[no subject]

50% dimming with respect to luminous intensity is achieved at ~76 degrees =
3.53 milliseconds delay.

50% dimming with respect to RMS voltage at ~114 degree = 5.26 milliseconds.

>The whole idea of trying to relate calculated values thru a transducer
>to human perception is covered by "perceptual coding."  It is especially
>critical in the fields of audio, photo and video digitization and
>compression.  No reason to digitize outside the perceivable range, and
>when doing lossy compression, to save space you might as well throw away
>everything inside that range that doesn't cause a perceptible
>difference.

But in the case of TRIAC dimmer control (see thread subject) a single byte
holds all the information needed to produce 2^8 = 256 levels *IF* one also
knows when the zero crossing occurs as is conventional. sylvan doesn't know
the z-crossing and so futilely tries/d to overcome that lack of critical data
by creating complex waveforms with large data requirements that by his
admission challenges the timely computing power of a PC.

So in sylvan's case, he has created the need for a much larger amount of
information, that indeed does need to be reduced.

But the single byte in the conventional approach is all the information that
needs to be transmitted to the dimmer, or held in a register of a
microcontroller or the latched input of a digital-to-analog (DA) converter.

Applying 'perceptual coding" to that single 8-bit byte, we could usefully
'compress' it to a 4-bit nibble to produce 16 levels if that is all that is
needed.

So, for example the table at:
http://www.econtrol.org/dimmers/TRIACDimmerCalcs_MFHult.pdf

can be used to select values for a new, equal intensity, 16-step dimmer curve
with Full ON, Full OFF and 14 intermediate steps each causing about 6%
reduction in light intensity.  This would be 'perceptually' plenty good enough
in nearly all practical home automation scenarios.

... Marc
Marc_F_Hult
www.EControl.org