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I am looking for a set of digitally usb-controllable potentiometers sample a range of resistances from 1 kilo-ohm up to 1 mega-ohm in ideally both linear and audio (logarithmic) taper. Here are some sample values:

Linear: 1K, 5K, 10K, 25K, 50K, 100K, 250K, 500K, 1 Meg
Audio: 10K, 25K, 50K, 100K, 250K, 500K, 1 Meg

I have found this link but they only have 10K, 50K, and 100K values:

http://www.controlanything.com/Relay/Relay/DPOTS

Does anybody know of a good source or solution to the problem? Thanks in advance for your help.

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2 Answers

up vote 2 down vote

If precise control of resistance is your goal, then digital pots are not a great solution. Their resistance varies quite a bit, initially and over temperature.

Usually potentiometers are used in a ratiometric way, where the exact pot resistance is not an issue.

The device you linked uses the MCP42xxx digital pots, which only come in 10K, 50K, 100K. (datasheet) Notice the initial resistance tolerance is ±30% and the typical drift is 0.8%/°C. Also notice the high wiper resistance, which is why digital pots at low resistances don't make much sense.

Can you explain what you are trying to do with all these potentiometers? You may find a different approach to accomplish your goals.

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Thanks for the quick reply, I appreciate it. I am trying to build an analog guitar effect pedal, replacing out the standard potentiometers with ones that can be controlled by a computer. It is my goal to preserve the sound of the circuit and to change the original tone as little possible. And I would hope to do this with the an amount of precision that could not be discerned by the ear. Are there motorized analog pots that can be digitally controlled? Just another thought... – user3394 Mar 16 '11 at 16:38
Digital pots won't be much more out of tolerance than the original pots in the pedal. – endolith Mar 16 '11 at 17:35
@Patrick Hogan I've seen motorized analog potentiometers controlled by microcontroller in a speaker system. I'll try to find out how exactly it was connected. – AndrejaKo Mar 18 '11 at 9:44
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As you can see from you example there is no basic component that does this. The one you point out are expensive. Basically you need a digital pot and a microcontroller. Take an arduino and any pot that will talke to it and build your own.

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