Connect with us

Digital Potentiometers - implementation ?'s

Discussion in 'Electronic Design' started by Jason Stoddard, Nov 15, 2003.

Scroll to continue with content
  1. I wonder if somebody can add a couple wrinkles to my grey matter. I am a
    bit new to these. I am looking at a digital potentiometer:

    (DS1866 - http://rocky.digikey.com/WebLib/Dallas/Dallas Web%
    20Data/DS1866.pdf)

    I am putting together a micro controlled circuit for a school project. I
    would like to have a micro output signals to drive the digital
    potentiometer and use it as a dimmer for some LED's or other low voltage
    light.

    My question is on how to read the data sheet to determine how much
    current I can run through the resistor network? Can I run my LED's
    directly through these resistors? or do I need to use these resistors to
    drive another circuit?

    Thanks!

    Jason
     
  2. I have not looked up the datasheet, but often these chips come
    with different resistor values, the smallest being 10K. That is
    a bit too high resistance for direct control of a led.

    You could use it to control a voltage, from 0V-5V, and use
    and opamp follower to give you a bit more current for your
    led(s).
     
  3. Luhan Monat

    Luhan Monat Guest

    Jason,

    Digital potentiomenters have their uses - dimming lights is not one of
    them. You can do it, but why not just drive a simple transistor with
    the micro's output. Vary the duty cycle of a series of pulses in
    software (PWM) and control a lot of power with very little loss.
     
  4. Ban

    Ban Guest

    Frank Bemelman wrote:
    |||
    ||| I am putting together a micro controlled circuit for a school
    ||| project. I would like to have a micro output signals to drive the
    ||| digital potentiometer and use it as a dimmer for some LED's or
    ||| other low voltage light.
    |||
    ||| My question is on how to read the data sheet to determine how much
    ||| current I can run through the resistor network? Can I run my LED's
    ||| directly through these resistors? or do I need to use these
    ||| resistors to drive another circuit?
    ||
    || I have not looked up the datasheet, but often these chips come
    || with different resistor values, the smallest being 10K. That is
    || a bit too high resistance for direct control of a led.
    ||
    || You could use it to control a voltage, from 0V-5V, and use
    || and opamp follower to give you a bit more current for your
    || led(s).
    ||
    ||
    || --
    || Thanks, Frank.

    It will much better to create the dimming by software inside the PIC with
    PWM.
    To the LED I would use this kind of interface, a current source:
    It needs only 1V, the rest is available for the LEDs, it is also short
    circuit proof.

    +5...20V
    o--|<--|<--o
    2N3906 | LED LED
    port ___ |/
    o--|___|--+--|
    4k7 | |>
    V |
    1N4148 - |
    | .-.
    | | |
    V | |R= 0.66V/20mA = 33 ohms
    1N4148 - '-'
    | |
    | |
    === ===
    GND GND
    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    ciao Ban
     
  5. Yes, 100% agreed. But the question seems to focus on using a digital
    pot, for educational purposes.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-