Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Fred_evans on January 06, 2012, 11:49:17 AM
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I am reading every now and then about something called a charge pump??
what is a charge pump??
regards fred
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ok, well its a safety divice.
Basically Mach3 when running can output a signal that turns on then off then on etc. If Mach3 is running OK then pulses happen, if not then no pulses. OK, thats the Mach3 / computer side of thigs. Now for the electronics. Outside of the computer is a relay that cuts power to either spindle, drives or both. Basically, it shuts down the machine so its in a safe condition. This relay is connected to a device which is connected to the output pin (look in general configs and set pin from there ). In essence, if there is a steady stream of pulses then the relay operates and motors etc will be active if required. However, if the stream stops (Mach3 crashed, PC crashed or PC switched off ) then the relay opens and cuts of power and makes machine safe.
All in all, its a device that ensures that the machine will only work IF Mach3 is in control of it.
There is a link on this forum somplace for charge pump circuits or just take a look at the gecko website.
PS, its a very good device to have. Machines DONT care if its metal, wood or hands thats being cut.
Regards.
Mike.
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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.
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Well thats me told then isnt it?
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Processor controls have historically used a method to detect when a system is not running for any reason in order to shut the system down, traditionally called a watch dog timer, all commercial systems and PLC's have one built in, the Mach charge pump signal can be used to operate a charge pump circuit, missing pulse detector or timer (time out).
From the tests I have done, the signal is present all the time Mach and the PC is running.
I prefer to use it in the E-stop string.
Nosmo.
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Thanks Guys --
Clear as mud-- ( Dont know how to put a smiley here)
How do I know if my machine has got one?
fred
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THe problem is that the signal can STILL be present when Mach3 or Windos is locked up. So much for being a dependabnle Estop.
Mach3 also has a watchdog BUT it is not dependable for Estop control either.
(;-) TP
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I guess one way of looking at it, if you do use it and IF it is detected you get an E-stop, on the other hand not using you will never ever get one for that reason. I don't intend using it as the only means of E-Stop.
If it is only intended to inhibit the drives during boot-up, this goes against normal practice of not allowing machine power until the system is up and running.
The drives/spindle should NEVER have power applied before or during PC booting.
There should be a Control Start or Control ON.
Nosmo.
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Using it as an additional part of an E-Stop system is in my mind fine, relying on it solely for an E-Stop is not, but thats just my opinion ;)
Hood