LED lighting technology has almost surpassed incandescent bulbs and fluorescent tubes and due to their .......

1) conservative use of electrical energy

2) superior longevity

3) and ruggedness.




          40 billion LEDs are made each year and the number rises each year





Photoelectric effect

In an incandescent lamp heat excites electrons to higher energy states. When they fall back to ground state and release a photon of light.

In an LED the forward voltage excites the electrons.

Fluorescent and neon lights also work by high voltage excitation of electrons in a tube filled with gas.



LEDs are diodes that are made using dopant atoms that make it more difficult for electrons to cross the junction. The resulting higher forward voltages impart the electrons with higher energy that release higher energy photons in the visible light spectrum.

A big breakthrough in LED technology was the development of the blue LED that allowed for the additive RGB system for flatscreens and the ultraviolet LED for medical use. (sterilizing, whitening teeth)

link to LED theory


L E D lights are a type of diode that are increasingly replacing incandescent lighting systems. Once relegated to the role of indicator lights on appliances and computers they are now found in service in industrial locations such as traffic lights, car signals, advertising billboards, lasers, recording and storage media and even medical therapeutics such as lasers and healing light sources. LEDs are also used as isolating switch triggers (Optocoupler) that separate power source from signal.
When designed into a circuit properly they have an unknown life span (long) however in industrial settings they are often over powered to give maximum brightness which results in shorter life spans due to over current/heat related issues.

They last up to 10 times longer than incandescent lights and provide more light per watt. This makes them an environmentally sound choice.


Blue LEDs have short wavelengths and thus feature greater bandwidth possibilities such as Blue Ray DVD

- RGB flat screens blue was the missing element in the RGB additive colour system  

Operation - LEDs are diodes made of N + P type crystal however the crystal materials are different.
Gallium arsenide dopants are used to make LEDs.
Various combinations of dopants are used to generate the various colours of the visible spectrum.
Light is emitted from the junction and reflected up and out by a lens embedded in the plastic jacket.

All 3 primary additive colours RGB can now be generated by LEDS and hence the full colour spectrum can be reproduced!! Great for Jumbotrons and other billboards.

Lasers are everywhere now that things are measured, scanned, printed, copied, read, counted, recognized, inventoried and so on ...
Eye surgery.



Bar Code readers



LED Tech sheet

Super bright LED FLASH LIGHT water cooled.
LED Driver circuit : note the bridge rectifier and the zener regulator


Did you known that if you hold an LED up to sunlight it will output 1.8v ?
Why? What do you think is happening? What would happen to the polarity

A - the LED is acting as a photo-voltaic cell

B - the LED polarity will reverse, current will flow backwards and out the cathode



Calculating the
Limiting Resistor Value for LEDs