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Human Following Robot Using Arduino and Ultrasonic Sensor

Submitted by Gourav Tak on

Working of Human Following Robot Using Arduino

In recent years, robotics has witnessed significant advancements, enabling the creation of intelligent machines that can interact with the environment. One exciting application of robotics is the development of human-following robots. These robots can track and follow a person autonomously, making them useful in various scenarios like assistance in crowded areas, navigation support, or even as companions. In this article, we will explore in detail how to build a human following robot using Arduino and three ultrasonic sensors, complete with circuit diagrams and working code. Also, check all the Arduino-based Robotics projects by following the link.

The working of a human following robot using Arduino code and three ultrasonic sensors is an interesting project. What makes this project particularly interesting is the use of not just one, but three ultrasonic sensors. This adds a new dimension to the experience, as we typically see humans following a robot built with one ultrasonic, two IR, and one servo motor.  This servo motor has no role in the operation and also adds unnecessary complications. So I removed this servo and the IR sensors and used 3 ultrasonic sensors. With ultrasonic sensors, you can measure distance and use that information to navigate and follow a human target. Here’s a general outline of the steps involved in creating such a robot.

 

Table of Contents

 

Components Needed for Human Following Robot Using Arduino

  • Arduino UNO board ×1

  • Ultrasonic sensor ×3

  • L298N motor driver ×1

  • Robot chassis

  • BO motors ×2

  • Wheels ×2

  • Li-ion battery 3.7V ×2

  • Battery holder ×1

  • Breadboard

  • Ultrasonic sensor holder ×3

  • Switch and jumper wires

Human Following Robot Using Arduino Circuit Diagram

Here is the schematic diagram of a Human-following robot circuit.

Arduino Human Following Robot Circuit Diagram

This design incorporates three ultrasonic sensors, allowing distance measurements in three directions front, right, and left. These sensors are connected to the Arduino board through their respective digital pins. Additionally, the circuit includes two DC motors for movement, which are connected to an L298N motor driver module. The motor driver module is, in turn, connected to the Arduino board using its corresponding digital pins. To power the entire setup, two 3.7V li-ion cells are employed, which are connected to the motor driver module via a switch.

Overall, this circuit diagram showcases the essential components and connections necessary for the Human-following robot to operate effectively.

arduino human following robot circuit

Circuit Connection:

Arduino and HC-SR04 Ultrasonic Sensor Module:

HC-SR04 Ultrasonic sensor Module

  • Connect the VCC pin of each ultrasonic sensor to the 5V pin on the Arduino board.

  • Connect the GND pin of each ultrasonic sensor to the GND pin on the Arduino board.

  • Connect the trigger pin (TRIG) of each ultrasonic sensor to separate digital pins (2,4, and 6) on the Arduino board.

  • Connect the echo pin (ECHO) of each ultrasonic to separate digital pins (3,5, and 7) on the Arduino board.

Arduino and Motor Driver Module:

  • Connect the digital output pins of the Arduino (digital pins 8, 9, 10, and 11) to the appropriate input pins (IN1, IN2, IN3, and IN4) on the motor driver module.

  • Connect the ENA and ENB pins of the motor driver module to the onboard High state pin with the help of a female header.

  • Connect the OUT1, OUT2, OUT3, and OUT4 pins of the motor driver module to the appropriate terminals of the motors.

  • Connect the VCC (+5V) and GND pins of the motor driver module to the appropriate power (Vin) and ground (GND) connections on the Arduino.

Power Supply:

  • Connect the positive terminal of the power supply to the +12V input of the motor driver module.

  • Connect the negative terminal of the power supply to the GND pin of the motor driver module.

  • Connect the GND pin of the Arduino to the GND pin of the motor driver module.

Human Following Robot Using Arduino Code

Here is a simple 3 Ultrasonic sensor-based Human following robot using Arduino Uno code that you can use for your project.

Ultrsonic Sensors on Robot

This code reads the distances from three ultrasonic sensors (‘frontDistance’, ‘leftDistance’, and ‘rightDistance’). It then compares these distances to determine the sensor with the smallest distance. If the smallest distance is below the threshold, it moves the car accordingly using the appropriate motor control function (‘moveForward()’, ‘turnLeft()’, ‘turnRight()’). If none of the distances are below the threshold, it stops the motor using ‘stop()’.

