help powering LED lights?

I have 2 LED lights i need to power. I bought a package of 2.8 volt and 1.8 volt. I will be using a switch to turn them on and off. I'm not really sure what i can use to power them. i bought a battery pack that holds 2 AA batteries but it doesn't seem to be enough.

I am making a T800 terminator skull. Any help or suggestions would be great

Update:

I haven't done anything with them yet. I just bought them and took them out of the package. I have not bought resistors but I will do that.

2 Answers

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  • Larry
    Lv 4
    1 decade ago
    Favorite Answer

    You need a voltage source that is greater that the voltage needed by the LED.

    2 AA alkaline batteries will give you 3 volts.

    That is just barely enough and will make it difficult to power the 2.8 volt LEDs.

    If your LEDs will handle 20 milliamps of current, your current limit resistor will be (for 1.8v led):

    (3V - 1.8V) / .020 A = 60 ohms

    The same 60 resisistor, used in series with the 2.8 volt LED will result in a current of :

    (3V - 2.8V) / 60 ohms = .0033 A or 3.3 milliamps. That may not be very bright. If the battery voltage drops much at all, the 2.8V LED will dim to nothing.

    You probably know that he LED will only work with voltage of certain polarity. If it doesn't work, you can try hooking it up backwards and see if it works. You can't hurt them if they are hooked up backwards.

    Source(s): Degree in electronics
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  • Anonymous
    1 decade ago

    Ummm. ..... How are you using them as of now? Can you test them individually. They have to be used with resisitors so they are not burned out, you know?

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