ESC works like the gearbox of the vehicle. In the vehicle, the gearbox suggests the wheel to rotate on its decided speed. Similarly, in the drone system, ESC determines the speed of the brushless motor. In this article, we will cover the basic concept of ESC, its function and the parameter to be considered while choosing it for your drone.
What is an ESC?
ESC is an Electronic speed controller which receives the throttle signals from the flight controller and run the brushless motor at its desired speed.
The good quality ESC gives a reliable and smooth flight experience. There is a number of factors that are considered while selecting the ESC and they are as,
- Current Rating
- Input Voltage Rating
- Weight and Size
- ESC Firmware
- Connection of ESC
- ESC processors
- ESC Protocols
Now, we will learn all these factors one by one,
1. Current Rating
The first thing to consider when selecting an ESC is the current rating or ampere rating. Motors draw current when they spin, if you draw more current than your ESC capacity then it will start to overheat and eventually damage. You should decide the current rating of the ESC after selecting a suitable motor size for your requirement.
- High KV ratings of the motor
- Larger propellers (length & pitch)
- Larger motor size (stator width & height)
There are 2 current ratings of ESC and they are continuous and burst. The continuous current rating indicates the maximum continuous current which ESC can handle safely. The burst rating means the maximum current that ESC can handle for a short period of time (e.g. 10 seconds) without damaging the ESC itself.
2. Input Voltage Rating
The voltage rating of an ESC is the maximum amount of voltage that your ESC can handle safely. Some of the ESCs supports for 3S-4S battery voltage, while others can support to 6S battery voltage. Here, make sure that they are compatible with the LiPo battery voltage. Powering your ESC with excessively high voltage will damage your ESC as well as the motor.
3. Weight and Size
The weight and size of an ESC are dependent on ESC current rating. It is challenging to make ESC’s with lighter and smaller size without losing its performance and effective cooling. Mostly, single standalone ESC’s are designed with the weight around 4 gram to 6 gram and the 4 in 1ESC weights around to 12 gram to 15 gram. Generally, the lighter ESC’s has lower heat dissipation, which leads to concerns of overheating.
4. ESC Firmware
ESC firmware is the software which is running on each ESC. It determines the performance of ESC. The ESC firmware gives information about its supported protocols and configuration interface. There are different types of ESC firmware are available,
Out of these, BLheli firmware and Simonk firmware are open sources and KISS firmware is closed source means it can run with only KISS ESC.
5. With or Without BEC
BEC stands for Battery Elimination Circuit. The BEC provides the constant current at a specific voltage. It has 5V output for powering the flight controller, a radio receiver (RX) and other 5V components. But nowadays, in the quadcopter system, the power distribution board is used so we really don’t need ESCs with BEC.
The ESC without BES is known as Opto ESC. Without the 5V BEC, your Flight controller and RX will require a separate power source. As per the above image, an Optp ESC doesn’t have the “red” servo wire. It uses only the signal and ground wire.
6. Connection of ESC with motor
ESC uses a LiPo battery to power up. The signal receives from the flight controller control the speed of the motor. A Brushless ESC has 3 wires which directly plugs or gets soldered to the 3 wires of the motor. The below image shows the single standalone ESC with LIPO battery, RC receiver and brushless motor.
7. ESC Protocols
Protocols are like the operating system of ESC. They determine how fast communication happens between the ESC and FC (flight controller) which plays a major role in the handling and performance of a quadcopter.
Here is a list of current protocols used on quadcopters, from oldest to latest:
- Standard PWM
To know more about it refer to ESC callibration Protocol.
8. ESC Processors
- ATMEL 8-bit is compatible with both SimonK and BLHeli firmware
- SILABS 8-bit is compatible with BLHeli or BLHeli_S only
- ARM Cortex 32-bit (e.g. STM32 F0, F3, L4) can run with BLHeli_3
Hope this article helps you to learn about the basics of an ESC’s. With the help of this article, you can easily choose the perfect ESC for your multirotor.
To calibrate your ESC with the motor and RC transmitter refer the tutorial, Connecting motors and calibrating ESC’s