How to connect Closed Loop Steppers to a 7i76E?

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09 Sep 2021 01:47 #220025 by Twizzlermill
Hello all,

I'm currently in the process of setting up my Mesa 7i76e card and I still have some questions.

Mainly it's this:

I have JMC closed loop steppers. I'm assuming the brand is not particularly important. Their drivers have six inputs and four outputs: 

In: Enable+/-, Step+/-, Dir+/-
Out: Position+/-, Alarm+/-

I decided not to bother with Enable, so it can stay unconnected for now.

Connecting Step/Dir is easy enough, but I'm not sure where I need to put W10, W11 and W13 to properly drive the steppers. Differential rather than single ended is my guess, so right hand position (I'm referring to page 2 of the manual)?

Also, I'm not sure where to connect the outputs Position and Alarm and whether I need to run external power through them (I'm assuming the driver will provide it?). Is the Mesa card in combination with LinuxCNC even capable of using position information from the steppers? I know I don't technically need them to run the motors, but they are there and I want to use them – especially Alarm.


I feel a little dumb for asking these questions because I feel like I should be able to find the answers on my own, but I really don't want to destroy my hardware… 

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09 Sep 2021 03:19 #220033 by PCW
W10,W11 and W13 set the input mode of the encoder,
they are not related to the step/dir outputs

For step/dir wiring I would wire the drives STEP+ and DIR+ to the 5V terminal on
the 7I76E's Step/Dir connectors and the drives STEP- and DIR- to the 7I76E's
Step- and Dir-.

For alarm, I would wire ALARM+ to +24V and ALARM- to a 7I76E field input

I would not bother with feedback position on step/dir systems
unless you have linear encoders
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09 Sep 2021 09:52 #220045 by Twizzlermill
Thank you​​​​​​ for your answer. I think I'm missing a lot of vital information here and I don't really want to burden you with answering all the questions I have, so do you happen to know a write-up or video or something that goes into detail about the essentials?

For example, I don't really know what you mean by the input mode of the encoder exactly. 

W10,W11 and W13 set the input mode of the encoder,
they are not related to the step/dir outputs

Isn't it kinda important whether I want to use differential mode or not?

For step/dir wiring I would wire the drives STEP+ and DIR+ to the 5V terminal on
the 7I76E's Step/Dir connectors and the drives STEP- and DIR- to the 7I76E's
Step- and Dir-.

I don't exactly understand this part about wiring. If I take a look at the connection sheet provided by Norbert here:
forum.linuxcnc.org/27-driver-boards/3191...76e-connection-sheet

forum.linuxcnc.org/media/kunena/attachme...hluss_2017-01-02.pdf

...where does the +5V wire actually go on the driver side?
I played around with a cheap breakoutboard and I know that I can drive the motors by just connecting Step+/Dir+ and putting Step-/Dir- on Ground on the board, but someone pointed out that I'd lose the differential mode this way. Is this a similar idea?

For alarm, I would wire ALARM+ to +24V and ALARM- to a 7I76E field input

I would not bother with feedback position on step/dir systems
unless you have linear encoders

PCW post=220033 userid=481

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09 Sep 2021 15:23 - 09 Sep 2021 15:28 #220062 by PCW
The encoder setup via W10,W11,W13 must match the type of
encoder you have (single ended or differential)

The step/dir wiring I suggested is as follows (using channel 0 in this example)


TB2 PIN       DRIVE CONNECTION
1 GND         NONE
2 STEP0-     STEP-
3 STEP0+    NONE
4 DIR0-        DIR-
5 DIR0+       NONE
6 +5V           STEP+,DIR+

 
Last edit: 09 Sep 2021 15:28 by PCW.
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09 Sep 2021 22:32 #220087 by Twizzlermill
Huh, interesting. According to the JMC manual, the steppers can be run like this, but also with differential mode. Is there a particular reason why you'd connect them up like this and not Step+ to Step+, Step- to Step- and so on? What are the advantages/disadvantages of the two approaches?

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09 Sep 2021 22:58 #220088 by PCW
You could run them differentially but this does result in lower
optocoupler drive current which can be an issue with some
drives.
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10 Sep 2021 12:23 #220122 by Twizzlermill
Ok, that makes sense. Is there any particular risk in trying both ways (apart from ruining whatever I'm currently working on)?

Also, would this mean that I have to change Jumper W10, W11, W13 positions?

Thank you yery much for your help btw., I think I understand a lot more now.

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10 Sep 2021 13:19 #220127 by PCW
No risk except missed steps is its marginal

W10,W11,W13 only set the spindle encoder mode
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10 Sep 2021 14:06 #220132 by Twizzlermill
Ah, got it. Thank you.

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