Light bulb power control/dimmer

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No, you\'ll see visible flicker.

"TT_Man"

** Cycle dropping causes a lamp to visibly flicker.

If that don't matter to you then go ahead.

....... Phil

John and Phil mentioned flicker. This is not only annoying but with some bad luck it could make part of the filament resonate and then ... POOF.

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Regards, Joerg

http://www.analogconsultants.com/

I believe it can also cause epileptic seizures in some people.

Tam

That would be really bad. Also, cycle skipping is very frowned upon by utilities.

--
Regards, Joerg

http://www.analogconsultants.com/

Thanks for the answers guys. I was wondering about the flicker and if it would be a real issue.So it's in the bin for that idea and saved me a lot of wasted time writing code.... on with the traditional solution.

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

Tam

>

yes you can drop cycles or drop intra-cycle pieces parts dropping ..;-) the change in perceived or actual power is not proportionate to absolute phase angle but is more porportinal to number of complete cycles "dropped" per 10 cycles.. any more and would see flicka..PLus you could use traic (or two scrs) and double the cycles you have (per

0.142 seconds..flicka period)for control by cycle dropping..

BTW, this zero volt switching is needed where the load would be sensitive to EMI like signal on the power. as you chopped intra-cycle the harmonic content increases, fundamental decreases.. the system has to handle and "filter" chopped AC... For a light bulb load, this is NOT th case, as the electric power is turned into heat and that is not noise or harmonic sensitive.. try it and see!

Happy designing

Marc

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.

But you can't see the 120 Hz component; at least I can't - for an incandescent lamp.

Tam

"Nobody"

** Skipping half cycles means you are loading the supply for half cycles - this creates a DC component on the supply.

Very bad idea.

....... Phil

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 ( snipped-for-privacy@misty.com)

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

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"it\'s the network..."                          "The Journey is the reward"
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The persistence of vision, the flicker frequencies for most folks is about 8hz, so when the proportion f 1/2 cycle arpoaches that some folks will begin to see it, and other will not, as you eat more cycles of course the drive is more choppy and you cant average out the photons as the other poster noted :-)

But, you can conceptually make this dimmer and thats what the poster wanted. The traditional and widely adopted intra-cycle modulation is used everywhere.... Perhaps there is a space where you want one, maybe one that can do both.. not sure?

OTOH, one poster suggested that , using 1/2 cycle non symmetry would result in a net DC component and that it was bad. Not sure what would dbe bad on a light bulb load, with a slight, very tiny mathemical sized DC component.. PLease advise what sort of effects you were envisioning??

best regards,

marc Popek

the

I dimmed neon in a disco by skipping WHOLE cycles going into the HV transformer (~1980).

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
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         America: Land of the Free, Because of the Brave

the

You can send decent optical-link audio by modulating the current into a regular light bulb or a flashlight bulb. I've heard that an auto headlight works, too, but I haven't tried that one.

Hmmm, one could do a kind of integral-AC-cycle delta-sigma thing.

John

"LVMarc"

** Complete bollocks. 50 Hz flicker is visible to most folk.

** Go and find what I actually posted - you PITA jerk off.

...... Phil

the

I remember an electrical engineering lab day in college many years back. One thing to be tried was to adjust the horizontal sweep rate of an oscilloscope to the point where with no vertical signal the trace barely did not visibly flicker. Maybe sweep was triggered externally, because this was to determine sweep repetition rate for the trace to borderline visibly flicker and not flciker.

Most of my classmates got frequencies in the 40's and low 50's of Hz for this.

- Don Klipstein ( snipped-for-privacy@misty.com)

That experiment would be affected by the choice of phosphor on the scope's CRT. I've had some with very fast phosphors, and some that took over 10 seconds to fade.

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