Re: Breakout board or cards - charge pump ?

Couple of things here, First, I don't know if anyone adequately
explained the charge pump circuit. It is not something that will be
fooled by a hi or a low on the parallel port pin. The charge pump
looks for a constant pulse train from that port, 15khz I think. That
pulse train can only be present if mach2 is up and running. It works
by having each pulse charge a capacitor. A resistor is connected to
that cap to discharge it during the off time of the pulse train. The
time constant was set up to react very quickly if that pulse train
stopped. Mariss of gecko designed the circuit, so I am sure it is
reliable.

Second, as for each of us building our own circuit, that is a
personal choice. For me I consider this busy work. The enjoyment of
hand wiring up an IC circuit is long gone.



Wally


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
<spadnos@s...> wrote:

> turbulatordude wrote:
>
> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
> ><spadnos@s...> wrote:
> >
> >
> >>turbulatordude wrote:
> >>
> >>
> >>
> >>>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)
> >>>
> >>>
> >>>
> >>>
> >>Yes - it is more complicated. If the software crashes and leaves
> >>
> >>
> >the
> >
> >
> >>port bit in the high state (or the POST routines happen to do
> >>
> >>
> >that),
> >
> >
> >>then everything looks fine to the comparator. This can easily be
> >>
> >>
> >solved
> >
> >
> >>with a microcontroller, or even easier with a one-shot in the
> >>
> >>
> >circuit.
> >
> >
> >>- Steve
> >>
> >>
> >
> >Correct, pulse detection needs to ignore the high and the low.
> >
> >A Charge Pump takes the frequency and by means of charging a
> >capacitor, generates a higher voltage from the signal voltage (or
> >something similar)
> >
> >
> Right - you need to throw in a diode or two to get a charge

pump. :)

> (an R-C circuit would just be a filter)
>
> >either way, the signal needs to detect in the pulse is present and
> >ignore the port being high or low in a steady state.
> >
> >And a PIC would offer a means of detecting a pulse and responding
> >accordingly.
> >
> >
> What's wrong with an AVR? :)
>
> >It is interesting to see how much of the posts are geard toward
> >buying things and less of the making things we had some years ago.
> >
> >Dave
> >
> >
> I've only been on this list for around 6-8 months, so I can't see

any

> specific trends. I think it's similar to a lot of other markets.

There

> are now enough old machines, and people interested in fiddling with
> them, that there is a hobby market for machine retrofit pieces.

I've

> thought about building some (and have built one item).

> I'm doing a retrofit because it's a neat thing to do, but I'll also

want

> to use the machine, hopefully to make some money. In the end, if

my

> schedule gets tight (like - other work butts in), then I might buy

some

> pieces that I otherwise would have built, just to save a little

time.

>
> I think that there's a general shift in attitudes today that time

is

> money, and that it's stupid to spend time (usually

called "wasting") on

> something that you can buy cheap.
>
> (personally, I'd rather spend the time, but I don't always have

that

> option, what with bills and all :) )
> - Steve