The letters LED stand for light-emitting diode. The movement of electrons through a semiconductor material causes tiny light sources to become illuminated. Since LEDs do not scatter light and energy they are more light and energy efficient than incandescent and compact fluorescent light. A lifetime of more than 50,000 hours is no exception for led lights, whereas a traditional lamp would struggle with less than half of that. Moreover, increased cautions concerning environmental issues drive companies and institutions to opt for eco friendly lighting solutions, such as LED lighting. LEDs do not contain the highly polluting Mercury, commonly found in halogen light bulbs. They also produce significantly less heat and thus waste less energy. LED is a ‘solid state’ electronic component with the characteristics of a diode i.e. it only allows electrical current to flow in one direction through it. When the current flows through a LED in the correct direction, the LED produces light of a specific color. How do LEDs work? At the heart of every LED there is a very small piece of semi-conducting material called the LED ‘die’. The base of the die is glued or soldered into a fine metal framework (the leadframe). A very fine wire called a wire bond is attached to the top of the LED die, which has a very fine conductive metal pattern on it. The wire is attached to the other side of the leadframe. When electricity of the correct voltage and polarity is applied to the LED via the leadframe contacts, current flows through the die. The different properties of the layers in the die cause between 50 and 90% of this electrical energy to be converted into light at the junction by a process called ‘injection electroluminescence’. Types of LED: Miniature : These are mostly single die LEDs used as indicators, and come in various size packages such as surface mount, Round, dome top Round, flat top Rectangular, Triangular or square . High power devices: High power LEDs (HPLED) can be driven at currents from hundreds of mA to more than an ampere, compared with the tens of mA for other LEDs. Custom designs which are application specific variations: Flashing LEDs, Bi-color LEDs, tri-leds, RGB LED, alphan .