On Thu, 8 Nov 2001, Josh Koffman wrote:

> Thanks for the reply Dale. That is basically what I want to do. Would I
> achieve any advantages to using a fixed resistor on one side?

None that I can think of.  The current through the pot will be the same
regardless of where the wiper is positioned, so using fixed resistors on
one or either end would only server to limit the input range (which you
may or may not want).

> Obviously your method wins in the parts number contest. Also,
> shouldn't that be ends to ground and Voltage Reference? In this design
> it won't make a difference, but just to be clear for the future.

Yes, you're correct.  When using the ADC for nothing more than a position
input like this, I always use Vdd for Vref - again, saves parts.

> Also, can anyone reccomend any analog multiplexer chips? Basically I
> want to read more than 8 potentiometers. At the moment, it'll probably
> end up around 12-24, but could be higher in the future. I'd like to
> stick with the ADC build into the chip, but multiplex the inputs. Any
> ideas?

Maxim makes a bunch, looks like up to 16:1:

http://para.maxim-ic.com/compare.asp?Fam=sw_mux&Tree=SwitchMux&HP=SwitchMux.cfm

Dale

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics