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Okay so I am definitely not knowledgeable in electronics and need some help involving a digital potentiometer.

I would like to know how I would use the AD5121 digital potmeter.

Lets pretend I had a simple circuit that consisted on a regular AA battery as the power supply, then the digital potentiometer, and then a transformer or whatever.

How would I connect the potentiometer into the described circuit and have it controlled by a microcontroller.

Also: I tried looking at the technical document but I had no idea what I was looking at.

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  • \$\begingroup\$ A digital pot works in the same way a regular pot would (only for small current draws). Your circuit is so vague that noone will be able to know what you mean. See Analog's digital pot tutorial white paper for some typical applications and background information. analog.com/static/imported-files/tutorials/MT-091.pdf \$\endgroup\$
    – Passerby
    Commented Jan 28, 2013 at 0:09
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    \$\begingroup\$ What described circuit? \$\endgroup\$ Commented Jan 28, 2013 at 0:12
  • \$\begingroup\$ @Passerby Yeah I guess the circuit I described isn't exactly useful for anyone. But are you saying it is essentially wired in the same way as an analog potentiometer \$\endgroup\$
    – user18336
    Commented Jan 28, 2013 at 0:12
  • \$\begingroup\$ @Chintalagiri Shashank Forget the "Circuit", because it is very vague and basic \$\endgroup\$
    – user18336
    Commented Jan 28, 2013 at 0:17
  • \$\begingroup\$ Yes, the pot side, Terminal A is the high end, Terminal B is the low end, and Terminal W is the wiper. The rest is the spi/i2c interface. \$\endgroup\$
    – Passerby
    Commented Jan 28, 2013 at 0:32

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You'd use it just as you would an analog pot, with caveats.

  1. The voltage on all the pins must remain within the supply voltages of the device or less. The datasheet would have specific details. The ICs usually have protection diodes which would clamp any voltage beyond the allowed range. If the situation persists, you can damage the IC.

  2. The resistance when the IC is turned off is usually infinite. Youd have to power it up for the wiper (centre pin of a regular pot) to be connected.

  3. When the device is powered up, it may not be in the condition it was it when it was powered down. If this is going to cause trouble, such as a low resistance path between V+ and ground, say, you should take precautions.

  4. They usually can deal with much less current than an analog pot can. Be careful and follow ratings carefully. ICs are more expensive than analog pots, and sometimes harder to replace and/or debug.

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  • \$\begingroup\$ Thanks a lot. I'm not great with electronics but your answer has helped me get a good idea about the digital potentiometer and how to use it :) They are a lot more expensive but I NEED to use them so I didn't want to screw anything up by trying to figure it out by myself. \$\endgroup\$
    – user18336
    Commented Jan 28, 2013 at 0:40
  • \$\begingroup\$ Its also worth noting, the end to end resistance is typically +/- 20% or something else ridiculous, but the resistance between steps in the pot will be in tight tolerance. That means they work very well as pots, but terribly as rheostats. \$\endgroup\$
    – Matt Young
    Commented Jan 28, 2013 at 1:21
  • \$\begingroup\$ @MattYoung: It's also worth noting that "wiper" resistance may be specified even less well than end-to-end resistance. \$\endgroup\$
    – supercat
    Commented Jan 28, 2013 at 18:12

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