"Roger Conroy" bravely wrote to "All" (14 Oct 05 09:06:17)
--- on the heady topic of " Pulsing LEDs for higher efficiency"

RC From: "Roger Conroy"
RC Xref: core-easynews rec.radio.amateur.homebrew:88243

RC If the brightness of an LED is a 1:1 linear relationship with the
RC power supplied, that suggests that perceived brightness of a pulsed
RC LED would be neither at the arithmetic mean (average) nor at the peak
RC but rather at rms (root mean square). Comments?


I'm pretty certain it is not a simple rms function because the
duration of the visual persistance effect must be taken into account.
If the peak brightness duration is long enough it will be perceived as
brighter than the average. Consider that the eye's retina cone signal
fades off say to 80% in 10 milliseconds after exposure to light. As
long as the light pulse repetition rate is high enough such that it
results in a drop of optic nerve signal less than the minimum light
change that can be perceived then the light will be seen as
continuously bright. You can always run a subjective experiment on
your workbench with an led and a 555 timer used as an astable.

A*s*i*m*o*v

.... Forcast for tonight: Dark.