Effectiveness of RAM induction? (AFM replacement)

[Brian Dessent]

> signal, I'll convert it to voltage.  Then I'll adjust the scale with an
> op-amp.  Then I'll have to plot volt v. rpm to see what kind of
> (non)linearity I have.  I believe chips exist which will do log and exponent
> functions on analog signals.  I'll bet they can be tuned to produce
> different functions.  When the MAP looks like the AFM, the AFM is GONE!
> 
> Hey, talk is cheep, but this is what I'm thinking anyway.
> 
> Comments?

You can certainly do nonlinear stuff directly in analog (there exist
chips to do exponential, log, 4 quadrant divide, multiply) but if *I*
were doing it I would definitely use a PIC or some other
microcontroller.  The PIC is perfect for this job, they are designed to
be cheap, complete, and powerful.  You could probably do the whole thing
with a single chip.  It could probably do the freq->voltage (or a/d if
you want to do f->v externally), loopup table conversion, and d/a (via
PWM), as well as storing your program code in flash or eprom, clock
generation, and automatic power-on reset, all on the one chip.  They can
be programmed with cheap (or build-it-yourself) hardware -- if you
choose a flash variety you don't need a UV source to erase and you can
make a programmer with your computer's serial or parallel port for about
$20.  Look at the 16F87X family for a start:

http://www.microchip.com/14010/lit/pline/picmicro/families/16f87x/index.htm

If assembly language isn't your thing then look at the Basic Stamp.  It
really doesn't get much easier than these -- you write your program on
your PC in a BASIC-like language, hit the download button, take the chip
out to the car, and drive away.  (the stamp usues the PIC as its guts so
that's why I mention them together.)

This would surely seem easier than cobbling something together with
various analog chips.

Brian
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