View Full Version : Strange issue with mach3 and limit switches! what could it be!!!!

21-04-2010, 09:30 PM
Ive finally set up my machine and ill is running ok apart from the pesky limit switches. ive wired them up in a continuos loop for x+- y +- and z+ but for some odd reason as soon as a enable my servo drives mach flashes up limit switch has been triggered.

the only thing i can think of what is doing this is electrical interference of some sort. but im unsure how to cure it.

How i have me setup is like this.. PC - Smoothstepper - C10 BOB - Drives, now if i wire the drives direct to the smoothstepper board with the C23 terminal board for some reason i cannot get my switches to work with mach3.

I enable the drive by a separate 12v supply on a independent switch so it has no physical contact with the C10 BOB.

The servo drives do generate a fair bit of electrical squeal when run is enabled. so my thoughts are interference of some sort.

Anyone have any other thoughts?


John S
21-04-2010, 09:45 PM
First off disconnect the switches to proove it is the switches.

Next [ should be last but it easier to do ] go to Config > general config and in the top right there is a box called Debounce Interval probably set at abour 20 or 40, up that to 200 and retry in steps of 200. Don't worry about large numbers it's in microseconds per square sandwich or something.

If by the time you have got to 5000 it doesn't do anything, rewire the limits with shielded cable but only earth ONE end of the cable, best to do this controller end.

Wire the switches in sections if you can and use normally closed switches, DON'T wire the switch to earth, wire it back to the board and make it open for limit.

21-04-2010, 09:50 PM
Thanks John, i was thinking i should have used shielded cable start with.. Bollox! my switchs are NC anyways so thats not a problem. ill give that Debounce malarkey ago first.