DDL (was: DIY-GOR ideas)

[Will McGonegal]

If you look at the specs of many modern microcontrollers they contain built in
A/D converters and multiplexers.  And many have PWMs as well.  Perhaps you'll
need an Op-amp buffer if the impedance of the sensor output is too high for the
sample and hold circuit (which is built into the microcontroller).  I disagree
with having to use precision resistors; you can measure the value and store it
in your microcontroller for calculations.  Microcontrollers are inexpensive, and
may lower the parts count.  And some of the tweaking can be done with software
instead of parts changes.

> 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.
> 
> FR Wilk

I'm not suggesting here that a digital microcontroller based design is the way
to go.  As an electrical engineer who has designed both analog and digital
circuits, I believe both methods of O2 wide-band circuits have merit.  I would
consider both design types if I was to construct a circuit.  Of course a circuit
that has been proven to work would probably be my first choice.  But there's
always room for improvements.

A microcontroller (with built in AD-- how does 10 bits sound?) can be used to
read the analog circuit output, scale it appropriately, then send the result to
a display.  (I would avoid setting up an AD feeding a ROM into a display
driver-- sounds like too many parts-- but it could be made to work).  Do you
want an LCD or LED display with that?

Will
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