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azurite2
05-03-2016, 01:47 PM
I need some help calculating resistors. I plan on using this LED (http://www.thecustomsabershop.com/RedGreenRoyal-Blue-Cree-XP-E2-CopperNova-P1016.aspx?ItemId=5486910) and this battery (http://www.thecustomsabershop.com/Panasonic-Li-Ion-18650-37V-3400mAh-PCB-Protected-Rechargeable-Battery-P853.aspx?ItemId=5487856). I got Green-0.2, Red-1.2 and blue I got 0.3. How do I use those values to come up with the resistor I want? Please give me some instructions, and the actual value so I don't mess anything up.

Thank you,
-Grayson M.
Greenie
05-03-2016, 01:54 PM
Ok, go on then. If you used Ohms law, the values you have calculated are the required values of resistance in ohms. Without checking, they look about right. Check the store to find resistors of the nearest value (rounded up). ;)
azurite2
05-03-2016, 01:56 PM
Ok, go on then. If you used Ohms law, the values you have calculated are the required values of resistance in ohms. Without checking, they look about right. Check the store to find resistors of the nearest value (rounded up). ;)

So I should have 2, .47ohm .5w resistor and 1, 1.2ohm 3w resistor, correct?
Greenie
05-03-2016, 02:01 PM
That's what I would use with that LED and battery. :)
azurite2
05-03-2016, 02:04 PM
Alright, thank you so much, that helps out a lot!
bunger
05-03-2016, 03:09 PM
I got 1 ohm, 2w for the red.... Hmmm.... That should be okay, correct?
bunger
05-03-2016, 03:38 PM
Just a quick follow-up: my calculations were based on driving each Led at 1000mA.

Ohms: (3.7 - 2.59 )/1 = 1.11
Watts: (3.7 - 2.59) * 1 = 1.11
Silver Serpent
05-03-2016, 06:08 PM
I personally wouldn't round down the resistor to 1 ohm. There's a 1.2 ohm available in the store.
bunger
05-03-2016, 06:44 PM
I personally wouldn't round down the resistor to 1 ohm. There's a 1.2 ohm available in the store.

My guess is that the 1.2ohm 3w resistor is probably the most common since the store carries it, but why 3w instead of 2?
Silver Serpent
05-04-2016, 05:01 AM
Tim probably found a better deal on the 3w resistors when he was buying them in bulk for the store. When shopping for electronic components, some sizes are just less common (and therefore more expensive).

Don't worry, the 3w will work just as well as a 2w, and they won't be bulky like the 5w and 10w resistors.