charge pump

[michaelf]

Hi all,
You’ll have to excuse my ignorance here but I’m very new to CNC.
I have an X2 on which I have installed a belt drive, CNCfusion #4 ball screw kit, Nema23 381 oz-in stepper motors, a Gekodrive G540 and I am using Mach3.
I’m at the stage of wiring the motors up to the drive unit and setting up Mach3.
My question is what is a "charge pump"?? Is it something to turn on a coolant pump “if you have one” or does it apply to something else? Do I need to have it switched on or off if I don’t have a coolant pump?
Thanks

[Starleper1]

Its basically a safety device on the G540 to keep electrical noise from making unwanted moves of your stepper motors. I have the G540 and have the charge pump switched off and have never had any issues with any motors moving.

[michaelf]

Starleper1, Thanks for the prompt reply. "so much information, so little time"

[ibuildstuff4u]

It has nothing to do with the coolant pump, but is a safety circuit designed so your machine can't move until it's under control by the Mach software.

Mach sends a signal to a breakout board telling the board that is has control of the machine. This signal tells the breakout board that the computer is on and Mach software is up and running which will allow your breakout board to send power to your stepper drives and spindle board if wired correctly. You have to have a breakout board that has this feature and the board has to be wired up to take advantage of this feature. It is not just a setting in the software.

I have a sound logic breakout board which supports this feature. I wired my board to send the machine into an E-Stop condition when it does not have the charge pump signal. My machine is wired so the stepper drives and spindle controller will not get power in an E-stop condition, but every machine is different so this can't be assumed. I'm guessing that the G540 has a build in breakout board? If so you will have to check with the instructions and see if it supports the charge pump feature and how it works with this specific board.

Hope that helps.

Dale P.

[Starleper1]

The G540 has a built in Charge Pump as well as a built in BOB. There is a dip switch on the back to turn it on and off.

[Jeff-Birt]

Just to be clear, the 'Charge Pump' describes a type of circuit that was originally designed to sense the 10kHz signal that Mach outputs to say "I'm in control". When you enable the 'Charge Pump' in Mach you are telling it to output the 10 Khz signal when ever Mach is running (and optionally during E-Stop condition or not.)

So the 'Charge Pump' output signal from Mach is just an interlock of sorts to give your control the thumbs up to start powering things up. It prevents the things in your machine from turning on as the computer boots, as during the boot process the pins on an parallel port can be in an unknown (HI or LOW) state.

The 'Charge Pump' signal is not a safety device though. It should not be relied upon to work as an E-Stop.

[Al_The_Man]

I would see the signal that Mach outputs as similar to what many systems have used in the past and more commonly used to keep a Watchdog timer reset, rather than a charge pump, but the effect is the same.
I would think putting it in any hard wired E-stop circuits, would not only prevent any operation until power up, but also if the PC were to crash or happen to go into the BSOD while running, also shut the operating systems down, and also maybe easier to implement?
This to me would give it a wider scope.
Al.

[Jeff-Birt]

An 'E-Stop' is a very specific type of circuit, a safety circuit. It's job is to stop a machine when things go wrong it can be initiated by an operator or by a control sensing an error condition, like a limit switch being triggered. Think of an E-Stop as a several NC switches wired in series. Each switch as to be in its normal unswitched state (closed) for the circuit to completed and things to work. Even a wire in this circuit is damaged it will break the circuit and cause an E-Stop condition.

The problem comes about when folks think they can use Mach and the charge pump to be the instigator of all things E-Stop. In other-words you have a switch hooked up to an input in Mach and set up in Ports & Pins as the E-Stop input. THEN you depend on Mach to quit outputting the chargepump signal in order for your BOB or other chargepump receiver to remove power from the drives. That is a very dangerous condition as the entire E-Stop system relies on a PC and a piece of software to always function properly in order for the E-Stop to work.

An E-Stop circuit should be able to do its job no matter what is going wrong. That is why I suggest using the Charge Pump signal as an Enable not as a safety device.

[Al_The_Man]

This is why I mentioned hard wired into the E-stop.
I agree the true E-stop circuit should be a hard wired circuit, the watchdog/charge pump relay contact can be an AND'd part of the string.
This has been done for many years now on industrial systems.
If the electrical code was applied to anyones emergency stop, then ALL motion devices would have the power removed.
I know the hobbiest community does not have to conform to the electrical code, but safety relays are becoming more prevalent and soon may be the code.
Al.

[michaelf]

Thanks everybody for all the information.
Some more questions, should I be turning things on in any particular sequence? Meaning should I be turning the controller on before the PC or vice versa, should I be turning the controller on with the e-stop push in?
My problem at the moment is that if I have the charge pump switched on and the switches set in Mach3 as recommended by Geko I get a red error light, if I switch the charge pump off on the Geko I get a green light. However, I can toggle the arrow keys and see movement on the DRO's, but nothing happens at the stepper motors, where should I be doing or where should looking to prevent the red error light from coming on, what haven’t I done?
I did load the setup file from Geko but there where too many things included in that file that I am not using at this stage, so I made my own settings to Mach3 as required, even so I still can’t get any movement out of the steppers.
Mike

[Jeff-Birt]

Sounds like you don't have Mach set up right. I would suggest using the Gecko supplied Mach profile and just disabling any axis that you are not currently using.

[phomann]

Originally Posted by michaelf Thanks everybody for all the information. Some more questions, should I be turning things on in any particular sequence? Meaning should I be turning the controller on before the PC or vice versa, should I be turning the controller on with the e-stop push in? My problem at the moment is that if I have the charge pump switched on and the switches set in Mach3 as recommended by Geko I get a red error light, if I switch the charge pump off on the Geko I get a green light. However, I can toggle the arrow keys and see movement on the DRO's, but nothing happens at the stepper motors, where should I be doing or where should looking to prevent the red error light from coming on, what haven’t I done? I did load the setup file from Geko but there where too many things included in that file that I am not using at this stage, so I made my own settings to Mach3 as required, even so I still can’t get any movement out of the steppers. Mike

Hi Mike,

What you need to do is go into Machs general config and tick the Charge Pump in EStop checkbox.

That should fix it.

Cheers,

Peter.