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Digitally-controlled pot?

Discussion in 'Electronic Design' started by Dungeon Dave, Dec 7, 2008.

  1. Dungeon Dave

    Dungeon Dave Guest

    Further to my last post about having a dimmer circuit (using the Bowden
    circuit mentioned previously), next stage is to try to replace to 50K pot
    with something more remotely controllable.

    The idea is that although I can manually turn up/down the dimmer, by
    having it controllable from a variety of sources I can replace manual
    control with either computer-based or timer-based (or a combination of
    all three) - so I'm looking at something I can ideally feed in a
    "increase" or "decrease" signal and it'll increment/decrement the pot
    driving the Bowden circuit.

    Is this feasible?

    Lastly, I wouldn't mind trying to do the same circuit idea but for mains
    lamps - like the Halogen dimmer circuits - to drive a set of Haloge
    spotlights used for lounge uplighters. I once attended a conference in
    which a rocker switch near the door was used to toggle on/off the lights,
    but holding down the switch would increase/decrease light intensity,
    allowing a light level dark enough to permit a projector to be used for
    presentations but still with enough light that attendees could scribble
    notes. The same switch was located over near the speaker's stand, as well
    as near another control panel - it was clear that the circuitry lay not
    behind the switch itself (as with some conventional rotary dimmers) but
    elsewhere with several switches all paralleled up to provide the same
    control from different locations.

    Again.. should I hunt around for a circuit to do this, or is there some
    off-the-shelf idea that I could utilise?
     
  2. Dungeon Dave

    Dungeon Dave Guest

    Is there some reason that you want to design and build this yourself?
    Or
    No reason whatsoever - I was looking for an off-the-shelf system,
    thinking someone would spam me with "have you tried Arglebargle
    controllers from lighting-gizmos.info" or "try this diagram from
    www.youcanbuildityourself.projects" but over in the other thread it seems
    a PCW dimmer ought to do the trick, so was looking at building one.

    I think my requirements are more complex than a simple plug-in-and-go-
    LED-driver box idea, but less than full-blown theatre-class dimmer packs.

    I did a veroboard layout for the Bowden circuit in readiness; I know it's
    not that difficult to construct but before I take the plunge, I don't
    want to find I could have just blown £20 or so on something that does
    everything I need it to (with cannibalisation tweaking).
     
  3. Dungeon Dave

    Dungeon Dave Guest

    Is there some reason that you want to design and build this yourself?
    No reason whatsoever - I was looking for an off-the-shelf system,
    thinking someone would spam me with "have you tried Arglebargle
    controllers from lighting-gizmos.info" or "try this diagram from
    www.youcanbuildityourself.projects" but over in the other thread it
    seems a PCW dimmer ought to do the trick, so was looking at building
    one.

    I think my requirements are more complex than a simple
    plug-in-and-go-LED-driver box idea, but less than full-blown
    theatre-class dimmer packs.

    I did a veroboard layout for the Bowden circuit in readiness; I know
    it's not that difficult to construct but before I take the plunge, I
    don't want to find I could have just blown £20 or so on something that
    does everything I need it to (with cannibalisation tweaking).
     
  4. Eeyore

    Eeyore Guest

    I don't know the 'Bowden circuit' but digitally controlled pots may not
    sustain the voltage requirements of many typical dimmer circuits.

    Graham
     
  5. Dungeon Dave

    Dungeon Dave Guest

    ah, my mistake:

    http://ourworld.compuserve.com/homepages/Bill_Bowden/page6.htm#dimmer.gif

    There's 12V across 52K (50K of a pot + 2x 1K). I did some calculations
    last night, thinking that standard quarter-watt resistors may not be up
    to it... and that entire series chain has about a quarter of a milliamp
    running through it, so I'm guessing most DIPs can handle that oompf.

    However, I'm on Brendan's link at the moment, sussing out the differences
    between each option (hell- there's so many to choose from!).

    Guess I'll google around for a suitable circuit that contains one of
    these driving a 50K digi pot.
     
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