A digital pot is certainly one alternative (and others have pointed you to
them). However,
another way to do this is with an FET. Not as handy, but cheap. You could
use PWM to generate a voltage on the gate of the FET, and the resistance
between source and drain will vary depending on the gate voltage. FET gates
are very high-z, too so they are good candidates to drive via PWM.

Good Luck,

Al WIlliams
AWC
*Solderless Stamp and PIC Protototypes at
http://www.al-williams.com/awce.htm

-----Original Message-----
From: PHXSYS <PHXSYS@aol.com>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>; stamps@parallaxinc.com
<stamps@parallaxinc.com>
Date: Wednesday, May 06, 1998 12:45 AM
Subject: [STAMPS] How to simulate resistance?


>Hello everyone
>
>I want to drive the OEM fuel gauge used on most common vehicles. Current
>gauges use a resistive device to ground to drive the gauge, for example
most
>Chevy use a 0-90 ohm sender ( 0=full, 90=empty) , Ford 160-10 or 70-0 ohm
and
>a few others.How can I use a stamp or PIC to drive these gauges. I was
>wondering if I could use PWM to drive the gauge to ground? I could utilize
a
>different table for each vehicle type. Any suggestions on how I might
>accomplish this. Feel free to offer other suggestions I don't know if PWM
will
>work, but I am sure someone out there has figured out a slick way to do
this.
>
>         Gauge----------------Sender-----------GND
>
>Thanks in advance
>
>Jon
>
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