How Brushless DC Motors Work and How to Control One with Arduino

Overview

This video explains what a brushless DC motor is, how it differs from a traditional DC motor, and why it is widely used for lifting applications such as drones, cooling fans, drills, and more. It covers the rotor and stator arrangement, three phase windings, and the advantages of brushless designs, including reduced wear and higher efficiency.

It also introduces how a BLDC motor is controlled with an electronic speed controller using pulse width modulation, and how an Arduino can be used to send control signals. The guide also points out the difference between in-runner and outrunner designs and explains common winding configurations such as the delta (DLRK) winding.

Introduction to Brushless DC Motors

The video starts with an overview of brushless DC motors (BLDCs) and their role in delivering mechanical energy from electrical input. It highlights typical applications including drones for lift, PC cooling fans, CD drives, and battery-powered drills. The key distinction from brushed DC motors is that BLDCs have no brushes and the stator remains stationary while the rotor turns, resulting in less friction, higher efficiency, and longer life. The video also mentions in-runner versus outrunner configurations, noting that outrunners offer more torque and are more common in practical use.

Motor Anatomy and Configurations

The speaker breaks down components such as the three windings (phases) and three wires, the rotor with permanent magnets, and the stator with laminated iron teeth to reduce eddy currents. Heat dissipation is addressed through venting holes in the rotor and stator housings. The delta winding configuration (DLRK) is introduced as a common wiring method that leads to a delta connection and three phases. The relationship between magnets and coils, and how the rotor is driven to prevent alignment, is explained to illustrate continuous rotation.

Control Systems: ESCs and PWM

The video explains that BLDC motors require an electronic speed controller (ESC) to manage current flow to the windings. A main controller sends PWM signals to the ESC, which in turn drives six MOSFETs arranged as three pairs for the three phases. The coils energize in a controlled sequence to generate a rotating magnetic field, producing smooth rotation and precise speed control. The PWM period is described as about 20 milliseconds, corresponding to 50 Hz, with the duty cycle dictating motor speed. The back-emf method for rotor position sensing is discussed as a Hall sensor alternative in many hobby motors, and the ESC uses this information to time commutation.

Back-EMF Sensing and Position Tracking

Back electromotive force (back-EMF) is described as the voltage generated when magnets move past a non-energized coil. The ESC uses back-EMF patterns to determine rotor position and commutation timing when Hall sensors are absent. The video also contrasts Hall-effect sensors with back-EMF sensing, emphasizing the importance of position feedback for proper motor commutation.

Building a BLDC Control Circuit with Arduino

For a hands-on project, the video outlines the required components: a BLDC motor, a speed controller (ESC), an Arduino, a potentiometer, a power supply, and connecting wires. The motor connects to the ESC, the ESC signal wire connects to Arduino pin 9, and a 5-volt supply powers the Arduino and a breadboard rail. The potentiometer is wired across the rails with its center pin feeding an analog input on the Arduino. The guide mentions downloading sample Arduino code and describes the code structure, including using a servo library to drive the ESC and mapping the potentiometer reading to a 0 to 180 PWM range. The code ensures the ESC outputs a 1 to 2 millisecond PWM pulse to avoid stalling at maximum potentiometer input. After uploading the code and powering the ESC, the motor can be controlled by turning the potentiometer.

Practical Notes and Next Steps

The video emphasizes that different motor and ESC combinations exist, and that the described setup serves as an educational example for understanding how BLDC motors operate and how to control them with PWM. It also encourages viewers to explore related content on DC motor operation and Arduino-based projects for deeper learning, while noting that the tutorial focuses on fundamental concepts rather than a full production build.