Resistors for Rebel Deep Red and Green LED's

[Molina00]

Need a little resistor help here. I am using both the resistor calculator and the manual calculation and coming up with different values on both LED's. This would be an NB v2 with 3.7V 18650 Li-Ion setup.

Deep Red
R = (3.7 - 2.4) / .7 = 1.86
P = 1.86 x .7^2 = .91

And the online calculator recommends a 2.2 Ohm, 2 Watt resistor.

Green
R = (3.7 - 3.4) / 1 = .3
P - .3 X 1^2 = .3

The calculator comes up with a 1 Ohm, 2 Watt resistor.
Which one do I need to use, my calculations (unless there is something wrong with mine) or the calculator recommendations?

[Forgetful Jedi Knight]

The calculator almost always tends to "overestimate" what you need. that's why I do it myself. With that said, you will also need to "round up" to the next common resistor value. I'm sure that if you go through the store's resistors, you'll find what you need, since I did the math, and suggested that certain "commonly needed" resistors were stocked. ;)

[Molina00]

Yep, no problems as far as the store having what I need. Just wanted to get clarification on which calculation method was best to use. I figured doing the math was probably better, but there was such a difference on the green LED I wanted to make sure. Thank you for your help. :cool:

[Bark]

Your numbers look good to me, assuming that you'll be making two single-die LED sabers. I think you're using "http://led.linear1.org/1led.wiz" for the calculator. I've noticed that it plays it safe too.

Deep Red
R = (3.7 - 2.4) / .7 = 1.3/.7 = 1.86 ohm
P = 1.86 x .7^2 = 1.86 x 0.49 = 0.92W (Always round up)

You'll want a 2 ohm, 1 watt (http://www.thecustomsabershop.com/2ohm-1w-resistor-P946.aspx) resistor.

Green
R = (3.7 - 3.4) / 1 = 0.3/1 = 0.3 ohm
P = 0.3 x 1^2 = 0.3 x 1 = 0.3W

You'll want a 0.47 ohm, 0.5 watt (http://www.thecustomsabershop.com/47ohm-5w-resistor-P947.aspx) resistor.

[Molina00]

Your numbers look good to me, assuming that you'll be making two single-die LED sabers. I think you're using "http://led.linear1.org/1led.wiz" for the calculator. I've noticed that it plays it safe too.

Deep Red
R = (3.7 - 2.4) / .7 = 1.3/.7 = 1.86 ohm
P = 1.86 x .7^2 = 1.86 x 0.49 = 0.92W (Always round up)

You'll want a 2 ohm, 1 watt (http://www.thecustomsabershop.com/2ohm-1w-resistor-P946.aspx) resistor.

Green
R = (3.7 - 3.4) / 1 = 0.3/1 = 0.3 ohm
P = 0.3 x 1^2 = 0.3 x 1 = 0.3W

You'll want a 0.47 ohm, 0.5 watt (http://www.thecustomsabershop.com/47ohm-5w-resistor-P947.aspx) resistor.

You are correct on both counts. At some point I will be upgrading a couple of stunt sabers to sound.
Thanks. :cool: