History Discoveries and early devices Green electroluminescence from a point contact on a crystal of SiC recreates Round's original experiment from 1907.Įlectroluminescence as a phenomenon was discovered in 1907 by the English experimenter H. Īs a transducer of electricity into light, LEDs operate in reverse of photodiodes. LEDs usually need electronic support components to function, while an incandescent bulb can and usually does operate directly from an unregulated DC or AC power source. In contrast to LEDs, incandescent lamps can be made to intrinsically run at virtually any supply voltage, can utilize either AC or DC current interchangeably, and will provide steady illumination when powered by AC or pulsing DC even at a frequency as low as 50 Hz. In exchange for these generally favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and generally to DC (not AC) power, inability to provide steady illumination from a pulsing DC or an AC electrical supply source, and lesser maximum operating temperature and storage temperature. LEDs have many advantages over incandescent light sources, including lower power consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. LEDs have also given rise to new types of displays and sensors, while their high switching rates are useful in advanced communications technology with applications as diverse as aviation lighting, fairy lights, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, lighted wallpaper, horticultural grow lights, and medical devices. Later developments produced LEDs available in visible, ultraviolet (UV), and infrared wavelengths, with high, low, or intermediate light output, for instance white LEDs suitable for room and outdoor area lighting. Early LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays. The first visible-light LEDs were of low intensity and limited to red. Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. Īppearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared (IR) light. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. A bulb-shaped modern retrofit LED lamp with aluminum heat sink, a light diffusing dome and E27 screw base, using a built-in power supply working on mains voltageĪ light-emitting diode ( LED) is a semiconductor device that emits light when current flows through it. Close-up image of a surface mount LED Close-up of an led with the voltage being increased and decreased to show a detailed view of its operation. The flat bottom surfaces of the anvil and post embedded inside the epoxy act as anchors, to prevent the conductors from being forcefully pulled out via mechanical strain or vibration.

Arduino led voltage