My Charge-Pump circuit

[Guillote]

Well I am starting the build of my control box. I have been simulating this circuit and it looks good. Here's the pic

Update 07-26-2007

The pump below is based on the Mariss’s circuit at http://www.artofcnc.ca/ChargePumpSafety.pdf. The circuit turns off in 1 millisecond, but it is turn on delayed 4 milliseconds in order to avoid a false triggering. It has spindle on/off control and three limit switches pairs that shuts down de geckos supply when are activated.



Comments always welcome,
Guillermo

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[Mongkol]

Hello Guillermo,

I am wondering with charge-pump. What is the function of it? I ever found
in DB-25 pin of parallel port,for Mach3. I am not good at electronic system.
Please advise if you know.

Cheers,
Mongkol

[David_Web]

The computer sends a lot of rubbish etc to the lpt ports and that could do anything from moving some axis to wreck havoc.

With a charge-pump you need to feed it a stable 12KHz for it to activate motors etc. The computer will not send out a similar signal by itself but need a program to do it.
Extra safety if you will so that you don't have to manually turn on and off things to prevent damage.

[Guillote]

Hi, Mongkol

Any machine tool is potentially dangerous. The charge-pump is a safety device. Mach3 will output on the parallel port a constant pulse train whose frequency is 12.5Khz whenever it is running correcty. You can use this signal to enable your axis and spindle drive. This function is often implemented in commercial breakout boards. Soon I will update the circuit to include spindle control.

Guillermo

[samakthachai]

Hi Guillermo,
It's possible or not if you will share the full option wiring diagram of cnc router.


Thanks
Samak

[Guillote]

Hello Friends,

The idea of using the internal supply of the PC to power de relays is tempting me . The problem I found is that when I measured the voltage difference of the parallel port's GND to the power supply's GND it was 0.25Volts . I can't connect them together since this might produce smoke or burn a track so I am thinking to use power supply's GND and leave parallel port's GND unconnected or at most connect the LPT_GND with Power_GND through a resistance. I would like knowing what do you think on the matter?


Comments always welcome,
Salu2, Guillermo

[ajaydevb]

Can anyone suggest a dedicated ic for charge pump function for use in mach3 bob?

[Al_The_Man]

Google for missing pulse detectors, or watchdog timer circuits, there are many IC's that can be used starting with the simple 555.
Al.

[dominic87]

Just as a piece of advice, I did a test on the output for the charge pump using an oscilloscope. Mine is not at 12.5KHz as stated but a steady 8.92KHz when mach3 is idle and working.

So worth noting if your homebrew charge pump starts acting erratically because it's not quite the frequency needed to flip the charge pump relay.

But I plan to make one using a microcontroller, but there are quite a few alternatives including the super cheap 555 timer ic.

[Al_The_Man]

There are Watchdog circuits out there based on missing pulse detectors, and they can be designed with less stringent frequency requirements.
Al.

[Adam-Fx]

If someone was looking for a solution for Arduino, here is a simple example (a movie in Polish but the code is available and you can see the connection on the film)
we can program the system so we do not need 12.5Khz