How would I get 10+ LEDs to work?

Discussion in 'General Electronics Chat' started by Zilikken, Jun 18, 2012.

  1. Zilikken

    Thread Starter New Member

    Jun 18, 2012
    I am working on a scale model and I want to hook up some LEDs to it. I want to hook up about a total of 10-13 blue LEDs. I want to connect them by an adapter to the wall socket but I am confused by something. If a blue LED runs at about 3v each, I would need about 30v or more. When an adapter says it is a 12v adapter, does that mean that it only gives out 12v? is that 12v the maximum or the minimum that the adapter can give out? Would I need a higher voltage adapter if I want to hook up 10+ LEDs?
  2. #12


    Nov 30, 2010
    If you put both the headlights in your car in series with each other, they would need 24 volts, but they don't. You put the LEDs in parallel.

    A 12 volt adapter provides about 12 volts, give or take accuracy, and yes, 12 volts is both the maximum and the minumum.

    Put 3 LEDs in series with each other and those in series with a resistor of 180 ohms and conect that to the 12 volt adapter.
    Do that 3 more times.
    Now you have 12 LEDs connected and working.

    Note to other helpers: I said 180 ohms because I expect the adapter to be a bit high at 80ma and you don't have to run LEDs at their absolute maximum current rating to get a good result.
  3. takao21203

    AAC Fanatic!

    Apr 28, 2012
    You need a smalll Dc/Dc booster.

    Depends on the making, some need current limiting resistor, some don't, for instance because the storage coil will have limited current supply capability.

    There is for instance MC34063,

    and using a small coil (which will have limited current supply capability actually), you don't need current limiting resistor.

    Suitable component values for your application need to be determined experimentally, or use a limiting resistor anyway.

    Or use a TL494 IC, easy to buy, cheap, for instance eBay.

    If you don't have to max. out efficiency/possible current, almost any storage coil will do.
  4. sheldons

    Well-Known Member

    Oct 26, 2011
    heres a circuit you can try...........

  5. Wendy


    Mar 24, 2008
  6. Audioguru


    Dec 20, 2007
    A cheap AC/DC adapter produces its rated output voltage (12VDC) only when its load current is at its rating. When the load current is less then its output voltage is higher.

    I have a cheap 12V adapter that produces 12.0VDC when its load is 100mA and is 17.5VDC when its load has a low current.
  7. Wendy


    Mar 24, 2008
    A cheap AC/DC regulated adapter always produces it rated output (12VDC). Kinda goes with the word regulated. A bit harder to find, but since there are no standards on wall warts, worth looking for.

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