(Dave Platt) writes:

In article ,
Silver Surfer wrote:

Does anyone recall those power saving "discs" for light bulbs they were
selling back during the oil embargo days of the 70's.

Oh, yeah, those things!

The disc was placed
in a standard light bulb fixture and the light bulb was screwed in next.
The disc was nothing more than a diode that "saved energy" by blocking power
to the bulb for half of each cycle.

Is anyone still making these things? If so, where can I buy them?

I think they've gone seriously out of favor for several reasons.
Somebody probably makes them but I don't think I've seen one in a
store in over a decade.

Disadvantages;

- They make the filament run significantly cooler, which both reduces
the absolute light output and shifts the peak of the bulb's
spectrum further towards the infra-red. I suspect that they
actually *decrease* energy efficiency, in that you get less useful
lumens-per-watt, because less of the filament's output is in the
portions of the spectrum to which the human eye is sensitive.

You're better off just buying a lower-wattage light bulb, or
(better yet) a compact fluorescent.

- They'll probably kill off halogen bulbs fairly quickly - dimming
halogen bulbs and reducing the filament temperature interferes with
the tungsten/halogen sequestration/redeposition cycle, and the
filaments burn out more quickly than they need to.

- By half-wave-rectifying the current on the line, they'll be
creating some fairly severe harmonic currents on the mains. This
results in additional losses in the power distribution system. The
utility providers *hate* harmonic currents.

- Similarly, by placing a half-wave-rectifying load on the circuit,
they'll have the effect of creating some amount of DC offset of the
voltage on the circuit. This is likely to cause buzzing of any
consumer-electronics device containing a toroidal power transformer
(e.g. some audio amps).

HeHeHe.... Well, in a fixture with two sockets, put bulb saver thingies
in with opposite polarity.

So, your two 100 W bulbs will use only perhaps 150 W of electrical power
and produce a total light output equivalent to a single 100 W bulb.

(All calculations very approximate!)

The entire idea of extending bulb life is ridiculous for incandescents
unless they are hard to reach for replacement.

The cost of the bulbs is minimal. It's the power to run them over their
life that dominates. So, efficiency ends up becomming much more important
than life in most cases.

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- I have a vague recollection that these discs were reported to have
caused overheating or fires... I'm not sure under what conditions.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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