From smartphones, to smart lighting, to smart toys, numerous products employ light emitting diode (LED) components to enhance the end-user experience. With such a large variety of smart products utilizing LEDs, it’s useful to understand the technology behind LEDs, the types of LEDs commonly used and its’ various applications.

The technology

An LED is a small device typically used as a visual feedback for an event occurring in a system.  It is a semiconductor device that emits visible light when an electric current passes through it. LEDs consist of two elements of processed material called P-type semiconductors (anode) and N-type semiconductors (cathode). These two elements are placed in direct contact, forming a region called the P-N junction (in this respect, the LED resembles a diode, although the LED has a transparent package, which allows visible light to pass through it). When a suitable voltage is applied to the LED, electrons immigrate from the cathode to the anode, releasing energy in the form of photons.

Different semiconductor materials have varying  bandgaps that emit photons at different  energy levels that determine the wavelength of the emitted light. Infrared and ultraviolet LEDs operate on the same principle, however the light they emit is not in the visible range of the spectrum.

 

The wavelength spectrum, indicating visual light, infrared and ultraviolet wavelengths.
The wavelength spectrum, indicating visual light, infrared and ultraviolet wavelengths. Image credit: facweb.cs.depaul.edu

Exactly the same technology is used in moderns displays. Tiny LEDs replace the tubes that light up HDTV displays to make dramatically thinner televisions.

Types of LEDs in smart products

LEDs are found in a wide range of size, colors and illumination intensity. There are four types of common LEDs:

  • 1-Color LED – simple indication LED
  • 2-Color LED – specifies two different modes using one LED
  • 3-Color LED – specifies three different modes using one LED
  • Multi-Color LED – for creates multiple shades of color; up to 256 shades.
LEDs eyes: This smart Cabbage Patch Kid uses LED technology to create its innovative eyes
The 2016 smart Cabbage Patch Kid features innovative LED eyes. Image source: toynews-online.biz

LED Applications for the Internet of Things

The two basic applications of LEDs are indicator LEDs and illuminator LEDs. Indicator LEDs are usually inexpensive, low-power and suitable only as indicator lights in panel displays for electronic devices. Illuminator LEDs are durable, high-power devices that are capable of providing illumination.