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Scrounging LED Christmas Lights

PileOfLEDsEarlier today I was at Walmart and noticed that Christmas lights were 50% off normal pricing. Some digging around yielded a 70 count white and 70 count multi-colored set for about $5 each or about 7 cents per LED. Of course you have to do some work to get the LEDs out but if you have the time… This is a short article with some information about scrounging from these LED Christmas lights. This article may be of interest If you have been considering scrounging one of these sets for a quick supply of LEDs.

The big wad of wires below is what you pull out of the pictured box. There are red, green, blue and yellow LEDs. I suspect that the number of each color is random, I had 11 blue, 11 green, 24 red, and 24 yellow LEDs. Two spare LEDs were included in the set as well.

LEDLightSet

I started the scourge by cutting the lights off the wires, I planned to keep the wire as well as the LEDs. You an always use wire in the work shop. I ended up with one long wire and several 6-foot segments. I discarded a large number of short pieces as well. The LEDs in the picture below have been partial removed from the LED holders.

 WireAndLEDs 

LEDHolder Each LED is mounted in a plastic holder. As seen in this picture the LED are just pushed into the plastic holder with its’ legs bent to form contact points and to hold it in place. To remove the LED you could straighten the legs or just tug the LED straight out. I did the later after poking a few holes in my fingers. Just grip the long plastic tail with a pair of pliers and pull the LED out. I used a medium sized pair of wire cutters to grip the LED. This does leave a small scratch but its not very noticeable.

Here is a close up of the 4 types of LEDs.

4Colors

Pictured below is each LED powered up at about 10mA. The camera flash was disabled but I would not trust the relative brightness as I did not attempt to control the shutter speed or aperture settings. They seem to be very high brightness LEDs.

RedLED GreenLED BlueLED YellowLED

There were several small cylindrical pieces in the wiring which turned out to be 740 Ohm resistors encased in plastic, I cut one open to find a standard color coded 1/4 Watt resistor inside.

Resistor

Warning!

These LED Christmas lights do run with High voltage. They are setup with a chain of series LEDs and a current limiting resistor. I can see a noticeable flicker to the LEDs when they are on in the string. I wanted to see the waveform driving an LED and accidentally blew one of the LEDs by connecting ground on my scope probe to one side of the LED wiring. I figure that the scope ground provided a short cut path to the 110 ground and instantly blew one of the LEDs. I did not seven see a spark or flash. I decided to leave that task out of my scourging exercise and just cut the set to pieces. I’m lucky it did not damage my scope or me.

I did not find a direct link to the Christmas lights at Walmart’s site but I did find these that seem to be a match. They are listed at about $10 a set. Walmart is dumping their excess inventory at 50% off right now.

Posted in Hacks, Parts, Projects, Scrounging, Scrounging Parts. Tagged with , , .

5 Responses

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  1. Berni said

    Thats a real cheap way to get a pile of bright LEDs.

    As for the waveform on the LEDs its probably a distorted 60Hz square wave, Also the LED strings are probably wired anti parallel so one light on the positive half of the sine and one on the negative.(Thats a very common way of connecting LEDs to AC)

    Oh and yeah that scope ground thing can be quite annoying. A lot of people forget it and short stuff that way.

  2. signal7 said

    It’s hard to work on anything using 110V ac without an isolation transformer. I would recommend buying one at the same time you buy or acquire your first ‘scope so as to prevent the inevitable short circuit.

  3. Alan said

    What brand name were these led lights from, I need to do some scrounging.

  4. mrmeval said

    I did pick up some strands at 75% off. Because they’re already strung and working I’m going to see how cheap I can make them individually addressable and run them from isolated DC. I have a pile of switchers which should work well.

    You need an isolation transformer for any AC work. You want the ‘device under test” to be on the transformer. It prevents blowing oscopes and killing you.

  5. Milton said

    I bought LED lights to replace my halogen MR16 bulbs the other day from a website called Eaglelight.com that I would recommend enthusiastically. They had good service (good phone and email support), great FAQs so I knew what I needed, and competitive prices; also, their shipping was fast and the LEDs were as good as advertised. http://www.Eaglelight.com. Highly recommended.