How to build a Robot with LEGO Mindstorms EV3

Before diving into construction, it’s crucial to understand what LEGO Mindstorms EV3 is and why it’s such an effective robotics platform. Launched in 2013 as the third generation of the Mindstorms series, the EV3 system is designed to introduce users of all ages to the principles of robotics, engineering, and computer programming.

The core components of the EV3 system include:

• The EV3 Intelligent Brick: This is the brain of your robot. It’s a compact, Linux-based computer that controls motors, reads sensor data, and executes programs. It features a monochrome display, built-in speaker, buttons for navigation, USB ports for connectivity, and microSD card slot for expandable memory. Crucially, it has four input ports for sensors and four output ports for motors.
• EV3 Motors: The kit typically includes large interactive servo motors and a medium servo motor. These allow your robot to move, grasp, or manipulate objects. They are equipped with rotation sensors, enabling precise control over movement.
• EV3 Sensors: These are the robot’s “senses.” Common sensors include:
  • Color Sensor: Detects colors and light intensity. Essential for line-following or object identification.
  • Touch Sensor: A simple button that detects physical contact. Useful for collision detection or activating actions.
  • Infrared Sensor: Acts as a proximity sensor, detecting objects and also communicating with the EV3 Remote Infrared Beacon.
  • Ultrasonic Sensor: Measures distance to objects using sound waves, similar to how bats navigate. Crucial for obstacle avoidance.
• LEGO Technic Building Elements: A vast array of beams, axles, connectors, gears, and wheels are included, providing the mechanical structure for your robot.

The beauty of EV3 lies in its modularity. The Technic elements allow for countless mechanical designs, while the EV3 Brick and its accompanying software offer a powerful yet user-friendly programming environment.

To practically demonstrate building a robot, we will focus on constructing a fundamental mobile robot base, similar to the “Robot Educator” model often used in EV3 starter guides. This design teaches core principles of chassis construction, motor integration, and wheel mechanics.

1. Preparation and Planning

• Inventory Check: Ensure all required LEGO Technic pieces, the EV3 Brick, motors, and selected sensors are accounted for. Refer to the EV3 kit instructions if building a specific model.
• Design Concept: For a basic mobile robot, the design goal is a stable platform capable of movement (driving forward, backward, turning) and potential future expansion with sensors or manipulators. A differential two-wheel drive with a caster wheel for balance is a common and effective starting point.
• Workspace: Clear a clean, well-lit area.

2. Building the Chassis

The chassis is the structural backbone.

• Central Beam/Frame: Begin by assembling a robust base using long Technic beams (e.g., 15-hole or 13-hole beams). This will support the EV3 Brick and motors. A typical setup involves two parallel beams with perpendicular connectors to form a rigid rectangle.
• EV3 Brick Integration: The EV3 Brick has specific mounting points. Secure it firmly to the chassis using Technic pins. Ensure easy access to its ports and buttons. The brick usually sits elevated to allow space for motors and wiring underneath.

3. Attaching the Drive Motors

• Placement: The two large interactive servo motors are the primary drivers. Mount them symmetrically on either side of the chassis, ensuring their output axles face outward. Their mounting points are designed to integrate seamlessly with Technic beams.
• Alignment: Crucially, ensure the motors are parallel to each other and positioned so their rotation can directly drive wheels without obstruction. Secure them tightly to prevent wobble.

4. Wheel Assembly and Attachment

• Wheels and Tires: Select appropriate wheels and tires for traction. The EV3 Education kit often includes durable tractor-style wheels.
• Axle Integration: Attach axles to the output points of the large motors. These axles will pass through the center of the wheels. Secure the wheels to the axles with Technic bushings or cross axles to prevent them from slipping off.
• Caster Wheel/Skid: For a two-wheel drive robot, a third point of contact is needed for stability. This can be a simple Technic skid or, more effectively, a free-rotating caster wheel mounted at the front or back of the chassis. This allows for smooth turning without dragging.

5. Incorporating Sensors (Example: Color Sensor)

• Strategic Placement: If adding a Color Sensor for line following, mount it on the front or underside of the chassis, facing the ground. It needs to be close enough to the surface to accurately detect colors but not so close that it drags. Use appropriate Technic beams to create a stable mount that positions the sensor correctly.
• Secure Attachment: Ensure the sensor is affixed firmly and doesn’t wobble, as this can affect readings.

6. Wiring

• Motor Connections: Connect the large servo motors to the output ports of the EV3 Brick (e.g., Ports B and C). The ports are labeled. Use the provided EV3 cables, ensuring they are long enough to reach without strain or becoming entangled.
• Sensor Connections: Connect the Color Sensor to an input port of the EV3 Brick (e.g., Port 3).
• Cable Management: Tidy up the cables using Technic clips or by routing them along beams. This improves aesthetics and prevents snagging.

With the hardware assembled, the next critical step is to bring your robot to life through programming. The LEGO Mindstorms EV3 Software (available for desktop and as a mobile app) uses a graphical, drag-and-drop programming environment based on LabVIEW, making it accessible even for beginners.

