From: "Boris Nogoodnik"
References: <firstname.lastname@example.org> <email@example.com>
Subject: Re: Limiting total wattage for a constant-current dummy load?
Organization: KGB, Ltd.
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Mon, 11 Nov 2002 07:44:52 GMT
NNTP-Posting-Date: Mon, 11 Nov 2002 02:44:52 EST
"James Meyer" wrote in message
> On Sat, 09 Nov 2002 20:54:20 GMT,
jmuchow@SPAMMENOTcamlight.com (John Muchow)
> >That's the way I'm doing it now and I typically prefer the
> >method myself, especially if the alternative involves a new
> >a higher cost in $$ and time. But, I also have 2 friends who
> >use this device to test their R/C airplane battery packs and
> >trust their math abilities at all. :-)
> OK. And I'm surprised that someone hasn't suggested it before
> about a cheap PIC microcontroller? Didn't you say you were a
> A PIC, simple keypad, and an LCD should allow you to have a
> input for the current setpoint. Then let the PIC use its
built in A/D converter
> to measure the battery voltage. The PIC calculates the power
and if its OK then
> it turns on the current controlled load using its PWM D/A
output facility. If
> the power is too high then an appropriate message is displayed
on the LCD and
> the current load isn't activated.
> If you wanted too, you could program the PIC to shut off the
> the battery drops to it's lowest safe operating voltage. And
since you, or the
> PIC, knows the current, voltage, and time, you could let it
> display both the AmpHour and WattHour rating for the battery
when it's finished.
> Parts cost should be $25.00 or so and it would be quick and
easy to do.
> Jim "With a calculator right beside the slide rule." Meyer
Using digital controls is another story. Always accurate,
always predictable, no hardware changes needed. But there is a
beauty in analog solutions. It's the art people don't remember
anymore. Using uCs is the obvious choice nowadays for
precession measurement and control. However you have to have
some kind of development system, proper interfaces, software,
etc. and you have to know how to program the thing.