What is an Electronic Speed Controller and How Does it Work?

What is an Electronic Speed Controller?

The electronic speed controller (ESC) stands as a pivotal component within the hardware of an electric propulsion system. Serving as the system's neural hub, the ESC conveys instructions to the motor, dictating its speed based on data signals it receives from the throttle controller.

For smaller applications such as drones and RC vehicles, this hardware is referred to as an 'ESC.' However, in larger manufacturing contexts, it might be known as an electronic control unit, inverter, or motor controller. This article explores the fundamentals of how ESCs operate, the protocols they employ, and their applications in controlling brushless motors and drones.

How Does it Work?

The ESC's primary function is to mediate between the battery and the electric motor, governing the motor's rotation by sending precisely timed electric signals. These signals are transformed into changes in speed. The ESC utilizes direct current from the battery along with a switch system to generate an alternating three-phase current that powers the motor.

The vehicle's throttle controller is used to regulate the motor's speed, whether in an electric car, plane, or drone. Increasing the throttle augments the power output, altering the rate at which the ESC's circuit switches open and close.

ESC Components

Within the ESC, several crucial components play vital roles, including the microcontroller, gate driver, MOSFETs, and, in some cases, the battery eliminator circuit and device manager adapter.

  1. Microcontroller (MCU): The microcontroller has three key functions in ESC operation: housing the firmware interpreting controller signals, tracking the motor's position for smooth acceleration, and sending pulses to the gate driver to execute commands.

  2. Gate Driver: The gate driver acts as an intermediary between the controller and the MOSFETs. It amplifies the low-voltage signal from the microcontroller, providing a high-voltage signal to the MOSFETs. This allows for faster switching and lower heat generation.

  3. MOSFET: These Metal Oxide Semiconductor Field Effect Transistors serve as switches, strategically delivering power to the motor. The ESC typically employs six MOSFETs to control the motor's three-phase current.

Battery Eliminator Circuit

ESCs often incorporate a built-in battery eliminator circuit (BEC), which regulates voltage to power onboard electronics, removing the need for a separate battery. This circuit lowers the voltage to a safe 5 V, which powers the throttle receiver and other onboard devices.

Device Manager Adapter (DMA)

The device manager adapter enables users to connect their ESC to a computer for firmware updates and advanced programming options. This feature keeps the ESC current and allows for the customization of settings such as voltage cut-off and motor direction.

What is PWM?

Pulse Width Modulation (PWM) is one of the oldest ESC protocols, still in use today. It conveys power pulses to control the motor's speed, based on input from the throttle controller. The width of the pulses determines the duration for which voltage is supplied, affecting the rotor's speed. Various ESC protocols have different signal frequencies.

ESC Protocols

ESC protocols serve as the language through which flight controllers communicate with the ESC to control motor speed. Common protocols include PWM, Oneshot125, Oneshot42, Multishot, and Dshot. Dshot stands out for its digital signal transmission, offering improved reliability and precision, particularly in reducing sensitivity to electrical noise.

ESC for Brushless Motors

The ESC acts as a power mediator between the battery and the brushless motor, controlling the power delivered based on the controller's input. In brushless motors, the ESC's task is to ensure a smooth acceleration by adjusting either voltage, speed, or a combination of both, depending on the firmware used.

How to Choose an ESC for Drones?

Selecting the right ESC is crucial for drone design. Several factors need consideration, including the ESC's current rating, voltage compatibility, and whether to opt for separate ESCs or a 4-in-1 ESC. A current rating slightly higher than the motor's is recommended to prevent overheating. Voltage limits should match the battery's specifications, and a 4-in-1 ESC can save space and weight.

In summary, this article delves into the functioning and components of ESCs, the significance of protocols, and the factors influencing ESC selection for drones and other electric propulsion systems. Understanding these key aspects can greatly enhance your knowledge and building capabilities.

Prasun Barua

Prasun Barua is an Engineer (Electrical & Electronic) and Member of the European Energy Centre (EEC). His first published book Green Planet is all about green technologies and science. His other published books are Solar PV System Design and Technology, Electricity from Renewable Energy, Tech Know Solar PV System, C Coding Practice, AI and Robotics Overview, Robotics and Artificial Intelligence, Know How Solar PV System, Know The Product, Solar PV Technology Overview, Home Appliances Overview, Tech Know Solar PV System, C Programming Practice, etc. These books are available at Google Books, Google Play, Amazon and other platforms.


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