resistor for led

[chrisatpsu]

i know i have calculators for resistor size...

and i know RJ explained this to me...  but it has escaped me...

to power a normal 20mA led with a regular resistor, what size resistor should i use wattage wise?
1/4 fine?  can i go smaller?

[chrisatpsu]

oh yeah...  5v supply

[rrowan]

1/4 watt resistor should be fine

btw: Are you just trying to raise you post per day stat?

LOL

Rick R.

[chrisatpsu]

nope, just helping where i can, and asking for help when i need it  : )

[pk]

The resistor will be dissipating less than 0.1 watt
. 

[chrisatpsu]

would 1/8 watt be ok, or cutting it too close?

[Dennis Cherry]

would 1/8 watt be ok, or cutting it too close?

Stay with the 1/4 watt, it is small.

[chrisatpsu]

so i have it written down (via a forum), how did you calculate the wattage?

[rrowan]

so i have it written down (via a forum), how did you calculate the wattage?

Ohms Law 

P x I(squared) = watts

or Power times current (sq) =

Rick R.

[chrisatpsu]

i feel like an idiot...   i actually knew that one!   lol

[Dennis Cherry]

Anything you want to calculate in Ohm's Law.

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[rrawlings]

so i have it written down (via a forum), how did you calculate the wattage?

Ohms Law 

P x I(squared) = watts

or Power times current (sq) =

Rick R.

P=I(squared) x R

P = Watts