In this section, we define the pin connections for the ultrasonic sensors and motor control. The S1Trig, S2Trig, and S3Trig, variables represent the trigger pins of the three ultrasonic sensors, while S1Echo, S2Echo, and S3Echo, represent their respective echo pins.

The LEFT_MOTOR_PIN1, LEFT_MOTOR_PIN2, RIGHT_MOTOR_PIN1, and RIGHT_MOTOR_PIN2 variables define the pins for controlling the motors.

The MAX_DISTANCE and MIN_DISTANCE_BACK variables set the thresholds for obstacle detection.

// Ultrasonic sensor pins
#define S1Trig 2
#define S2Trig 4
#define S3Trig 6
#define S1Echo 3
#define S2Echo 5
#define S3Echo 7
// Motor control pins
#define LEFT_MOTOR_PIN1 8
#define LEFT_MOTOR_PIN2 9
#define RIGHT_MOTOR_PIN1 10
#define RIGHT_MOTOR_PIN2 11
// Distance thresholds for obstacle detection
#define MAX_DISTANCE 40
#define MIN_DISTANCE_BACK 5

Make sure to adjust the values of ‘MIN_DISTANCE_BACK’ and ‘MAX_DISTANCE’ according to your specific requirements and the characteristics of your robot.

The suitable values for ‘MIN_DISTANCE_BACK’ and ‘MAX_DISTANCE’ depend on the specific requirements and characteristics of your human-following robot. You will need to consider factors such as the speed of your robot, the response time of the sensors, and the desired safety margin

Here are some general guidelines to help you choose suitable values.

‘MIN_DISTANCE_BACK’ This value represents the distance at which the car should come to a stop when an obstacle or hand is detected directly in front. It should be set to a distance that allows the car to back safely without colliding with the obstacle or hand. A typical value could be around 5-10 cm.

‘MAX_DISTANCE’ This value represents the maximum distance at which the car considers the path ahead to be clear and can continue moving forward. It should be set to a distance that provides enough room for the car to move without colliding with any obstacles or hands. If your hand and obstacles are going out of this range, the robot should be stop. A typical value could be around 30-50 cm.

These values are just suggestions, and you may need to adjust them based on the specific characteristics of your robot and the environment in which it operates.

These lines set the motor speed limits. ‘MAX_SPEED’ denotes the upper limit for motor speed, while ‘MIN_SPEED’ is a lower value used for a slight left bias. The speed values are typically within the range of 0 to 255, and can be adjusted to suit our specific requirements.

// Maximum and minimum motor speeds
#define MAX_SPEED 150
#define MIN_SPEED 75

The ‘setup()’ function is called once at the start of the program. In the setup() function, we set the motor control pins (LEFT_MOTOR_PIN1, LEFT_MOTOR_PIN2, RIGHT_MOTOR_PIN1, RIGHT_MOTOR_PIN2) as output pins using ‘pinMode()’ . We also set the trigger pins (S1Trig, S2Trig, S3Trig) of the ultrasonic sensors as output pins and the echo pins (S1Echo, S2Echo, S3Echo) as input pins. Lastly, we initialize the serial communication at a baud rate of 9600 for debugging purposes.

void setup() {
  // Set motor control pins as outputs
  pinMode(LEFT_MOTOR_PIN1, OUTPUT);
  pinMode(LEFT_MOTOR_PIN2, OUTPUT);
  pinMode(RIGHT_MOTOR_PIN1, OUTPUT);
  pinMode(RIGHT_MOTOR_PIN2, OUTPUT);
  //Set the Trig pins as output pins
  pinMode(S1Trig, OUTPUT);
  pinMode(S2Trig, OUTPUT);
  pinMode(S3Trig, OUTPUT);
  //Set the Echo pins as input pins
  pinMode(S1Echo, INPUT);
  pinMode(S2Echo, INPUT);
  pinMode(S3Echo, INPUT);
  // Initialize the serial communication for debugging
  Serial.begin(9600);
}

This block of code consists of three functions (‘sensorOne()’, ‘sensorTwo()’, ‘sensorThree()’) responsible for measuring the distance using ultrasonic sensors.

The ‘sensorOne()’ function measures the distance using the first ultrasonic sensor. It's important to note that the conversion of the pulse duration to distance is based on the assumption that the speed of sound is approximately 343 meters per second. Dividing by 29 and halving the result provides an approximate conversion from microseconds to centimeters.

The ‘sensorTwo()’ and ‘sensorThree()’ functions work similarly, but for the second and third ultrasonic sensors, respectively.

