I did not do a write up on this. I will do my best to walk you through this.
The easiest way to do this is to leave the factory switching as it is and add a double pole double throw switch. With the switch in one position it would operate as is manually. With the switch in the other position it will bi-pass the manual control and allow for control by Mach3.
There are two contractors (also known as motor starters) labeled KM1 & KM2. These are basically switches and they are activated by a built in coil. When the coil is energized it closes all the NO (normally open) contacts and opens the NC (normally closed) contact.
On your machine KM1 turns on the motor in reverse (CCW) and KM2 turns on the motor in forward (CW). The way the coils are wired across the contactors prevents both contactors from being energized at the same time. Matt did a good write up on this in the manual.
The only wire we will be touching on the contactor is at terminal A1. This is the load side of the coil or 110vac in. A2 goes to neutral which we won't touch.
Here is a picture of the contactor showing the A1 terminal. You will probably have to loosen and back out the wires in terminal L1 directly above it to access the A1 terminal screw.
Here is a simple wiring schematic. Unfortunately this forum shrinks everything so if you can't read it PM me your email address and I will send it directly.
Here is a typical DPDT switch.
Also look at the simple wiring diagram in the G540 manual for wiring the DC power supply. The SSR relays work best with 12vdc or 24vdc.
It looks like the electrical box may be too small to fit the SSR's and a power supply so you might need a second box or a larger enclosure.
Look it over and let me know if you have any questions.
