LED voltage?

Question

1. Do all LEDs of the same size made to operate on the same voltage? What is the ideal Voltage that a LED should be fed? 3V? 5V?
2. are there any technical details that i should look out for if i want to replace some LEDs in my electronics gadgets? Measure it with a multimeter?
3. Plus They come with all kinds of descriptions like Super Bright or High Density.......so i wonder how different they are technically...

Answer 1

First, you can use any LED with any voltage, you only need to calculate the right value of the limiting current resistor!
For example : you have an amplifier that use 35 Volts DC and need an indication trough out LED and you use a 20 mA unit.
As the first try use 1.65 Volts like the tension the LED use.
1.-(35-1.65)/0.02 and you get 1667.5 Ohms.
2.-Choose the next superior available value : 1800 Ohms.
3.-Now the resistor power : (35-1.65)*0.02 and you get 0.667 Watts so you can use the next available value of 1 Watt.
That's the way to work with any voltage, and next if you like you can take the voltage across the LED and change the resistor for the value that give you more or less mA and more or less light from the LED.
The super-bright or high density units give you more light on the same amount of current, that's all!

Answer 2

You can't apply the voltage directly to the LED, you must put a dropping resistor in series with the LED. Generally they will drop about 1 volt so put a resistor of the proper size to drop the voltage and to an acceptable level the will allow the LED to glow. The resistor must be able to dissipate the power as well.

Answer 3

Most typical LEDs are designed to operate with no more than 30-60 milliwatts of electrical power. Around 1999, Philips Lumileds introduced power LEDs capable of continuous use at one watt. These LEDs used much larger semiconductor die sizes to handle the large power input. Also, the semiconductor dies were mounted to metal slugs to allow for heat removal from the LED die. In 2002, Lumileds made 5-watt LEDs available with efficiencies of 18-22 lumens per watt.

In September 2003 a new type of blue LED was demonstrated by the company Cree, Inc. to have 35% efficiency at 20 mA. This produced a commercially packaged white light having 65 lumens per watt at 20 mA, becoming the brightest white LED commercially available at the time. In 2006 they have demonstrated a prototype with a record white LED efficiency of 131 lumens per watt at 20 mA.

Answer 4

not only is size a factoe, but the individual colors all have different voltages..

red is 2volts
yellow is 2.4 volts
green is 2.7 volts
blue is 3 volts
white is 3 volts

Answer 5

http://www.theledlight.com/LED101.html


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