hi i am planning to install two small white light LED on my car as parking lights.
so basically i am using the reflector along woth LEDs from a torch that uses 3 AA cells(4.5v), the power of LED in manual is 3.2 V and the 1/2or .5W,
as we know
V=I*R which Implies I=V/R and R=V/I
and P=V*I, by following these equations i get 154ohm resistance to be used but i used two individual resistors of 60 ohms with each LED, so my question is will it work (well ofcourse its working as of now but for longer durations like 2-3 hours continous working and also with charging system engaged, i guess the power source will change from 12v to 13.5 V.
any help will be appreciated.
Best Answer
If you have no data sheet information about the expected current of the LED (because you extracted it from an existing appliance, or something like that), then you should measure the voltage and the current while still in its original position and use those values for further calculations.
I do not recommend that you base your calculations on the nominal voltage and nominal wattage figures found in non-technical documents.