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Thread: Sorry!!! Resistor Help

  1. #1

    Default Sorry!!! Resistor Help

    Hello,

    I’ve started to gather the parts to build my first saber and I’m sorry to say I have a resistor question. I’m planning on using a Nano v3, 18650 3.7v battery and a tri-rebel Lime/Lime/White. TCSS site says the forward voltage on the lime is 2.75. If I did the math correctly, it looks like I need a .95 ohm .95 watt resistor (round up to the 1 ohm 2 watt available on the site). However, I also watched the TCSS video for calculating resistors and Rob suggested rounding the battery voltage to 4. If I do that, it looks like I would need a 1.25 ohm 1.25 watt resistor. Which calculation/resistor do I go with?

    1 ohm 2 watt, 1.2 ohm 3 watt or 1.5 ohm 5 watt?


    Similarly for the white, if I use 3.7 volts I should need a .6 ohm .6 watt but if I use 4 volts I’d need a .9 ohm .9 watt. Since this is just the Flash on Clash, can I get away with using a .5 ohm 3 watt resistor just to give it some protection or should I go with a 1 ohm 2 watt?

    Thanks for the help. I’m really looking forward to starting my build.

  2. #2

    Default

    I calculate at 3.7v and I've yet to blow resistor or LED. However, Rob is a pro and has built hundreds of sabers, he is or tutor.

    Oh, and welcome to the forums.

    Greenie

  3. #3
    TCSS MODERATOR
    All n00bs READ these first (PLEASE)!!!:
    1. Forum Guidelines
    2. FJK’s “Down and Dirty” guide to Ohm’s Law

    "Yeah, yeah, I've heard it all before... you want blindingly bright, super loud, running 1138 blinkies off of the cheapest sound card you can find AND you want all of it to run on a battery the size of a dime, and run for a very, VERY long time. That one cracks me up every time..."
    My email: fjk_tcss@yahoo.com

  4. #4

    Default

    Calculating at 3.7v is perfectly acceptable. The Rebel LEDs and especially the Cree LEDs are fairly resistant to overdriving. For the brief period that the battery is giving 4v, you'll be fine. Just be sure the LED is securely attached to your heatsink with a thermal pad before you fire it up.
    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!

  5. #5

    Default

    Thank you all for the replies. I've been reading through a lot of threads and everyone seems so willing to offer help and advice. As I learn more, hopefully I can be a more active member.

    FKJ, your sticky was the first thing I looked at on this. I feel like I did the math right, but if someone sees a mistake, I'd love to me made aware so I can see where I went wrong.

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