You can control the resistance by using a digital pot. You just send the
values of the resistance you want via SPI and then the digital pot will
adjust to it. Microchip, among others, makes a variety of them. Their part
number (Microchip's) starts with MCP41 /MCP42-then the value of the pot.
Application note AN746 from Microchip's website shows you how to interface a
PIC16F876 to their digital pots. I am sure you can figure out how to port it
over to the 16F628. Hope this helps.

AN746
http://www.microchip.com/download/appnote/analog/mcp4xxxx/00746a.pdf

\manu
_______________________
Manu Nair
mnair@email.sae.org





-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jai Dhar
Sent: November 1, 2002 9:54 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: [PIC]: Controlling resistance


Hello,

I am looking to make a simple linear psu using lm317/337's adjustable
regulators. Basically, they use a pot from 0 -> 5k to adjust the Vout. I was
wondering if there is a way I can control a resistance using a 16f628, so I
can incorporate a sort of digital feel to my psu. Thank you for your time,

Jai

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