Hi All I'm using grbl v1.1 and on my controller I've a halt and resume pin. Functionality works fine when I use a normal switch. Signals are active low and pulled high by default. When connected to ground respective function takes effect. I do not know internally how grbl uses these pins for halting or resuming... I assume arduino generates an interrupt on falling edge and halts grbl state machine. Not sure if the pins need to be pulled high again(that would matter if halt/resume use the same interrupt and have a common handler, so unless previous pin is pulled high it'll not be able to find which pin is asserted) I need a sample circuit to do this automatically based on 12V supply power failure. Is there a reference circuit available for this ? Cheers Ritu
you need a 12v relay with NC and NO contacts. power the relay from the PSU. at this time the NC contacts will be open. just like an open switch. connect those contacts exactly like a switch to the hold/resume pin and controller ground. Now, when the PSU goes off the relay will release and the contacts will close and GRBL will halt.
