Winter lights, wires cut, third core.

adrianxw · 2024-11-24T16:26:16+0000

We have a very long string of white LED's which, in the dark months, are connected to a time switch in the hallway, and run outside. The string is festooned around, over, under, or whatever my wife chooses to do with them this year. At the end of the season, the string comes indoors, and I coil it up, secure the coil with a couple of cable ties, and store it away.
In a bored moment, my wife decided it was time to install this years extravaganza. Using a pair of scissors, she cut the first cable tie. She then cut the second cable tie.... and two small wires leading to one of the LED's. It arrived on my desk. I now need to reconnect these and restore the chain. My assumptions:
1. The unit built into the plug end of the chain contains a transformer, bridge rectifier, and probably some capacitors to drop the mains voltage to low DC chain voltage.
2. Each LED in the chain has four wires emerging from a, presumably heat shrunk, weather proofing surrounding the LED terminations, anode and cathode, presumably two wires, voltage in, two wires voltage out to the next LED along the chain.
3. I need to remove the encapsulation to reconnect the two wires.
4. Trial and error will be sufficient to establish which way the wires connect, either the chain will light, or it won't, if it does not, reverse the connections.
5. I will need to find some suitable compound to establish a weather proof unit.

The chain has a third wire, I do not know what it is for, any ideas?

ProDave · 2024-11-24T16:33:06+0000

Photos please.

There are so many variations in how this could be done, it is impossible to generalise. Can you not just offer the 2 cut ends together and work out which joins to which?

adrianxw · 2024-11-24T16:58:31+0000

I don't see how a photo will help. Explain. My point 4 above is what you are suggesting.

ProDave · 2024-11-24T17:05:23+0000

I am not suggesting trial and error. Get it wrong and thing might go bang. Surely if the two cut ends are offered together, you will see which core joins to which and re make them?

Richard-the-Ninth · 2024-11-24T17:56:54+0000

Almost all "Christmas lights" are made for as less money as possible, you would have thought there would be a transformer in the "Wall wart" but they went years ago, often now used is a "capacitive dropper" (Often just a capacitor in series with a bridge rectifier and a few resistors)

In some lights a 3rd wire is used (It runs from the start to the end, and has no connections en-route.) This wire is used for the "return" as to make the lights flash the polarity is often reversed in the "left wire" then the "right wire" The first (and some cheap) LED strings used to just change the polarity of both string wires, but it is preferable to have 3 wires.

As the lights are not that expensive, I would say although its more landfill, you would be better off disposing of the lights your wife damaged and buy a new set* Click HERE

*Yes it is a shame to have to bin them, but you will spend more time/money trying to get "a suitable compound" or enclosure only to find that it leaks or water has travelled by capillary action.