Speed controllers – in the English-speaking community are called – Electric Speed Controller (electronic speed controller) or abbreviated – ESC. The main task of the ESC is to transfer energy from the battery to the brushless motor. The need for their use arose due to some features of the BC – motor. In short, the battery supplies direct current, while the brushless motor receives three-phase alternating current.
Principle of operation
Communication with other components of the multicopter.
The ESC input receives voltage from the battery and signals from the flight controller, and the ESC outputs control voltage for the actuator. Accordingly, the regulator must ensure:
- Flight controller compatible.
- Maximum current for motor (calculated from motor and propeller specifications) plus 20 – 30%.
- The current consumption is less than the current supplied by the battery divided by the number of ESCs.
*Simple wiring diagram.
What are the regulators?
BEC and UBEC
In addition to the main function, the ESCs can also supply power to other components of the drone: the flight controller, servos, and so on. This is achieved by introducing a Battery Eliminator Circuit (hereinafter referred to as BEC) into the regulator.
The use of BEC greatly simplifies the design of the drone, but this scheme has a number of disadvantages. The battery exclusion unit may overheat under large voltage fluctuations and heavy loads. In addition, ESCs with BEC tend to be more expensive than ESCs without an ECU.
Agree, it would be more logical and cheaper to make a separate ESC and a separate BEC. There is such a solution and it is called the Universal Battery Eliminator Circuit, hereinafter referred to as UBEC.
Benefits of UBEC
UBEC – connects directly to the battery and powers the desired node of the drone. The advantages of this approach are very significant:
- ESCs will overheat less as BEC is removed from them
- UBECs are highly efficient
- Therefore, from the previous two points, UBEC is capable of delivering more current with less risk.
- No overpayment for a few extra BECs located in the ESC. For some flight controllers it is strongly discouraged to connect more than one ESC BEC
- Less weight regulators
Types of BECs and their benefits
There are two types of BEC: linear (LBEC) and pulsed (SBEC).
- Linear converts energy into heat, and turns off when overheated. Which can lead to unpleasant results: at best, the copter will not be able to take off, and at worst, an uncontrolled fall. In this connection, it began to be used in assembly with servo drives, which, in turn, do not consume much current, preventing the unit from overheating.
- Pulse regulates the voltage by quickly turning the power on and off, this approach eliminated overheating, increased output power, and made it possible to achieve an efficiency of 90%, and pulsed BECs outperform linear ones in weight. Interference that occurs in the circuit, which adversely affects the operation of radio equipment, is eliminated by adding an LC filter.
Given that many manufacturers install filters on their UBECLCs (and if there is still no filter, then it can be bought cheaply and easily installed), professionals use SBEC regulators in their quadcopters.
Since the speed controller performs some conversions at a high frequency and can be configured for various modes of operation, a separate software called firmware is written for it. This allows you to correct past errors in control algorithms, create more advanced firmware (and thereby, for example, reduce battery consumption at medium throttle) and make flexible settings. In copters of well-known companies such as DJI, the controller software is changed automatically using the flight controller.
Attention! Overwriting software for speed controllers can lead to various kinds of damage to the drone, as well as removal from warranty service! Remember that you are doing this at your own risk!
How to change software?
There are several ways to change the controller software:
- Using a dedicated control board
- Using the flight controller
- Using the ASP programmer
The third option is simpler and is currently being actively introduced into new models.
Speed controller selection
Based on all of the above, we can distinguish special criteria for choosing a speed controller for a drone:
- Flight controller compatible. The flight controller must support BEC and ESC firmware.
- Compatible with motor and battery specifications.
- Presence or absence of BEC and its type (LBEC or SBEC).
- Heat dissipation and tightness.