LED Christmas lights have a series lump, what is it for?

hrho...@att.net

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Feb 15, 2016, 12:15:08 AM2/15/16

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I have noticed that about half of the LED Christmas light strings have a "lump" about 1.5 inches long and 1/2 inch diameter in series with the lights, which have polarized sockets. I assume that it must either be a diode or a resistor or perhaps both. What puzzles me is what limits current and polarizes the AC into pulsating DC in the light strings that do not have any visible "lump"? Perhaps there are resistors built into each individual lamp, but the lamps that I have taken loose have the LED leads going directly out the bottom of the socket. And, I haven't seen any sign of any resistors built into the sockets themselves.

Anyone know for sure what's going on???

Jeff Liebermann

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Feb 15, 2016, 12:50:58 AM2/15/16

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On Sun, 14 Feb 2016 21:14:54 -0800 (PST), hrho...@att.net wrote:

>Anyone know for sure what's going on???

Dunno. There are a bunch of LED wiring schemes:
<https://www.google.com/search?q=led+christmas+light+wiring+diagram&tbm=isch>
The diode or resistor might be hidden inside the AC plug. Or, the LED
might have an internal current limiter (which I doubt because these
types of LED's are expensive).

Or, the lump might be a flicker suppressor:
<http://electronics-diy.com/eliminating-led-christmas-lights-flicker.php>

When you're done solving the LED problem, could you work in this one?
<http://www.cbc.ca/news/canada/manitoba/squirrels-go-nuts-for-tasty-christmas-lights-1.720643>
The local squirrels would take a few bites out of the incandescent
wiring. I could easily fix that every year. Now, they trash the LED
lamps in a manner that is not easily repairable. I end up replacing
the entire string each year.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

N_Cook

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Feb 15, 2016, 3:13:23 AM2/15/16

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On 15/02/2016 05:14, hrho...@att.net wrote:
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> I have noticed that about half of the LED Christmas light strings have a "lump" about 1.5 inches long and 1/2 inch diameter in series with the lights, which have polarized sockets. I assume that it must either be a diode or a resistor or perhaps both. What puzzles me is what limits current and polarizes the AC into pulsating DC in the light strings that do not have any visible "lump"? Perhaps there are resistors built into each individual lamp, but the lamps that I have taken loose have the LED leads going directly out the bottom of the socket. And, I haven't seen any sign of any resistors built into the sockets themselves.
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> Anyone know for sure what's going on???
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RFI suppressor ferrite cylinder?

N_Cook

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Feb 15, 2016, 5:44:09 AM2/15/16

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LED xmas lights with their long wires and smps are one of the best ways
of corrupting wifi connections.

Allodoxaphobia

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Feb 15, 2016, 12:57:04 PM2/15/16

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I really doubt that cheap communist chinese manufacturing would go to
that expense...

hrho...@att.net

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Feb 18, 2016, 12:03:09 PM2/18/16

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Jeff Lieberman,

The wiring web site was interesting in how poorly it was done, but didn't really give me any answers to my questions.

Jeff Liebermann

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Feb 18, 2016, 1:35:47 PM2/18/16

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Well, I indicated that I didn't have an easy answer. Basically, I
would need to know what's inside the lump before making yet another
guess(tm). It could be anything (diode, capacitor, ferrite bead,
resistor, etc). The same components could also be molded into the
power plug. Also, unless the series current limiter is in the plug or
in the LED's, I don't see how it could be done without something
inside the lump.

hrho...@att.net

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Feb 19, 2016, 9:33:02 PM2/19/16

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I am sure there is nothing in the power plug, I have taken apart several of both types of LED light strings, and there is nothing in the plug except for fuses. I am guessing that maybe the internal diode resistance is enough to limit the current when there are enough bulbs to almost reach 120V just using the internal diode drops. I will have to count how many bulbs are in series in each of the two types of lights and see if that shows any pattern

I rebuild old Christmas light (filament and LED) sets that are given to our local recycle center and then donate the lights to local charities that have resale facilities, and I have several strings of each type in my rebuild boxes so that is mostly a matter of getting to it. I'll post the results after I have done my research.

hrho...@att.net

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Feb 21, 2016, 5:44:00 PM2/21/16

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I took apart five individual LED Christmas light bulbs, from a string of lights that did not have a "glob" in series with the bulbs. Each of the lights had a really tiny resistor in series with the bulbs. The stripes and body color on the resistors were so small I could not tell which was the body and which were the stripes. My cheap HF multimeter said the actual resistors were 260 ohms. I didn't try to clip lead the bulbs into a working string of lights so I wasn't able to measure the forward drop across the LED diode itself. I will try that later this week when I work on some more LED light strings. Right now my repair shop is working on filament light strings.