Howdy, Sarge here. I "backed" into this: my brother is buying the parts to build 2 X/Y tables ~30" x 60"; one for him as a plasma cutter, one for me (uncommitted as yet). Bro doesn't have the electronics / programming skillset nor the time to build. I come from 30+ yrs electronics design, 15+ on my own, 10+ in microcontrollers. A collegue recommended Mach3: a choice move!
I built the stepper drives & torch control relays, figured out the axes w/pinouts & tuning, but turned to the forum for help on torch control. Special thanks to the posters in "Plasma On/Off", I should have it good soon.
A fast "cookie" of thanks: the charge pump is a great drive enable, but may have a lag as presented due to capacitive time constant. I used a 74123 retriggerable one-shot with:
> charge pump signal through 680 ohm to pin 9 (a* inp), with .1 uF to gnd. (noise supression & signal loading)
> 47k (pins 16 & 7) & .01uF (7 & 6) to set the one-shot time constant
> pins 10 & 11 to + (pin 16) and pin 8 to gnd
While pump is active; pin 5 is high & 12 is low. It tolerates the occasional missing pulse, but miss 2+ and it changes state.
I use it to disable the FET drivers (ST type L293B at inhibit) Thanks for the help, I'll be visiting again soon... <<<)))