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LED lightbulbs and X10 dimmer switches?

Discussion in 'Electronic Basics' started by Tom Horsley, Mar 19, 2007.

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  1. Tom Horsley

    Tom Horsley Guest

    As an experiment, I ordered an LED bulb advertised on its web site
    as "compatible" with dimmer switches. As I sort of expected, "compatible"
    doesn't mean it actually changes luminosity - it just means it works :).
    In practice, it comes on at some point and goes off at some point, and
    no dimming seems to be evident.

    With the light bulb police gaining ground all over the world, someone
    must have figured out that there will be a market for replacement
    bulbs that still work with X10 dimmers.

    Surely it would be possible to build a bulb that measures the duty
    cycle of the input AC and controls the brightness of the LEDs
    from it (possibly a bit more expensive than the already expensive
    LED bulbs, but what the heck, the switches are more expensive too)?

    Anyone know of any LED bulbs that actually work well with X10 dimmers?
    Anyone monitoring this newsgroup for new product ideas? :).
  2. Bob

    Bob Guest

    I'm surprised that LED bulbs act this way. They should respond to the change
    in duty cycle.

    I've had no luck with fluorescents either. They won't start. I suspect it's
    because their load doesn't meet the 10mA thrystor hold current right at
    startup (but I really don't know).

  3. Lord Garth

    Lord Garth Guest

    I'm running X10 as well and I suggest that you easiest move is to include
    a load that the X10 wants to see in parallel with the fluorescent lamp. I
    this in two rooms using a small 7 watt incandescent bulb in each room.

    The other solution is to replace the triac within the X10 switch with a
    solid state relay though this eliminates dimming.
  4. Many LED "lightbulbs" only draw current over some smallish portion of
    each half-cycle of AC, probably around and just ahead of the voltage peak.

    Ones lacking filter/smoothing capacitors should do better but will still
    differ from incandescents by having "bottom" being higher, light output at
    "midpoint of dimming" being higher, and "visually effective midpoint of
    dimming range" being lower and a little close to the bottom.
    Ones with the filter/smoothing capacitors do worse in this area as well
    as draw current spikes that make RMS current draw well above ratio of
    watts to volts.

    - Don Klipstein ()
  5. The way I would design the led bulb replacement suitable for dimming, would
    be have some of the led's in the array be voltage switched in steps. As in
    as the line voltage is lowered, some of the led's switch off in the array.
    I have not seen one made like that, but as a home project maybe? How bright
    is the led lamp you have - how does it compare for you to the lamp you
  6. Bob

    Bob Guest

    It's good to hear that the parallel load (min hold current) technique works.
    I was going to construct a male-to-female socket adapter with an integrated
    power resistor, but your solution is much simpler and it would probably
    satisfy U.L., too.

  7. Tom Horsley

    Tom Horsley Guest

    It didn't replace anything - it was just an experiment, but it isn't very
    bright. The web page (in addition to talking about dimmer compatibility)
    also talked about "reading light", but any standard Mom would give you
    hell for trying to read in the light this thing produces :).

    On the other hand, there are LED bulbs that I'm sure are plenty bright,
    like this one (which I wasn't willing to buy merely as an experiment):
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