Re: low voltage & bulb species

From: Robert Coyote (
Date: Thu Jul 05 2001 - 23:17:07 MDT

What about LED's?

----- Original Message -----
From: "Michael M. Butler" <>
To: <>
Sent: Thursday, July 05, 2001 8:13 PM
Subject: Re: low voltage & bulb species

> There are two factors here. Simplifying slightly:
> 1) there is a thing called the "strike voltage" which must exist so that
the mercury vapor inside the tube will turn
> into plasma. If the strike voltage isn't present, at least briefly, the
lamp will not light properly. The voltage
> required to maintain the plasma is lower than the strike voltage, so once
on, the lamp might stay on through some
> voltage dips. I don't know the innards of your light bulb, but I am
guessing they have an "electronic ballast"--that
> circuit might be able to handle a slight undervoltage as long as it's a
relatively clean near-sinusoid. This brings us
> to:
> 2) ordinary incandescent-compatible light dimmers are a no-no for
fluorescents because they do not produce the
> aforementioned RCNS. Instead, they typically use a thyristor (triac or
quadrac) which is triggered periodically to
> conduct current at some point in the applied external ("mains") sinusoid.
So the waveform they produce looks like a sine
> wave with part "chopped off"--in the extreme case of nearly-off, only a
tiny part of the wave gets through, looking like
> a series of tiny sawtooths separated by zero volts. As one increases the
dimmer dial setting toward "bright", an
> increasing part of the wave gets through. Problem: there is an abrupt rise
in voltage every half-cycle. Fluorescents and
> their driver circuitry tend to not like that.
> Apples and mutant pomegranates, sort of.
> Damien Broderick wrote:
> >
> > At 07:37 PM 7/5/01 -0700, Spike wrote:
> >
> > >> incandescent bulbs produce about half
> > >> their normal
> > >> illumination that low (and if they are 130 volt long life bulbs, they
> > >> will be even less bright), while still using 91% of the energy, which
> > >> will prompt people to have more lights running at the same time to
> > >> up the same illumination, thus wasting 40% more energy.
> >
> > >it incentivizes her to replace her incandescent
> > >bulbs with low power flourescent.
> >
> > I reveal my elementary ignorance: do fluoros work if you lower the
> > I have a couple of dandy little long-life 15-watt lamps = 75 watt
> > incandescent or maybe 100 watt, but they are explicitly said not to work
> > with a standard light-dimmer rheostat.
> >
> > Damien Broderick

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