Hi, i recently bought these leds: http://cgi.ebay.com/ws/eBayISAPI.dll...1358&rd=1&rd=1

But they said they are 13,000 mcd (hard to belive for me) i wanted to know first what are mcd?, and if those leds wont melt my car because of they intensity.

 

leds give off little or not heat. mcd = millicandella which is a measure of light intensity. you have nothing to worry about with regards to melting.

 

Thats who I bought mine from. I got white, 3mm LEDs. they are bright, in fact, they were to bright for my climate control, I had to use cellophane to reduce the intensity.

 

Thanks. for the info, also what are resistors for?

 

your car is 12 volts.
LED's are 3.3volts (give or take depending on the color)
you need the resistors to reduce the voltage from 12V to the required voltage otherwise the LED will overheat and melt. the amount of resistance needed depends on how many LED's you are hooking up to a particular resistor. just remember that LED's are polar (current is only permitted to flow in one direction) so if you hook it up to the proper voltage source and it doesnt turn on, switch the terminals around. if you are doing the MOD for our cars, you will only need resistors for the dimmer/cruise/hazard/rear defogger switch and for 3 bulbs in the manual climate control. for the window switches etc, it is all remove and replace. resistors already in place. for the door lights and cluster bulbs you can buy premade bulbs that are plug and play,

to figure out what type of resistor you will need remember r (resistance) = V (voltage) / I (current)
(to find the voltage it is 12v - the voltage of a single LED)
(to find the current it is the sum of all of the LED's connected to each resistor)
the voltage of the LED and current needed should be supplied by the LED provider.

 

oh boy...
resistor is to limit the current going through the LED
you don't want more than 30mA going through the LED typically. so...
there are two ways you can wire up those LEDs. The most power efficient way is to wire them in series and then just use a single smaller resistor in the series (usually 4-5 LED will work in series, but it all depends on the forward voltage required to run the LED). You can also just solder a resistor to each LED and run them all in parellel. Find out what the Forward voltage drop across each LED is and then subract that from 14v, then divide that by .030 amps (30 milliamps) and that gives you the value of the resistor you need for that LED, or if you wanna put a few LEDs in series, divide by the forward voltage times how ever many you wanna put in series (don't put 6 in series if the forward voltage drop is 3 volts...) Get the idea.

So if you wanna wire one LED up to act as a back light for some control in the dash, and it has a forward voltage of 3 volts. Then take 14 volts (about what voltage the car runs at) subtract 3 to get 11 volts, divide by .030. That tells us we want a resistor of about 366 ohms (they don;t make 366 ohm resistors so just get a 360 ohm or close to that). If you wanna wire 3 in series then subtract 9volts from 14volts to get 5 volts. Then divide that by .030 to get 166 ohms.

Also if you find that the LED is too bright just use a larger resistor. Make sure wire up the positive side to the longer lead coming off of the LED

Try not to short out anything.

Now that I look at it those LEds have a 3.2volt forward voltage and 20 milliamp current rating. so if you wire them up individually just use the 510ohm resistors they send with them.

 

So i should wire them individually, and use the resistors they will send me with the leds and thast it?

 

I am changing the lights on my P/W P/L switches, climate control, and on the needles for the speedometer and so on

 

you might be better off just doing it that way. Do you know how to solder? don;t hold the solder tip on it for more than a few seconds, that can mess up the LED or shorten it's life.
I'm just saying that if you have a spot where you need 3 LEDs that you can wire them all in series and just use a single resistor for those 3, but you have to know how to calculate the proper resistance (it's not hard though)

Also heat shrink tubing and electrical tape are your friends don't leave anything uninsulated and just hanging around. Otherwise you may just hit a bump one day and all your dash lights go out.