about transformers

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08 May 2022 14:14 #242302 by new2linux
Over the weekend, I used the 5.6 v DC transformer (power supply to TB-1) & then, used a 12 v rechargeable battery to supply power to TB-2. The same error message appears both times, "5i25.0.7i77.0.1.analogoutout0-scalemax not found". To be clear, TB-5, pins 1 & 2 are not connected to anything, yet. I have ordered replacement 24v DC transformer.

Many, many thanks for helping, all suggestions are warmly welcomed.

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