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

Re: [Rant] LED lights are ugly crap

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!