What is an Electronic Speed Controller All Explained

Electronic speed controllers (ESCs) play a vital role in modern electric drive systems. Whether in drones, RC cars, or electric motorbikes, ESCs can effectively regulate the speed and direction of the electric motor to ensure the smooth operation of the device. In this article, we will discuss the working principle, types, selection points, and application scenarios of Electronic speed controllers (ESCs).

What is Electronic Speed Control

The term ESC stands for “electronic speed control,” which is a circuit designed to adjust the speed of an electric motor, change its direction, and serve as a dynamic brake. ESCs are commonly used in radio-controlled models powered by electricity, particularly for brushless motors, which provide electronically generated 3-phase power at low voltage. An ESC can be a standalone unit connected to the throttle receiver control channel, or it can be integrated into the receiver itself, as often seen in toy-grade R/C vehicles. Some R/C manufacturers incorporate specialized hobbyist electronics in their entry-level vehicles, tanks, or aircraft, combining these functions onto a single circuit board.

Electronic Speed Controls(ESCs)

Types of an Electronic Speed Controller

There are two main types of electronic speed controllers available in RC model shops: brushed ESCs and brushless ESCs, each catering to specific needs.

brushed ESCs and brushless ESCs

Brushed ESC

Brushed ESCs are the original type of electronic speed controller, widely used in various ready-to-run (RTR) electric RC vehicles due to their low cost.

Brushless ESC

Brushless ESCs represent a technological advancement in electronic speed control. While they are generally more expensive, they connect to brushless motors, providing greater power and performance compared to brushed ESCs, and typically have a longer lifespan.

ESC Components

Inside the ESC, several key components are present, such as the microcontroller, gate driver, and MOSFETs (see figure 3), along with a battery eliminator circuit and a device manager adapter in certain instances.

The key components of an ESC

Microcontroller (MCU)

The microcontroller plays three key roles in the operation of the ESC: 1) housing the firmware that interprets the signals from the controller and feeds them into the control loop, 2) tracking the position of the motor to ensure smooth acceleration, and 3) sending pulses to the gate driver to implement the desired commands

The firmware used in ESCs is usually pre-installed by the manufacturer, but open-source versions are also available from third-party sources. In hobbyist drones, the pre-installed firmware is usually a variant of BLHeli (BLHeli_S or BLHeli_32), although other software (e.g. SimonK and KISS) is also available. The chosen firmware must be compatible with the hardware, as it will determine the performance of the ESC and which protocols can be used.

The microcontroller also determines the position of the motor through a system with or without sensors. Sensored systems use electronic sensors in the motor to track the position of the rotor, which is ideal for low-speed, high-torque applications such as ground vehicles. The more popular sensorless system uses a counter-electromotive force to determine the position of the rotor relative to the stator. This works well at high speeds, but sensorless systems do not work well when the motor is spinning at lower speeds and there is less counter-electromotive force. This is usually not a problem when driving propellers. Overall, for high-speed applications, sensorless systems are more efficient, cheaper, and more reliable.

Gate driver

The role of the gate driver is to act as an intermediary between the controller and the MOSFET gate. After receiving a low-voltage signal from the microcontroller, the gate driver amplifies the signal and delivers a high-voltage signal to the MOSFET. The driver has a lower resistance than the microcontroller, so it can deliver a higher current, which also amplifies the speed of the signal. This allows faster switching and lower heat generation. Some ESCs have insulating optics between the low-voltage microcontroller and the high-voltage transistor. Manufacturers may refer to these ESCs as Opto-ESCs.

MOSFET

Metal-oxide-semiconductor field-effect transistors (MOSFETs) are the switches that provide power to the motor. The ESC has six of these transistors, with each of the motor’s wires connected to two of them. The MOSFETs receive signals from the microcontroller, which then supplies power to the motor so that each of its coils is in one of three phases: high-voltage, low-voltage, or off/earth.

As the motor rotates, signals from the MOSFETs switch the phases of the coils to keep the rotor spinning. the ESC uses DC power coupled to a switching system for three-phase AC power (Figure 4). The ESC uses DC power coupled to a switching system for three-phase AC power. The higher the throttle input, the faster the switching frequency and the higher the speed of the motor. Several signaling protocols are available to control this process, each with different performance and signal frequencies.

How Does an ESC Work

The role of the ESC is to act as a regulating intermediary between the battery and the motor. It controls the rotation of the motor by providing timed electrical signals that are translated into speed changes. It uses DC power from the battery combined with a switching system to enable AC three-phase current sent to the motor.

How ESC works

Throttle controllers for vehicles are used to vary the speed of the motor, whether it is an electric car, an aircraft, or a drone. Increasing the throttle increases the output power, which changes the rate at which the switches in the ESC circuit open and close.

There are several signaling protocols used to transmit throttle information from the remote control to the ESC, each with slightly different capabilities, the most common being PWM, Oneshot, Multishot, and Dshot.

The most important difference between them is the frequency of the signal they transmit. The shorter the frequency, the faster the signal is transmitted and the shorter the response time of the drone. In addition, the Dshot protocol is different from the others because it sends a digital signal instead of an analog one. This makes the signal more reliable because it is less sensitive to electrical noise and has a higher and more accurate resolution.