Limit switch and E-Stop configuration

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03 Apr 2021 19:19 #204650 by Bearfood
I get a few steps forward and despite many searches I can't seem to find what I'm looking for and end up back here.

I have a 7i96 board and I'm trying to get the E-stop and limit switches working. I've wired the E-Stop to +12v into the isolated TB3 input 0, X limit into input 1, Y1 to input 2 and Y2 into input3. I haven't done the Z limits yet because I can't get any of them working at the moment. :)

In pncconf is as follows:
000 = E-stop, GPIOInput
001 = X minimum limit + home, GPIOInput
002 = Y1 minimum limit + home, GPIOInput
003 = Y2 minimum limit + home, GPIOInput

HAL and INI files attached. Thanks for your help!
Attachments:

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03 Apr 2021 19:25 #204651 by Michael
What do you have connected to the 7i96 common pin? Believe it is TB3 pin13 or near there. You need to have the reference voltage connected to that pin. For your estop that would be connected to the 12v-.

What type of limit switches? This will also determine how to wire the TB3 common pin. The hal file looks fine.

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03 Apr 2021 19:49 #204656 by Bearfood
Ah, so the -12v goes to the common? No I don't have that. That makes more sense. I'm nervous as he'll connecting anything above 5v to this board.

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03 Apr 2021 20:14 #204658 by Bearfood
Okay, that got my E-stop working and to a degree the limit switch.

On the X, if I check the INV box and the x isn't touching the limit switch it will home to the limit switch and then I can do nothing more because I have a "joint0 on limit switch error on the LinuxCNC console. If I leave the INV button unchecked I get that error right out of the gate. Any thoughts?

It would be good to have a section on limit switches but maybe I'm just a bigger idiot than others. :)

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03 Apr 2021 20:21 - 03 Apr 2021 20:43 #204659 by Bearfood
Limit switches are wired to the Normally Closed position.

I tried rewiring to the NO positing and unchecking the INV box but I get the same issue. It homes but then stops and gives me an error on Joint0.
Last edit: 03 Apr 2021 20:43 by Bearfood. Reason: I was wrong in my original

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03 Apr 2021 22:51 #204679 by Bearfood
I managed to get a working configuration by switching all the limit switches in pnconf to home and not home + minimum limit. Now I don't get the error at least. Is this the way I should have had this all along?

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04 Apr 2021 01:44 - 04 Apr 2021 01:53 #204701 by Michael
In your ini file it looks like the x axis is homing to -.001" and its home position is 0.000 which means you are probably still on the limit switch after the homing move and getting that error. There is a certain amount of throw you will need to account for in the switch itself. When homing is complete all axis will be at the G53 0 position. So you aren't moving much off the switch, that reverts back to a limit switch after the homing operation. Make your home position further from your limit position.
Try:
MIN_LIMIT = -0.050
MAX_LIMIT = 47.900
HOME_OFFSET = -0.100

You can experiment but to break it down:
MIN_LIMIT = -0.050 is the lowest the dro/axis will go during movement

MAX_LIMIT = 47.900 is the highest the dro/axis will go during movement

HOME_OFFSET = -0.100 is where the switch is. The only time it will intentionally move to this switch is when you ask for it to home. If something goes wrong during normal motion/program then it will be a limit point and trigger motion stop.


The common pin is basically what you are referencing to. So using the 12v- means that all inputs will need to have the circuits negative end terminated to the input and will be True at 12v (circuit closed) and false at 0v (circuit open). In this setup a loose or broken wire will trigger an estop or limit error.
Last edit: 04 Apr 2021 01:53 by Michael.
The following user(s) said Thank You: Bearfood

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09 Apr 2021 16:20 #205442 by Bearfood
That seems to have worked.

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