Explain Different Types of LEDs and Working Applications for Engineering Students

In 1972, the first yellow LED was invented by M. George Craford, and he was a student of Holonyak. In 1980s, the first superlight LEDs were developed and these LEDs were cost effective, more stable and brighter. From 1990s onwards, the use of LEDs has become real in various applications like personal computers, traffic signal installation, telephones and various display systems. There are different types of LEDs that use diverse materials for their functioning.

Light Emitting Diode

LED is a semiconductor P-N junction diode. Mostly it is made up of GaAsP, and for the high bright LEDs GaAlAs is used. When a diode is switched on, the electrons from the N-region moves towards the P-region and combine with the holes; finally, the form of light energy is released. The color of the LED is determined by the energy gap of the semiconductor. Most of the LEDs work between 1.5 to 2V – but, bright LEDs require 3V.

There are 8 parameters to consider in LEDs (light emitting diodes); they are, luminous flux, luminous intensity, luminous efficiency, forward voltage, forward current, viewing angle, energy level and wattage of LED. Depending on these parameters, various LEDs are available in the market today that varies in color, size, rating, and so on, and even the LED TVs are also available.

Different Types of LEDs

LEDs are classified into several types, but only a few of them are explained below.

• LED stripes
• Miniature LEDs
• High-power LED
• Application Specific LED

1. Miniature LEDs

In our day-to-day life, these LEDs are used as indicators in Television sets, mobile phones, model railway layouts, compact electrical equipments, etc. Miniature LEDs are available in the market with a standard size and shape. These LEDs have less than 3mm diameter, they can come with ready to fit mode with that they can be directly mounted on the circuit boards. These LEDs don’t need support of any additional cooling systems. In the range of 5v and 12v, different companies manufacture these LEDs.

2. LED Stripes

These LED stripes consist of high-powered LEDs that are placed on a thin flexible circuit board and backside of the strip is coated with an adhesive material. Once the power is applied to the LED strip, the owl length of the strip is illuminated producing a forward light. These stripes are inexpensive and easy to install.

Different types of LED strip lights include:

• Digital RGB LED strip
• Rhythm following flashing lights
• Flexible LED strip
• Waterproof SMD LED strip
• Decorative blue-colored self-adhesive LED strip
• Decorative Red-colored self-adhesive LED strip
• Decorative White-colored self-adhesive LED strip
• Hit lights red flexible ribbon LED strip
• ACE gold LED strip light
• Multicolor five-meter waterproof flexible LED light strip
• Philips Linea LED light strip
• Philips Lines flexible LED strip
• Hit lights weather proof green flexible ribbon LED strip light

3. High-Power LEDs

High-power LEDs come in different sizes and shapes with a very high output. These LEDs have heat dissipation so they need to be mounted along with a cooling system (heat sinks), and they can run over 60,000 hours. High-power LEDs are used as LED street lights, table lamp, home appliances, indoor & outdoor lightings, etc.

4. Application Specific LED

As the name indicates these are manufactured for a particular application alone. These applications include digital display boards in various annunciation systems, digital bill boards, bi color and tri-color LEDs. A bicolor LED consists of two diodes mounted on a single frame with two pins, in which one pin is anode or cathode. At different times, this LED can produce two colors while it is in a forward bias or reverse bias condition. Similar to a bicolor diode, a tri color LED consists of two diodes mounted on a single frame, but with three pins.

LED applications

1. LED for Lighting Applications

From the last few years LED lighting systems have become very popular among various applications, such as street lightings, traffic signals, exit signs displays, etc. All the LED lighting systems are not the same, but vary with the diverse parameters and configurations. These LED systems offer tremendous energy, maintenance-free disposition, saves electrical energy and come with a longer life span. Some of the applications of LED lighting systems are as follows:

• LED in offices
• LED in hospitals
• LED for outdoor spaces
• LED in health care
• LED in Retail
• LED in industry

2. Display Elements

• LEDs are used in active display, unlike the LCD full-color display, and also in the daytime programmable displays for advertisements.
• LEDs are used in indicators, such as 7-segment array to generate alpha numerical characters.
• Used in automobile break lights and traffic signals.

3. Communication

• Laser diodes are used in long distance communications.
• LAN (local area network)

4.Opto Isolators

• LED as light emitter provides very high degree of isolation in opto isolators.
• In some medical instruments or devices, such as the electrocardiograph amplifiers, during medical treatment very high degree of isolation is need to ensure patient safety, so these LEDs do this job perfectly.

These are the different types of LEDs and their applications. It is our suggestion on behalf of the energy conservation with a social responsibility that please use LEDs for energy efficient lighting in your homes, discotheque light stroboscopic flasher, road ways of your premises and offices, which give better lighting at low cost. And, also please share your views on this article in the comment section.

Photo Credits

• Different types of LEDs by calce