ive seen that LED need resistors, so what r they and their exact purpose? and r their any other parts needed for LEDS?

 

The Resistors limit how much voltage gets to the leds...just so they dont burn out cus each different type of LED has its own voltage rating...you dont wanna go above that limit or it will smoke it. Resistors come in different values, depending on how much voltage you need to keep away from the LED...Not sure on the exact one to use, but thats their purpose

 

This answer is incorrect. It changes the current draw so that the LED's blink at the normal rate.

 

The resistor is to limit current. Too much current(amps) will destroy the LED. An LED drops about 0.8-1.0V per diode, depending on how many are in series determines the voltage for the LED. Ohm's law will allow you to calculate the value of resistor required. Since resistors "waste" electricity you must know the volts and amps required by your particular LED installation and match the watts the resistor must dissipate as heat. Use a starting voltage of 14 for the 12V electrical system with the alternator charging. The caclulations are pretty easy.
(14V-.9V/LED)/.030A/LED=R(ohms).

Example: 1-led just to light up.
14-0.9=13.1 13.1/.030=436.7ohms.
13.1X.030=0.393Watts
So use a 470ohm 1/2 watt resistor in this example. They come in standard sizes both ohms and watts.

Yes, I am an electrical engineer.

 

Current is drawn, not pushed.