1. Software Installation and Connection

• Install EV3 Software: Download and install the LEGO MINDSTORMS EV3 Software from the official LEGO Education website or relevant app stores.
• Connect Robot: Connect the EV3 Brick to your computer via USB cable. Alternatively, you can connect via Bluetooth or Wi-Fi (if supported by your EV3 Brick and a Wi-Fi dongle is present).

2. Creating Your First Program (Driving Forward)

• New Project: Open the EV3 Software and create a new project.
• Programming Canvas: You’ll see a white canvas where you drag and drop programming blocks. Programs flow from left to right.
• Start Block: Every program begins with a “Start” block.
• Move Steering Block: From the “Action” palette (green blocks), drag a “Move Steering” block onto the canvas, connecting it to the Start block.
• Configure Move Steering:
  • Port Selection: Ensure the ports correspond to your drive motors (e.g., B and C).
  • Steering: Set to 0 for straight movement.
  • Power: Set a positive value (e.g., 50) for forward motion.
  • Mode: Choose “On for Rotations.”
  • Rotations: Specify how many rotations the wheels should make (e.g., 3 rotations).
• Stop Moving Block: After the “Move Steering” block, drag a “Stop Moving” block to halt the motors.
• Download and Run:
  • Download: Click the “Download” button (usually a downward arrow icon) to transfer the program to your EV3 Brick.
  • Run: On the EV3 Brick itself, navigate to the program and select “Run.” Your robot should drive forward.

3. Basic Control: Turning and Reversing

• Turning: To make your robot turn, modify the “Steering” parameter in the “Move Steering” block. Positive values (e.g., 50) will turn one way, negative values (e.g., -50) will turn the other. Experiment with values to understand their effect.
• Reversing: For backward motion, set the “Power” parameter in the “Move Steering” block to a negative value (e.g., -50).

4. Incorporating Sensor Feedback (Line Following Example)

Let’s use the Color Sensor to create a simple line-following robot.

• Principle: The robot will drive forward. If the Color Sensor detects the line (e.g., black), it will correct its steering to stay on the line. If it detects off-line (e.g., white), it will steer back. This is achieved using a “Loop” and “Switch” block.
• Program Structure:
  • Start Block
  • Loop Block: Drag a “Loop” block onto the canvas. Set it to run “Unlimited.” This will make the robot continuously check the sensor.
  • Switch Block (Color Sensor Mode): Inside the loop, drag a “Switch” block. Set its mode to “Color Sensor” and then “Compare” -> “Reflected Light Intensity” (or “Color”).
  • Threshold Value/Color: Define a threshold (e.g., 50% reflected light intensity) to differentiate between black and white. Or, if using “Color” mode, specify “Black” and “White.”
  • Inside the Switch:
    • True Branch (e.g., Detecting White/Off-line): Drag a “Move Steering” block. Set power (e.g., 30) and a steering value that turns the robot back towards the line (e.g., -30).
    • False Branch (e.g., Detecting Black/On-line): Drag another “Move Steering” block. Set power (e.g., 30) and a steering value that keeps the robot on the line or gently corrects (e.g., 5).
  • Download and Test: Place the robot on a black line on a white surface and observe its behavior. Fine-tune power and steering values for smoother line following.

Building a basic mobile robot and programming it to follow a line is just the beginning. The EV3 platform allows for significant expansion and complexity:

• Advanced Movement: Implement PID (Proportional-Integral-Derivative) control for precise line following, obstacle avoidance, or reaching specific targets.
• Manipulators: Add a medium servo motor to build an arm, gripper, or other mechanism for interacting with objects.
• Multiple Sensors: Combine the Ultrasonic Sensor for obstacle avoidance with the Color Sensor for navigations. Use the Infrared Sensor for remote-control capabilities.
• Data Logging: The EV3 Brick can log sensor data, which can be analyzed to understand robot performance and debug programs.
• My Blocks: Create custom “My Blocks” to encapsulate frequently used code sequences, making programs cleaner and more modular.
• Communication: Program two EV3 robots to communicate via Bluetooth, enabling cooperative tasks.
• Beyond Graphical Programming: For more advanced users, the EV3 Brick supports alternative programming languages such as MicroPython (via EV3DEV) or RobotC, offering greater flexibility and control.

Building a robot with LEGO Mindstorms EV3 is an incredibly rewarding experience. It seamlessly blends mechanical design with logical programming, providing a hands-on introduction to the core disciplines of robotics. From the initial thrill of seeing your creation move for the first time to the challenge of programming it to perform complex tasks, EV3 fosters problem-solving skills, computational thinking, and creative engineering. It proves that within a box of versatile plastic bricks and an intelligent core, the potential for innovation is limited only by imagination. Whether you aim to compete in robotics challenges, inspire young learners, or simply indulge a passion for technology, the EV3 system provides a comprehensive and engaging pathway into the exciting world of robotics.