s2kZac

alright so i wanted to make my own led foot things for my s2000 in blue,

i want to put 5 leds in it and was wondering how many resistors i need and what size

Eric220

I'm not sure on the resistor rating, but if you check E-Bay they have a few S2000 led lighting kits with built in resistors.

BelowRadar

Please I wish people would stop using resistors as little helpers to LEDs. Go for proper voltage using diodes (zener, etc) instead of making a fake load in series with your LED to make the car think it's a big burning filament.

Sorry, I'll get off my high horse now.

GregFarz78

hmm I always see people using resistors got any useful information about diodes? sounds a lot more simple too

BelowRadar

there are several ways to use resistors to accomadte what the car's electrical system is expecting. However, you are talking about a non-relay controlled, new addition to the wiring harness. This means the only problem you have to deal with is that your source voltage is 12VDC. What I mean is you don't need a resistor to "fool" the car into thinking there is more load than there is.

Most LED's are built with a much lower turn-on (technically, "breakdown") voltage than 12V. All an LED is is a special diode. The problem with LEDs in cars is that if it's not built to "breakdown" around 12V, it will literally burn, making the LED useless, and sometimes shorting the circuit. Most fail open now, thankfully.

Anyway I am rambling: All you need to do is drop your source voltage at some point to the voltage your LEDs require. Let's say that's a common 3V. Instead of putting a resistor in series, or using a voltage divider (two specifically chosen resistors with attachment in the middle) why not just deliver the proper voltage and then wire all of your LEDs in parallel?

You can do this by the use of a Zener diode, or similar device. A zener is simple - it "breaks down" at a certain voltage in one direction (polarization) and a totally different voltage the other way. You can arrange zener diodes to give you a poor-man's voltage regulator. let's say you need 3V, you'll need a 9V Zener diode to drop the voltage to a safe level for those LEDs. If you need 5V, another common LED voltage, then you'd use (12-5) 7V Zener diodes.

Of course if your LEDs are made to withstand 12V, then all of my rambling is pointless.

Cheers and good luck.

Claus

one thing about resistors...

usually we, electrical engineers, do put a resistor inline with the LEDs even if the input voltage is correct. The reason for doing so is to limit the amount of current going through the LED, thus protecting it.

BelowRadar

Claus, I am an EE, too. Why do you put a resistor in series with the LED to limit current through the LED? Would a proper voltage source (say, 5v) and a fuse be all you need?
(honest question, not being sarcastic. I do IC work, not larger circuits anymore. )

GregFarz78

Interesting...thanks