// Function to measure the distance using an ultrasonic sensor
int sensorOne() {
  //pulse output
  digitalWrite(S1Trig, LOW);
  delayMicroseconds(2);
  digitalWrite(S1Trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(S1Trig, LOW);
  long t = pulseIn(S1Echo, HIGH);//Get the pulse
  int cm = t / 29 / 2; //Convert time to the distance
  return cm; // Return the values from the sensor
}
//Get the sensor values
int sensorTwo() {
  //pulse output
  digitalWrite(S2Trig, LOW);
  delayMicroseconds(2);
  digitalWrite(S2Trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(S2Trig, LOW);
  long t = pulseIn(S2Echo, HIGH);//Get the pulse
  int cm = t / 29 / 2; //Convert time to the distance
  return cm; // Return the values from the sensor
}
//Get the sensor values
int sensorThree() {
  //pulse output
  digitalWrite(S3Trig, LOW);
  delayMicroseconds(2);
  digitalWrite(S3Trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(S3Trig, LOW);
  long t = pulseIn(S3Echo, HIGH);//Get the pulse
  int cm = t / 29 / 2; //Convert time to the distance
  return cm; // Return the values from the sensor
}

In this section, the ‘loop()’ function begins by calling the ‘sensorOne()’, ‘sensorTwo()’, and ‘sensorThree()’ functions to measure the distances from the ultrasonic sensors. The distances are then stored in the variables ‘frontDistance’, ‘leftDistance’, and ‘rightDistance’.

Next, the code utilizes the ‘Serial’ object to print the distance values to the serial monitor for debugging and monitoring purposes.

void loop() {
  int frontDistance = sensorOne();
  int leftDistance = sensorTwo();
  int rightDistance = sensorThree();
  Serial.print("Front: ");
  Serial.print(frontDistance);
  Serial.print(" cm, Left: ");
  Serial.print(leftDistance);
  Serial.print(" cm, Right: ");
  Serial.print(rightDistance);
  Serial.println(" cm");

In this section of code condition checks if the front distance is less than a threshold value ‘MIN_DISTANCE_BACK’ that indicates a very low distance. If this condition is true, it means that the front distance is very low, and the robot should move backward to avoid a collision. In this case, the ‘moveBackward()’ function is called.

if (frontDistance < MIN_DISTANCE_BACK) {
    moveBackward();
    Serial.println("backward");

If the previous condition is false, this condition is checked. if the front distance is less than the left distance, less than the right distance, and less than the ‘MAX_DISTANCE’ threshold. If this condition is true, it means that the front distance is the smallest among the three distances, and it is also below the maximum distance threshold. In this case, the ‘moveForward()’ function is called to make the car move forward.

else if (frontDistance < leftDistance && frontDistance < rightDistance && frontDistance < MAX_DISTANCE) {
    moveForward();
    Serial.println("forward");

If the previous condition is false, this condition is checked. It verifies if the left distance is less than the right distance and less than the ‘MAX_DISTANCE’ threshold. This condition indicates that the left distance is the smallest among the three distances, and it is also below the minimum distance threshold. Therefore, the ‘turnLeft()’ function is called to make the car turn left.

else if (leftDistance < rightDistance && leftDistance < MAX_DISTANCE) {
    turnLeft();
    Serial.println("left");

If neither of the previous conditions is met, this condition is checked. It ensures that the right distance is less than the ‘MAX_DISTANCE’ threshold. This condition suggests that the right distance is the smallest among the three distances, and it is below the minimum distance threshold. The ‘turnRight()’ function is called to make the car turn right.

else if (rightDistance < MAX_DISTANCE) {
    turnRight();
    Serial.println("right");

If none of the previous conditions are true, it means that none of the distances satisfy the conditions for movement. Therefore, the ‘stop()’ function is called to stop the car.

 else {
    stop();
    Serial.println("stop");

In summary, the code checks the distances from the three ultrasonic sensors and determines the direction in which the car should move based on the 3 ultrasonic sensors with the smallest distance.

 

Important aspects of this Arduino-powered human-following robot project include:

  • Three-sensor setup for 360-degree human identification
  • Distance measurement and decision-making in real-time
  • Navigation that operates automatically without human assistance
  • Avoiding collisions and maintaining a safe following distance

 

 

Technical Summary and GitHub Repository 

Using three HC-SR04 ultrasonic sensors and an L298N motor driver for precise directional control, this Arduino project shows off the robot's ability to track itself. For simple replication and modification, the full source code, circuit schematics, and assembly guidelines are accessible in our GitHub repository. To download the Arduino code, view comprehensive wiring schematics, and participate in the open-source robotics community, visit our GitHub page.

