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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Setting up AMC BE25A20 in torque mode?
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  1. #1
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    Setting up AMC BE25A20 in torque mode?

    Can anyone help me out, I'm trying to setup Linuxcnc with Mesa 5i25 and 7i77 and AMC 25a20 servo drives, I'm told it's easier and better to have the servos run in torque mode, but I can't seem to find anything that tells me how to do this. I would really like to find a wiring diagram, that would really help me out alot if someone could point me in the right direction, I've searched everywhere and can't find what I need.
    Any help would be greatly appreciated.
    Thanks Mike

  2. #2
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    Re: Setting up AMC BE25A20 in torque mode?

    Quote Originally Posted by CATCH22 View Post
    Can anyone help me out, I'm trying to setup Linuxcnc with Mesa 5i25 and 7i77 and AMC 25a20 servo drives, I'm told it's easier and better to have the servos run in torque mode, but I can't seem to find anything that tells me how to do this. I would really like to find a wiring diagram, that would really help me out alot if someone could point me in the right direction, I've searched everywhere and can't find what I need.
    Any help would be greatly appreciated.
    Thanks Mike
    Wiring of a analog drive in torque mode is no different than velocity mode with the exception that the drive will not use tachometer feedback, so the tachometer will not be connected to the drive
    You do need to setup the drive in torque mode (this is like done with jumpers or dip switch settings and this should be covered in the drive manual)

  3. #3
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    Quote Originally Posted by PCW_MESA View Post
    Wiring of a analog drive in torque mode is no different than velocity mode with the exception that the drive will not use tachometer feedback, so the tachometer will not be connected to the drive
    You do need to setup the drive in torque mode (this is like done with jumpers or dip switch settings and this should be covered in the drive manual)
    OK thanks very much.

  4. #4
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    Quote Originally Posted by CATCH22 View Post
    OK thanks very much.
    OK so I got everything wired up and all the switches on the drive set but it is still giving me the red fault light.

    TB5 GRD to REF-
    TB5 AOUT to REF+
    TB5 ENABLE+ to INHIBIT
    TB5 ENABLE- to GRD

    Any ideas why I'm still getting a fault on the drive.
    Thanks Mike

  5. #5
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    Re: Setting up AMC BE25A20 in torque mode?

    1. I would expect a fault when linuxCNC is enabled because normally with AMC drives the inhibit input is open when enabled and
    grounded when disabled ( which is rather crazy since an unconnected input enables the drives ) You probably need a relay
    driven by enable and wire the NC contacts to the "inhibit" lines change the "inhibit" to "enable"

    2. I would first try with no control connections to the drive, if you still get a fault, the trouble maybe in the drive, drive power, drive--> motor connection etc

  6. #6
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    Re: Setting up AMC BE25A20 in torque mode?

    I have worked with this drive and Galil motion control cards.

    Enable/inhibit goes to an open collector https://en.wikipedia.org/wiki/Open_collector on the galil card.
    basically the drive needs to see either an open or a ground through a correctly sized resistor to enable the drive. Same idea needs to be done with your control.

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    Re: Setting up AMC BE25A20 in torque mode?

    Quote Originally Posted by Karl_T View Post
    I have worked with this drive and Galil motion control cards.

    Enable/inhibit goes to an open collector https://en.wikipedia.org/wiki/Open_collector on the galil card.
    basically the drive needs to see either an open or a ground through a correctly sized resistor to enable the drive. Same idea needs to be done with your control.
    Right thats doable with the 7I77s optocoupler outputs, _except_ that in most cases the AMC drives are assembled/jumpered with the "inhibit when grounded option"
    so the default optocoupler enable circuitry will not work since the outputs are "on" when enabled and the drive needs an "off" when enabled signal

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    Re: Setting up AMC BE25A20 in torque mode?

    This may not hep the OP, but here are the instructions for flipping the output on a Galil card:

    The standard configuration of the AEN signal is TTL active high. In other words, the
    AEN signal will be high when the controller expects the amplifier to be enabled. The
    polarity and the amplitude can be changed if you are using the ICM-1900 interface board.
    To change the polarity from active high (5 volts = enable, zero volts = disable) to active
    low (zero volts = enable, 5 volts = disable), replace the 7407 IC with a 7406. Note that
    many amplifiers designate the enable input as ‘inhibit’.

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    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:

    https://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:

    https://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.

    I am currently working on tuning this and can get it to a following error of < 0.0005 at specific cutting speeds but currently need a max following error of around 0.005 to handle high speed direction changes. I think my encoders may not be helping here (magnetic AMT113Q-V). I haven't actually tried making chips with it yet in CNC mode as I currently have the upper end of the head torn apart for maintenance and to add a spindle encoder (J head clone).

    Sean

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    Quote Originally Posted by seanano View Post
    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:

    https://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:

    https://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.

    I am currently working on tuning this and can get it to a following error of < 0.0005 at specific cutting speeds but currently need a max following error of around 0.005 to handle high speed direction changes. I think my encoders may not be helping here (magnetic AMT113Q-V). I haven't actually tried making chips with it yet in CNC mode as I currently have the upper end of the head torn apart for maintenance and to add a spindle encoder (J head clone).

