What Resistor Do I Need?

Question

I i am trying to power a 12v led strip with a 14.4 volt power source and was wondering if i need a resistor and if i do which one should I get.

Thanks Please Relply

Answer 1

You did not giving the current rate of LED strip,nobody is able to give you the resistor value. Here is another way to get arround......

buy a voltage regulator IC called 7812. It is very cheap,99 cents or lower.  Connect 14.4 volts + to the input of 7812.  Connect 14.4 volts -

to the ground of 7812. From the output of 7812 between ground,it has 12 volts,use it to power your LED strip.  7812 is able to support up to one ampere. Of course you need to mount it into a heat sink,any 2" X 2"  metal plate shall do the job. If 7812 does not become very hot,you do not need the heat sink.

Answer 2

I was typing this long answer, but just cancelled it. If your strip is rated for 12V there is already a resistor in it and 14.4 Volt should be fine, it will just burn a bit brighter and maybe not last that long. But don't worry on exact resistor sizes, lets say you have a rather large strip, using 500mA - 1A, Then if you use a small resistor, 5ohm, you should be fine. But don't even bother, just use 14.4 Volt. If you really don't wanna blow your strip, put it in serie with a 100ohm resistor and see how bright it burns, just adjust accordingly.

Answer 3

An LED strip might come with power resistors, and then again it might not.  Also, it depends upon how many LEDs are in the array.  And it depends upon whether or not you want to illuminate it to the max!  A good place to start is with a 470 ohm resistor for each LED at 14V.  If they are in parallel, then divide the number of LEDs into 470 and you will have the final value, as a starting point.

If they are in series, then figure about 2.4V per LED forward diode voltage drop, then you could only have 5 LEDs and a current limiting resistor of about 47 ohms.

This is a starting point, so adjust accordingly.