Resistor LED

To use leds for 12 Volt applications you must simply connect a resistor in series with the led or leds. The resistor will drop the excess voltage and limit the current. See the Forward Voltage spec on the spec sheets (click the LED pert numbers on the main LED page) for typical and maximum forward voltage, they're not all the same. Use a 1/8th watt or larger resistor soldered to the anode of the led and connect the +12 to the resistor. The chart below shows you the forward current for each color led with a single led in series with a 470 ohm resistor connected to 12 VDC. The current (and led brightness) will be slightly higher when the vehicle's engine is running because the battery charging system keeps the voltage up at around 13~14 volts. You can connect up to 4 red, orange, or yellow leds in series with each other and one resistor to power with 12 volts. The value of the current resistor must be lowered, depending on how many leds are in series. A maximum of 3 of the other colors can be in series across 12 volts, because of their higher forward voltage requirement. See our LED car bulb pages for LED bulbs designed to work on 12 Volt systems
LED COLOR	RESISTOR - Ohms	CURRENT @ 12 VDC
WHITE	470	18ma
BLUE	470	18ma
GREEN	470	18ma
AQUA	470	18ma
RED	470	20ma
YELLOW	470	20ma
ORANGE	470	21ma