The Mach3 charge pump was never intended as a safety feature, and should NOT be counted on as part of a safety circuit. It's original intent was to simply disable the drive motors, spindle controls, etc. during boot-up, and before Mach3 was running. Without it, there is a tendency for some systems to turn on during PC boot-up. The charge pump prevents that. However, since the charge pump output from Mach3 is software controlled, there are MANY ways in which Mach3 and/or Windows can crash and leave the charge pump running, so it cannot be counted on to reliably disable the machine under any conditions other that on boot-up. Similarly, any well-designed E-Stop mechanism should function WITHOUT depending on Mach3 to do ANYTHING AT ALL. This means both the charge pump circuit, and E-Stop switch(es), should act directly on the power supplies, typically though a power contactor, and NOT simply provide an input to Mach3, then depend on Mach3 to disable the drives/spindle/coolant.
Many BOBs (Break-Out Boards) have on-board charge-pump circuits, and E-Stop logic, that will directly force all BOB outputs to their inactive state whenever the Mach3 charge pump signal is not present, or the E-Stop switch is disabled. I've used a number of the Homann Designs BOBs (
www.homanndesigns.com) on my machines, and am very happy with them. They're cheap (under $40), very well designed and built, and small (about 3"x5"), making them easy to mount almost anywhere. The latest ones contain both E-Stop inputs and charge pumps circuits. Peter Homann is also a regular on these forums, and always provides great support.
Regards,
Ray L.