Limit Switches and One Way Jogging

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21 Sep 2021 16:19 #221276 by gmr
Hi All,

I have a setup of an XY milling table to which I've attached stepper motors and position encoders.

I have fitted limit sensors at the extreme end of the travel for each axis, but rather than disabling the motor drivers when they are active, I want to configure it so that I can use the jog wheels to move out of the extreme position and back into normal mode. However, I don't want the table to be able to travel further in the direction that has reached the limit, i.e. I want the jogging to become uni-directional when the limit sensor is active.

It seems that soft limits might be a way to do this, but I don't have room to add home switches and the encoders are all incremental with no index pulse.

Thanks (and thanks to all the historic posters, I have learned much from studying this forum).

Greg


 

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21 Sep 2021 18:07 #221282 by tommylight
No need for home switches, LinuxCNC can work with limits and use one side as a home also.
Pretty sure everything you require is already there, just needs to be set up in HAL.
Attaching the config files might help...

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22 Sep 2021 13:24 #221341 by gmr
Thanks, my apologies, I misunderstood the excellent documentation, which is here for the next person:

linuxcnc.org/docs/html/config/ini-homing.html

I setup the joint section of the INI file like this:

# machine units are mm
[JOINT_0]
HOME = 0
HOME_OFFSET = 150
HOME_SEARCH_VEL = 8
HOME_LATCH_VEL = 0.25
HOME_FINAL_VEL = 8
HOME_IGNORE_LIMITS = YES
HOME_USE_INDEX = NO


And the relevant bit of my HAL file looks like this:

# inputs from the Hall effect sensors
net x-limit-min <= hm2_7c81.0.gpio.038.in_not
net x-limit-max <= hm2_7c81.0.gpio.039.in_not

# ---setup home / limit switch signals---
net x-limit-max   =>  joint.0.home-sw-in
net x-limit-min   =>  joint.0.neg-lim-sw-in
net x-limit-max   =>  joint.0.pos-lim-sw-in

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