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charge pump
« on: May 05, 2010, 02:53:10 AM »
Hi there I'm new in this field. Can i use the 12.5 kHz signal as is or must I add any special circuit to drive the relais?
Spike

Offline Hood

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Re: charge pump
« Reply #1 on: May 05, 2010, 06:25:03 AM »
There are a lot of Breakout Boards that support the Charge Pump but if you dont have one then you can make a circuit up, there is info on the documentaion page of a chargepump circuit, see here http://www.machsupport.com/docs/ChargePumpSafety.pdf
Be aware though that the Charge Pump was not intended as a safety device when Mach is running, it was designed as a means of stopping the twitching of motors that can occur when Windows is booting and before Mach is running.

Hood
Re: charge pump
« Reply #2 on: May 05, 2010, 09:28:23 AM »
Be aware though that the Charge Pump was not intended as a safety device when Mach is running, it was designed as a means of stopping the twitching of motors that can occur when Windows is booting and before Mach is running.

Hood

I have always thought it strange that the 12.5 khz signal was originally only intended to disable the drives when loading and shutting down windows, and not used it in the traditional sense to detect the program or PC processor not running or failure. period.
This has traditionally been done by inserting the output in the E-stop string, to me it makes more sense to make full use of it at all times.
Nosmo.
  

Offline Hood

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Re: charge pump
« Reply #3 on: May 05, 2010, 09:54:37 AM »
Be aware though that the Charge Pump was not intended as a safety device when Mach is running, it was designed as a means of stopping the twitching of motors that can occur when Windows is booting and before Mach is running.

Hood



I have always thought it strange that the 12.5 khz signal was originally only intended to disable the drives when loading and shutting down windows, and not used it in the traditional sense to detect the program or PC processor not running or failure. period.
This has traditionally been done by inserting the output in the E-stop string, to me it makes more sense to make full use of it at all times.
Nosmo.
 

Nothing to stop anyone using it as part of their safety circuit, just a lot of people think it is  the safety circuit.

Hood

Offline Jeff_Birt

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Re: charge pump
« Reply #4 on: May 05, 2010, 12:44:20 PM »
The problem is that the chargepump signal does not guarantee anything other than Mach did start up and that the part of the parallel port driver that sends out the chargepump signal is working. It cannot guaruntee that your of Mach is working properly.

As Hood says the problem is that some folks thing that Mach and the chargepump signal are the safety devices. (Generally speaking)A Estop chain should not depend on your PC, Mach or any other piece of circuitry working right in order to function properly.
Happy machining , Jeff Birt
 
Re: charge pump
« Reply #5 on: May 05, 2010, 02:16:54 PM »

As Hood says the problem is that some folks thing that Mach and the chargepump signal are the safety devices. (Generally speaking)A Estop chain should not depend on your PC, Mach or any other piece of circuitry working right in order to function properly.

I don't necessarily agree with that statement, the watchdog timer which essentially is what the charge pump is, has been used for decades to shut a system down if the processor is not running for any reason whatsoever,  this is usually ANDed with the rest of the E-stop string, wired fail-safe, I know I would want spindles or any other motors that were under the command of the processor to stop if the system failed for any reason.
My Galil cards and the Advantech PC boards both have watch dog timers to use for this purpose.
Nosmo.
« Last Edit: May 05, 2010, 02:18:54 PM by NosmoKing »

Offline Jeff_Birt

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Re: charge pump
« Reply #6 on: May 05, 2010, 03:26:20 PM »
A watchdog timer is a HARDWARE device, the chargepump signal is software driven and there is no guarantee that just because it is present that Mach is working right. At  most it means that the parallel port driver is functioning to the point that the signal can by output.

Using it as a supplementary condition is not a problem, using the EStop input to Mach and the chargepump signal as the only safety circuit is a problem. Some people think that a EStop consistes of a switch input into Mach and Mach then turning off the chargepump and their BOB sensing the chargepump dropping out and cutting out a relay; that is NOT a safety circuit.
Happy machining , Jeff Birt
 
Re: charge pump
« Reply #7 on: May 09, 2010, 12:19:14 PM »
Thanks for your speedy answer and your advice. However the confusion arises from the fact that in the manual, the signal from the charge pump goes direct into the hex inverter 7406 without showing any timing circuitry as you indicated.

Spike
Re: charge pump
« Reply #8 on: June 06, 2010, 12:45:47 AM »
Hello, I read  about charge pump, One question.
I have a Hobby CNC pro controller,, this board support Charge pump.?
Sorry my question,,,, is totally new for me.
Thanks in advance
Rene