🚀 go-pugleaf

In article <1hhum3INNfau@usenet.INS.CWRU.Edu> wb8foz@skybridge.scl.cwru.edu (David Lesher) writes:
>I'm a little confused by the present discussion.
>
>If you only turn ON at the zero-crossing, you will, I suspect, avoid
>RFI problems. But, first off, does this not give you problems in
>modulating the output? You could only have setting that are multiples
>of the number of {half} cycles. [I suppose that is not TOO limiting,
>though, is it?]

You would have to vary the duty cyle more discretely (only at zero crossings)
but that still lets you turn the the triac on or off up 120 times per second
(sin2pift = 0, t = n/120). You would get 0% to 100% duty in 0.83% steps
>
>Secondly, won't such a dimmer make the lamp singing problem far worse?
>The filament gets heated, and cools, over a much longer period than
>with chopper-type dimmers.

Since the dimmers make the bulb ring even at 100%, (the triac should be 
on constantly), the harmonics must be coming from non-linearities in
the triac (or diodes etc.). The bulb rings more at lower duty cycles.
and it doesn't ring at ALL if the dimmer circuit is removed.


>
>I suppose the solution is to use line power of a frequency far above
>the audio range. Back when I was taking a course on electronic power
>control, I recall reading of scheme to provide large office buildings
>with ~100khz to run the gas discharge lighting. The idea was to reduce
>the losses in the ballasts. Not only does that increase the "light/kw$"
>but it would also reduce the "waste heat/lumen" that has to be cooled
>by the HVAC.  Wonder what ever came of that idea....

not gonna rewire my dining room!
>--
>A host is a host from coast to coast..wb8foz@skybridge.scl.cwru.edu
>& no one will talk to a host that's close..........................
>Unless the host (that isn't close).........................pob 1433
>is busy, hung or dead....................................20915-1433


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 John Paul Morrison                     |  
 University of British Columbia, Canada |  
 Electrical Engineering                 |   .sig file without a cause
 jmorriso@ee.ubc.ca              VE7JPM |  
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