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Old 10-23-2011, 12:37 PM   #1
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LED Christmas lights


I appreciate everyone's help on this... I have a kid project where the boys are making thier own lawn orniments for Christmas this year. For the lighting, I purchased a number of LED light sets with 50, 70 and 100 LEDs (C5).

My current question is can I remove the extra 20 LEDs at the end of the string?

The end of the string has a block where the three wirescome in, two wires come out and the lines terminate at a female end.

Thanks

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Old 10-23-2011, 08:11 PM   #2
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You can not safely modify the light strings.

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Old 10-23-2011, 08:54 PM   #3
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If you did, it may cause the string to be brighter, since the manufacturer in China has determined proper size diode for that circuit. Modifying is your choice, since most of these strings are throw away anyways after first use.
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Old 10-23-2011, 10:01 PM   #4
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Its probably not a straight forward disconnect and rewire. Nobody on here is going to be able to tell you how those are wired without having them on hand and testing them. Your best bet is to order some LED's off ebay, get a small transformer from an old electronic device, measure the actual voltage of the transformer under load (don't use whats stamped on it) then do the math and get a properly sized resistor
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Old 10-23-2011, 10:04 PM   #5
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Quote:
Originally Posted by jimmy21 View Post
Its probably not a straight forward disconnect and rewire. Nobody on here is going to be able to tell you how those are wired without having them on hand and testing them. Your best bet is to order some LED's off ebay, get a small transformer from an old electronic device, measure the actual voltage of the transformer under load (don't use whats stamped on it) then do the math and get a properly sized resistor
Don't even have to do that, since these strings do not use a transformer. It is just taking them, make the cut and see how much brighter they are. If you add to them, then yes the diodes can be dimmer.
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Old 10-23-2011, 11:03 PM   #6
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The voltage drop across an LED can be dependant on the color....

As noted above, there is no transformer, so, they string the lights in series so that the voltage drop x # of LED's = supply voltage. Depending on the # of LED's, you may have 2-3 parallel strings within a given light string.

You could remove those 20 LED's if you replace them with a zener diode that has an equal voltage drop to the 20 LED's.

But, then again, because you asking the question you are....I do not recomend making any modifications....not safe...especially if kids are involved.
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Old 10-23-2011, 11:09 PM   #7
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ddawg16, if they were to do the mod's and figure the zener needed, they could use heatshrink and di-electric coating to make nice and safe outside. The best is also to make sure that they are hooked up to gfci protected outlets, and when working with the strings, to not eat food, touch mouth, eyes or nostrils, wash hands after handling, due to the lead dust that is on them. If they measure out the length of the run, they may be able to get strings that are sized appropriately to begin with.
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Old 10-23-2011, 11:30 PM   #8
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Quote:
Originally Posted by ddawg16 View Post
As noted above, there is no transformer, so, they string the lights in series so that the voltage drop x # of LED's = supply voltage. Depending on the # of LED's, you may have 2-3 parallel strings within a given light string.

Thats what i was talking about about testing them. Their may be 3 individual paralleled strings that are 120v each, but who knows without looking at them. Also, who is to say there is no transformer? I don't recall the OP mentioning there wasn't one


I'll stick to my advice that the best solution is to start from scratch and get a transformer and 100 pack of led lights and a couple resistors

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