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wiring home switch and index to PP

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13 Sep 2021 15:16 #220447 by mikeT
I have both home switches and index switches on the X and Y axes on my mill. How do I connect them to the parallel port. Can it be done through stepconfig?

Thanks for your hep and advice

MikeT

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13 Sep 2021 18:09 #220479 by mikeT
Stepconfig will allow me to allocate ONE home switch to the X and Y axes. I wish to allocate a home switch PLUS a index switch to the each of the X and Y axes. I am looking for help and advise on how to do this.

Thanks

MikeT

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13 Sep 2021 21:34 #220510 by tommylight
Most probably it can be done, but i fail to comprehend why would you use 2 switches for the same thing, it will not help with homing precision. Index homing is used for servo systems to always home at the same motor position.
Uses
home_use_index = 1
in the .INI file, but it should also have an entry in the .HAL file connecting the input with the index pin.
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13 Sep 2021 21:55 - 13 Sep 2021 22:52 #220516 by mikeT
Thanks for getting back.

I have been told?? that a home switch plus an index switch will give higher homing precision than a home switch alone. Any switch timing/position  error would be significantly smaller on the faster index disc movement, than on the slower carriage movement.

My machine is a modified EMCO VMC, now running on LinuxCNC. It uses steppers, not servos and has both magnetic home switches and magnetic index switches installed. They must have done that for a good reason

Thanks again for you help

MikeT
Last edit: 13 Sep 2021 22:52 by mikeT.

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13 Sep 2021 23:02 #220526 by tommylight
Are the indexes on the motors or near the home switches?
If near the home switches, they are home and limit switches, but LinuxCNC does not require that, it can use the same switch for home and limit.
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14 Sep 2021 09:32 #220567 by mikeT
Thank you tommylight for showing an interest.

The 'home' switch is tripped by the table as it approaches end of travel. The 'index' switch is tripped, once per revolution, by the pulley on the leadscrew; that's every 4. 0 mm of travel.
I assume that homing is done at rapid speed until the 'home' switch is tripped (course homing) and then at slower speed until the next 'index' switch is tripped for fine homing.
I know nothing about the accuracy and repeatability of the magnetic switches, so can only assume they were adequate; neither good or bad.
It's definitely two switch homing

Miket

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14 Sep 2021 09:38 #220568 by tommylight
OK that is the case when index is useful, so have a look at the docs, homing section should have info on index use and setup for sure.
On phone so cant do much.
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14 Sep 2021 10:04 - 14 Sep 2021 11:02 #220570 by mikeT
The homing section in the docs talks only about index use and the ini settings.
I am still trying to find a way to connect the switches to the parport.
It looks like I will need to change the hal as well.
It's getting to be a bit beyond my pay scale. Think I'm gonna need some help on this one

MikeT
Last edit: 14 Sep 2021 11:02 by mikeT.

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14 Sep 2021 14:31 #220602 by Clive S

The homing section in the docs talks only about index use and the ini settings.
I am still trying to find a way to connect the switches to the parport.
It looks like I will need to change the hal as well.
It's getting to be a bit beyond my pay scale. Think I'm gonna need some help on this one

MikeT

I think its time to post your hal and ini files and the version of Linuxcnc that you are using

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14 Sep 2021 15:29 #220613 by mikeT
Hello Clive,

Thanks for taking an interest.

My ini and hal files are as delivered on the 2.7.0 distro.
I have made no changes and have not yet connected any limits and index switches. Not until I know what to do.

MikeT

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