Replacing Mechanical Pots with Digital

Sep 11, 2008 2 Replies
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Hello all, I'm looking at replacing mechanical potentiometers in a variety of existing devices with digitally controlled ones. I find several manufacturers of digital pots, but I don't seem to be able to reliably match up the resistance of the existing pots with the digital ones.



For example, I can find 25K, 50K, 100K, even 1Meg digital pots, but two values I would commonly need, 250K and 500K, just don't seem to be available in digital. I can't change the design of the existing devices, I would need to adapt to them.



I'm not entirely ignoring current-capacity issues, but most of the time the digital pots would be fine in that regard.



I wonder if anyone could suggest a way to address this, even using a standard-value digital pot to control some other resistive device.



Thanks! Patrick Keenan



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I can't change the design of the existing devices, I would need to adapt to them.

Well, you are changing the pot. Why can't you tweak the circuit a bit. It's hard to imagine a circuit with a 250k pot that couldn't be changed to use a 100k. Show a circuit fragment? George

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Are you looking to the pot to provide a varying resistance, or a varying voltage divider? Check those data sheets carefully if it's the former.

Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
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