Okay, I know you can't just straight-up wire an LED to a 12v electrical system. My question then is, what resistors (or other parts) will I need to solder onto the LEDs to make them compatible with a 12v electrical system??

Just FYI, I'm basically planning to replace my OE warning indicator lights with LEDs in my custom gauge cluster panel...

 

IIRC LEDs are typically 2V and 10mA. That being the case, you'd need a resistor that would limit current to 10mA with a 10-12V drop (12-14V minus 2V). A 1Kohm to 1.2Kohm resistor would do the trick, in series with the LED.

 

5 of my LEDs are rated @ 20mA (continuous forward current), and one is rated @ 30mA. What size resistor would I need for that, then? 500-ohm? 2k-ohm? I'm a novice when it comes to this sort of electrical stuff...

 

Those 20 and 30mA ratings are usually MAX continuous ratings at 25°C (room temperature). I personally would stick with Dave's recommendations and give yourself a margin of reliability.

 

So, is it the higher the resistance, the brighter the LED, or the lower the resistance? If I went with the suggested range of resistors, would the 1.2k-ohm or 1k-ohm resistors yield the brighter LED display?

 

The lower the resistance, the brighter the LED will be. I'm not sure you could actually see a brightness difference between the 1K and 1.2K resistors, as they're pretty close in value ...??

 

Some Additional Help

And probably a good place to purchase the bulbs themselves

 

That's actually where I ordered mine from...

 

a 1k ohm will be fine

 

I've bought several of these from Radio Shack with the resistor built in. Should be able to source them cheaper if you look around or if you need a couple, just go there.

 

on ebay you can get like 100 of any color you want that are of the superbright style for like 3 bucks. and then you can get 1000 of the 1kohm resistors for a buck. i have every color in varring mah and use a 1k ohm resistor on them all and there bright as hell.

 

Umm, please excuse my retardedness, but which side do I solder the resistor onto? The longer terminal, or the shorter one?

 

It doesn't matter.

 

Hmm, I was under the impression it did...oh well, if I blow something up, I'll send you the bill...

 

it does matter solder the resistor onto the long leg of the led. The resistor is there to reduce the voltage flowing into the led . If you solder it onto the short leg then it had no way of loweing the incomming voltage.

Rember these things.

• long leg is always positive
• short leg is always negative.
• Resistor goes on either the positive feed wire or the long leg of the led.
• It only can go on the positive feed wire when not running alot of leds as this could cause the resistor to heat enought to cause a fire.
• A 1k ohm resistor is good for almost every led you find.
• 1/4 watt and 12/watt resistors will both work.