first build, Need a Math check on my resistor calculations....

[Darth_Banyon]

so my first build is going to be a NBv4 driving a Tri-Cree XP-E2 running off an 18650 (3.7V) the dies are going to be Amber, Amber and White. white will be FoC

Amber Cree Part# XPEBPA-L1-0000-00D01
107 Minimum Luminous Flux @ 350mA
Forward Voltage @1000mA = 3.28v

White Cree Part# XPEBWT-L1-0000-00F51
266 Minimum Luminous Flux @ 1000mA
Forward Voltage @1000mA = 3.15v

ok so now for the math I need checked.....

Amber dies running together one resistor on each
R = (3.7 - 3.2 .42 * 1.0A =.42Ω
P = (3.7 - 3.2 .42 / 1.0A = .42W
closest resistor I found in the TCSS store was .47Ω .5W

White die running as a periodic FoC one resistor
R = (3.7 - 3.15) .55 * 1.0A = .55Ω
P = (3.7 - 3.15) .55 / 1.0A = .55W
Closest resistors I found were .47Ω .5W, .5Ω 3W and 1Ω 2W


Am I even close to being right? or am I waaaay off, and why?

[jbkuma]

are you sure that Vf is correct for the amber? looks like it should be 2.2v @ 1000ma.
http://www.cree.com/led-components/m.../XLampXPE2.pdf

[Darth_Banyon]

are you sure that Vf is correct for the amber? looks like it should be 2.2v @ 1000ma.
http://www.cree.com/led-components/m.../XLampXPE2.pdf

The numbers I listed are what TCSS had listed in the shop

[Darth_Banyon]

OMG!! so I'm having a hard enough time calculating ohms law for the numbers listed on TCSS for the LEDs and now this data sheet (which I cant make heads or tails of ) tells me that the numbers TCSS has listed on the page with the LEDs is wrong....? This is extremely frustrating....I'm already feeling discouraged.

[Forgetful Jedi Knight]

OMG!! so I'm having a hard enough time calculating ohms law for the numbers listed on TCSS for the LEDs and now this data sheet (which I cant make heads or tails of ) tells me that the numbers TCSS has listed on the page with the LEDs is wrong....? This is extremely frustrating....I'm already feeling discouraged.

Don’t get discouraged. You used the correct information in the shop, so your calculation results will also be accurate. For the white you could go with the .5 Ohm 1W. Carry on.

[Darth_Banyon]

Don’t get discouraged. You used the correct information in the shop, so your calculation results will also be accurate. For the white you could go with the .5 Ohm 1W. Carry on.

I didn't see a .5ohm 1W available in the shop but I can order it online if need be...