LED resistor

[atsf3751]

I have seen arguments for where the resistor goes for LED lights, each one seems to have a sound argument.

What is the consensus here? Does the resistor go on the white lead, blue lead, or does it matter?

[lyled1117]

From a purely electrical standpoint it does not matter. The electrons have to pass through both, it doesn't matter the sequence. A minor advantage in placing the resistor on the blue side is .....  should one inadvertently short a resistor/LED to a live frame while putting a shell on and the short is between the LED and resistor, the resistor will survive the short. On the other hand, if the LED is between the two voltages, the LED will likely be destroyed. From a pure safety view, the resistor on the blue side of the lamp gives some protection in the event of certain shorts.

Lyle

[peteski]

Like Lyle stated - it makes not difference electrically since in a series-connected circuit (which is what LED and a resistor are) the location of each component is irrelevent.  But other considerations might dictate where the resistor is located.

To add to Lyle's explanation, here is another example (for placing the resistor on the blue, or common positive side). You have the headlight LEDs on F0F and F0R functions outputs. Since in normal operation only one will be on at the same time, you can tie the anodes of both LEDs together and then hook up a single resistor between those anodes and the blue wire. The LEDs will share the same resistor and you save yourself from using 2 resistors (if the space is tight).  And if for some reason you get both headlights turned on, no damage will occur. In that scenario both LEDs will turn on but they will be dimmer than when just a single LED is on (since the current going through the resistor and the rest of the circuit will be split between the LEDs).