Quote Originally Posted by Neale View Post
Connect one end of the resistor to +24V, not to PSU -ve. What you then have is the BOB input driven from the 24V with the resistor lowering the voltage to the BOB to a nominal 5V. When the proximity switch operates, it shorts out the BOB input to ground. Should be OK although it's not quite a conventional way to wire things, and it might not work reliably as it depends on the proximity switch bringing the BOB input voltage close enough to ground to trip the BOB input. You will have to figure out whether you then want active high or active low configured in Mach3 to do want you want - probably active low.

Unfortunately the ZP5A manual is very vague on the details of the input connections. I don't remember now if the limit switch inputs have a common ground or if they are separate. I used to use one of these BOBs myself but that machine didn't use any limit switches so I never had to sort this one out. Can you check with a meter if the limit switch input ground connections are all connected together? It's possible that they are not, and in that case there is a better way to wire the switches. Take +24 via the resistor to the BOB input. Then connect the BOB input ground to the black wire on the prox switch. Brown and blue wires stay as they are on your diagram. This would probably need active high in Mach3 and from an electrical point of view is the "right" way to do it. However, it does depend on the limit switch grounds being electrically isolated from each other.
Hi Neale
Thanks for your response. It seems to tie up with what is on the switch label anyway. The ZPA5-INT has a seperate ground for each pin input. I'll give it a go.

Regards
Mike