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Author Topic: What is a charge pump?  (Read 10325 times)

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What is a charge pump?
« on: January 06, 2012, 11:49:17 AM »
I am reading every now and then about something called a charge pump??

what is a charge pump??

regards fred
think of the trees-- use both sides of the computer paper
Re: What is a charge pump?
« Reply #1 on: January 07, 2012, 08:40:39 AM »
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.
Re: What is a charge pump?
« Reply #2 on: January 07, 2012, 01:36:01 PM »
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.
Regards,
Ray L.
Re: What is a charge pump?
« Reply #3 on: January 07, 2012, 01:40:54 PM »
Well thats me told then isnt it?
Re: What is a charge pump?
« Reply #4 on: January 08, 2012, 12:16:51 AM »
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.

Re: What is a charge pump?
« Reply #5 on: January 08, 2012, 11:46:40 AM »
Thanks Guys --

Clear as mud--  ( Dont know how to put a smiley here)

How do I know if my machine has got one?

fred

think of the trees-- use both sides of the computer paper

Offline BR549

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Re: What is a charge pump?
« Reply #6 on: January 08, 2012, 11:47:18 AM »
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
Re: What is a charge pump?
« Reply #7 on: January 08, 2012, 12:08:40 PM »
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.

Offline Hood

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Re: What is a charge pump?
« Reply #8 on: January 08, 2012, 12:08:41 PM »
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