How LED Works - Unravel the Mysteries of How LEDs Work!

LEDs emit light due to a semiconductor material that releases energy in the form of photons when voltage is applied. The color of the emitted light, such as red or blue, depends on the specific materials and structure used in the LED. When external light shines onto an LED, it can reflect back photons into it.

LEDs, or light emitting diodes, operate on the principle of semiconductor materials that emit photons when electrons combine with holes. Unlike standard diodes which produce infrared light and generate heat, LEDs are energy-efficient as they convert electrical energy directly into visible light without significant heat production. They come in various shapes and sizes for different applications; common types include through-hole LEDs ideal for learning electronics and SMD (surface mount device) versions used in compact designs like modern bulbs. The color emitted by an LED depends on the wavelength of the photon produced within a range of 400 to 700 nanometers.

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LEDs come in various colors and transparent versions, with the casing color indicating the light emitted. The actual color is determined by the semiconductor material inside, not the case itself. LEDs only illuminate when connected correctly to a power source; identifying polarity can be done through lead length or flat edges on their cases. If leads are trimmed, checking manufacturer datasheets or testing may be necessary for proper connection identification. Automated blinking of LEDs can be achieved using simple circuits involving resistors and transistors.

Bidirectional LEDs feature a tiny internal controller that manages color transitions, allowing for fast or slow changes. These LEDs consist of two components arranged oppositely; when current flows in one direction, one LED lights up, and the other activates with reverse current. Additionally, three-pin bi-color types allow manual switching between colors or simultaneous activation of both. Four-pin RGB LEDs contain red, green, and blue diodes sharing a terminal but cannot be activated independently to create mixed colors.

LEDs can produce various colors, including white light by controlling voltage and current. Connecting an LED directly to a 9-volt battery will damage it due to excessive electron flow; thus, a resistor is necessary to limit the current and protect the LED. The resistor dissipates energy as heat while allowing only the required voltage for proper operation of the LED. Adjusting resistance alters brightness within safe limits defined in manufacturer datasheets, typically around 20 milliamps for standard LEDs. For consistent performance without flickering in applications like lamps or USB strips, dedicated drivers ensure stable power supply.

LEDs can be cut to various lengths, affecting current flow; removing more LEDs reduces the current. Each LED has two leads: the longer anode and shorter cathode, with a flat edge on the case indicating the cathode side. Inside, both leads connect to metal plates separated by a gap; these plates help define polarity. The structure includes n-type and p-type semiconductor layers forming a p-n junction that emits photons when powered, producing light.

Understanding Semiconductor Functionality Electricity flows through conductors like copper but struggles in insulators such as rubber. In semiconductors, n-type layers have excess electrons while p-type layers contain holes for electron movement. The combination of these two forms a PN Junction that creates an electric field preventing further electron flow until sufficient voltage is applied, typically around 0.5 to 0.7 volts for diodes and higher for LEDs.

Color Production in LEDs The energy levels within atoms dictate how electrons behave; the valence band holds outermost electrons while the conduction band allows free movement when energized by voltage application. Silicon emits near-infrared light due to its specific energy gap, whereas mixing gallium arsenic with gallium phosphide enables production of visible colors by adjusting their ratios—leading to red at approximately 1.7 eV and yellow at about 2.13 eV—and ultimately allowing creation of white light from combined colors.