How to use 6 limit switches to limit 3 axis at both extremes

[MecTechMike]

Hey folks,

I need some help here. I know inputs 1-3 nominally control home/limit switches, but I'm trying to get dual switches working on each end of 3 axes. I wired up six NPN proximity sensors in pairs to the three inputs, but found I need both switches to trigger in order to trip the limits. I have NPN NC. Do I need NPN NO for this approach to work? What other options do I have with the current NPN NC sensors that I got.

Please advise, Thanks,
Mike

[galyion]

you could wire them up in series so either would break the common connection. there is 8 inputs so if you have more open you could set 3 as home and 3 as hard limits

[Gary Campbell]

Mike...
In lieu of a more elegant solution you could use a relay module for the low lims and another for the hi lims. Example and more info here: viewtopic.php?f=60&t=1508

[MecTechMike]

Thanks for the quick advise guys. It took me a few tries, but hooking them in series does in fact work. For those considering the same, both switches get 24V power, but only the second switch is grounded. The first switch common goes to the signal input of the second switch. The first switch signal goes to the Acorn.

I'll try to draw it here tomorrow for a post.

Thanks for the help gentlemen,
Mike

[martyscncgarage]

Thanks for the quick advise guys. It took me a few tries, but hooking them in series does in fact work. For those considering the same, both switches get 24V power, but only the second switch is grounded. The first switch common goes to the signal input of the second switch. The first switch signal goes to the Acorn.

I'll try to draw it here tomorrow for a post.

Thanks for the help gentlemen,
Mike

Did you use the HOME ALL input?

[Gary Campbell]

Mike...
Have you verified that both your switches work as intended? I.E., will both stop motion if triggered?

[MecTechMike]

Thanks for the follow up. Right now I don't have the switches on the axes. I am using the Alt-I menu to watch limit tripping. I am also getting messages on trip and clear. When tripped, the axes are frozen. So pretty confident things are working. I get a better idea once they are installed.

Mike

[cnckeith]

wire all the home side swtiches into one input, use the wizard to call that input "homeall"
wire the other three switches in series with the Estop with a momentary override (so you can back off if you hit it) and you will have 6 switches and only use one input and have auto homing. have your cake and eat it to.

[Muzzer]

Keith - you say "wire the other three switches in series with the Estop with a momentary override" - do you mean to wire in a push to test switch that will take the e-stop line down to ground so you can move away from the limit condition? Trying to understand how to implement this - sounds like a good solution.

Murray

[cnckeith]

Yes exactly it's an old school trick the early old Bridgeport cnc machines used to have that setup as they were limited with the number of inputs as well.

Alternatively you could wire the limits in series and pipe them into one input. (Just like the home switches) you can use any of the limit input selections on the drop-down box in the Wizard for that input.

In a future cnc12 release will we will we will be adding a "limit_all" label as a input selection in the Wizard for this use as well.