Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Sheldon Dingwall on June 14, 2008, 11:59:15 AM

Title: Explanation of "Charge Pump" needed
Post by: Sheldon Dingwall on June 14, 2008, 11:59:15 AM
I'm not seeing this in the manual or in forum searches.

Could someone explain what Charge pump means and how it's used?

I'm using an Ascension controller.  The setup guide suggests leaving it unchecked in the logic config menu.  However whenever a reset is triggered, power to the steppers is cut causing potential loss of position and gantry creep. 

If I check Charge Pump in the logic config then power to the steppers is maintained during re-set.  This is how I'd prefer it, but I want to make sure I'm not missing something.
Title: Re: Explanation of "Charge Pump" needed
Post by: Hood on June 14, 2008, 12:24:20 PM
Basically the charge pump is Mach putting out a certain frequency on the pin you choose to use it on. If this signal is not present then your breakout board (if it supports the chargepump) will stop all outputs to the drives.
Title: Re: Explanation of "Charge Pump" needed
Post by: jimpinder on June 14, 2008, 12:33:37 PM
As far as I understand it, the charge pump is included to activate the axis - but after your P>C> has started up. Apparently a PC and particularly Windows can send out some odd signals on the various ports while it is starting up. These could, if power had been applied to your machine, before the PC was up and running and mach 3 was settled, lead to your machine taking of at random (and I am told, nearly achieving orbit)

The idea was to include a system where the outputs would be disabled until the system was ready to go.
The perceived wisdom is to start up your P,C, and then only apply power to your machine after Mach3 is installed and settled.

I dont have the charge pump activated, therefore I follow that advice at start up.

If it suits you keep it ticked.

Title: Re: Explanation of "Charge Pump" needed
Post by: xtal on June 15, 2008, 07:04:33 PM
I am planning to use the charge pump to enable me to apply power to my cnc machine....hopping to not use battery ,,,,but not looking good...
ie start up mach3 ..which starts the charge pump .. which applys power to the machine....

While looking into doing this I found that I cannot use PIN 1 for charge pump ie pin 1 acts dead ?????

I can use Pins 14,16,17 with no problem.... cable continuity on pin 1 is ok....

I will use an Mcode to power machine off....and yes I could use Mcode to power on

Not sure im my parallel port has a problem or not...

Is there anybody using pin 1 for charge pump...

I playing with the latest demo code....
Title: Re: Explanation of "Charge Pump" needed
Post by: jimpinder on June 15, 2008, 11:14:12 PM
You seem to be a bit at odds here. The charge pump system does not need any M Code to activate it. It is automatic as your machine starts up.

As Hood expained the charge pump gives out a signal to your stepper motor ( or servo motor ) drives not follow any signals until Mach 3 is properly unstalled and up and running. It only works if your driver cards support it. When Mach is turned on the signal ceases and the drivers then respond to control signals.

Are you talking about then turning on the machine - i.e. doing some work with it - in a program and activating the spindle, an M3 or M4 command.

If you have Mach 3 installed on your computer, you can test the four output pins by allocating them to M3 and then typing in the M3 command on the MDI line (page 2 of the Mill screens).  M3 should turn the pin on, M5 should turn it off.

If you are only using pins 2 to 9  for three axis, you will have two spare output lines there as well. You can also use these.
Title: Re: Explanation of "Charge Pump" needed
Post by: xtal on June 16, 2008, 05:00:17 AM
 I start mach3 pgm ..It starts the 12.5khz charge pump signal,,I detect the 12.5khz signal ind turn on a solidstate relay
which turns on the raw 36volt powersupply....then I take 5 volts from control card to hold the solid state relay......

I was wanted to develop enough voltage from the charge pump to energize the SSR without using an external 3.6volt battery
but I don't believe I will be able to achive this......

Now to power it off I will use a mcode to control another output pin....

I figured this would be an easy way to pwr machine on/off while testing......

Now since it appears I will need a 3.6volt battery,, I may just use some seldom use m-codes to apply and remove power...
or may just add a toggle button on screen to control it

I just toying with this idea,, I don't like walking 20 feet back and forth power cycling machine...

The main concern is no signal on pin 1
Title: Re: Explanation of "Charge Pump" needed
Post by: Hood on June 16, 2008, 06:59:07 AM
Not sure if you can use Pin 1 or not, never used it for the Charge pump. Can you set the pin up as for example the coolant and switch it on and off and see if the state changes, this will let you know if your pin is OK.
Title: Re: Explanation of "Charge Pump" needed
Post by: Chaoticone on June 16, 2008, 09:50:44 AM
I couldn't use pin one on a BOB I had once. Not sure if this is true for all though. I try to use pin 17 for the Charge pump.

Title: Re: Explanation of "Charge Pump" needed
Post by: Hood on June 16, 2008, 11:11:49 AM
The PMDX122 breakouts use Pin1 for the relay, never used the relays on either of the PMDX I have so cant be sure it works but would think there would have been a lot of posts if it didnt.
Title: Re: Explanation of "Charge Pump" needed
Post by: melcat on June 17, 2008, 08:26:37 AM
My charge pump is simple.

Switch on CNC mill all is dead.

Switch on the PC and start up Mach3. All is still dead.

Press the space bar and all comes to life.

The whole board is dead until reset button is pressed. Pin 1 is still spare and can be used to wire up extra boards when needed. is where I purchased mine from. All for £14.00. Wire up a power supply to it, in my case a 24V supply.

Red led off for dead board, press the space bar LED lights up and away you go.

Title: Re: Explanation of "Charge Pump" needed
Post by: Jeff_Birt on June 18, 2008, 10:09:06 PM
I don't see how this compares to the function of a charge pump style circuit. As has been mentioned the LPT pins are in an undefined state on power up. The charge pump circuit looks for a 12.5kHz signal being out put by Mach. This signal will only be output when Mach is running and not in an ESTOP mode. You can use the output of the charge pump circuit to drive a relay and only power the drive motors when Mach is in active control AND not in ESTOP mode.