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Thread: Issues With Resistors

  1. #1

    Default Issues With Resistors

    Hey Everyone, I recently decided to build a saber from scratch as my first one but have come across some unfamiliar concepts. I am not very familiar with wiring and as a result I don't feel comfortable ordering the parts until I resolve this issue. I am planning on using a Nano Biscotte V4, a "Red/Green/Royal Blue Cree XP-E2 CopperNova" LED, and a "Li-Ion 18650 3.7V" Battery. Additionally I see something called a power extender while looking at the NBv4 manual, but am not sure what purpose it is supposed to serve. My main issue is that I cannot figure out what types of resistors I would need in order to properly wire the build so that I do not short anything out. Any help on this matter would be greatly appreciated.

  2. #2


    I wrote a nifty tutorial which explains the concept and how to do the calculations...
    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:

  3. #3


    To answer your question regarding the Power Extender, the Power Extender is a small separate board that can be wired to the NBv4 to give you a third "channel" for an LED. It's important for an RGB led since it allows you to get the third color for mixing. Otherwise there's only enough LED negative pads to wire up two colors rather than 3. For help wiring it up when the time comes, Shameem has an excellent NBv4 wiring tutorial on Youtube that really helped me out a lot.

    Sounds like you're pretty much going for the same thing I wanted for my first build. Here's the wiring diagram/check for that build

    Forgetful Jedi Knight's tutorial will help with the resistor calculations, but you'll find that the Green and Blue LEDs don't need too large of a resistor. The Red is the larger one.

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