Converting solar led lights

Discussion in 'Lights - Store Bought and Home Made' started by indudio, Nov 11, 2012.

  1. indudio

    indudio Guest

    Hi,

    Since the cool white color is hard to come by this year, I earlier on picked up a few boxes of containing about 50 to 100 packs of the 200 led cool white solar lights. These run at 2-3 volts. I would like to know if I could run these at 12 or 24v if I add a resistor to them. They only have the + and - ( basically 1 channel).

    I attempted this with some 1/4 watt carbon resistors however they ended up smoking.

    I assume it can be done, maybe with 1/2 watt resistors or higher?

    Any thoughts?

    (ps if anyone has any cool white big w or Kmart strings I will gladly purchase them off you)
     
  2. David_AVD

    David_AVD Good news, everyone!

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    Do you want to run them from a DC controller? (flash and dim them)
     
  3. OP
    OP
    indudio

    indudio Guest

    Yup!

    Have a spare ray wu board
     
  4. David_AVD

    David_AVD Good news, everyone!

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    Best bet is to run them at 5V, with a smaller series resistor. I did that in 2011 with battery operated candy canes.

    12V or 24V operation is not really an option due to the large amount to power you'd need to waste.
     
  5. OP
    OP
    indudio

    indudio Guest

    So @ 5volts, be looking at about 50 ohm resistor?
    Or less?
     
  6. David_AVD

    David_AVD Good news, everyone!

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    Some of the solar light sets contained a single AA (rechargeable) cell and a small circuit board. The board contained a specialised IC to charge the AA cell from the solar panel and also act as a boost converter for the LEDs.

    Thinking about it now, for a 50/100 string of parallel connected LEDs setting the current with a resistor will be tricky as the value will be critical.

    If you assumed 2mA per LED (solar LED sets are often not very bright), 50 in parallel would draw 100mA @ approx 3.2 Volts. That means you need to get rid of 1.8V (5.0V - 3.2V) at 100mA which will require an 18 Ohm resistor, rated at 0.5W or more.
     
  7. AntinOz

    AntinOz New Elf

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    So, to add a totally silly question to the thread and, hopefully, not take it too far off topic. Could I run this off the 3.3v rail on my Arduino (which I could control through Vixen), or would the current draw be too high?
     
  8. David_AVD

    David_AVD Good news, everyone!

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    You would need to determine the voltage required and the current drawn by the LED set you want to use.
     

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