Code Schematics Download Icon

 

Frequently Asked Questions

⇥ How does an Arduino-powered human-following robot operate?
Three ultrasonic sensors are used by the Arduino-powered human following robot to determine a person's distance and presence. After processing this data, the Arduino manages motors to follow the identified individual while keeping a safe distance.

⇥ Which motor driver is ideal for an Arduino human-following robot?
The most widely used motor driver for Arduino human-following robots is the L298N. Additionally, some builders use the L293D motor driver shield, which connects to the Arduino Uno directly. Both can supply enough current for small robot applications and manage 2-4 DC motors.

⇥ Is it possible to create a human-following robot without soldering?
Yes, you can use motor driver shields that connect straight to an Arduino, breadboards, and jumper wires to construct a human-following robot. For novices and prototyping, this method is ideal.

⇥ What uses do human-following robots have in the real world?
Shopping cart robots in malls, luggage-carrying robots in airports, security patrol robots, elderly care assistance robots, educational demonstration robots, and companion robots that behave like pets are a few examples of applications.

 

Conclusion

This human following robot using Arduino project and three ultrasonic sensors is an exciting and rewarding project that combines programming, electronics, and mechanics. With Arduino’s versatility and the availability of affordable components, creating your own human-following robot is within reach.

Human-following robots have a wide range of applications in various fields, such as retail stores, malls, and hotels, to provide personalized assistance to customers. Human-following robots can be employed in security and surveillance systems to track and monitor individuals in public spaces. They can be used in Entertainment and events, elderly care, guided tours, research and development, education and research, and personal robotics.

They are just a few examples of the applications of human-following robots. As technology advances and robotics continues to evolve, we can expect even more diverse and innovative applications in the future.

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Build a Simple Optocoupler Tester Circuit for Fault Detection

Submitted by Bharani Dharan R on

Optocouplers frequently fail without a sound in labs or during repairs. The package appears to be undamaged, but there may be no output from the LED source or the photosensitive output stage. Testing for failure with a multimeter is only partially effective, whereas a dedicated optocoupler testing circuit provides clear results in just seconds. For related tutorials and step-by-step build guides, explore Circuit Digest's Electronic Circuits hub.

Table of Contents

What is an Optocoupler Tester Circuit?

An optocoupler tester is a small device that helps verify whether an optocoupler is functioning properly or has failed. In labs and repair work, optocouplers often fail without clear signs. They may look fine from the outside, but the internal LED or photo part may not function properly. Guessing in such cases wastes time and can damage the main circuit. This tester dispels that doubt by checking whether the internal LED turns on and whether the output side responds to light. The circuit stays simple, runs on a 3.7 V lithium-ion battery, and can be built on a dot board without using any measuring tools. It does not aim to test detailed performance, but it works well for quick and reliable checks at the workbench. More details about the Optocoupler and its applications are provided on the Optocoupler tutorial page. Also, you can explore more applications and other electronic circuits on our resources page.

What does an Optocoupler Tester Check?

∗ The IR LED at the input side is conducting and producing light (IR emission)
∗ The Photodetector at the output side is triggering due to the IR light that the IR LED is producing
∗ The testing circuit is able to conduct both a 4-pin DIP and a 6-pin DIP with no wiring changes being required.

Components Required to Build the Optocoupler Tester

The image below shows the list of components used to build the Optocoupler Testing circuit.

Components required to build the DIY optocoupler tester circuit on a dot board

The circuit uses only commonly available components. It avoids special or complex parts, making it easy to build and understand.   The table shows every component used in this DIY optocoupler tester build.

ComponentQuantityFunction in Circuit
Optocoupler1To use it as a test component
Red LED1Indicates power to the optocoupler input
Green LED1Indicates the output response of the optocoupler
Push Button1Turns the tester ON during checking
Li-ion Battery1Supplies power to the circuit
470 OhmResistor (R1)1Limits the current to the optocoupler input LED
470 Ohm Resistor (R2)1Limits the current to the output indicator LED
IC Base (4-pin)1Holds 4-pin optocouplers for testing
IC Base (6-pin)1Holds 6-pin optocouplers for testing
Dot Board1Mounts and connects all components

The circuit uses IC bases instead of soldering optocouplers directly. This avoids heat damage and allows the same tester to be used repeatedly with different optocouplers.

