True however all previous light sources still had either an ionized gas or hot element or both and this gave an afterglow that carried through the AC sine wave's pass through zero. One of the reasons that common dimmers do not work on ballast supported lamps is that they do not in fact reduce the amplitude of the in coming sine wave but rather due to the variable trigger point of the solid state device used reduce the area under the curve, or if you prefer the RMS power factor. Ballasts and many other devices do not like the rise time at the leading edge of a Triac. This sharp rise time is also the reason that cheap dimmers cause radio interference because this leading edge is very rich in radio frequency harmonics.
Dale in the Flatlands.
David Cox wrote:"diodes...that we have never had with any other light source" is basically true except the 1st PAR halogen bulbs (PAR20 and 30) did have a diode.
If you are saying the degree of flicker is different in the LED bulbs over the afore mentioned, pardon me.
The 1st PAR bulbs could not be dimmed with an incandescent dimmer because of this. You had to use an inductive dimmer (ceiling fan or low voltage dimmer). If I recall, this was the Sylvania brand but GE did not have the diode.
On 1/17/2013 7:23 AM, Dale S wrote:
I suppose I could hook up a photo diode and my oscilloscope to find out if there is a "flicker rate" that bugs don't like, but LED's being diodes to start with will have an instant flicker rate that we have never had with any other light source. However since this would be at either 60 or 120 hertz it is beyond the persistence of the eye and would appear to us to be a steady light, much the same as moves and video are. Without cutting one apart to find out, I suspect there is a small bridge rectifier and dropping resister in the base of each one, other wise they would need to daisy chain them in multiples much like Christmas lights as the normal DC voltage drop across a diode is less than 2 volts.
Dale in the Flatlands.
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