JP 1482 Spindle Over current signal output

I have a 3020t CNC that has a JP 1482 spindle controller. It has a built in over current switch. If I try to take to deep or fast of a cut the spindle shuts off. This is great and all but it doesn't stop the rest of the machine. Has anyone every hacked the circuit board to take the over current signal and wire it to an output on the parallel port so that Linux CNC can tell the machine to stop if the spindle stops?

If the drive outputs a digital signal, then you could connect that, through HAL, to the pin halui.estop.activate
linuxcnc.org/docs/2.7/html/man/man1/halui.1.html

That might be an over-reaction. Perhaps the feed-hold in motion is what you want.
linuxcnc.org/docs/2.7/html/man/man9/motion.9.html

Thanks andypugh, the feed hold is what I am trying to accomplish.

Unfortunately the drive does not output a digital signal directly.

I did find this: hackaday.io/project/6776-3040-cnc-millin...controller-schematic

I attempted to connect an output to the pin marked "sp fb sig" on the integrated circuit. I induced a fault but it wasn't detected. Other forums have suggested a relay on the spindle. Not ideal but may be the way I have to go.

doityourselfer wrote: I attempted to connect an output to the pin marked "sp fb sig" on the integrated circuit. I induced a fault but it wasn't detected.

Are you trying to force a spindle fault from the software, or have the software detect a spindle fault?

In the latter case you would need to connect an _input_ to the sp_fb_sig and then would need to check that the pin changed state.
It is possible that the input pin is pulled high, and so the sp_fb_sig going high has no effect on the input state.

You should be able to detect the state with a multimeter. Also, bear in mind that unless the spindle logic and IO logic share a GND it is unlikely that signals will be reliably measured. You might not want to do that, in which case a second Opto-Isolator driven from the opto-inputs on the board might be appropriate. (But only bother with this if it is necessary, as an alternative to a relay or whatever)

Hmm, I’ll do some poking around with a multi-meter when I get home.