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Thread: First timer, question on the resistor

  1. #1

    Default First timer, question on the resistor

    Trying to build my first (easy) saber. I'm planning to use a 4AAA battery pack (6V) with a RED Cree XP-E2 Star LED (2,65V at 1000mA), no sound. Is a 3.9 ohm 5W resistor the right choice? Thanks in advance for the help!

  2. #2

    Default

    A 3.7 volt lithium ion battery would be the best choice, but if you really want to use alkaline batteries, use 2 AA batteries instead of 4 AAA batteries. You'll get longer run time.

  3. #3

    Default

    Thanks a lot for the suggestion. For now I think I'll use 2AA batteries. In this case a 2.2ohm 5W resistor should be fine right?

  4. #4

  5. #5

    Default

    The resistance should be (4.5 - 2.65) / 1 = 1.85 ohm while the power is (4.5 - 2.65) * 1 that is again 1.85 doubling it up it should be near 3. The nearest higher resistor is a 2.2 ohm with 5 W. Am I missing something?

  6. #6

    Default

    The 4.5 in your calculation is the battery pack voltage. If you are using 2 alkaline batteries, that would be 3v, if you are using 4 alkalines it would be 6v. 4.5 is the value for 3 alkaline batteries.

    Using 2 AA batteries is an acceptable solution if you can't use a li-ion cell (3.7v)
    We all have to start somewhere. The journey is all the more impressive by our humble beginnings.

    http://led.linear1.org/1led.wiz for the lazy man's resistor calculator!
    http://forums.thecustomsabershop.com...e-to-Ohm-s-Law for getting resistor values the right way!

  7. #7

    Default

    so you are telling me that 1.5 + 1.5 is 3... thank you so much for wasting your time with a fool!! I'll go for a 1ohm 2 watts
    Last edited by Shaitan; 04-18-2017 at 09:11 AM.

  8. #8

    Default

    No worries. Sometimes a second set of eyes is necessary to see what has been missed. Good luck with your build!
    We all have to start somewhere. The journey is all the more impressive by our humble beginnings.

    http://led.linear1.org/1led.wiz for the lazy man's resistor calculator!
    http://forums.thecustomsabershop.com...e-to-Ohm-s-Law for getting resistor values the right way!

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