Make LEDs Dimmer?

[RockMonkey]

I'm decidedly not an electrical engineer. This is probably an exceedingly simple question, but my mechanically oriented mind doesn't comprehend amps, ohms, watts and what-not. I have a 12 volt 4-LED light, and I need it to make it half as bright. It doesn't have to be exact, but noticeably lower light output is required. I presume I can just wire a resistor into the positive input, but which resistor? How many watts and ohms do I need to get the job done? Sorry for the remedial question, and thanks for your help!

[ash]

Welcome to CE, RockMonkey!

Oh.. are those LEDS used in cars? Is there by any chance an amp rating on the package when you got it? That will determine what range of resistance values you can use to make it dimmer.

In normal electronics, the standard LED needs around 220 ohm of resistance for protection. The one you have might already have built in.

[RockMonkey]

Originally Posted by ash

Welcome to CE, RockMonkey!

Oh.. are those LEDS used in cars? Is there by any chance an amp rating on the package when you got it? That will determine what range of resistance values you can use to make it dimmer.

In normal electronics, the standard LED needs around 220 ohm of resistance for protection. The one you have might already have built in.

Yes, automotive. They came unpackaged, basically sold in bulk. So no amp rating on the package, or on the light itself.

[ash]

Can you send a picture of it?

I did a quick search of it just now, theres quite a range of 12V 4-LED bulbs. Festoon LEDs seem like a popular one, though they are quite hard to get specifications on.