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Effect of light dimming circuits on line voltage sockets

Discussion in 'Electronic Design' started by [email protected], Jun 27, 2005.

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  1. Guest

    I am having my house re-wired. On one floor, the lamps are fed from a
    lighting controller (a bit like a Lutron controller) which outputs a
    chopped waveform to dim the lights.

    It is very difficult to avoid routing some of the 2A lighting circuits
    right next to the main power circuits feeding the socket outlets.

    Is this likely to cause a RFI problem for my electrical appliances?
    Other than separate the lighting and power cables by a few feet (very
    difficult), are there any steps that I can take to minimise
    interference?
     

  2. Don't worry about it. The dimmers are undoubtedly
    designed to avoid disrupting radio communication for
    miles around. The chances of those chop wavefronts
    getting past the input power conditioning of electronic
    equipment and causing problems are very remote.
    Power lines are expected to be noisy. Anybody who
    tried to sell equipment that could not take the little bit
    of hash from your dimmers would see so much of it
    being returned to the retailer that they would soon go
    bankrupt. Your worry is the worst problem here.
     
  3. Joerg

    Joerg Guest

    Hello Larry,
    Well, not quite. It gets radiated off the line and into antennas, radios
    and so on. Most AM radios start to buzz and whine and I have even seen
    sparkles on TV channel 3 when a dimmer to an outside lamp is going.

    Cable to cable coupling isn't a big issue as far as I know. RF Radiation
    is. It's also a good idea to run Hifi equipment off a circuit that
    doesn't have dimmers. Sure, filters and all take care of stuff but only
    to a degree.

    Regards, Joerg
     
  4. Guest

    I hope that you're right, Larry.

    Lutron do issue an application note to advise on how to minimise the
    problem. But it would be a real pain to lay the lighting circuits in
    steel conduit.

    http://www.lutron.com/applicationnotes/360484.pdf
     
  5. Guest

    By "cable-to-cable coupling", do you mean the coupling of noise in
    cables laid side-by-side? Or conducted from noisy circuits through the
    distribution panel to "clean" circuits? The first one is radiated
    noise, and the second one is conducted.
     
  6. Mark

    Mark Guest

    best bet is to buy lamp dimmers that include RFI filters

    nip it in the bud.

    Mark
     
  7. Hi, Joerg.
    I was not addressing such phenomena.
    That is the "it" the OP was worried about and asked about
    and which I have advised him to not worry about.
    Yes, although most people do not notice dimmers' RF
    output messing up their reception, living in cities near
    the stations they receive. But the OP was not asking
    about that. He wanted to know whether he should
    bother separating some power cabling.
    It would be a sad audio amplifier that let that kind of
    garbage through from the line to its output audibly.
     
  8. Guest

    There are different ways to dim ac lights. Consider how much you are willing
    to spend :)

    1) Backedge chopping useing triacs. Will chop the end of the sinus wave.
    This is the standard one on sale in normal shops.

    2) Frontedge chopping useing igbt?, Will chop the start of the sinus wave.

    3) Pwm + filter useing ibgt/mosfet will smooth out the load over the whole
    sinus wave.
     
  9. Joerg

    Joerg Guest

    Hello Larry,
    Well, most of the "modern" stuff that I have seen is of pretty sad
    design quality. Nothing is grounded anymore and you easily get caught in
    a few ground loops. Turn on the dimmer lamp and a faint "bzzzzz" is heard.

    Regards, Joerg
     
  10. Joerg

    Joerg Guest

    Hello,
    Both. Cable-to-cable carries much of the higher frequency components
    that can mess up AM reception. Conducted happens because the line
    impedance at the panel isn't zero because the transformer is located
    away from the house. Even if it wasn't, the transformer doesn't provide
    low impedance at higher frequencies anyway.

    Regards, Joerg
     
  11. Tim Mitchell

    Tim Mitchell Guest

    Actually, that is the wrong way round, triacs chop the start of the sine
    wave and igbts chop the end (or both the start and the end).
     
  12. The fourier transform should be the same for chopping
    the front or the rear.

    Rene
     
  13. w_tom

    w_tom Guest

    You could try twisting the electric wire as it is put into
    the walls. Same idea used to make CAT-5 cable immune to
    receiving and making interference. I never did this so I
    don't know how effective twisting would be. But you are right
    to consider this noise problem that adversely effects radio
    equipment.
     
  14. Guest

    What I've read, in practice igbt approach is less rfi-noisy. Even thought what
    you say maybe is correct in theory.
     
  15. Rich Grise

    Rich Grise Guest

    Maybe over the long term, but what aobut the transients? I ddin't get
    that math course, but it just _feels_ different - like the difference
    between applying a voltage to an inductor versus removing current from
    it.

    Then again, I just fix stuff. What the **** do I know? ;-)

    Thanks,
    Rich
     
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