Digital Potentiometer Help!

Discussion in 'General Electronics Chat' started by vinit1973, Mar 24, 2011.

  1. vinit1973

    Thread Starter New Member

    Mar 24, 2011
    1
    0
    Hello,

    I have a fully working vibratory feeder circuit wherein the electromagnet is energized to magnetize it. I use PWM for controlling the frequency of vibration and LM317 for controlling the amplitude. Both frequency and amplitude are currently varied using mechanical potentiometers. The circuit works perfectly well tillhere.

    I now want to be able to adjust the frequency and amplitude using Up/Down pushbuttons. Can somehow suggest the simplest way to do so? I want the simplest way of doing it! I also want to display the settings on a small LCD screen so that the user can remember the frequency and amplitude settings for future use - though however the displayed information may have nothing to do with the actually frequency/amplitude. It may just show values from 0 to 64 (for a 64 step pot or whatever) for both frequency and amplitude.

    Hope I've been able to explain my requirement!

    I'll be obliged if some of you experts could help me!!!

    Looking forward to your help!

    Vinit Verma
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    One option is to change the potentiometer controls to 10 turn types for better resolution and use turn counters to indicate the setting on each - http://parts.digikey.com/1/parts/746349-counting-dial-0-20-turns-h-46-6a.html

    You give no information on the adjusting voltages and currents, which makes it hard to come up with a DPOT. They are usually unipolar and very power-limited.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Digital pots usually want to "see" only 5v between the "ends" of the "wiper", and have fairly high values of resistance. An LM317 requires a minimum of 10mA load to guarantee output regulation. That may be difficult to accomplish with a digital pot.

    An LCD display would be rather complex to drive with anything other than a microcontroller, and the uC would require programming. 7-segment LED displays might be used with discrete CMOS IC components, but the project would require a number of ICs and other discreet components (a number of resistors, for example) for an R-2R ladder.
     
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