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>Hello,
>I am presently designing a magnetic sensor device using the PIC16C71 as the
>controller for the project. What I am looking for is a linear output
>Hall effect sensor. In the past I've used Allegro Inc. for these parts but
>presently they are sold out! Any sources that you are aware of will be
>considered. Other magnetic sensor types will also be considered. As is typical,
>cost is an issue. To save bandwidth please drop replies to my Email address.
>
>If anyone has run across a list or net site that focuses on sensors I would
>also like to know about them.
>
>Thanks in advance.
>
>Mark Herold Email: herold@research.bfg.com
>

Whereas the world is Analog, it is also true that it is non Linear.

So a linear device may be a proublem.  A way around this is to
plot the output of the device vs input and derive a formula that
reflects this.  Then use the formula in a pc program to generate
'data' statements to put in the pic program.  I think the 'load
w reg and return from subroutine' instruction could be used as a
table lookup.  As this would take 256 instructions, perhaps it
would be better to have a sixteen byte lookup table for the high
nibble of the value and then a table with the 'interperalation'
for the low nibble of each value of high nibble.  It may be
necessary to have the low nibble table contain a mixed value.
that is a value in which the bits do not represent one, but represent
1/2 or 1/4 or 1/8 of the value.  With this it would be possible to
have the interpralation be 3/8 at points where the change per unit
input does is less than one.

A word of advice, if you do this, don't loose the formula.  You
may need it latter for something.

All that said, how expensive is a magnetic pickup for a guitar?

   ---------
   Bill Cornutt
   billcorn@infoserv.com
   Located in Ione California USA.
   A small town in Northern California.
   Sitting against the foothills of the Mother Lode.
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