Re: Breakout board or cards - charge pump ?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Joe Macmurchie <jrmac@s...>
wrote:

> Jeff,
>
> Thanks to you and the others for the help on this. I kinda had an

idea it

> was a safety device... But it still begs the question to me how it

ever got

> the name "charge pump". I am sure it made sense at the time.
>
> BTW folks, still need to hear from someone who has a simple home

brew

> spindle speed PW to voltage circuit.
>

As I understand, Mach2 is the only software that uses the feature.

It outputs a frequency signal on one pin.

with a comparitor, resistor and cap, you can generate a simple filter
that will be charged with the signal and the comparitor can see the
elevated voltage, then turn on a curcuit that would allow the rest of
the board to be live.

It is more complicated than that. I would put a PIC on the input and
do it in software, or an op-amp to boost the signal, filter it and
act as both the comparitor and output filter (to prevent noise
problems)

With an on-board relay to allow power to the other relay circuits you
can isolate the outputs to eleminate the annoying and possibly
dangerous POST (Power On Self Test) of the PC's bios on start-up.

That relay can also act as a e-stop feature.

As for your drivers, the Geckos have e-stop inputs so the question of
switching the control to software becomes one of staging. Which
comes first ? the software command or the hardware command ?

For guys making a PCB machine, they already know this stuff and
already know how to make their own boards and are only looking for
faster board making.

Dave