The Campbell-Designs relay board has 12vdc relays on it, which is just what the G100 "Digital Outputs" will provide (up to 100ma) each.
The Gecko documentation poorly describes the usage of the Digital Outputs, so here's the deal:
Connect one leg of 12vdc relay coil to a G100 Digital Output (1-16), connect the other leg to the power supply positive (+).
Functional description of G100 Digital Output (port):
The Digital Output is @ HI (+12vdc) when off (no output/indicator not lit). When the Digital Output is on/enabled it goes LOW (becomes 0vdc/Ground) and its indicator light is lit.
The next step is to configure Mach3:
Configure | Ports and Pins | Output Signals...
Outputs are listed as "Output #1(-16)"; assign the Output of choice "Port #" = 1 (very important!!); The "Pin Number" is not used, so its value doesn't matter; "Active Low" is set to X
If Digital Ouputs are used for the Spindle and/or Flood/Mist Control then also do the following:
Configure | Ports and Pins | Spindle Setup
Assign appropriate "Output #" for "Relay Control"-"Clockwise(M3)" and CCW(M4) and also for "Flood Mist Control"-"Mist M7" and "Flood M8" if used.
... and that's it!
The G100 is much smoother, the steppers are quieter and more responsive and can go faster without stalling. There's some exclusive G100 path and velocity settings that affect the results of G-Code and I'm still experimenting with those. Previously, (in Windows XP) some apps when launched or closed and while Mach3 was open would ping the LPT port of my computer causing the machine to jump and lose position even though G-Code was not running... that's gone now. Overall, it's just a cleaner and more reliable approach and has greater possibilities for extending the machines capability. Certainly worth the $400 and the conversion labor.
One Mach3 caveat is that the Tool Path info is virtualized so Mach3's tool pathing green dots are an estimate of reality, so what they show you is approximate. I spoke with Art about this and did my own tests and the reality is that the G-Code is accurate and the programmed part is true.
-Haik