Re: [sdiy] Digital Pots

[Roman]

what IC you mean, Harry?
There are:
AD7376 +/-15V digital pot 128 pos., 10, 50, 100k, 1M
AD5290 +/-15V digital pot, 256 pos., 10, 50, 100k
all 3 leads of the digipot can be at any voltage between -15 and +15V.
In some cases most if not all current output DACs with external reference input can be used as digipot too, offering higher resoulution than typical 128-256 steps of a digipot. But then we get something like a resistive divider with one end connected to GND.

Roman

---- Wiadomość Oryginalna ----
Od: Harry Bissell Jr <harrybissell at prodigy.net>
Do: Jeff Farr <moogah at gmail.com>, synth-diy at dropmix.xs4all.nl
Data: Thu, 4 Aug 2005 10:49:35 -0700 (PDT)
Temat: Re: [sdiy] Digital Pots

> Check the voltage levels they can be used at. MOST
> are 5V supply (or less).
> 
> The one that Analog Devices lists as +/-15V is more
> properly called a multiplying DAC
> 
> Putting a resistor in parallel will change the
> 'taper' of the pot. It will not be linear anymore.
> This could be a 'bug' or a 'feature' depending on if
> you like the effect.
> 
> H^) harry
> 
> --- Jeff Farr <moogah at gmail.com> wrote:
> 
> > SO, while scouring the net for a way to connect a
> > MIDIBox SEQ to a 808
> > clone so that all the parameters are digitally
> > controlled I've come
> > across a series of IC's at analog devices and
> > maxim-ic called digital
> > potentiometers.  There is a large variety of them in
> > many different
> > resolutions, of specific interest are the ones with
> > 127 possible
> > values.  Has anybody tried to use these as an in
> > between from encoders
> > + digital interface to regular VC circuits?  Some of
> > them are 2
> > terminal and are listed as , but others have three
> > which would seem
> > ideal.
> > 
> > Quote from site:
> > "The AD5247 provides a compact 2 mm x 2.1 mm
> > packaged solution for 128
> > position adjustment applications.
> > 
> > This device performs the same electronic adjustment
> > function as a
> > mechanical potentiometer or a variable resistor. The
> > low temperature
> > coefficient makes this device ideal for high
> > accuracy and stability
> > variable resistance adjustments. "
> > 
> >
> http://www.analog.com/en/subCat/0,2879,761%255F797%255F0%255F%255F0%255F,00.html
> > 
> >
> http://www.analog.com/en/prod/0,,761_797_AD7376%2C00.html
> > 
> > Seems with such a selection there should be at least
> > one that will
> > work.  There aren't alot of available resistance
> > values, but if I'm
> > not mistaken I can place it in parallel with a
> > regular resistor to
> > achieve the desired range through 1/Rt = 1/R1 + 1/R2
> > etc.
> > 
> > 
> 
>