Rant: Why don't LED Christmas lights run on DC?

[Red Squirrel]

Or at very least have a full bridge rectifier. Bought a set and plugged it in, holy epilepsy central batman! I plugged it into a full bridge rectifier which helped, but the way it's wired, the inner sets are not all the same polarity so a lot of them don't light up. I can probably modify it, but I don't really want to splice wires that will be going outside. it's pennies in parts to just have a bridge rectifier built in!

That's my rant of the day.

 

[Imp]

Epilepsy central, huh... Is the pulsing that noticeable?

 

[BoomerD]

Don't buy the cheapest lights sold at Canadian Tire. Find better quality ones and there's no flickering.

 

[Eug]

You can buy Xmas lights that run on DC.

 

[Red Squirrel]

Don't buy the cheapest lights sold at Canadian Tire. Find better quality ones and there's no flickering.

That's about the only place to really get them that has a decent selection. Home Depot is another option but they'd sell the same stuff. There's Amazon/Ebay etc but then you really don't know what you're getting. It might set the house on fire. lol.

Not like I have to stare at them all day, so meh, I just find it's an annoyance that they could fix by spending under a dollar in parts.

For the house I actually want to look at addressable LED strips controlled by an Arduino or RPI eventually. They would stay up permanently and be used for different times of year or as general purpose lighting off season.

 

[Matthiasa]

Hmm at least its not just me... I tried to show the flickering to relatives and they for the most part thought I was crazy. Maybe 2 or 3 of the nearly 20 of them could also see it.

 

[Red Squirrel]

Yep I find it's very noticeable. It has to do with how LEDs work, they are diodes, so only work with current going one way, so it's basically a 60hz flicker with a 30% (guessing here, it may be lower) duty cycle. Just bridge rectifying them increases it to 120hz and doubles the duty cycle as they will light up on the negative (now positive) part of the AC sine wave. I still notice with 120hz but not as much. In my tree they are all the same polarity which worked out nicely. I built a bridge rectifier box so anything I plug into it is full bridge rectified. Debating on if I do look into modifying the set, as if I can get all the LEDs on the same polarity, then it will work. Or screw it and just put them on as intended and call it a day.

 

[disappoint]

Yep I find it's very noticeable. It has to do with how LEDs work, they are diodes, so only work with current going one way, so it's basically a 60hz flicker with a 30% (guessing here, it may be lower) duty cycle. Just bridge rectifying them increases it to 120hz and doubles the duty cycle as they will light up on the negative (now positive) part of the AC sine wave. I still notice with 120hz but not as much. In my tree they are all the same polarity which worked out nicely. I built a bridge rectifier box so anything I plug into it is full bridge rectified. Debating on if I do look into modifying the set, as if I can get all the LEDs on the same polarity, then it will work. Or screw it and just put them on as intended and call it a day.

Then put a big fat capacitor in there and smooth it out even more.

 

[Red Squirrel]

Then put a big fat capacitor in there and smooth it out even more.

Yeah I was actually originally going to do that with the bridge rectifier box I made, but then that also brings the voltage from 120v rms to 170vdc... might be pushing the leds to their limits. It would make them nice and bright though if they can handle it. Eventually I may build a 120vdc SMPS though. I want to put tons of lights in my two trees one of these days, it would be a summer project, would have to rent a scissor lift or cherry picker or something, then I'd build a proper SMPS unit and modify strings as needed so they are all the same polarity. I want it to be like National Lampoon's Vacation when I plug that thing in!

 

[Imp]

Sounds like you should try that projector thing they always show on the TV.

https://www.amazon.com/Shower-Static-Laser-Lights-Projector/dp/B01GTC10SI/

Can barely read the label on the picture... Is that a Class 3R laser?

 

[Red Squirrel]

Sounds like you should try that projector thing they always show on the TV.

https://www.amazon.com/Shower-Static-Laser-Lights-Projector/dp/B01GTC10SI/

Can barely read the label on the picture... Is that a Class 3R laser?

I was looking at those too actually, kinda neat. The ones at Canadian tire were like over $100 though wonder if that amazon one is just as good. I does in fact look like it uses a laser, I recall hearing something about airline pilots not liking them because if not aimed fully at the house it actually is like being hit with a laser. Does look like it says class 3R <5mw. So basically a bit more powerful than a laser pointer. I imagine it works with some kind of prism or disco ball type system that spins fast so each dot is just the same laser pulsed? That's my guess anyway. They are decently bright too.

 

[Red Squirrel]

Well I decided to overclock them. After some analasis of how they are wired it was not that hard to figure out where I had to swap wires. Got it so they're all the same polarity now. I just need to make another bridge rectifier box and make it outdoor rated, as the one I used is for my Christmas tree.

A bit of a bodge... but the solder connection is very secure and then shrink wrapped, then each wire has electrical tape, then more electrical tape to hold them together. So it should be safe and secure and semi water tight.





Bridge rectifier box:


With rectification: (camera set to manual, settings unchanged for both photos)


Without rectification:


Not only does it remove the flicker but it makes them brighter. The 120hz flicker is barely noticeable so not even worth trying to put a capacitor in there.

Now I just need to string these in the garlands, I'll do that tomorrow. The big bulbs in the garlands should be interesting too, I could have gone with the LED mini lights but wanted something different.

 

[sdifox]

Good job, I didn't notice any flicker in the picture :awe:

 

[disappoint]

Good job, I didn't notice any flicker in the picture :awe:

I don't either even though it's flickering at 60Hz. That is the refresh rate of my monitor.

 

[sdifox]

I don't either even though it's flickering at 60Hz. That is the refresh rate of my monitor.

In the CRT days I can tell between 60,72 75 and 90Hz.

 

[Red Squirrel]

Oh man it was brutal when I ran into a monitor that was set to 60hz. I think some even went lower. Was the first thing I'd change even if it's not my computer. I remember someone saying they always had a head ache when they used the computer for too long, I was their hero when I changed the setting. I can't remember what was typical, think the next step was 75 but think it was typical to go to like 80 or 95 or something. Some monitors would start to make really weird noises if you tried to set it too high.

 

[sdifox]

Oh man it was brutal when I ran into a monitor that was set to 60hz. I think some even went lower. Was the first thing I'd change even if it's not my computer. I remember someone saying they always had a head ache when they used the computer for too long, I was their hero when I changed the setting. I can't remember what was typical, think the next step was 75 but think it was typical to go to like 80 or 95 or something. Some monitors would start to make really weird noises if you tried to set it too high.

coil whine. I made sure my CRTs can do 120Hz.

 

[Red Squirrel]

coil whine. I made sure my CRTs can do 120Hz.

Actually yeah that may have been it.

I also remember some of the Dells that used to sometimes make a very loud BOOOOONNNNG sound when you turn them on, it would run a degaus. You could also press the button, but it was always louder when it first turned on. It would always startle people lol. "woah!" Actually it's kinda funny because I remember when those were new, it was all state of the art at the time, and now it's pretty much considered ancient technology.

 

[slugg]

My Christmas lights run on DC. No flickering. But mine aren't cheap and require 2,200 watts to operate...

 

[freeskier93]

Pretty interesting DigiKey article on LED flicker.

http://www.digikey.com/en/articles/...nimizing-led-flicker-in-lighting-applications