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Thread: how to wire a status LED?

  1. #1
    Variable Bitrate
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    how to wire a status LED?

    So i want to wire a toggle switch between my car battery power and my car computer to allow me to turn off the main power line if i ever do not want my computer to turn on when i start the car. So, with this normal toggle switch, how do i wire in a.....3-4volt led so that the light will turn on when the switch is on (power flowing) and light is off when switch is off (cut power)

  2. #2
    Variable Bitrate
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    Good questions I'd like to know this too....
    New CarPC on the way again I think. I miss my old one!!!

  3. #3
    FLAC shakes's Avatar
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    you won't want to use a 3-4v LED as then you'll need to use some resistors to limit the current flowing through the LED ...

    If you must have a separate LED, you can get 12v LEDs from radio shack. Then you'd just wire the negative side to ground, and the positive side to your power line after the switch.

    your best bet will be to get a 12v switch from radio shack that has an LED built in. These will have 12v LEDs built in. The light will be on when the switch is closed and off when the switch is open.
    My JeepPC Install

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  4. #4
    Variable Bitrate
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    How about buying an automotive switch that lights on it's own when on, and is off when off?
    http://www.radioshack.com/search.asp...d+switch&SRC=1
    any of the first three would work. Any auto store sells them. Look around you can find just about any color. Otherwise, do as follows:

    The two resistors create a voltage divider. You could also replace both resistors with a potentiometer (POT) and put the sweeper (usually the center leg) to the LED. This will allow you to vary the brightness of the LED, just be careful not to burn it out. Anything that you wish to run off the 12 volts needs to be connected above the 1K resistor and below the switch. The resistences I gave are aprox, you may need to use like 500 and 200 to get the correct intensity for the LED. Also, if you're not using LEDs with the built in 330 ohm resistor, you'll need to adjust the resistances for that. Best bet is really to buy a 1K ohm POT and use that.
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  5. #5
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    damn shakes, you posted whilst I was using paint to make the "pretty" pic. Ah, gotta love slow days at work
    2006 Chevy Colorado: VIA M10000 EDEN, 1 GB RAM, 80 GB 2.5" Seagate HDD, USB Slim Slot DVD/RW, Holux GPS, MobileVU 10.4" LCD (touch not working yet), VOOMPC Case (blue), 70W DC-DC supply.

  6. #6
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    well, i already have a switch that i wanted to use...so i dont want to use anything else. What kind of resistors/how many do i need to get to work properly with a 3-4volt led?

  7. #7
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    opps, you guys beat me to it, answered my question before i asked it

  8. #8
    FLAC shakes's Avatar
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    if you're going to use a switch with an external LED and resistors ... make sure you do as Jackso said and put the computer and anything else running off this line between the switch output and the first resistor ... otherwise you'll pump too much current through the resistors and they're burn like paris in flames.
    My JeepPC Install

    "there are no stupid questions, just stupid people."

    "it's been agreed the whole world stinks so no one's taking showers anymore"

  9. #9
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    after invisioning the poor guys car going up in flames, thanks to shakes statement, I decided I'd cover my *** and edit the pic.
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  10. #10
    Constant Bitrate
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    whats the 400 ohm resistor for?
    leds are current sensitive devices not voltage per se
    there are a few good led resistor calculators online

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