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LED "Rope Light" Flicker

I bought a "Rope Light" made for holidays, in an after xmas sale, which was 75% off. I couldn't beat the price. It's a string of white LEDS. I always leave a light on at night, so I thought I'd just use this a night light to save on electric.

It works, but there is a noticable flicker, which is kind of annoying. When I look inside the "rope", a plastic hose, I can see resistors and the LEDs. Thats all. I dont know if these are wired in series, or if each LED is separately connected to the 120V AC power line. There is no "box" on the end, where there would be a circuit board. So, it appears this is running the AC power directly to the LEDs. (I thought they had to run from DC???)

I'm thinking a capacitor should be used to stop the flicker (AC ripple), but there's no way to really add one without ripping the whole thing apart, so I'll just have to live with it.

However, I am curious how this is wired to the AC line. Does anyone know? (Maybe there are some diodes in there, it's hard to actually see the components, but what look like resistors may be diodes, or both).

Reply to
boomer#6877250
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Some 6 years ago I bought a rope like that. Only it had different colors LEDs and a controller. The LEDs were group-wise connected in series and each group in series with a resistor. With each group connected in reverse polarity wrt the previous group, which made it possible for the controller to make some color effects by reversing the polarity and thereby addressing another color group.

Yes, I think it is just a bunch of LEDs in series with a resistor.

You could try a bridge rectifier and find out the correct polarity, if that is uniform among the groups.

I'm not sure, I'm afraid they just trust the voltages distribute evenly among the LEDs when they are in blocking mode.

joe

Reply to
Joe Hey

Yes, and depending on how close the (sum of the) forward drop is to the line, the lower the conduction angle and the higher the flicker. the ones I bought five years ago were so bad I couldn't even look at them. I only left them up a day before I couldn't stand it anymore and ripped them down and binned 'em.

It's going to be a large capacitor. I'd just get a better string. They vary a lot.

LED leakages aren't insignificant. I'd expect it to be good enough for once-a-year consumer use.

Reply to
krw

You could probably feed it off a DC supply and lose the flicker.

But is it worth the effort? FWIW the flicker is even more annoying in the UK with 50Hz mains and so 100Hz flicker.

These days for safety reasons most outdoor ones are lowish voltage DC.

For a series string pulling a total of perhaps 100mA or so off 110v? Bridge rectifier and a capacitor >10uF @ 200v ought to be good enough.

Don't they do it with back to back LEDs so that it emits on both phases of the waveform much like the old red/green LEDs were done?

--
Regards, 
Martin Brown
Reply to
Martin Brown

That's not what I meant. I meant only a bridge rectifier. With a single diode you get a 60 (or 50) Hz flicker, if you use a bridge rectifier that will become immediately 120 (or 100) Hz. Barely visible if you ask me. :) Or darkness, if you got the polarity wrong.

Mine worked a long time, until the controller gave up...

joe

Reply to
Joe Hey

No, it's 50 Hz flicker because there's only a single diode in series. You need to put a bridge rectifier first (no capacitor required) to get

100 Hz. And that's barely visible.

Try it first with the rectifier only, you'd be surprised. :)

Never heard of that. How should I interpret that, 2 LEDs on 1 chip and then anti-parallel?

joe

Reply to
Joe Hey

Probably wired in anti-parallel across the AC line. ...Jim Thompson

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Reply to
Jim Thompson

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