12 5mm led to 12V DC 1000mA adapter

Discussion in 'General Electronics Chat' started by oupulino, Nov 20, 2010.

  1. oupulino

    oupulino Thread Starter New Member

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    Hi can someone help me out how to connect 12 X 5 mm leds on 12 V DC 1000mA adapter here is spec for led they are pre wire with own resistor any wiring diagram is really appreciated
    The led are rated for 12V

    The resistor = 470 ohm 1/4W.

    The LED voltage = 3.0v - 3.4v

    The LED amp = 20mA

    If the adapter output = 1000mA then it is sufficient to connect more than 40 LED together. How to do it Im using it as a background
  2. tom66

    tom66 Senior Member

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    I use this website: http://led.linear1.org/led.wiz

    It suggests putting 3 LEDs in series in 4 parallel chains. Each has a 150 ohm resistor in series to limit current.

    Be careful with your wall wart. Very likely it isn't outputting 12V - it is probably unregulated, basically a transformer, diodes and a capacitor. In order to get it to output 12V you need to load it down with the maximum 1A - otherwise the output can be as high as 18V, which will overheat your LEDs.

    Perhaps try a switching power supply which should keep 12V or thereabouts no matter what the load, up to 1A. CUI supplies are quite popular. Ideally, chose a 9V supply, which would allow you to put 3 LEDs in series with no resistors maximising efficiency.

    Also you might want to follow the buck regulator thread where a single LED supply is being designed, however it should still work with series LEDs.

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  3. oupulino

    oupulino Thread Starter New Member

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    the power adapter is Regulated and this led are pre wire so each led has already resistor 470 ohm 1/4W.How to wire 12 of them to one 12V DC 1000mA adapter do I have to add another resistor or cut of existing resistor
  4. SgtWookie

    SgtWookie Expert

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    Just wire them all in parallel.
    Since each LED-resistor string will draw ~20mA current, you can connect up to 1000mA/20mA = 50 pairs.
  5. oupulino

    oupulino Thread Starter New Member

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    Thank you very much it work I was posting every were about this issue and only you resolve it properly other recommended replacing resistor,cutting of existing ones all nine yards long story

    Thank you one more time SgtWookie
  6. Bill_Marsden

    Bill_Marsden Moderator Staff Member

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