LED control 3.0

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this lesson, you will use Arduino together with two Ultrasonic Sensor Modules and a row of LEDs to create an automatic directional light-flow effect.

When the left sensor detects an object, the LEDs light up in a forward flowing pattern. When the right sensor is triggered, the LEDs flow in the opposite direction.

Each sensor controls one direction of the animation, allowing the LEDs to respond dynamically based on which side an obstacle is detected.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	1kΩ resistor	Several	BUY
6	Ultrasonic Sensor Module	2	BUY
7	LED	Several	BUY

Wiring

Common Connections:

LED
- Connect the LEDs cathode to the negative power bus on the breadboard, and the LEDs anode to 1kΩ resistor then to 5 to 10 on the Arduino.
Ultrasonic Sensor Module Right
- Trig: Connect to 11 on the Arduino.
- Echo: Connect to 12 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
Ultrasonic Sensor Module Left
- Trig: Connect to 3 on the Arduino.
- Echo: Connect to 4 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 Minima) and the correct port before clicking the Upload button.

// ================= Ultrasonic pins =================
// Left ultrasonic sensor
const int trigLeft  = 3;
const int echoLeft  = 4;

// Right ultrasonic sensor
const int trigRight = 11;
const int echoRight = 12;

// ================= LED pins =================
int ledPins[] = {5, 6, 7, 8, 9, 10};
int ledCount = 6;

// ================= Distance levels (cm) =================
int farLimit  = 15;   // slow
int midLimit  = 10;   // medium
int nearLimit = 5;    // fast

// ================= LED speed =================
int slowDelay = 100;
int midDelay  = 60;
int fastDelay = 30;

void setup() {
  // Set ultrasonic pins
  pinMode(trigLeft, OUTPUT);
  pinMode(echoLeft, INPUT);
  pinMode(trigRight, OUTPUT);
  pinMode(echoRight, INPUT);

  // Set LED pins
  for (int i = 0; i < ledCount; i++) {
    pinMode(ledPins[i], OUTPUT);
  }

  Serial.begin(9600);
}

void loop() {
  // Read distance from both ultrasonic sensors
  float leftDistance  = readDistance(trigLeft, echoLeft);
  float rightDistance = readDistance(trigRight, echoRight);

  // Get LED speed based on distance
  int leftSpeed  = getSpeedByDistance(leftDistance);
  int rightSpeed = getSpeedByDistance(rightDistance);

  // Left sensor → LEDs flow left to right
  if (leftSpeed > 0) {
    flowForward(leftSpeed);
  }

  // Right sensor → LEDs flow right to left
  if (rightSpeed > 0) {
    flowBackward(rightSpeed);
  }

  delay(80); // short pause between measurements
}

// ================= Functions =================

// Convert distance to LED speed
int getSpeedByDistance(float d) {
  if (d <= 0) return -1;       // invalid reading
  if (d < nearLimit) return fastDelay;
  if (d < midLimit)  return midDelay;
  if (d < farLimit)  return slowDelay;
  return -1;                  // no trigger
}

// Measure distance using ultrasonic sensor
float readDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH, 25000);
  if (duration == 0) return -1; // no echo

  return duration / 58.0;       // convert to cm
}

// LEDs flow from left to right
void flowForward(int d) {
  for (int i = 0; i < ledCount; i++) {
    digitalWrite(ledPins[i], HIGH);
    delay(d);
    if (i > 0) {
      digitalWrite(ledPins[i - 1], LOW);
    }
  }
  digitalWrite(ledPins[ledCount - 1], LOW);
}

// LEDs flow from right to left
void flowBackward(int d) {
  for (int i = ledCount - 1; i >= 0; i--) {
    digitalWrite(ledPins[i], HIGH);
    delay(d);
    if (i < ledCount - 1) {
      digitalWrite(ledPins[i + 1], LOW);
    }
  }
  digitalWrite(ledPins[0], LOW);
}