ivp wrote:
>> think of the switches as bits of a D/A and wire them up in
>> a R-2R ladder
>>    =20
>
> http://en.wikipedia.org/wiki/Resistor_ladder
>
>  =20
The problem is for the ladder to work corrrectly you need switches that=20
switch between 0V and 5V, not switches that switch between a defined=20
voltage level and open circuit.

You could use pull up (or pulldown) resistors) of much lower value than=20
in your ladder but this would increase power consuption considerablly=20
(you would probablly want a factor of 100 or so difference between the=20
pullups and the ladder resistors).

 >As I'm looking for 15 reasonably-well-defined discrete steps and
> not the precision of absolute voltages, 1% resistors should be OK
>
> I can use the same search and compare s/w, the only difference
> being that the expected A/D results will be in order of the binary
> value of the switches
>
> Joe
>
> *
> *
> **********
> Quality PIC programmers
> http://www.embedinc.com/products/index.htm
>  =20

--=20
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