# Parallel limit switch connection problem

13 May 2018 16:51 #110686

Looking at your picture, I'd suggest your machine is currently in a position that represents X & Y at the maximum positive extents of their travel.

It represents the minimum positive extents. On my first picture, the machine is at 0:0:0 (it's the bottom left corner, like a simple Cartesian system)
I'll try to play around with those variables and see what I get. As soon as I test it I'll put the results here
13 May 2018 16:54 #110687 by DanMN
No worries, you can just flip the directions around. the spindle on the "back" side of the gantry threw me off. But my machine is against a wall, making that configuration way too gymnastic for tool changes
13 May 2018 17:02 - 13 May 2018 17:07 #110688 by DanMN

Also, if you're going to use the limit switch as homing switch also, make sure you leave physical distance for overshoot during latching. Usually the trip plate will be oriented so that overshoot won't crush the switch - like the example in my pic. That's why no-touch sensors are preferred for homing, but it's possible to use microswitches if you use very slow latch velocities and the trip arm of the switch doesn't get bent in overshoot.
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Last edit: 13 May 2018 17:07 by DanMN.
14 May 2018 05:13 #110715 by cmorley
So to have one pin for all limits - you need to connect that pin (in HAL) to all the limits: positive and negative.
usually the switches are wired in series with power normally running through them - so that a broken switch or wire triggers a limit.

Are you using a master version of linuxcnc? in that case the axis limits and the joint limits both must be set properly in the INI file.

I might add the stepconf can make a variety of different limit/home switch configurations - you could build a sample and look at the code.

Chris M
14 May 2018 06:53 #110718

cmorley wrote: So to have one pin for all limits - you need to connect that pin (in HAL) to all the limits: positive and negative.
usually the switches are wired in series with power normally running through them - so that a broken switch or wire triggers a limit.

Are you using a master version of linuxcnc? in that case the axis limits and the joint limits both must be set properly in the INI file.

I might add the stepconf can make a variety of different limit/home switch configurations - you could build a sample and look at the code.

Chris M

Look at my first post, please. I connected all of them to all limits. The problem is that they cannot be overridden when the 0 position is reached

Are you using a master version of linuxcnc?

Most probably. But I'm not sure. It was about a year ago when I downloaded and installed it
14 May 2018 16:21 #110731 by cmorley

net XYZ-max-lim parport.0.pin-12-in-not => axis.0.pos-lim-sw-in axis.1.pos-lim-sw-in axis.2.pos-lim-sw-in

those are not the only limit switches - there are negative switches too.

You also have the z axis negative switch and home switch connected to another parport pin, based on your HAL file pic.

You are using linuxcnc 2.7.0 based from the pics.

Chris M
15 May 2018 09:01 #110751

net XYZ-max-lim parport.0.pin-12-in-not => axis.0.pos-lim-sw-in axis.1.pos-lim-sw-in axis.2.pos-lim-sw-in

those are not the only limit switches - there are negative switches too.

You also have the z axis negative switch and home switch connected to another parport pin, based on your HAL file pic.

You are using linuxcnc 2.7.0 based from the pics.

Chris M

Sorry, I must have misunderstood you
This settings were the ones I found on the web here wiki.linuxcnc.org/cgi-bin/wiki.pl?Homing_And_Limit_Switch
I'd appreciate if you could tell me what exactly I should do with my config to make it work properly
15 May 2018 21:12 #110773 by cmorley
My guess is you might have a combination of axis going in wrong direction and misconfigured limits in the HAL file.
But try this:

Now you said you wired all the limit switches together yet your HAL file says you are using two parallel port pins.
For now I'm gonna assume that all the limits switches are through one parallel port pin

remove the two lines of HAL code that set limits.
```net XYZ-lim    parport.0.pin-12-in-not
net XYZ-lim    axis.0.pos-lim-sw-in    axis.0.neg-lim-sw-in
net XYZ-lim    axis.1.pos-lim-sw-in    axis.1.neg-lim-sw-in
net XYZ-lim    axis.2.pos-lim-sw-in    axis.2.neg-lim-sw-in```

Then carefully test and let us know what happenned.

Chris M
The following user(s) said Thank You: caseyryan
20 May 2018 08:08 #110921
Hi Chris!
I've just tested your config, and it worked just as I wanted. Now I can override limits in both directions. Thanks a lot!
20 May 2018 13:57 #110926 by cmorley
You're welcome... glad you got it working the way you want.

Chris M
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