The light emitting diode, commonly known as an LED, is one of the most important and widely used components in modern electronics. Whether you’re building circuits as a hobbyist, designing consumer products, or exploring lighting solutions, understanding how LEDs work and how to use them is essential.
Table of Contents
- What Is a Light Emitting Diode?
- How Does an LED Work?
- Types of LEDs and Their Applications
- LEDs in Hobbyist Electronics
- Light Emitting Diode Tips and Hints
- General Uses for Light Emitting Diode Technology
- Tips for Light Emitting Diode Use
- Did You Know About Light Emitting Diodes?
- Frequently Asked Questions About Light Emitting Diodes
- Light Emitting Diode Conclusion
What Is a Light Emitting Diode?
A light emitting diode (LED) is a special type of diode that emits light when current flows through it in the forward direction. Unlike standard diodes, which are used mainly for controlling current flow, an LED is designed to produce visible or infrared light as a byproduct of electrical energy.
What Does LED Stand For?
LED stands for Light Emitting Diode.
LED Symbol
The following image shows the LED symbol used in circuit diagrams to represent a light emitting diode. These are two common forms, one with a filled or solid body and one without.
As can be seen in the image, the LED symbol body consists of a diode symbol with two arrows. The two arrows denote that light is emitted from this device. An LED has an anode and cathode terminal. In the image, the anode is on the left and cathode on the right.
How Does an LED Work?
An LED works by electroluminescence. When a suitable voltage is applied across its terminals (anode and cathode), electrons recombine with electron holes within the semiconductor material, releasing energy in the form of photons—visible light or infrared.
Key characteristics of LED operation:
- LEDs are polarity sensitive – they must be connected the right way around. That is, anode to positive of the power supply and cathode to the negative or 0V terminal of the power supply.
- They require a resistor in series to limit current and prevent damage.
- LEDs only allow current to flow from the anode (positive) to the cathode (negative).
Types of LEDs and Their Applications
Modern electronics use many types of LEDs, each suited to specific applications. Here are some common examples:
| LED Type | Description | Typical Use |
|---|---|---|
| Red LED | Basic low-power LED | Indicators, signals |
| Infrared LED | Emits infrared light | Remote controls, sensors |
| Pixel LED | Individually addressable RGB LED | Displays, lighting effects |
| WS2812 | Smart RGB LED with integrated controller | Animation and color effects |
| Neopixel LED | Adafruit-branded WS2812 or similar pixel | Hobby and custom LED projects |
| LED Module | Pre-mounted LEDs with circuitry | Ready-to-use lighting solutions |
| RGB Strip | Flexible strips with RGB or RGBW LEDs | Decorative and ambient lighting |
LEDs in Hobbyist Electronics
Before LEDs became common in household lighting, they were—and still are—a staple in hobbyist electronics. Originally, diffused LEDs (which emit a soft, scattered light) were the most widely available. These were perfect for simple indicators or decorative purposes. The following image shows examples of typical LEDs used in hobby electronics.
As technology advanced, ultra-bright LEDs emerged, offering greater visibility and vibrant colors. Today, programmable LEDs like WS2812 and Neopixel LEDs allow hobbyists to create dynamic displays with full color control.
Common hobbyist uses include:
- Status indicators on microcontroller boards
- Light animations for Arduino or Raspberry Pi projects
- DIY LED cubes and clocks
- Infrared LED-based communication systems
Light Emitting Diode LED Polarity
The type of LEDs shown in the previous image must be connected with the correct polarity and always include a current-limiting resistor in series to prevent damage.
An LED has two leads: the anode (positive) and the cathode (negative). It is essential to connect the LED the right way around in a circuit—LEDs are polarized components, and reversing the polarity will prevent them from working.
The accompanying diagram shows how the LED schematic symbol corresponds to the physical LED.
On the physical component:
- The longer lead is the anode.
- The shorter lead is the cathode, often marked by a flat edge on the rim of the LED body.
You can also identify polarity by examining the internal structure of the LED:
- The larger internal plate (connected to the short lead) is the cathode.
- The smaller plate is the anode.
Always double-check polarity before powering the circuit to ensure proper LED operation.
Light Emitting Diode LED Circuits
To see practical examples of how LEDs are connected in basic circuits, take a look at the Simplest Circuit post. It includes a diagram of a standard LED with a current-limiting resistor, as well as a circuit using a special type of flashing LED that doesn’t require a resistor. Both circuits clearly illustrate how to connect LEDs with the correct polarity.
LED Colors, Voltages, and Shapes in Hobbyist Electronics
LEDs are among the most popular and accessible components in hobbyist electronics. They’re widely available in various colors, sizes, and shapes, each with slightly different electrical characteristics.
Common LED Colors and Forward Voltages
Here’s a helpful reference table of standard hobbyist LED colors and their typical forward voltage ranges:
| LED Color | Typical Forward Voltage (V) | Notes |
|---|---|---|
| Red | 1.8 – 2.2 V | One of the lowest-voltage LEDs |
| Yellow | 2.0 – 2.2 V | Often used for indicators |
| Green | 2.0 – 3.0 V | Voltage varies based on brightness level |
| Blue | 3.0 – 3.2 V | Requires higher voltage than red/yellow |
| White | 3.0 – 3.3 V | Often uses a blue LED with a phosphor |
| Orange/Amber | 2.0 – 2.2 V | Similar to red but visually distinct |
| Infrared LED | ~1.2 – 1.5 V | Used in remote controls and sensors |
| RGB LED | Depends on color channel | Combines red, green, and blue LEDs |
Standard LED Sizes for Hobbyists
Hobbyist LEDs are typically packaged in standard sizes, identified by the diameter of the lens:
- 3mm: Compact, good for tight spaces.
