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Digital Pots?

Discussion in 'General Electronics Discussion' started by dizwold, Sep 29, 2014.

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  1. dizwold

    dizwold

    17
    1
    Nov 14, 2013
    I'm new to digital pots and have no experience with them, so forgive my lack of knowledge.

    Can a digital pot be connected to a µC to be many different resistances.

    IE;

    If you had a digital pot connected to a µC could you press a switch 'or whatever' to change the value of the digital pot. Press the switch the pot becomes a 10kΩ, press again the pot becomes a 20kΩ, press again it becomes a 50kΩ, etc?

    Any advise would be welcome.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,012
    2,506
    Nov 17, 2011
    Basically: yes. The controller needs to read the state of the switch and issue a commen to the digital pot if the controller detects a pressed switch.

    Details will depend on the type of digital pot and the controller you use. A sensible choice would be the use of a digital pot with serially controlled settigs (e.g. via SPI).
     
  3. dizwold

    dizwold

    17
    1
    Nov 14, 2013
    Thanks for that Harald.

    Basically what i wish to achieve is to have 1 rotary device to act as a variable resistor, but to be capable of being any value at the flick of a switch or push of a button.
    Lets say i use an Arduino for the μC, what else would i need, for EG would i need a rotary encoder and a digital pot connected?
    I would like to be able to make the 1 rotary device become any of the typical variable resistor values. I think i'm correct in stating 1kΩ to 1mΩ are the normal values available? I'm looking at the Analog Devices digi pots, but which 1 to use?
    Can you point me to a circuit diagram to do such a job? A big ask, i know.
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    Digital pots are best used as adjustable voltage dividers, rather than variable resistors, because their end-to-end resistance is not very well-controlled.

    They are not a general replacement for resistors because all terminals need to be kept within the device's supply rails (or slightly outside them, in some cases). Also they can't dissipate much power.

    From your description, I think a resistor wheel or resistance box would be what you want.
     
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