Optocoupler Tester Circuit Diagram and Schematic

Optocoupler tester circuit diagram showing input LED path with R1 and red LED, output phototransistor path with R2 and green LED, push button, and 3.7V Li-ion battery on a dot board

How to Read the Schematic

The optocoupler tester schematic consists of two main sections: the input and output parts of the optocoupler. On the input side, the Li-ion battery supplies power via a resistor, and the push button determines when the power is delivered. When the button is pressed, current flows through the optocoupler's internal LED, causing the red LED to light up, indicating that the input side is receiving power and is functioning.

On the output side, the light from the internal LED reaches the light-sensitive component inside the optocoupler. This allows current to flow through the green LED, turning it on and showing that the output side is working correctly. Both the input and output sides are connected to the same ground. This optocoupler tester circuit is constructed on a dot board with IC bases. The optocoupler tester circuit diagram shows that this configuration enables testing of both 4-pin and 6-pin optocouplers without changes to the wiring.

How the Optocoupler Tester Works 

Understanding the optocoupler tester working principle requires only three concepts: IR LED emission, phototransistor activation, and current-limited indicator LEDs. The optocoupler tester works based on optical isolation. When you press the button, power flows to the input LED inside the optocoupler. If everything is working properly on the input side, the internal LED lights up and the red LED turns on to indicate that current is flowing correctly.

The light from the input LED then reaches the light-sensitive part on the output side of the optocoupler. This allows current to flow through the green LED, causing it to glow and indicating that the output side is working correctly. This optocoupler test helps you quickly identify issues. If only the red LED turns on, it means there's a problem with the output side or the light isn't transferring properly. If neither LED turns on, the input LED may be faulty, or the optocoupler may not be connected correctly.

Red LEDGreen LEDTest ResultAction
ONONPASS — Good optocouplerSafe to use in a circuit
ONOFFFAIL — Output stage deadReplace the optocoupler; the phototransistor is damaged
OFFOFFFAIL — Input LED open or wrong insertionCheck pin orientation; replace if correct
OFFONSUSPECT — Output shorted or wiring errorCheck tester wiring; the output transistor may be shorted CE

Practical Working Demonstration

In real use, insert the optocoupler into the correct IC socket and verify that it is positioned properly. Then press the button to activate the circuit. A working optocoupler will light up the red LED immediately, showing that the input side is active, followed by the green LED, which confirms that the output side is responding. If only the red LED lights up, the optocoupler is faulty and should not be used. If neither LED turns on, the device may be damaged or inserted incorrectly. This DIY optocoupler tester is especially useful when checking salvaged components or verifying a batch of parts. To better understand why optocouplers are used for electrical safety and isolation, you can read more about galvanic isolation. 

Alternate Methods to Test the Optocouplers

Different methods are used to test an optocoupler, depending on the tools available and the level of accuracy required. A multimeter can quickly check the internal LED, and simple testing circuits built on a breadboard can show how the input and output work. For more detailed testing, labs use advanced tools such as component testers and curve tracers. Here are the commonly used testing methods. 

1. Comparison Method

In this method, the optocoupler suspected of being faulty is removed from the circuit and tested with a multimeter. Then, the readings from the multimeter are compared with those from another optocoupler known to be working properly and of the same type. The test measures the forward and reverse resistance of the internal LED and the resistance between the transistor pins. If the measured values differ significantly from those of the good optocoupler, the tested optocoupler is likely damaged. This approach is straightforward and fast, but it only gives a general idea and does not guarantee that the device will work correctly in real situations.

2. Digital Multimeter Detection Method

This is the most widely searched approach. Here is a structured procedure for how to check an optocoupler with a multimeter:

A digital multimeter can be used to test both the input and output parts of a circuit separately. To start, check the input LED using the diode setting to make sure it conducts properly when forward-biased. Next, measure the output pins while the LED is on to see whether the transistor switches on or if there is a change in current or gain. If the readings change when the input is activated, the optocoupler is working correctly; if there is no change, it may be faulty. This method provides more detailed information than a simple resistance check, but the setup and results can be confusing for someone new to electronics and still need some interpretation.

3. Photoelectric Effect (Battery and Resistor) Method

This method directly tests the optocoupler's working principle by powering the input LED with a small battery and a current-limiting resistor, while monitoring the output pins with a multimeter. When the LED turns on, the light inside the device should activate the output transistor, causing the meter reading or pointer to change. If the reading changes or the pointer deflects, the optocoupler is working; if there is no change, the device is defective. Because it checks real input-to-output behaviour, this method is more reliable and practical than simple resistance measurements.

