False Estop detection

[michel-cnc]

Hello !
I am building a CNC; i experience some problem with inputs signals (ES, limit switch): Mach3 "seen" some bad signals among those inputs.
For example, The input voltage is 4.9v just behind the parallel port of the PC for ES signal & detection is set active to low. Mach3 seen an "emergency
stop request" even if resetted. All input signals on the CNC are shielded. I have found that it is the power block for the spindle that put some trouble (400Hz).
If i do not plug it, there is no more problem with Mach3.
I have also seen that the PC wired together the ground (sector) and the 0V on the parallel port - do you think it's normal ?
Do you think that the power spindle block can produces interferences via the ground & the 0v ?
May be, i need to use a filter on the 220V input of the power spindle block ?
What do you think of that, do you have encountered the same problem ?

Thanks & happy new year !!!

[HimyKabibble]

Add stiff pull-up resistors (220 ohm) to +5V, and/or small capacitors (100pF) to ground on ALL switch inputs.  That should dramatically reduce their noise sensitivity.

Regards,
Ray L.

[michel-cnc]

Thank you Ray, the problem was coming from 400Hz, i have to shielded also the spindle output & put a filter on the input VAC of the spindle driver.

[HimyKabibble]

So did you get it resolved?

[michel-cnc]

I had to improve this solution in time, but it seems to be solved.