leds how and where from?

[exuptoy]

I have previously fitted ultra blue leds to 8210 and 5210's but now I have a project in mind for my car, if I connect 4 leds to the 12 volt supply on the car, what value resistor should be connected in series with them?
Also where is the cheapest source for led's at present?

[vadur999]

Hi,Exuptoy

Normally a LED need to have 4-10 miliAmps to flow - driven by different minimum "burn"voltages for the different core material- to ensure bright light.
If you have 12-14 V as supply (a car electro system delivers approx....)
from the Ohm's rule (hopefullly learned in the school...if you have willingness to solder LED's into a car !)
So if you get 14V and divide by 10 (mA) the result is 1.4 (kOhms) serial for each LED connected to the power...
The average value is approx. 1.2-1.5 kOhms to get the brightest light from a
normal LED, connected to 12V car power.

Cheers
vadur