E stop on Smartbob424

[Terry Newlands]

Hi,
I am currently setting up my Chinese CNC 3 axis router with Mach4, a PMDX-424 and a 407 spindle control. ( I couldn't get the Chinese hardware or software to work). I have configured my motors etc and I am almost ready to fire it up, exciting!!
So question 1. E Stop. The router has an emergency stop that interrupts 220v,50hz supply to the machine. The PMDX 424 quick start guide (Doc rev 6.0) sect 4.10 says to connect the emergency stop to the ground terminal on J14. Is this correct, in my case this would mean 220v applied to the ground terminal under normal operation. (I don't wont to blow up the board!)?
Question 2. My x, y and z axis are all at random positions. There are limit switches at each home position. How do I "home my machine"?

Thankyou in anticipation
Terry Newlands

[Steve Stallings]

E-Stop switches should have two sections. One should directly control the
power to hazardous portions of the machine using only electromechanical
devices such as relays. The other section should be used to inform the
control system that an E-Stop event has happened. These two sections
are electrically isolated from each other.

If your E-Stop switch has only one section, you cannot do both, and you
should retain the setup that directly controls power.

Connecting line voltage to the E-Stop input of a breakout board will cause
damage.

Sometimes the E-Stop system will control a power contactor that has an
extra set of contacts that can be used to signal E-Stop to the breakout
board. These contacts must be isolated from line voltage power.

If you have switches at the home position, they can be used for both
home and limit functions. When configuring Mach4 inputs you can assign
an input signal to multiple functions by simply selecting that input on
the configuration line for each function.