On Thu, 17 Mar 2011 21:43:03 -0700, Timothy Daniels rearranged some
electrons to say:

"david" tried again:
Timothy Daniels wrote:

"david" wrote:
Timothy Daniels wrote:

"edfair" wrote:

Most of the stuff I've dealt with used 330 ohm 1/8W resistors with
standard LEDs on 5V supply. Doesn't let thru enough for full
brightness but doesn't lead to premature death.

For peace of mind you might want to ask for flame proof resistors.
Nothing like miscalulating the required value or getting a
defective one and ending up with a candle.

IIRC the LED drop is 1.7V which would put 3.3V across the 330 ohm
resistor.

Assuming that P=VI (power = voltage x current), or V**2/R,
that works out to .033watts, or about 3.79 times the 1/8watt rating.
The 1/4watt resistors mentioned previously in this thread should
suffice quite nicely.

*TimDaniels*

No. 1/8W = 125 mW, not 8 mW


(.125W)/(.033W) = 3.79 . Review your math.

*TimDaniels*

Review yours. Do I need to remind you of what you wrote?

that works out to .033watts, or about 3.79 times the 1/8watt rating.

33 mW is 26% of the 125mW rating.

Which says the same thing. Learn some arithmetic.

No, it's not the same thing at all. Learn some arithmetic.

X does not equal 1/X.


You should have said: "A 1/8W resistor has a power dissipation rating
that is 3.79 times greater than the power dissipated by the LED
circuit, so it will be more than adequate for this application".


Which is the same thing. Learn some arithmetic.

*TimDaniels*

No, it's not the same thing at all. Learn some English.