LEDs, short for Light Emitting Diodes, are semiconductor devices that efficiently convert electrical energy into light, in contrast to less efficient incandescent light bulbs that produce light through the conversion of electrical energy into heat energy.
Structurally, an LED is a specialized semiconductor device with a p-n junction. The structure consists of three layers: a P-type region at the top, an N-region at the bottom, and an active region or depletion region in the middle. When a forward-biased voltage is applied, electrons from the N-region and holes from the P-region move into the active region and recombine. This recombination of charge carriers releases energy in the form of photons, resulting in visible light.
While the illuminated lights could be red, yellow, green, and white, the color of LEDs is determined by the specific semiconductor materials used. Each semiconductor material possesses a unique energy bandgap, representing the energy difference between the valence band (where electrons are normally located) and the conduction band (where electrons are free to move and participate in electrical conduction).
The following table shows some common semiconductor materials used in LEDs and the colors of light they emit:
Diode and LED Polarity
LEDs are polarized components, meaning they require a specific orientation when connected to a circuit. In terms of circuit symbols, LEDs share a symbol similar to regular diodes. Diodes have two terminals: the positive terminal, called the anode, and the negative terminal, known as the cathode. In the diode’s symbol, a black arrow (▶) indicates the direction of the forward current, which flows from the anode (positive) to the cathode (negative). LEDs employ this same symbol but enhance it with two small arrows to signify their light-emitting capabilities.
To identify the cathode side of a diode, look for a line on the diode’s surface that corresponds to the line in the diode’s symbol. For LEDs, finding the cathode is often even easier: look for the longer leg of the LED, which typically represents the positive anode pin. If the legs are damaged or not easily distinguishable, check the LED’s outer casing for a flat edge. The pin closest to this flat edge is the negative cathode pin.
Special types of LEDs
Beyond the typical DIP LEDs and SMD LEDs, you can achieve captivating lighting effects through different means. Two special types stand out: addressable LEDs and wireless LEDs.
Addressable LED
Addressable LEDs can be controlled individually or in groups, which is what makes them ‘addressable’ and unique. They enable you to create dynamic lighting effects on different parts of the LED strip simultaneously or in customizable intervals, offering a wide range of creative possibilities. Each LED has a built-in controller that communicates through a digital protocol, allowing data to pass from one LED to the next in a serial daisy-chain. This enables a microcontroller or LED controller to send precise instructions for individual colors and brightness. This level of control stands in contrast to common RGB strips with a single control chip, offering enhanced versatility and creative potential.
Wireless LED
If LEDs could light up without any wires or soldering, it sounds really interesting right? That’s what wireless LEDs or inductive LEDs can achieve. Inductive coupling is the most common type of wireless power transmission for LED lights. It works by using two coils of wire to create a magnetic field. When the two coils are close together, the magnetic field induces a current in the receiver coil. This current can then be used to power the LED lights. The possibilities with these special wireless LEDs are virtually limitless. Imagine using them for a whimsical and eye-catching cosplay outfit, or employ them for stunning and versatile lighting decoration in your home.
