Re: Light bulb power control/dimmer

On Sun, 18 Nov 2007 17:16:22 +0000 (UTC), the renowned
don@xxxxxxxxxxxxxx (Don Klipstein) wrote:

In article <pan.2007.11.16.21.28.25.395724@xxxxxxxxxxx>, Nobody wrote:
On Fri, 16 Nov 2007 10:55:56 -0500, Tam/WB2TT wrote:

Remember, with cycle skipping the frequency changes. At 10 percent power the
fequency would be 6 Hertz.

The flicker will be 12 Hertz (as opposed to 120Hz at full power). You
don't have to skip whole cycles; half-cycles will do. The polarity doesn't
matter for a resistive load.

In extreme cases, I have seen incandescents visibly flicker from
skipping every other half cycle. The main example is a 4 watt or 7 watt
120V incandescent nightlight with a diode. The thin filament warms and
cools fast enough to have significant 60 Hz flicker. 60 Hz flicker is
sometimes visible.

- Don Klipstein (don@xxxxxxxxx)

Yes, you can't practically dim an incandescent bulb by skipping
cycles. I tried it many years ago and the results were miserable.
Maybe if you had control over the bulb design and could add some
thermal mass to the filament, but I tried it with a huge incandescent
(kW, IIRC) and even that thick filament responded too fast. I used
some kind of clever (I thought) CMOS circuit (I forget the details)
using something like a rate multiplier to get a relatively fast cycle
time (eg. 50% would be a 30Hz cycle). OTOH, it worked a charm on
relatively fast-response heaters for tight temperature control, which
was the intended purpose.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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Relevant Pages

  • Re: Light bulb power control/dimmer
    ... The flicker will be 12 Hertz. ... skipping every other half cycle. ... 120V incandescent nightlight with a diode. ...
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  • Re: Light bulb power control/dimmer
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    (sci.electronics.design)
  • Re: Light bulb power control/dimmer
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  • Re: Light bulb power control/dimmer
    ... I have seen incandescents visibly flicker from skipping every other half cycle. ... The main example is a 4 watt or 7 watt 120V incandescent nightlight with a diode. ... Don Klipstein ...
    (sci.electronics.design)
  • Re: Let me simplify it for you...
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