What kind of homeswitch do i need?

Hello,
I want to retrofit my wood milling machine with a Mesa 5I25 and 7I77. What kind of home switch is possible? A normaly open or normaly closed? Can i select this in the configuration, or is only one of these kinds possible?

Thanks

Hans

Normally closed switches are generally a bit safer for limits and home switch use
since a broken wire/open switch will be detected

If you use normally closed limit/home switches with a 7I77, you wire them like this:

+24V --> limit/home switch --> 7I77 digital input

and you connect the inverted input pin (ends in -not) to the hal limit or home signal
in the hal file

I do prefer the inductive prox switches, they can't get dirty. But many do have problematic output logic levels that require some conditioning.

Recommend combining with a hard stop, you don't want it to be physically possible to run the axis off the rails.

Make it so your switch won't get smashed if it continues to move. It will overshoot a bit due to deceleration times.

Hello,
many thanks for your answers. On my machine are mechanical switches installed, at first i will use them. I can wire them as NO or NC. When these are not exact enough i can use the indeximpuls from the encoder additional.

Hans

Hello,
i make some work on my cnc. Encoder scale = O.K., Encoder count direction = O.K., avis moving direction = O. K., moving with keyboard arrows = O.K.. I connected my x/y/z home switch as normally closed= +24V > homeswitch > 7i77(pin16/17/18).
The reference moving works not correct. The homeswitch is not found.
Hal file:
net home-x <= hm2_5i25.0.7i77.0.0.input-16
net home-x => axis.0.home-sw-in-not(without -not LinuxCNC starts but the referencepoint isn't find)
Error message:
./BIMA600.hal:88:Pin'axis.0.home-sw-in-not' does not exist 6727
Shows the window LinuxCncStatus the pinstatus the real pinstatus? Can i see there the real status of the home swtich? Change the display between 0 and 1 when i push the homeswitch? In my case the pins are with the normally closed switch connected to 24V, but window shows for these pins allways zero.

Thanks

Hans

You probably want:

net home-x <= hm2_5i25.0.7i77.0.0.input-16-not
net home-x => axis.0.home-sw-in

There is no axis.0.home-sw-in-not (as you found out)

You can show all the available pins with:

halcmd show pin

When linuxCNC is running.

You can also show the state of the pins with the Axis menu:

Machine --> Show Hal Configuration --> Watch --> (select the pin or parameter to watch)

Hello,
my homeswitch is normally closed. Wiring = +24V > homeswitchNC > inputpin 7i77.
With halscope i can see that the homeswitches are working correct.
Entry hal-file: net home-x <= hm2_5i25.0.7i77.0.0.input-00-not
net home-x <= hm2_5i25.0.7i77.0.0.input-01-not
net home-x <= hm2_5i25.0.7i77.0.0.input-02-not

When starting the homeseqence the axis move in the correct direction. When the homeswitch opens
there is the following message: "Home switch inactive before start of latch move" and the homingsequence is abort.

Does someone knows what do i wrong?

Thanks

Hans

sounds like ether the motion overan the home switch when decelerating or you
have enough contact bounce that you need to de-bounce the home switch signals

Hello PCW,
when I start the homing sequence the axis move in the normally closed homeswitch and the switch opens so its inactive( no more 24V on the inputpin ). My opinion is that linuxcnc had to know that in this case the swiching point is when the homeswitch toggles to active.
Or is the correct homing sequence only possible with a normally open switch?

Thanks

Hans

Any switch type is usable if the correct polarities are used, NC switches are preferred
for limit and home switches since a broken wire will usually cause a fault rather than a crash

As far as LinuxCNC is concerned, the homing starts with the home switch inactive
( The 7I77 xxxxx-not pin will be inactive until the switch is tripped )

Once the home switch is tripped LinuxCNC starts decelerating to 0 speed and then
makes the latch move to determine the final home position. It expects that the switch is still tripped
at this point, but it seems to be no longer active (the xxx-not pin is low)

This is why I asked if the switch had been overrun (this might happen because your acceleration values are too low
or the homing speed is too high or both)