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Replace 12V DC lighting with LED

Discussion in 'Electronic Basics' started by [email protected], Oct 5, 2008.

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  1. Guest

    We have a older boat with 12V DC lighting. I would like to rewire the
    existing fixtures with current LED components. Can anyone advise me
    on the specifics of this project? I know I can get components from I need advice on specific components, resistors
  2. Jamie

    Jamie Guest

    You need to know which LED's you plan on using.

    Also, LED's are polarized which means they'll only work
    in one direction..
    Any ways.

    Assuming you have some common LED which could be around
    1.7 volt of a drop, lets say 25 ma's of drain on the power source.

    Taking your 12 volts into consideration, you would need a resistor
    to drop the current to the diode.

    R = (SourceVoltage-LEDVoltage)/LEDcurrent =
    (12-1.7) / 0.025 = 412 Ohms.

    Wattage needed for this.
    W = (12-1.7) * 0.025 = 0.2575

    I think a generic 1/4 R should work for this.
    You can place these diodes in series.
    assume you use 4 in series 6*1.7 = 10.2 volts required..

    You need to keep the required voltage below what your
    supply voltage is because the diodes need current flowing
    through them..
    Now with this, you can use a different value R in series.

    R := (12-10.2)/0.025 = 72 ohms..

    A note that you should know, the closer you get to the
    source voltage using mulitple LEDS in series and lowing
    the R value, the more shoft of brightness you're going to
    see when the battery voltage starts to drop.

    So you may want to use a lower series count of LEDS into
    an array cluster."
  3. whit3rd

    whit3rd Guest

    It's likely that an RV or boat dealer can get you a variety of LED
    or other (fluorescent) fixtures and lamps. Buying is the easy
    route here. I've seen auto lamps that are bayonet-mount
    dropin replacements for incandescent bulbs.

    If you must build, be aware that low-power lighting (like, 1W or
    less) can be done with an LED flashlight lamp, available in the
    $5-or-under range, and high power (like, 10W) requires an array
    of devices, and probably requires a bit of 'ballast' design
    work. Switching power supplies and linear regulators and simple
    power-wasting resistors all have their place, you'll need to
    study all the alternatives, if only to eliminate them.

    The '12V' power is NOT clean and reliable, you will want
    all your work to survive brief 50V spikes and various kinds of
    brownout and overvoltage.
  4. Phil Allison

    Phil Allison Guest

    ** So why not just buy them ??

    ** Most 12 volt LED lighting products come ready to use on 12 volt AC or

    What are you crapping on about ?

    ...... Phil
  5. JeffM

    JeffM Guest

    It would be smarter to just buy finished goods that fit what exists.
    ....and you can get finished goods from about a billion other places
  6. neon


    Oct 21, 2006
    First of all you need superbrights LEDS color white. They do comes in all kinds of color inkluding blinking and also in different sizes. FIRST STEP measure your 12v you may find that to be 13.68v or more. you may break your existing lamps and install LEDS into them so that becomes totaly compatible. for 12v asume `15ma current each and the voltage drop of each will tell you how many LEDS you can install in series if it lets say 2.3 v @15ma then you may install 5 in series with a resistor to limit the current to ~15ma or 33 ohms. I will not ever worry about a spike across a battery that is just not knowing anything about it. you may make as many lamps as you wish the above sample is only 180mw.WAS probably 14w or more.good luck
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