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TarHeelTom
05-01-2010, 02:31 AM
I understand, basically how "charge pump" works, and why it is needed.

But what is the origin of the term?


Tom
:confused:

Al_The_Man
05-01-2010, 09:34 AM
The term given to the pulse itself as the charge pump signal is a bit of a misnomer as it all depends on how the pulse is detected.
The most common term originally applied to detecting system failure in processor based systems was 'Watchdog timer' and still is in such systems as processor based motion cards, whether PC based or not.
This operates on the same principle as the charge pump, they differ in the way the pulse loss is detected.
Both methods can be used with the Mach signal, for example either a watchdog timer, which operates on the principle of the pulses repeatedly resetting a timer with a duration slightly longer than the pulse signal or a charge pump which relies on capacitive charge by the pulses.
Both methods originally came under the common term of Watchdog timer.
Traditionally this safety feature is/was commonly inserted in the E-stop string to detect any failure, start up, or shut down of the processor and shut the system down.
Hence "Watch Dog"
Al.

Andre' B
05-01-2010, 10:20 AM
Charge pump circuits have been around about as long a electrical circuits have been around. The application of the term charge pump to CNC controls is relatively recent.

http://www.edacafe.com/books/McGraw_Hill/Charge_Pump_Circuit_Design/45xch01.pdf

HuFlungDung
05-01-2010, 10:55 AM
That is interesting, I've seen the term watch dog timer and never really knew what it meant or what it was doing.

I've always been intrigued by all those 'smarties and biscuits' soldered to circuit boards :D I'd like to take a laymen's course in how this stuff all works and is related to each other in systems. I'm not interested in the maths part of it so much, and that is where it seems a lot of official instruction wants to take one. I've gathered bits and pieces here and there over the years, but there seems to be a lot of hardware on circuit boards that exist outside the realm of the simple operation of various circuits.

Al_The_Man
05-01-2010, 11:15 AM
The Watchdog timer is a relatively easy circuit to put together, in the case of the Mach signal which evidentally can be either 12.5Khz or 6.2Khz, a 555 timer can be used in what is commonly called a missing pulse detector.
If the pulses stop, the timer times out and releases a relay coil.
Al.

TarHeelTom
05-01-2010, 12:35 PM
Thanks, Al and Andre. I'm familiar with voltage doublers, and the charge pump seems to be a big brother to the voltage doubler.

Tom

Al_The_Man
05-01-2010, 01:15 PM
and the charge pump seems to be a big brother to the voltage doubler.

Tom

Thats about it.

In all the years I have been involved in machine controls-PLC/CNC, the first time I had heard of the term charge pump as applied in place of the W.D. was from Mach.
Al.