Let the fun begin !!! ???

[JAZZCNC]

I thought that if i use 1 input for the limits and estop i won;t be able to reset because the m/c will be on a limit thereby inhibiting a reset. or have i got this all wrong?

Sorry delay replying went out last night for a pint which turned into Gallon then Amnesia.!! . . Well No and yes to getting it wrong.?
Mach as feature called Auto Limit Override which lets you Reset after Limit trip so you can Back off.

But With the E-stop then if your combining Limits and E-stop in same circuit and using Relays for hardware driven system (which you really should be) then you will need some Limit over ride Switch to reset the Relays. If using this setup then you can use the same Relay to inform Mach e-stop Happened and then just set Limits to watch same Pin if you want. With a Hardware driven safety system all your really doing is informing software an E-stop happened so it halts the Code and won't Reset until fault cleared. The actual safety side is done by the Relays and Never should be done by software.

Now personally I don't combine E-stop and limits because limit trip isn't an Emergency it's more positional error. I have Limits and Homes combined and limits do 2 jobs they Inform the Control limit as tripped and they disable the Enable on the drive so Motors are still locked but won't recieve signals.
Again a Limit override button is needed if disabeling the Enables on drives. If you don't disable the drives and just Inform the control you can get away with using Mach's Auto limit override feature.

[PAULRO]

that's the way i would like to have my set up . a separate estop that drops out the power supply which in turn drops out the drives.
my limits and home switches combined and informing mach 3 when they are triggered.
so if i'm reading you correctly then the limit switch when triggered is also wired to the enable on the drive thereby disabling the drives so that's when the override is required? or i can use the limit switch trigger input to MACH 3 to stop the motors and use the Auto Limit Overide feature. ?
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[JAZZCNC]

so if i'm reading you correctly then the limit switch when triggered is also wired to the enable on the drive thereby disabling the drives so that's when the override is required? or i can use the limit switch trigger input to MACH 3 to stop the motors and use the Auto Limit Overide feature. ?

The way I do it is to use a Relay for limits. This means I can use 24V thru the switches to power the relay coil, in my case Proximity switches, which gives best immunity against noise.
The drive enables are then sent thru one set of NC contacts, The Limit input is sent thru another set NO contacts.
Override is by way of Momentary button and Alarm buzzer to between 24V and relay coil to allow limit switch to be over ridden.

picture paints 1000 words.!

[PAULRO]

yeah, the picture makes it all clear now. thanks Jazz. that's a great circuit i'll have to use that if you don't mind.
that has cleared up a lot of queries for me . the enable was really puzzling , as in do i wire it or do i leave it unconnected, but that picture, as you say paints a thousand words. if i connect the enable +,- as in the picture does that mean i don't need the enable +,- connected to the BOBs corresponding terminals?
1 last query to get me further down the road if you don't mind, am i right in saying that the limit input to the bob and on to MACH 3 is enough to get the motors into reverse when the override is triggered?

[JAZZCNC]

if i connect the enable +,- as in the picture does that mean i don't need the enable +,- connected to the BOBs corresponding terminals?

Probably not but Depends on the BOB.! . . . what are you using.?
It's common for the Enable on drives to not be connected but in this case we are using it to ensure no signals get to the drives so no movement can happen while at same time leaving the motors energised and Holding position.

1 last query to get me further down the road if you don't mind, am i right in saying that the limit input to the bob and on to MACH 3 is enough to get the motors into reverse when the override is triggered?

Yes but you have to Hold down the Override Button to allow Mach to Reset so you can Reverse off the switch at which point the Relay will stay ON and mach will remain Reset untill something changes. Over riding anything should be warned about and thats why I use a buzzer but it is optional.

[PAULRO]

i'm using a PLC4x-G2 breakout board .

[JAZZCNC]

Ok well think things could all change now if you wanted because I'm pretty sure that Bob can handle 24v thru it's inputs.? The manual certainly shows them using 12V.

So in this case you could remove the Relays and run 24V thru the Limit switches wired in series just the same but directly to the BOB Limit inputs. I think you'd still need an Over ride button as the Inputs are driving the Enable output so Mach's Auto limit override won't turn these back on.
Then connect the Enables on the BOB to the Enables on drives.

Or just go with my first suggestion if you prefer and want to play safe regards what the Inputs can handle.!

New pic.

Edit: Yes those inputs have 30V Max so your good to go with this Pic.