20 PCS Blue LED Diodes | 5mm Through-Hole | Breadboard Friendly

20 PCS Blue LED Light Diodes – 5mm Through-Hole LEDs for Prototyping, Indicators, and STEM Projects

This pack includes 20 blue 5mm through-hole LEDs designed for fast, low-cost visual output in embedded prototypes, education kits, and simple indicator circuits. Each diode uses a standard 2-pin through-hole form factor that drops neatly into breadboards, perfboards, and soldered PCB assemblies, making the set a practical fit for learners as well as engineers building quick proof-of-concept hardware.

These LEDs are well suited to status indication, user feedback, and low-power display effects when paired with a current-limiting resistor. They can be driven from common microcontroller platforms such as the ELAB Nano V3 or an Arduino UNO R3 compatible board, and they are easy to install on an MB-102 Breadboard Kit for quick testing. For broader classroom and starter-project use, they also pair naturally with kits such as the DFRobot Arduino Beginner Starter Kit.

For circuit design, treat these as standard blue indicator LEDs and always add a suitable series resistor based on your supply voltage and target current. If you want a reference point for common 5mm blue LED electrical behavior, the Kingbright 5mm blue LED datasheet is a useful guide for forward-voltage range, wavelength, and handling considerations.

Technical Specifications

Board Layout & Label Guide

• Lens Head – The 5mm round epoxy head is the light-emitting portion and should face outward for maximum visibility.
• Anode Lead – The longer lead is typically the positive terminal and should connect to the GPIO or supply side through a resistor.
• Cathode Lead – The shorter lead is the negative terminal and normally returns to ground.
• Flat Edge Marker – The flat edge on the LED body indicates the cathode side when lead length has been trimmed.
• Lead Spacing – Standard two-lead spacing fits common solderless breadboards and prototyping PCBs.
• Series Resistor Position – Place a resistor in series with each LED to limit current and protect both the diode and the controller pin.
• GPIO Drive Direction – A HIGH output can source current in simple circuits, while other designs may use sink-current wiring depending on the controller.
• Brightness Control – Use PWM-capable pins when you want dimming, fading, or pulse effects instead of simple ON/OFF behavior.
• Thermal Handling – Avoid excessive soldering time on the leads to reduce the risk of heat damage to the LED package.
• Operating Note – These are bare LEDs only; there is no onboard resistor, driver, or reverse-polarity protection.

Application Scenarios

1. Arduino Breadboard Status Indicator

Use a blue LED as a basic digital output indicator during Arduino lessons, GPIO validation, or first-time circuit assembly on a breadboard.

const int ledPin = 8;void setup() { pinMode(ledPin, OUTPUT);}void loop() { digitalWrite(ledPin, HIGH); // LED on delay(500); digitalWrite(ledPin, LOW); // LED off delay(500);}

2. ESP32 PWM Fade Demo

This example creates a smooth brightness ramp for UI feedback, wearable prototypes, or decorative light effects when the LED is connected through a resistor to an ESP32 PWM pin.

const int ledPin = 5;const int pwmChannel = 0;const int pwmFreq = 5000;const int pwmResolution = 8;void setup() { ledcSetup(pwmChannel, pwmFreq, pwmResolution); ledcAttachPin(ledPin, pwmChannel);}void loop() { for (int duty = 0; duty <= 255; duty++) { ledcWrite(pwmChannel, duty); delay(8); } for (int duty = 255; duty >= 0; duty–) { ledcWrite(pwmChannel, duty); delay(8); }}

3. Raspberry Pi GPIO Heartbeat Light

A heartbeat blink is useful for showing that a Python application or edge device is still running normally during setup or remote maintenance.

import RPi.GPIO as GPIOimport timeLED_PIN = 17GPIO.setmode(GPIO.BCM)GPIO.setup(LED_PIN, GPIO.OUT)try: while True: GPIO.output(LED_PIN, GPIO.HIGH) time.sleep(0.25) GPIO.output(LED_PIN, GPIO.LOW) time.sleep(0.75)finally: GPIO.cleanup()

4. Threshold Alarm Output

In sensor projects, a blue LED can act as a simple threshold indicator that turns on when a reading crosses a defined limit.

const int ledPin = 9;const int sensorPin = A0;const int threshold = 600;void setup() { pinMode(ledPin, OUTPUT); Serial.begin(115200);}void loop() { int sensorValue = analogRead(sensorPin); Serial.println(sensorValue); if (sensorValue > threshold) { digitalWrite(ledPin, HIGH); } else { digitalWrite(ledPin, LOW); } delay(100);}

5. Multi-Step Sequencer Practice

This simple chaser pattern is useful for helping students understand arrays, loops, and timed digital outputs in introductory programming classes.

const int leds[] = {2, 3, 4, 5};const int ledCount = 4;void setup() { for (int i = 0; i < ledCount; i++) { pinMode(leds[i], OUTPUT); }}void loop() { for (int i = 0; i < ledCount; i++) { digitalWrite(leds[i], HIGH); delay(120); digitalWrite(leds[i], LOW); }}

6. Logic-Level Verification LED

When debugging a custom PCB or breadboard signal line, this example gives a quick visual indication of whether an input pin is reading HIGH or LOW.

const int inputPin = 7;const int ledPin = 13;void setup() { pinMode(inputPin, INPUT_PULLUP); pinMode(ledPin, OUTPUT);}void loop() { int state = digitalRead(inputPin); digitalWrite(ledPin, state == LOW ? HIGH : LOW);}

Packing List

• 20 Blue 5mm LED Light Diode

FAQ

Q: What is this product mainly used for?
A: It is mainly used for visual indication, simple lighting effects, STEM lessons, and breadboard-based electronics experiments.

Q: Do I need a resistor with each LED?
A: Yes. A current-limiting resistor should be added in series with every LED to prevent overcurrent damage.

Q: Can I use these LEDs directly with Arduino or ESP32 pins?
A: Yes, as long as you wire them correctly and include an appropriate resistor based on the board voltage and desired brightness.

Q: How do I identify the positive and negative leads?
A: The longer lead is usually the anode (+), while the shorter lead and the flat edge on the body indicate the cathode (-).

Q: Are these LEDs solderless-breadboard friendly?
A: Yes. Their through-hole lead format is suitable for standard solderless breadboards and perfboard-style prototypes.

Q: Can they be used for PWM dimming effects?
A: Yes. When connected to a PWM-capable output pin through a resistor, they can be dimmed or faded in software.

Q: Are these high-power LEDs for illumination projects?
A: No. They are standard indicator-class LEDs intended for signaling, display effects, and light educational use rather than high-power room lighting.

Q: What should I check if the LED does not light up?
A: Verify polarity, resistor value, wiring continuity, GPIO output logic, and supply voltage first. Reversed polarity is one of the most common setup errors.