View Full Version : Help on LED's

09-25-2008, 07:04 PM
Hi folks,
I had gone through some of the materials on electronics and have got a few doubts on LED's voltage and current schemes.

1. Can someone give me a small and brief summary on why the different coloured LED's are consuming different voltages? And can someone give me some light on the voltages that have to be given for the different LED's?

2. Also, in the market, I've seen some LED's called "Super bright" and "Oridinary" and many more. Can someone throw some light on this classification of the LED's?

Thanks and Regards.

[This post is irrelevent in the Microcontrollers Forum. It is moved to Technical forum -Mod]

09-25-2008, 08:56 PM
I had skimmed through the details when I read about LEDs a long time back, so can't give an expert answer... Roughly the different voltage drops are because of different semiconductor materials being used in the fabrication and doping. Basically, photon wavelengths being emitted depend on the semiconductor used and each semiconductor has some particular voltage drop.

Usually I drive LEDs by having a 470 ohm resistor in series. Never checked the exact specs of the commonly available LEDs.

Superbright LEDs are used for lighting applications. You don't need them for general purpose electronics, where LEDs are mostly used for indication rather than illumination.

09-25-2008, 11:50 PM
Google search revealed these interesting results:


They answer all of your questions.


09-26-2008, 07:12 PM
Oh! ok guys... So the semiconductor determines the input voltage eh! Great..

So any more inputs from any of you guys are most welcomed!

09-27-2008, 01:28 AM
Unless you are doing some sort of research which leads to the design of a new technology in the field of LEDs, all this information is trivial and a waste of time.. your basic digital systems are 5V, so instead of how much voltage to give to a certain LED, how to make an LED glow without burning in a 5V system is a better approach.

As said by Mohit in his post, a 470ohm resistance is more than enough for most of the LEDs you get in the market. IF not, just use a 1K pot and and tune it as per your satisfaction.