- --- In firstname.lastname@example.org, "Jim Bell" <jiminwoodstock@...> wrote:
> My limit switches are wired normally closed. If you wire the switches that way and configure Mach3 to handle the normally closed switch, it is the much preferred connection method. If a wire breaks or gets disconnected, the limit will be on and you will know that there is a problem. If wired normally open, if a wire breaks or get disconnected, you will only know when you reach the limit and the carriage tries to keep going.
> Another reason, which may directly apply here, is that when the switches are wired normally closed, the limit signal is "grounded" by the switch being closed and the wiring from the switch to the interface box is MUCH less susceptible to noise.
> My switches here are high quality micro-switches. When I first installed them, I would sometimes get a x axis limit error after the carriage would cross a certain point. After much troubleshooting, the problem was a brand new defective switch. Replacing the switch fixed the problem and no more false limit problems. You may have a defective switch in your system.
> Hope this helps.
My limit switches are wired from ground to the interface board inputs. The interface board is configured so that +5v is present until the switch is closed which will bring the input to 0V. This way any possible noise on the wire is shunted to ground by the normally closed switch.