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kruser
Premium
join:2002-06-01
Eastern MO

1 edit
reply to Anonymous_

Re: [Rant] LED lights are ugly crap

said by Anonymous_:

LED lights suck for Christmas lights... 99% of them have a shitty refresh rate of 59.8hz. The ghosting or flickering effect is what bothers me the most.
You do not get that "flicker" with incandescent bulbs.

The flicker is because they only use half wave rectification for the dc supply. Remember, LED's run on DC and not AC. This allows them to flicker at 30 Hz and not 59.8 Hz like you stated. It is not a refresh rate either. That is something that maintains the contents of ram or an image on a display screen. Xmas lights (LED or incandescent) do not have refresh rates.
Some people (woman and children) see the flicker more than others and it can actually cause some to have seizures.
There is a very easy cure for this that I tried on entire trees at work. I simply built full wave rectifier boxes and plugged the lights into those. Flicker was gone and all the complaints about flicker also ended.
The one thing I could not fix was the color temp used for the "white" or "clear" LED lights.
They run more at a Cool white color temp which makes them appear blue to many people. They are actually closer too true white than the old incandescent mini clear Xmas tree lamps. Those tungsten type lamps burn with more of a warm white or lower color temp than most LED mini Xmas lights do.
I've seen some manufacturers claim theirs burn with a warmer color temp to look more like the older incandescent mini lights but I never tried them as they were simply too expensive when I'd need to purchase 10's of thousands of them.

The flicker is an easy fix and a nice hour or two project that is very easy to do. The color temp is another story and one that cannot be fixed. Sometimes dimming the lamps along with using full wave rectification does help with the color temp by reducing the overall lumen output which just makes them not stand out as bad.

Then you have some of the colored led lights where the blue bulbs look purple! Those suck as purple is an Easter color and not a XMAS color if you ask me. The other colors in LED Xmas lights are not bad but sometimes they seem "too" colorful when compared to the old incandescent.

The great thing about LED light strands is that you could hook thousands together (in theory) without worry of blowing the tiny cheap ass Chinese fuses in the first set or two of the string.
When you are talking hundreds of thousands of lamps, there is a very significant savings in electrical energy used to power the things.

As far as rectification goes, you can build a small box with a low current bridge rectifier that will power several sets or you can build one with a higher current handling ability and plug entire trees (or sets of trees) into the one bridge rectifier.
Some manufacturers are also selling sets that do have full wave rectification now as well but I've never bought any so can't speak for the quality.

TheMG
Premium
join:2007-09-04
Canada
kudos:2
Reviews:
·NorthWest Tel

said by kruser:

said by Anonymous_:

LED lights suck for Christmas lights... 99% of them have a shitty refresh rate of 59.8hz. The ghosting or flickering effect is what bothers me the most.
You do not get that "flicker" with incandescent bulbs.

The flicker is because they only use half wave rectification for the dc supply. Remember, LED's run on DC and not AC. This allows them to flicker at 30 Hz and not 59.8 Hz like you stated.

Actually, half-wave rectified LEDs will "flicker" at 60Hz.

Full-wave rectified LEDs will also "flicker", but at 120Hz, which makes it much less noticeable.

Toss in a capacitor and now you've eliminated the flickering entirely.

Unfortunately, it seems that manufacturers of LED light strings don't find the cost-benefit ratio worth it, even though we're talking about pennies worth of extra parts.

kruser
Premium
join:2002-06-01
Eastern MO

said by TheMG:

Actually, half-wave rectified LEDs will "flicker" at 60Hz.

Full-wave rectified LEDs will also "flicker", but at 120Hz, which makes it much less noticeable.

Toss in a capacitor and now you've eliminated the flickering entirely.

Unfortunately, it seems that manufacturers of LED light strings don't find the cost-benefit ratio worth it, even though we're talking about pennies worth of extra parts.

Not sure what I was thinking on the frequency. I'd just finished getting zapped by a phone ringer circuit that I think is 20 Hz so maybe that confused me as it did hurt a little bit!

I was talking about building a filtered rectifier circuit but failed to mention the need for a cap or two depending on what you have laying around.

I used lytics pulled from switching power supplies such as the kind found in today's HDTV power supplies. Those usually have a decent voltage rating as well as a high enough capacitance value so they filter very well. I could fit the assembly into a extra deep handy box along with a duplex receptacle.
The cap(s) and rectifier and fuse(s) would fit under the receptacle as long as I found the right caps.
Some of the caps rated for 350 volts or higher can get pretty large in physical size depending on how they were designed to fit the application they were used in!