Comparison Between the Optocoupler Tester and Multimeter Method

Using a Multimeter

A multimeter is convenient because it is already available in most labs and does not require any extra hardware. It can check basic things like LED continuity and diode behaviour, which helps with a quick preliminary inspection. However, it only tests the input LED of the optocoupler and cannot verify the output side properly. This means the device may appear fine even when it is actually faulty. The process also involves manual probing and interpretation of readings, which can be slow and confusing for beginners. As a result, a multimeter provides only a rough estimate rather than a clear confirmation.

Using an Optocoupler Tester

An optocoupler tester circuit is designed specifically for testing optocouplers and checks both the input LED and the output transistor simultaneously. It directly shows whether the device is working or faulty using simple LED indicators, so no probing or analysis is required. The test is fast, easy, and reliable, making it suitable even for first-year students or beginners. The only disadvantage is that an extra circuit must be built or purchased, but once it's available, it provides a clear, accurate optocoupler test every time.

Optocoupler Tester vs. Multimeter Method

CriterionDedicated Optocoupler TesterDigital Multimeter
Tests input LED✔ Yes✔ Yes (diode mode)
Tests output phototransistor✔ Yes- simultaneouslyPartial -  requires extra setup
Result readabilityInstant LED pass/failNumerical values need interpretation
Test speed<2 seconds per device2–5 minutes for the full 3-step test
Additional hardware neededThe tester itself (~₹50 / $1 in parts)Multimeter already in the lab
Detects partial output degradationOnly gross failuresOnly gross failures (without scope)
Suitable for batch testing✔ Yes — very efficient✘ No — too slow

Advantages and Disadvantages of the Optocoupler Tester

AdvantagesDisadvantages
Checks optocouplers quickly without using any instrumentsDoes not show the output signal strength
Small size and runs on a batteryNot useful for very fast or special optocouplers
Works with both 4-pin and 6-pin optocouplersCannot clearly find weak or ageing optocouplers
LED lights make the result easy to seeOnly checks basic working conditions
Low cost and easy to build againNot meant for detailed testing

Troubleshooting Optocoupler Testing Issues

These are some troubleshooting methods for optocoupler testing issues

Problem ObservedPossible CauseSolution
The input LED is not glowing.Wrong pin connection or reversed polarityCheck the pinout and reconnect correctly
Input LED ON, but no output responseOutput transistor damagedReplace the optocoupler
No diode reading in the multimeter testInternal LED openReplace the optocoupler
Output always ON or always OFFWiring mistake or short circuitInspect and correct connections
The tester is not working or is showing unstable readingsLow battery or loose contactsReplace the battery and secure connections

Frequently Asked Questions About Optocoupler Testing

⇥ Can an optocoupler be tested using only a multimeter?

Yes, but only partially. A multimeter can check the internal LED using diode mode, but it cannot fully verify whether the output side is working. It provides a basic check, not a complete functional test.

⇥  Why is a dedicated optocoupler tester better than a multimeter?

An optocoupler tester checks both the input LED and the output transistor simultaneously. It provides a clear pass-or-fail result instantly, making testing faster, easier, and more reliable.

⇥ What is the simplest way for beginners to test an optocoupler?

Using a small optocoupler tester circuit with LEDs is the easiest method. It requires no calculations or measurements and shows the result visually.

⇥ Can an optocoupler look normal but still be faulty?

Yes. Physical damage is rarely visible. The internal LED or photo-transistor may fail even when the package looks perfect. That is why functional optocoupler testing is necessary.

⇥ Is a breadboard test circuit enough for learning purposes?

Yes. A simple breadboard-based optocoupler testing circuit is good for understanding how the device works. However, for regular lab or repair work, a dedicated tester is more efficient.

Conclusion

This optocoupler tester circuit gives a simple and reliable way to check whether 4-pin and 6-pin optocouplers are working. The LED indicators clearly indicate whether the input side receives power and whether the output side responds correctly. The small, battery-powered design makes it useful for quick checks during assembly, learning, or repair work. This optocoupler tester circuit diagram focuses on basic working checks rather than detailed electrical testing. It helps detect faulty optocouplers early, saving time and preventing mistakes during installation. The tester delivers consistent, practical results without unnecessary complexity. Find practical, real-world Electronics Projects and step-by-step tutorials at this resource hub

Projects Using Optocoupler Isolation

These projects demonstrate how optocouplers provide safe electrical isolation between high-voltage AC circuits and low-voltage electronics. They are used for applications like zero-cross detection and AC power control in embedded systems.

