Re: Controlling Holiday Lights

[sylvan butler <ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxxxxxxxx>]

On Mon, 23 Oct 2006 23:42:22 -0400, Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote:
> No I am not ;-) What you describe is a very low-resolution way ( max 8 dim
> levels at 1000 hz) to dim AC power using TRIACS or back-to-back SCRs.

Your prediction of 8 dim levels is without basis or merit.

Assuming 60hz.  Typical phase control the triac must be triggered 120
times per second at a TBD offset after the zero crossing.  If the triac
is instead triggered exactly twice as often, it will function exactly
the same -- the output A.C. waveform will be identical.  Same if the
triac is triggered exactly 4x as often.  Or 8x as often.  8x is 960/sec.
If I instead trigger at 1000/sec, that is a max of 4% error when it
happens at random instead of synchronized to zero crossings.  This error
has imperceptible effect (to my eye when using incandescent lighting).

sdb
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