    Sean
    Hey Sean, I would like a drawing of your electronics if you wouldn't mind, I could possibly copy it to get mine setup.
    Thanks Mike

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    Re: Setting up AMC BE25A20 in torque mode?

    Quote Originally Posted by CATCH22 View Post
    Hey Sean, I would like a drawing of your electronics if you wouldn't mind, I could possibly copy it to get mine setup.
    Thanks Mike
    Sure, here are some pics of the wiring diagrams and the board I made to do the interfacing. The analog pairs don't go through the board but rather are direct connected. The EStop connection shown is to my EStop relay which for this item is wired normally open (E-Stop tripped) to digital ground. R1, R2, and R3 should be 200 - 1K ohms and R4, R5, and R6 should be 1K - 6K ohms. I used 1K for all 6. Ideally R4, R5, and R6 would be closer to 5K to reduce the current draw. Let me know if you have any other questions on this.

    Attachment 421156
    Attachment 421158
    Click image for larger version. 

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  12. #12
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    Quote Originally Posted by seanano View Post
    Sure, here are some pics of the wiring diagrams and the board I made to do the interfacing. The analog pairs don't go through the board but rather are direct connected. The EStop connection shown is to my EStop relay which for this item is wired normally open (E-Stop tripped) to digital ground. R1, R2, and R3 should be 200 - 1K ohms and R4, R5, and R6 should be 1K - 6K ohms. I used 1K for all 6. Ideally R4, R5, and R6 would be closer to 5K to reduce the current draw. Let me know if you have any other questions on this.

    Attachment 421156
    Attachment 421158
    Click image for larger version. 

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    Thanks Sean, now all I have to do is figure out how to read electrical schematics. Lol

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    Quote Originally Posted by CATCH22 View Post
    Thanks Sean, now all I have to do is figure out how to read electrical schematics. Lol
    Hey Sean where did you get the stuff to make your own boards?

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    Re: Setting up AMC BE25A20 in torque mode?

    Quote Originally Posted by CATCH22 View Post
    Hey Sean where did you get the stuff to make your own boards?
    Most of the parts I had left over from previous projects. The only thing I had to buy were the CPC1333G chips and I got those from DigiKey:

    https://www.digikey.com/product-deta...388-ND/3077506

    Mouser also has them. I tend to get most of my chips from those two places. The circuit board and terminals can be found in sets at a lot of different places including Amazon and eBay. I just bought a set off of Amazon for making my spindle encoder board:

    https://www.amazon.com/gp/product/B07PD1HFHQ

    I haven't actually used it yet so this is not an endorsement of that particular item. You can solder the CPC1333G chips directly to the board but I prefer to use IC sockets so they are easier to replace if necessary. A single 24 pin DIP socket is sufficient for this board. I had a couple of 14 pin sockets laying around so I used those with a gap between each pair of chips. You can find the sockets at DigiKey, Mouser, Amazon, or eBay. Depending upon where you live there may still be an actual electronics store locally that may have them.

    For the resistors, 1/2 watt and pretty much any tolerance will work. Might as well get them from where you are getting the chips. Note that if you aren't using 24VDC for the 7i77 Field I/O then the resistor values may need to be changed.

    As for reading the schematic, just follow the lines. Any big dots are junctions. Squiggly lines are resistors. The CPC1333G chip pins are labelled on one of the drawings. Pay attention to orientation. For each axis, I have the chips flipped 180 degrees since one chip is output from the 7i77 and the other chip is output from the AMC drive.

    A disclaimer... I am not an electronics pro, just a hobbyist. I have only been using the board for about a month and it functions as I expected. Before you go through the effort of making this, do make sure your drives are functioning properly if you haven't done so already. Go through the drive setup section in the manual I referenced earlier as it walks you through this.

  15. #15
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    Quote Originally Posted by seanano View Post
    Most of the parts I had left over from previous projects. The only thing I had to buy were the CPC1333G chips and I got those from DigiKey:

    https://www.digikey.com/product-deta...388-ND/3077506

    Mouser also has them. I tend to get most of my chips from those two places. The circuit board and terminals can be found in sets at a lot of different places including Amazon and eBay. I just bought a set off of Amazon for making my spindle encoder board:

    https://www.amazon.com/gp/product/B07PD1HFHQ

    I haven't actually used it yet so this is not an endorsement of that particular item. You can solder the CPC1333G chips directly to the board but I prefer to use IC sockets so they are easier to replace if necessary. A single 24 pin DIP socket is sufficient for this board. I had a couple of 14 pin sockets laying around so I used those with a gap between each pair of chips. You can find the sockets at DigiKey, Mouser, Amazon, or eBay. Depending upon where you live there may still be an actual electronics store locally that may have them.

    For the resistors, 1/2 watt and pretty much any tolerance will work. Might as well get them from where you are getting the chips. Note that if you aren't using 24VDC for the 7i77 Field I/O then the resistor values may need to be changed.

