DDL (was: DIY-GOR ideas)

Bernd Felsche bernie at innovative.iinet.net.au
Fri Nov 24 16:49:26 GMT 2000


944Technologist tapped away at the keyboard with:

> From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
> > Where is the data to support that those sensors can't be driven
> > pulse-mode? Is there a published paper/patent on the effect of
> > ion-diffusion in pump cells somewhere which examines the effect?

> Sorry Bernd....... Pulse width modulation is an analog process.
> Not digital.  Hanging digital controls on another analog process
> does not make it a digital process.

Sorry, but pulse-width modulation *is* a digital process if
implemented like that. If you look at the circuit and try to
understand how the thing is intended to function, you will see that
the process of pulse-width modulation is entirely digital.

The only analogue circuit components in DDL (the raw implementation)
is a few resistors used for scaling voltages, sensing and limiting
currents. All the control *policy* and logic is done in software.
Feedback may be analogue but that is entirely irrelevant.

Oh, there is a supply-voltage regulator and precision voltage
reference shown as well...

And if you wanted to add an RS232 level convertor that would be
"analogue" as well wouldn't it? Even though it's a digital signal.

> Good luck with your design. For your information, it is impossible
> to measure voltage, resistance and current with a computer. You
> need precision resistors, constant current sources, op amps, and
> analog to digital conversion (A/D). You will need a shit load of
> A/D and D/A converters to make this work. When it is done, you
> will still have a computer interfaced to a whole lot of analog
> circuitry. If you can design this without a single op amp or a
> single A/D converter, I will be the first to say I was wrong.

It may have escaped your attention but the microcontroller in DDL
has "a shit load" of ADC channels for precisely that reason. Yes; in
a $10 chip. A precision voltage reference increases the accuracy of
analogue measurements.

You seem to be making a religious issue out of thin air.

Take a look at the DDL schematic and read the description.

-- 
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