Cris Bessette wrote:Christmas LED strings generally do not use any rectification, they simply put the LEDs in series to drop the current and run them on AC
(The LEDs are only on during the positive going cycle, thats why you can see a 30hz flicker)
How would current drop by adding bulbs?, I think what you meant was what I said about adding enough leds in series to match the 120 volts of the ac supply. generally multiples of 30.
I never cut them open to check, but most(all?) of the strings I've played with seem to have a solid molded plastic bit attached just after the plug and I assumed it was a cheap mini rectifier circuit. Since leds are all diodes anyway, adding 4 more in a rectifier circuit would seem to be a minor thing and give twice the light.
I admit that i've never checked the voltage past that suspicious plastic to see if it was ac or dc, sounds like a good project sometime, would pulsing dc show up as dc on a cheap multi meter, cause I don't have an oscilloscope.
Location: North Georgia / Appalachian mountains , Zone 7A
posted 3 months ago
Each LED uses about 10-15 ma. Red LEDs use about 2 volts and blue/green/white LEDs use about 3 volts.
The only LED Christmas lights I've seen that run on DC are small battery powered sets and ones that have controllers integrated for different flash patterns.
Yes, Christmas light sets would look better without the 30hz flicker, but they are cheaper to produce without the extra diodes / capacitors necessary to make smooth DC to run them.
Very interesting discussion! Some points I had never heard or considered.
Pretty happy with the LED bulbs we have here, and doubt incadescent would work well with our DC Microgrid. Being able to have light in the evenings year-round, even through weeks-long cloudy spells, with just one 100 amp-hour battery set providing light (and electronic charging) for the twelve of us, is pretty awesome. The LEDs might not be quite as "cozy," but they are making some with warmer yellow light, and the passive solar and straw bale insulation help keep us warm in the winter.
Don't know how the complexity and toxicity of DC LED bulbs compares to AC, but are LEDs really a lot more toxic than an incadescent? Pardon my ignorance, but I never heard mention of this before.
In any case, since using DC LED bulbs allows us to provide lighting with a small, affordable set of durable, non-toxic nickle-iron batteries (http://livingenergylights.com), which (together with "daylight drive" DC energy right off the solar panel to power larger motors - https://www.youtube.com/watch?v=N5Wk7inoIxI) allows us to break our dependence on the grid and more destructive approaches to off-grid living, I still stand by them as the best option, at least for our systems.
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