LED Christmas Light Hack

Discussion in 'The Projects Forum' started by williamj, Jan 27, 2013.

  1. williamj

    Thread Starter Active Member

    Sep 3, 2009
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    I use a lot of "LED Ultra Slim Wire Light Set"s over the holidays. I can find no electrical specifications for the lights, voltage or amperage. Each set has 36 LEDs and uses 3 AA batteries per set. (I go through a LOT of AA batteries.)

    I was thinking on the feasibility of removing the battery boxes, installing plugs and using a wall wart to power multiple sets. Three AA batteries work out to about 4.5 volts, so a 5 volt wall wart should be capable of handling several light sets at least. Using a gang box wired directly to the wall wart I can have multiple extensions and light sets plug into the gang box.

    Are there any problems or pit falls I'm overlooking?

    Thanks in advance,
    williamj
     
  2. GRNDPNDR

    Member

    Mar 1, 2012
    435
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    depending on the colour of the leds, ultra bright leds are typically 20mA per bulb and 3V. chances are one of the batteries is wired in parallel to provide extra current, not voltage, while two are in series to provide the necessary 3V.

    36 leds = 720mA total current.
     
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  3. tindel

    Active Member

    Sep 16, 2012
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    Seems like your logic is sound to me.

    I would check to see how much current the batteries are using to power the LED's then size your wall wart appropriately for the number of strings you are powering.
     
  4. williamj

    Thread Starter Active Member

    Sep 3, 2009
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    Thanks for the replies. :)

    Not being well versed in solid state I would never have thought to check for series/parallel battery connections. I'm VERY glad I asked!

    Thanks again,
    williamj
     
  5. GRNDPNDR

    Member

    Mar 1, 2012
    435
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    The batteries aren't using anything, they are providing the current. :)

    Do you have a digital multimeter with which to perform the above test?
    and if so do you know how to test current??

    Also, at this point I'm only making an assumption that the batteries are series/parallel, but I'm almost certain it would be because putting more than 3V through an LED is going to fry it, and you say you use a lot of batteries so that tells me the LEDs are probably drawing that 720mA which is a LOT for battery power.

    it would make sense that the company would add another battery to boost the current so the lights would last a little longer.

    can you get pics of this thing if you still need help?
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
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    You can't use three 1.5V cells to provide 3V at higher current than you would get with two 1.5V cells, unless you use a switching regulator. The single unparalleled cell will be depleted twice as fast as the other two.
    OK, I guess you will get some small advantage, but I doubt that's how they are wired.
     
    Last edited: Jan 29, 2013
    williamj likes this.
  7. GRNDPNDR

    Member

    Mar 1, 2012
    435
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    Never said I was right :) I was just throwing a guess out there.

    Why would there be 3 batteries ? unless the LEDs are 4.5V, or have resistors to run at 4.5V.

    Did I just answer my own question?
     
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