I would like to repeatedly close a circuit  using g-code. What is the best way to accomplish this? I want to activate a pneumatic cylinder during the program.

Thanks,
-jim

Probably easiest is to use Flood or Mist coolant outputs to switch a relay.
Hood

Thanks Hood,

So I would use M8 to turn coolant mist on and M9 to turn all coolant off, correct? How do i assign the the pins for this? I do not see "Mist on" and "All coolant off" in the pin outputs section. Thank you!!! -jim

Mist is M7, Flood M8 and switch either off is M9.
To set up go to Config, Ports and Pins, OutPuts and choose an output you are not currently using and set the port and pin number, next go to the Spindle Setup tab and enable the Flood/Mist relays option and enter the output number you have just set up into the M7 or M8 (or both if you want) and thats it.
Hood