limits & estop on 7i77

Planning on wiring e-stop circuit and limit/home on tb7. I am assuming at this point that the positive leads go to tb7 and the negative are grounded somewhere but not sure where is best. Not really familiar with setting up i/o so im making sure i do it right. I see "e-stop out" on the output tabs and "external e-stop" as an input which im assuming would go with a pendant. Also if there is a good source for understanding i/o that would help. Thanks.

Hello,

The Estop pin, should be connected to normally connected contacts (pendent should be included on the same logic) that are powered by your power supply and if something is wrong or pressed, the contact should open and therefor preventing the 24VDC signal to reach the input. Something like this:

IN3 (on 7i77) __________ Button1 normally closed _________ Button n normally closed _________ +24VDC

Is is assumed that the 24VDC power supply also supply's the 7i77 in the appropriate power pins (never versions the connector if of different color).


The "e-stop-out", that I presume from pncconfig is probably an output that will signal that linuxcnc is out of estop.

Ok so the e-stop/limits are all set up as inputs on tb7. Where do the grounds go? Should i ground the switches on the field power block?

Edit: I think I know what your saying now......The lim/home/estops are hooked directly to the 24v source and the other end goes to the assigned pin on 7i77? ...........I was thinking that the 24v was suppied by the 7i77. Please confirm. Thank you very much.

Yes 7I77 inputs are sinking type inputs (you must supply +voltage for an input to be sensed) so wiring is:

+24V --> switch --> 7I77input

Also note that E-Stop circuits are independent of linuxcnc and typically done
all with relays and switches

You must be able to power down the servo drives when in E-Stop, this is
independent of any software control

The E-Stop input to Linuxcnc is just so LinuxCNC is aware of the E-Stop state

I'm getting on limit switch errors on all three axes when i try to enable the drives. It's wired nc and i get good signals in halshow. It's wired with two switches per axis......one at each end of travel. so one input per axis. It shows true in the nc condition. Any way to switch it?

That's expected, to the motion component a true limit switch state is on-limit.
NC limit switches will be read as true by the 7I77's inputs when not actuated

What this means is that you must use the inverted input pins with NC limit switches.
in other words for example instead of using:

hm2_5i25.0.7i77.0.0.input-00

you would use

hm2_5i25.0.7i77.0.0.input-00-not

in the hal file