- 5mm: Most common size, easy to work with.
- 8mm: Larger lens for greater visibility.
- 10mm – 12mm: High-brightness or decorative use.
LED Shapes and Packages
In addition to size, LEDs come in a variety of shapes:
- Round domed (diffused or clear): The most traditional and common for through-hole use.
- Flat-top LEDs: Good for panel indicators.
- Rectangular or square LEDs: Often used in bar graphs or matrix displays.
- Straw-hat LEDs: Designed to emit light at a wide angle.
- Pre-wired LEDs: Convenient for plug-and-play connections.
Different shapes and lens types affect the beam angle, diffusion, and brightness of the emitted light. This variety makes LEDs highly versatile for use in prototyping, indicators, displays, and custom lighting effects.
Surface Mount LEDs
In addition to through-hole mounting LEDs, surface mount LEDs are available that are soldered directly to the top of circuit boards.
Notice the small green surface mount LED that is lit up in the image below, near the bottom left corner. This Arduino Uno R4 Minima board has three other surface mount LEDs that are not lit up in the image. They are labelled L, TX and RX. The green LED that is glowing is the ON indicator LED that shows that the board is powered on.
Light Emitting Diode Tips and Hints
Never connect an LED directly across a battery or other power source – it will burn out. Always connect a light emitting diode (LED) in series with a resistor.
LEDs are diodes which means that current can only flow through an LED from the anode to the cathode and not the other way around.
If an LED is connected the wrong way around in a circuit (anode to negative and cathode to positive) it is said to be “reverse biased” and will not emit light. When connected the right way around the LED is said to be “forward biased”.
LEDs, unlike other diodes, can not withstand large reverse bias voltages.
General Uses for Light Emitting Diode Technology
LEDs have become an essential part of modern electronics and lighting systems due to their efficiency, compact size, and long lifespan. They are now found in a wide range of everyday applications. Here are some common uses and related terms:
- LED lights refer to energy-efficient lighting devices used in homes, vehicles, streetlights, signage, and electronic displays. They consume less power and last significantly longer than incandescent or fluorescent alternatives.
- LED lamps are complete lighting units that contain one or more LEDs along with any necessary optical, mechanical, or electronic components. These are often used as replacements for traditional light bulbs in household and commercial fixtures.
- LED drivers are electronic circuits or modules that supply a consistent, controlled current or voltage to an LED or group of LEDs. Since LEDs require specific electrical conditions to operate safely and efficiently, the driver ensures reliable performance and prevents damage due to overcurrent or voltage fluctuations.
How LED Lighting Works from 12V and Mains Power
While individual LEDs typically operate with a forward voltage between 1.7V and 3.2V, higher-voltage lighting systems such as 12V DC or 120V / 230V AC mains require additional circuitry to safely and efficiently power multiple LEDs.
- 12V LED Lighting: Common in automotive, strip lighting, and low-voltage home systems, 12V LED lights usually consist of groups of LEDs connected in series-parallel, along with current-limiting resistors or constant current drivers to ensure proper operation. The LED modules or strips are designed to divide the 12V supply voltage across multiple LEDs.
- Mains-Powered LED Lighting: LEDs used in AC mains-powered lamps or bulbs include built-in LED drivers that convert high-voltage AC (e.g., 230V or 120V) to a suitable low-voltage DC output. These drivers often incorporate:
- Rectifiers to convert AC to DC,
- Step-down converters or switching regulators, and
- Current control circuits to prevent overdriving the LEDs.
This internal driver circuitry allows LED bulbs to be a direct replacement for incandescent or CFL lamps in household fixtures while operating efficiently and safely.
Tips for Light Emitting Diode Use
- Always use a resistor in series with an LED unless it’s part of a module that includes one.
- Mind the polarity: Long leg = anode, short leg = cathode.
- Use diffused LEDs for soft lighting and clear/ultra-bright LEDs for maximum visibility.
- Don’t exceed voltage or current ratings – even brief overvoltage can permanently damage an LED.
- Consider using constant current drivers for high-power or high-quantity LEDs like RGB strips.
Did You Know About Light Emitting Diodes?
- The first practical LED was developed in the early 1960s and emitted red light.
- Diffused LEDs with a frosted epoxy case were standard for decades.
- Ultra-bright LEDs revolutionized signage, vehicle lighting, and backlit displays in the late 1990s.
- RGB Neopixels are capable of 16 million colors with 8-bit control over red, green, and blue.
- Today, LEDs are the primary source of lighting in many energy-conscious homes and cities.
Frequently Asked Questions About Light Emitting Diodes
What is an LED?
An LED is a Light Emitting Diode, a semiconductor device that emits light when an electric current passes through it.
How does an LED work?
An LED emits light through a process called electroluminescence when current flows from the anode to the cathode in forward bias.
What is an LED driver?
An LED driver regulates the power supplied to an LED or group of LEDs, maintaining consistent brightness and protecting against electrical damage.
What are LED lights used for?
LED lights are used in general lighting, backlit displays, signage, vehicles, and countless consumer electronics due to their efficiency and long lifespan.
What is the difference between a Neopixel and a WS2812?
A Neopixel is a branded name (often from Adafruit) for the WS2812 or similar RGB LED that has an integrated driver for individual control over color and brightness.
Light Emitting Diode Conclusion
The light emitting diode is a fundamental building block in electronics, from simple circuits to sophisticated lighting systems. Whether you’re using a red LED as a power indicator, exploring RGB strip lighting, or experimenting with WS2812 pixel LEDs in a hobby project, understanding how LEDs work and how to use them properly is essential for any electronics enthusiast. Their evolution from simple diffused types to programmable smart LEDs has made them more versatile than ever.