Light Emitting Diodes (LEDs) are essential electronic components for various applications and prototypes. They are easy to use and perfect for exploring different concepts. In this blog post, we will focus on 5mm LEDs commonly used for prototyping.
An LED has two leads: the anode and the cathode. The anode is usually longer than the cathode. It is crucial to connect the anode to the positive lead (+) and the cathode to the negative lead (-) correctly to ensure the LED functions properly.
It is worth noting that the cathode has a shorter lead, but if the leads are cut, it may be challenging to identify the cathode. In the case of a 5mm LED, the cathode has a small cut through its shape, distinguishing it from the anode.
LEDs function similarly to diodes but emit light. Here’s a comparison of LED and diode connections:
[Image: LED and Diode Connection Comparison]
LEDs come in various colors and act as tiny lightbulbs. When a specific amount of tension and current pass through the LED’s wires, it lights up. The exact mechanism behind this reaction is complex and beyond the scope of this blog post. However, it is essential to use a resistor in conjunction with a battery to limit the current flowing through the LED. Without a resistor, the LED can burn or even explode due to excessive current.
The value of the resistor determines the voltage drop across the LED. For example, with a 3kΩ resistor, the LED’s voltage drop is 1.87V (exact value may vary depending on the LED model), and the resistance has a voltage drop of 7.12V. If a 300Ω resistor is used, the LED’s voltage drop increases to 2.10V, and the current through it becomes 22.9mA.
Determining the maximum allowable current for an LED is crucial. This information can be found on the LED manufacturer’s specification sheet. For instance, the 5mm LEDs I obtained from the Elegoo box indicate a continuous forward current of 50mA with a peak of 100mA. It is important to stay within these limits to prevent damage to the LED.
Multiple LEDs can be connected in series, where the anode of the second LED is connected to the cathode of the first. In this configuration, the voltage drop across each LED remains the same as before, but the resistance causes a minor voltage drop. This allows for more efficient circuits.
Different LEDs exhibit different voltage drops, often referred to as the nominal forward voltage. This depends on factors such as color and can be determined through direct measurement. The nominal forward voltage can range from 1.7V up to 4V.
To ensure proper illumination, LEDs require a specific range of current, typically between 5mA and 30mA. It’s important to consider this when designing LED circuits. For example, if three LEDs are connected in series and a 9V power supply is used, the LEDs will shine brightly with a current of 13.3mA. However, adding a fourth LED will reduce the light output as the current drops to 5.72mA, resulting in a dimmer light.
In summary, LEDs are essential electronic components that emit light when current and tension are applied. They have specific polarity and voltage drop requirements, and the use of resistors is crucial to ensure safe operation. Understanding these characteristics allows for the proper design and utilization of LEDs in various electronic projects.