Do I need to include a resistor when I hook up a single 3 volt led to a 3volt power supply?

The power supply is an AA battery enclosure with 2 batteries, each battery is 1.5volts. My led is a single, red 3 mm, low intensity, led, rated for 3 volts with a 15ma current.

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  • 9 years ago
    Favorite Answer

    Hi "WhatsUp":

    A resistor is used with LEDs as a current-limiting device. Using E=IR, you should use a 200 Ohm resistor in series with the LED to limit the current draw to 15milliAmps.

    hope this helps,

    --Dennis C.

     

    Source(s): Ham radio & electronics hobbyist since the 60's.
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  • steve
    Lv 7
    9 years ago

    You will still need a resistor to limit the current as an LED is only rated for about 10 milliAmps (10mA).

    So if you have +3V and need 10mA the resistor is 3.0 / 0.010 = 300 ohms.

    If you use 15mA the resistor is 200 ohms, but will be brighter than with 300 ohms.

    If you really want a low intensity use 600 ohms to get 5mA.

    Source(s): my brain - it does a brain cell good !
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  • lare
    Lv 7
    9 years ago

    a fresh AA battery is 1.65 volts, two in series is 3.3 volts. the LED will draw too much current until the battery becomes wore down. that is why it is customary to use a higher voltage source (ie 5 volt) and a series resistor to help regulate the current to the LED.

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  • 9 years ago

    LED can be connected directly to the 3 volts battery without a resistor. It is still safe for a LED.

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