Re: Need a calculator that knows about coulombs
On Tuesday 22 December 2015 21:02:31 John Hasler wrote:
> Gene Heskett writes:
> > In this case, the size of a capacitor hooked to a square wave
> > source, and I want to know how much charge is transfered for every
> > full cycle of the input square wave.
>
> Zero assuming linear source and load impedence.
Ahh, but its being fed to a voltage-doubler with schottky diodes, so
there should be a calculatable amount of charge delivered to the output
capacitor Cf, by the pump capacitor Cp, per cycle. With Cp being of a
capacity such that with the usual logic circuits output impedance,
capable of delivering 10 to 20 milliamps into a resistive load, IOW not
a zero impedance source. Cf would be sized such as to be about 50x Cp,
and will be driving an enhancement mode fet which will turn on a 40 amp
SSR once the charge has built up on Cf to make the fet conduct.
A charge pump detector to control a 2 kw DC power supply startup, one
turning it on but with a 51 ohm 200 watt resistor in series with the AC
line, and another identical circuit turning on a 2nd 40 amp SSR to short
circuit the 51 ohm 200 watt resistor but timed to be 5 seconds later,
after the capacitors are charged up. The PSU has a quite high
capacitance input filter, and without this soft start timed power up,
needs a 30 amp breaker in the service in order for the breaker to
withstand the power up event. NEC says I can't service a duplex with
more than a 15 amp breaker. The actual draw, once powered up, doesn't
exceed 15 amps even with a vacuum cleaner being powered by a similar
circuit enabled that is plugged into this same 4-plex.
All part of a CNC milling machine setup. And theres no reason for it to
be enabled when the CNC control program isn't running. The program will
generate the 500 hz square wave these charge pump detectors will detect,
and will control the time delay for the 2nd one. 1/4 to 1 second
response time is not a concern for something like this. It just needs
to be 101% dependable. :)
Cheers, Gene Heskett
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