Re: Singing light bulb on dimmer switch

[Jeff Wisnia <jwisnia@xxxxxxxxxxxxxx>]

David D. wrote:
> Most light bulbs hum loudly when dimmed via a dimmer switch.  A few are ok,
> because they contain extra filament supports at critical positions.
>
>
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> My hanging (swag) kitchen tiffany-style light takes a G40-150w bulb.  It
> hums badly when dimmed.
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> (1) Is there a brand of G40-150 bulb that does not hum when dimmed?
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> (2) Alternatively, is there a small, in-line filter available, or a
> filtered, table-top dimmer switch, that would create a smoother
> short-duty-cycle output than the intermittent, alternating square-wave
> created by a typical dimmer switch?   Would that be safe for a household
> lamp application?  Would that eliminate the audible humming?
>
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>  - David
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>

I don't think there's much you can do in a practical sense to "filter
out" the the non-sinusoidal waveform without engineering a special
purpose high chopping frequency dimmer, which would prolly waste a lot
much power in the form of heat.

BTW, it's not an alternating square wave, it's a sinusoidal waveform
which has a portion "removed" from every half cycle when you turn the
dimmer down from full brightnes. The lower you set it the less of the
original waveform is left, but the parts that are left follow the line
voltage waveform.

Before solid state stuff was a twinkle in Shockley's eye they used to
make wall mounted variac light dimmers for use in rich folks houses, and
I'd bet that they didn't make the light bulbs hum. <G>

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Life is like a sewer -- what you get out of it depends on what you put
into it."