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Adding a Wi-Fi Camera to the LiteWing ESP32 Drone for Hobby Flights.

Submitted by Vishnu S on

We love tinkering with our LiteWing ESP32 drone, and this time we gave it a simple but exciting upgrade, a WiFi camera module! With this addition, the drone can now stream live video while flying, perfect for hobby flights, aerial experimentation, or just having fun seeing the world from above.

On the technical side, the setup remains straightforward. The camera module uses its own built-in WiFi to stream video directly to a nearby device, while the LiteWing supplies stable power from its onboard battery during flight. Because the camera operates independently from the flight controller, the drone continues to fly normally while continuously transmitting live video.This build gives you real-time aerial footage without spending on a commercial drone with a camera.

Beyond its core functionality as a flying drone with a camera, the ESP32-based system can be further enhanced by integrating a Bluetooth speaker for wireless audio output. This upgrade enables the drone not only to capture live aerial footage but also to broadcast real-time voice announcements, making it suitable for surveillance, public addressing, or smart monitoring applications. For detailed guidance, refer to the project titled “How to Add a Loudspeaker to LiteWing ESP32 Drone for Wireless Audio Announcement”.

LiteWing ESP32 Drone with Camera – Overview

ParameterDetail
Drone platformLiteWing ESP32 Drone
Camera typeDual WiFi camera module (toy-drone type)
Camera operating voltage3.3 V (onboard regulator accepts up to 5 V)
Power source1S LiPo battery (high C-rating recommended)
Data connection to flight controllerNone required
Camera WiFi password (default)12345678
Viewing appWebCam / IP Camera (Android & iOS)
Control appLiteWing drone control app (separate WiFi)
Key troubleshooting fixUse higher C-rating battery to reduce video jitter

Components Required for the LiteWing ESP32 Drone Camera Build

This project requires only a compact flight platform with essential components for smooth aerial operation. The LiteWing ESP32 drone serves as the core system, paired with a dual WiFi camera module for real-time video streaming. A lightweight Li-Po battery powers the setup, while basic wiring and mounting accessories ensure secure assembly. Together, these components create a streamlined and efficient mini drone with camera designed for stable flight and live monitoring.

  1. LiteWing ESP32 Drone
  2. WiFi - Camera Module
  3. 1S LiPo Battery(Need High C Rating)

How the LiteWing ESP32 Drone  with Camera Works

This drone system works through two separate pathways that don't interfere with each other. The LiteWing ESP32-Drone connects to your phone's Drone Control Application through its own Wi-Fi network, letting you fly the drone smoothly.

LiteWing ESP32 drone WiFi camera workflow diagram showing two independent WiFi channels for flight control and live video streaming

By splitting control and video into two separate channels, you get lag-free flying even while watching live video Feed. Use a high-C-rating battery to ensure the camera receives stable and sufficient power during flight. It’s like having two walkie-talkie frequencies, one for giving directions and one for receiving updates, so neither signal gets jammed or slowed down.

Workflow Summary:

» Channel 1 - Flight control - The LiteWing ESP32 has an in-built WiFi Access Point (AP). Your phone will connect to the LiteWing's drone control application to control throttle, roll, pitch, and yaw.

» Channel 2 - Live video - The WiFi camera module establishes its own Access Point (AP) and is completely separate from the LiteWing. You will connect to this Access Point (AP) through your phone using the WebCam application.

» No interference from either system - Because each system operates on its own WiFi Network, neither system's signal will slow down or jam the other system's signal; therefore, you will be able to fly with zero lag while simultaneously receiving smooth real-time video.

WiFi Camera Module Details

We used a dual-camera module from a toy drone. The module features two cameras, allowing you to switch between them easily, which is great for capturing different angles during flight. The cameras operate at 3.3V, but the module includes a built-in voltage regulator that can handle up to 5V, making it easy to power directly from the drone’s battery without additional circuitry.

Dual WiFi camera module used on LiteWing ESP32 mini drone with camera for live aerial video streaming

Because the camera has its own WiFi connection, it can stream live video independently of the drone’s flight controller. This means you get continuous video even while the LiteWing ESP32 handles stable flight. Its compact design also makes it simple to mount on the drone without affecting weight or balance, making it a perfect fit for hobby video flights and experimentation.

