NEED HELP WITH PLASMA CNC TABLE

[yoelba]

HI
i finish buildung my plasma cnc table about 2 weeks ago (and tring to debug since then)
it was working very good but when i moved it to its final location i sart to have problems with the Mach 3 software
when plasma start i get error "emergency stop pressed"
the plasma is old machine called PLUS 90
thw brakout board was damaged (2 chips fried)
i made direct connection with DB25 and some wires to the drivers of the step motor
all axis work fine when plasma is off
but when i press to start the arc the machine stop like emergency stop is pressed
it hapens only when the + leed of the plasma is connected to the bed

any idea how to fix this
i traied improving ground
and make all wires shorter

thanks

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[CL_MotoTech]

Make sure your emergency stop is properly shielded and grounded. You can turn debounce up and if that helps you are almost certainly experiencing some sort of interference on the emergency stop. Plasma machines create a lot of EMF so I'm sure proper grounding is very critical.

[yoelba]

thank for your reply
i also tray to disconnect and disable the emergancy stop but have the same problem

[rodw]

I would say you are experiencing noise from the plasma cutter that is spuriously triggering your circuits.

There is a Hypertherm document that deals with proper grounding of a plasma table via a "Star ground" that I found useful. Search for it on Google. Using hardware that allows 24 volt signals will also help as the higher voltage is less prone to noise.

[yoelba]

thank you for your reply
i fixed the brakout board and added some ferit rings and tubes
the problem almost gone
almost because if plasma torch tach the material the "emergency stop "message appears
i guess i need to add THC