12Vdc 5mm LED Bulbs

[Al Skierkiewicz]

Originally Posted by mtaman02

I am currently in the market for a couple / few (not a whole lot) of 12Vdc 5mm White LED Bulbs so that I can replace the ones that are bad in my truck. I was wondering if anyone on CD has come across this kind of item or has purchased this item. I looked all over the web and I find the 5mm White LEDs but they are not 12Vdc. Radio Shack only sells LED's at 1 - 4Vdc.

Mike,
All LEDs are about 2 volts forward voltage drop. You need to put a resistor in series with the LED to limit the current for the power supply you are using. There are some manufacturers that make filament lamp replacements from LED/resistor combinations for different voltages. If your plan is to replace filament style bulbs in your truck, it is also necessary to provide for reverse polarity using some diodes in addition to the resistor. The unfortunate problem with LED replacements for filaments is the directivity of the LED vs. lamp. If the application uses a lens or reflector, you may be unhappy with the results of an LED. If you are replacing LED's then there may be other problems that caused them to burn out in the first place.

In general, a single LED will require about 500 ohms in series to drop the voltage from 12 volts@20ma. 470 or 560 ohm resistors are the standard values close to 500. If you purchase a particular high brightness LED, follow the specifications for that device.