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Thread: Resistor brain cramps

  1. #1

    Default Resistor brain cramps

    Hi all, I'm making a hilt with a green LED for the emitter. It will be a Cree XP-E2 green(3.7V), hasbro toy board and its speaker(.25 watt 16 Ohm), 4xAAA battery pack, Radioshack momentary switch, Radioshack TIP42G PNP tranisitor. I know the toy board can handle a max voltage of 6V and I have the 4xAAA holder to work with. Do I need a resistor and what type? My concern is if the saber is left on for to long the LED will burn out.

    Thank you all

  2. #2

    Default

    I think this was answered before, but you should be ok without a resistor.

    Did you meter the forward voltage going to the LED's? When it was original?

    16 ohm sounds really high for impedance. I figured 4-8 ohm max would be perfect.

    What are you planning on using the transistor for?

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