Usually the replacement type LED bulbs (many LEDs per bulb unit) are designed to divide the 12 volts across each of them to achieve the correct voltage on each individual LED (~ 1.9-3.6 volts usually). The bulbs have a couple rows of 3 or 4 LEDs in series (12v / 4 = 3 volts) bunched together. Part of a larger circuit? Series? Parallel? Playing with LEDs is supposed to be fun, and figuring out the answers to these questions is actually part of the fun. There's a simple formula that you use for figuring it out, Ohm's Law. That formula is V = I × R, where V is the voltage, I is the current, and R is the resistance. Why drive current matters…. The amount of light (Lumens) an LED emits depends on how much current is supplied. Current is measured in milliamps (mA) or amps (A). High-power LEDs can take currents from 350mA to 3000mA. LEDs vary on their current ratings so be sure to keep track of this when picking an LED and driver. Without getting too technical, this simply means that the circuit experiences some additional current through the resistors when the LED signal comes on. So there you have it. Install one of these resistors into the circuit near your LED signal and you will increase the amount of current the OEM relay sees when the LED signal lights up When a series LED connection is in question, you will just need to replace the "LED forward voltage" with "total forward voltage" in the formula, by multiplying FV of each LED by the total number of LEDs in the series. Suppose there are 3 LEDs in series then this value becomes 3 x 3.3 = 9.9. LED Current or I refers to the current rating of the Choosing a resistor to work with an LED is fairly simple, but does require some knowledge of the LED and a small amount of maths. Some LEDs such as colour changing LEDs, flashing LEDs and 5V LEDs are designed to run off a 5V supply and therefore don't need a resistor. t0RNy7.

do 12v leds need resistors