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Anonymous
Anonymous asked in Science & MathematicsEngineering · 1 decade ago

Could I power an LED light off a headphone jack?

Okay, the reason why I'm asking is long, but, with some electrical know-how, could I power an LED light off a headphone jack?

It's a weird question, I know, but it's a serious one.

To my knowledge, they're both DC power, and the voltage should be similar, so i think they should work, but I might need to throw in a resistor. I'm not sure.

If it were possible, could i turn Morse, or maybe binary code into a visual signal? (that's the end result I'm looking for.)

Thanks a lot for any help with this!

7 Answers

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  • 1 decade ago
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    This depends on your headphone driver (and it's ability to source current), but I'm thinking it may power the LED. A few things you should know however:

    Generally, audio signals are not DC. You will have to create a very specific audio file to play in order to accomplish something like morse or binary code. Do this in WAV format, or something uncompressed, as MP3 and other audio compressions encode frequency content, and will ignore the bias that you are looking to create.

    A normal LED drop is not 0.7V, it depends on the type of LED you buy. You can expect LED drops to be approximately 1.7 to 3.3V, with a current draw of approximately 20mA. Try to find an LED with a lower voltage drop, this will allow it to turn on in a lower range. Again, your headphone driver may not be able to accomplish this.

    If you have a multimeter handy, try creating a WAV file with the maximum bias on it, and measure the DC voltage on your headphone driver with a small known resistive load on it (try 100 ohms, as most mid-range headphones are around this impedance). This can let you know the current/voltage your driver is capable of, so you can make the best resistor choice.

    Good luck!

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  • 1 decade ago

    An l.e.d. is a current operated device, usually rated at 20mA maximum.

    At that current the forward voltage will be about 1.8 to 2 volts for a red l.e.d. and some other colours (look them up on Google).

    Other colours develop 3 or 4V across them.

    For successful operation the audio output must be able to deliver at least 10mA or the l.e.d. will be a bit faint.

    As has been suggested, try it. Although the l.e.d. should have a current limiting resistor in series with it, you may find a serendipitous setting of the source's volume control which doesn't destroy your le.d.s.

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  • 1 decade ago

    You can use virtually any signal to turn an LED.

    If you find that the headphone jack cannot supply enough current, just build yourself a comparator circuit and you'll be all set...at least for the application mentioned here.

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  • If you can pull 15-20 ma, you can light an led. You may have to up the volume a bit, but I bet you could! And you would not have to use a limiting resistor.

    Very interesting...

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  • 1 decade ago

    When it comes to LED's, just try it. Worst case scenario is you either blow the 3 cent LED or it doesnt light up (not enough voltage). I know blue LEDs run at about 3.5V, but i'm not sure what the jack puts out..

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  • 1 decade ago

    Leds are .7 volts

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  • Anonymous
    1 decade ago

    sure one lead to the anode one lead to the cathode

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