[sdiy] digitally controlled potentiometers

[rob]

Hi,
I plan to use an Analog Devices AD5290 10k Digital Pot to control filtering
in an Op Amp stage (as part of an updated Digisound VCDO). Its 15V friendly
8-bit, SMT (10 MSOP). I just ordered some free samples yesterday, Digikey
sell them for 4.00 US Dollars. The Digipot will run from a PIC with SPI,
which also reads a front panel pot for the values. I'll be going with 7 bit
resolution, as 128 values is about as fine as I can adjust my pots.... The
values will be stored in EEPROM, so that the shape of the wave in terms of
filtering can be saved with the wave number.

Whilst there are 10-bit digipots about they are much lower voltage devices.
For critical frequncy applications I'd stick with DAC technology and have 2
control pots - coarse and fine. 

Regards
Rob
www.emulatorarchive.com


Hi All,

I have been working recently on digitally controlled potentiometers. The
idea is to be able to use these potentiometers as drop-in replacements for
cloning projects and new synth projects. The potentiometers will be
controlled by a rotary encoder on the panel of the synth or by MIDI and a
supervisory microcontroller. This will make it possible to make real analog
synths that have patch memory and will be able to dump the movements of the
knobs as automation tracks via MIDI.