    As for reading the schematic, just follow the lines. Any big dots are junctions. Squiggly lines are resistors. The CPC1333G chip pins are labelled on one of the drawings. Pay attention to orientation. For each axis, I have the chips flipped 180 degrees since one chip is output from the 7i77 and the other chip is output from the AMC drive.

    A disclaimer... I am not an electronics pro, just a hobbyist. I have only been using the board for about a month and it functions as I expected. Before you go through the effort of making this, do make sure your drives are functioning properly if you haven't done so already. Go through the drive setup section in the manual I referenced earlier as it walks you through this.
    Awesome, thanks Sean.

  16. #16
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    Quote Originally Posted by seanano View Post
    Most of the parts I had left over from previous projects. The only thing I had to buy were the CPC1333G chips and I got those from DigiKey:

    https://www.digikey.com/product-deta...388-ND/3077506

    Mouser also has them. I tend to get most of my chips from those two places. The circuit board and terminals can be found in sets at a lot of different places including Amazon and eBay. I just bought a set off of Amazon for making my spindle encoder board:

    https://www.amazon.com/gp/product/B07PD1HFHQ

    I haven't actually used it yet so this is not an endorsement of that particular item. You can solder the CPC1333G chips directly to the board but I prefer to use IC sockets so they are easier to replace if necessary. A single 24 pin DIP socket is sufficient for this board. I had a couple of 14 pin sockets laying around so I used those with a gap between each pair of chips. You can find the sockets at DigiKey, Mouser, Amazon, or eBay. Depending upon where you live there may still be an actual electronics store locally that may have them.

    For the resistors, 1/2 watt and pretty much any tolerance will work. Might as well get them from where you are getting the chips. Note that if you aren't using 24VDC for the 7i77 Field I/O then the resistor values may need to be changed.

    As for reading the schematic, just follow the lines. Any big dots are junctions. Squiggly lines are resistors. The CPC1333G chip pins are labelled on one of the drawings. Pay attention to orientation. For each axis, I have the chips flipped 180 degrees since one chip is output from the 7i77 and the other chip is output from the AMC drive.

    A disclaimer... I am not an electronics pro, just a hobbyist. I have only been using the board for about a month and it functions as I expected. Before you go through the effort of making this, do make sure your drives are functioning properly if you haven't done so already. Go through the drive setup section in the manual I referenced earlier as it walks you through this.
    Hi Sean, I am just starting to get back to it, just wondering if you have had a chance to try your boards out yet and if you have made any changes before I drive in.
    Thanks Mike

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    Quote Originally Posted by CATCH22 View Post
    Hi Sean, I am just starting to get back to it, just wondering if you have had a chance to try your boards out yet and if you have made any changes before I drive in.
    Thanks Mike
    Hey Sean, could you also tell me what size boards you used.
    Thanks Mike

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    Re: Setting up AMC BE25A20 in torque mode?

    Mike,

    That CNC mill project is currently on hold. Other projects have had a higher priority. I'm hoping to get back to it in the next few months but we'll see how that goes... However, I have ran the board I made for about 5 hours while tuning the axis and it functioned without issues so I'm not expecting it to need any additional changes. The board I used had a 25x15 hole grid. You could probably go down to 22x14 with the same layout and components I used but I wouldn't recommend going any smaller. The holes are spaced the standard 0.1 inches so my board is 2.4 x 1.4 inches for the working area. Looking at the board kits on Amazon, 7x5 cm boards seem to be a common size that should be fine (24x18 hole grid). Let me know if there is anything else I can do to help.

    Sean

  19. #19
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    Re: Setting up AMC BE25A20 in torque mode?

    I have made up boards in the past very similar to this, I prefer to use Vero Strip Board Board and the other components from Digikey.
    Boards. half way down. https://www.futurlec.com/Protoboards.shtml
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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    Re: Setting up AMC BE25A20 in torque mode?

    Thanks alot Sean.

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    Re: Setting up AMC BE25A20 in torque mode?

    Quote Originally Posted by Al_The_Man View Post
    I have made up boards in the past very similar to this, I prefer to use Vero Strip Board Board and the other components from Digikey.
    Boards. half way down. https://www.futurlec.com/Protoboards.shtml
    Al.
    Thanks Alot.

  22. #22
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    Quote Originally Posted by Al_The_Man View Post
    I have made up boards in the past very similar to this, I prefer to use Vero Strip Board Board and the other components from Digikey.
    Boards. half way down. https://www.futurlec.com/Protoboards.shtml
    Al.
    Thanks Alot The Man

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    Re: Setting up AMC BE25A20 in torque mode?

    Hey Sean for the drive fault out of the drive, where did you put it on the 7i77.

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    Hey Sean, where did you wire the drive fault into the 7i77 Mesa board.

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    Quote Originally Posted by CATCH22 View Post
    Thanks Sean, now all I have to do is figure out how to read electrical schematics. Lol
    I made one of these boards that Sean so kindly shared with me, but I can't figure out where the fault goes into the 7i77 board, can't see anything in the manual about it.
    If anyone can help me out I would really appreciate it.
    Thanks Mike

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