 WiFi Camera Module vs ESP32-CAM

FeatureDedicated WiFi Camera ModuleESP32-CAM
Power requirementUp to 5 V via built-in regulatorStable 5 V, higher current draw
Integration complexityPower only (VCC + GND)Requires firmware configuration
Stability on 1S LiPoGood with a high C-rating batteryProne to resets under motor load
Onboard image processingNoYes
Best suited forSimple live streaming buildsProjects requiring custom logic
Weight impactMinimal – compact moduleSlightly heavier with antenna

Hardware Connections

For this project, the hardware setup is very simple. We used the LiteWing ESP32 drone as the flying platform and mounted a dual WiFi camera module taken from a toy drone onto the frame. The camera does not require any data connection to the flight controller. We only connected the VCC of the camera module to the VBUS line and the GND to the common ground of the drone.

Hardware connection diagram for LiteWing ESP32 drone camera module — VCC to VBUS and GND to common ground

The system runs on a 1S LiPo battery, which powers both the drone and the camera. Proper mounting and secure wiring are important to keep the setup balanced during flight, and using a higher C-rating battery helps maintain stable performance.

How to Connect a Drone Camera to a Mobile Phone: Step-by-Step

Once the camera is powered on, it automatically creates its own WiFi access point. To view the live feed:

Step 1 ⇒ Connect your mobile phone to the camera’s WiFi network using the default password 12345678.

Mobile phone connecting to LiteWing drone camera WiFi access point with default password 12345678

Step 2 ⇒ Download and open a compatible Web Cam app (many camera modules support apps like “IP Camera” or “WebCam” on Android/iOS).

Step 3 ⇒ In the app, click on the start button to start getting the live feed

Step 4 ⇒You should now see the live video feed streaming directly from the drone.

This setup keeps the camera completely independent of the LiteWing ESP32 flight controller, allowing smooth drone operation while continuously viewing live video. The key advantage of a dual-channel architecture for a drone with camera at hobby scale.

Working Demo

When the system is powered on, the LiteWing ESP32 manages the drone’s flight, which you can control through the LiteWing mobile app. At the same time, the WiFi camera powers up independently and creates its own network. To view the live video feed, you connect to the camera’s network using its dedicated viewing app. This setup lets the drone fly smoothly while streaming live video at the same time, showing how both systems work together.

Troubleshooting the LiteWing Drone Camera Setup

In some cases, noise or jitter may appear in the live video feed when the drone motors start operating. This issue can occur even if the camera footage looks clear while the drone is stationary. The disturbance is mainly caused by PWM switching noise from the motor control MOSFETs, which can introduce power fluctuations affecting the WiFi camera module.

To avoid this problem, it is recommended to use a battery with a higher C-rating, as it can supply stable current during rapid motor load changes. Using a higher C-rating battery significantly reduces power-related interference, resulting in smooth and jitter-free video streaming during flight.

Frequently Asked Questions

⇥ Can an ESP32-CAM be used instead of the WiFi camera module on the drone?

Yes, an ESP32-CAM can be used on the drone, but it requires more careful design compared to a standalone WiFi camera module. The ESP32-CAM needs a stable 5V supply and draws higher current, which can be difficult to maintain on a 1S LiPo battery when the motors are running, leading to possible resets, frame drops, or WiFi disconnections. It also adds extra processing load and power consumption to the system, increasing overall complexity. For simple live video streaming, a dedicated WiFi camera module is easier and more reliable, while the ESP32-CAM is better suited for projects that require onboard image processing or custom control logic.

⇥  Why does the drone’s video feed show noise or jitter during flight?

The video jitter or noise usually happens due to a voltage drop when the motors draw high current during flight. If the battery cannot supply enough current consistently, the voltage fluctuates, which can affect the WiFi camera module and cause instability in the video feed. Using a battery with a higher C-rating helps maintain stable voltage under load, reducing video noise and ensuring smoother transmission.

⇥ How to connect the drone camera to a mobile phone?

To connect the drone camera to a mobile phone, first power on the drone so that the WiFi camera module turns on. Once powered, the camera automatically creates its own WiFi access point. Open the WiFi settings on your mobile phone and connect to the camera’s WiFi network using the default password 12345678. After connecting, open the Web Cam app (available on the Play Store), and the live video feed will be displayed on your phone in real time.

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