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power requirements for xmas lights

Discussion in 'Troubleshooting and Repair' started by Marnok, Dec 7, 2012.

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  1. Marnok

    Marnok

    3
    0
    Dec 7, 2012
    I am trying to fix up some xmas lights to run on battery instead of mains. I got 24v of battery together, cut the wires into the controller box so I have some bare ends to feed in to, but when I touch the wire ends together the lights just flash once then off.

    OK the back of the "Flasher Unit" says
    24v - 50Hz, 1.0A

    The 50Hz thing makes me, (electronics skill level: Vandal) think that the supply requires AC not DC.

    Is that a reasonable thing to think? and if so, I suspect inside the box this is being converted to DC, as I would be surprised if the LEDs themselves were AC. So, I might be able to solder my batteries in to a different point if I crack the case on the flasher unit?
     
  2. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    As you say, LEDs need DC, they also need a current controlled supply, not voltage controlled.

    An easy way of controlling current in an AC circuit is to place a capacitor in series. If this is followed by a rectifier, then that is all the necessary circuit.

    If you go to a DC supply you will need some way of controlling current. This can be done with a (hot) resistor or with a special constant current circuit
     
  3. Marnok

    Marnok

    3
    0
    Dec 7, 2012
    Thanks, I've opened the box and the inputs are labelled AC, I think I can see where this is converted to DC and all I need do is connect my batteries and cut the converter out, should work... in theory.
     
  4. Marnok

    Marnok

    3
    0
    Dec 7, 2012
    Well, due to general fail, I now see there is a connection between one of the AC in lines and the IC (via a resitor) which I am guessing wildly was used for timing by the IC.
     
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