Brushless Motor - How they work BLDC ESC PWM

This is a

brushless

motor

, it is often used to create lift and uses three phase electricity. I'm going to show you how

they

work

and even how to control one with an arduino in this video sponsored by shiny.org. get 20 off using the link below. More on this later. A

brushless

DC

motor

looks like this. They come in various sizes and designs, but all convert electrical energy into mechanical energy. We can use that mechanical rotation, for example, in a drone to rotate. the blades and create lift, we find these motors used in PC cooling fans, this DC drive uses a brushless motor and even this battery powered electric drill also uses a brushless motor, which differentiates it from a standard DC motor .

When we compare the two, we can notice that Both have magnets on the outer casing and both have wire coils in the center. However, with a standard DC motor we find these brushes at the rear, this refers to the arms and carbon blocks that rub against the commutator plates and allow electricity to flow. the coils as it rotates the gaps in the commutator plates cause the coils to turn on and off in a certain order to cause rotation because the brushes rub against the commutator plates,

they

wear out over time due to friction so the motor will need to be repaired or replaced when we look at a brushless motor there are no brushes because in this design the outer casing rotates and the coils remain stationary as there are no brushes there is very little friction which makes the motor more efficient and last longer.

We can also get rolling motors where the rotor spins inward, but most applications use rolling motors where the rotor spins outside the motor. Treadmill motors generally spin faster, but treadmill motors have much more torque so they are used more often, so in this video we only look at this version with a standard DC motor, we have only two wires and It spins as soon as we connect it to a sufficient power supply, however, a brushless motor has three wires that connect to an electronic speed controller, a main controller sends signals. By using pulse width modulation in the speed controller, the speed controller increases, maintains or decreases the speed of the motor by controlling when current can flow through the three wires and into the motor.

By the way, we'll see how he does it later in the video. We've covered how DC motors

work

in detail before and you can even learn how to build your own motor. In the links below, when we look at the brushless motor, we notice that there are three wires that go into the base of the motor and they are usually different colors. To represent the different phases, the base of the motor has some threaded holes that are used to mount the motor to a surface. There is also a clip that holds the shaft in position. The shaft runs the length of the engine and also extends towards the front. of the motor we can attach accessories to this to make use of the rotation notice when the shaft rotates, the front half of the motor housing also rotates, therefore this is the rotor and this part is the stator, the rotor and the stator They have holes in their casing to vent the heat generated by the coils, because if too much heat builds up inside, it will melt the protective enamel insulation on the wires, causing a short circuit that will destroy the motor if we remove the clip on the back.

We can remove the shaft and rotor to look inside. Looking at the stator, we can see that the shaft passes through a set of bearings to ensure smooth, low-friction rotation. There are 12 teeth on the stator in this design, they are made of thin laminated sheets of metals that are electrically insulated from each other. This is to reduce eddy currents within the motor. These are caused by the magnetic field and waste energy by creating heat instead of rotation. We can also notice that there are 12 coils of wire grouped into three different sets. The cable is enameled, which insulates it electrically.

This means that the current has to pass along the entire length of the cable to reach the other end. If it were not insulated, the current would take the shortest path possible and we would not get a strong magnetic force. field so that the motor does not work each set of coils is connected to a different phase there are three phases in total if we look at the back of the stator we can see that the ends of each coil are attached to another set of coils from which the cables come out The speed controller is then connected to these points to provide the electrical current.

Note that in this design the two adjacent coils are wound in opposite clockwise and counterclockwise directions. We will see why later in this video this is the most common method of wiring a brushless motor is known as dlrk winding, we see that it creates a delta connection. There are other configurations, but this is the most common. Now, inside the rotor, we find a series of high-strength permanent magnets that surround the inner surface. These are actually magnetized meaning the polarity is different on each side, these are arranged so that the polarity alternates with each magnet. Notice that in this example there are 14 magnets but 12 stator coils, so we have 12 stator poles and 14 magnetic poles, which is a common design, the difference prevents the magnets and coils from lining up as the rotor rotates constantly when trying to align, but you won't be able to understand how the motor works, but first, where have you seen brushless motors used?

Let me know in the comments section below, so now let's understand how this engine works. But don't forget to visit shiny.org, where you can take courses on everything from electricity and magnetism, classical mechanics, scientific thinking, computer science, and even cryptocurrency. Its hands-on, interactive problem solving makes learning fun and easy to visualize so you can master the essentials. skills with confidence I have personally enjoyed updating my knowledge of relativity with interesting problems to solve and I think you will enjoy this too, which is why our viewers can get started for free by visiting shiny.org, clicking on the engineering mindset or by doing Click the link in the video description below and the first 200 people to do so will get 20 off their annual premium membership.

I recommend you check out the links below. The brushless motor has three wires that connect to the three sets of coils inside the motor. This is also connected to a controller which sends a pulse width modulation signal to the speed controller telling it at what speed to spin the motor. The signal could be sent from something like an arduino or a simple servo tester. We will learn how to control the speed of the motor with an arduino later in this video. Speed ​​controllers usually have a very compact design like this, but we can also get larger units like this where you can see the components more easily.

The speed controller uses six mosfets which are a type of electronic switch the mosfet will block the flow of current unless we provide a voltage to the control pin this then closes the switch and allows current to flow through it the mosfets are Grouped into three pairs, one pair for each phase, these are connected across the battery positive and ground. The pulse width modulation signal is received by the internal controller which controls the mosfets by turning them on and off the coils inside the stator. then it connects to the phases between the mosfets the motor uses wire coils because when we pass a current through the coil it generates an electromagnetic field which we can see with a compass, we can reverse the polarity by simply reversing the direction of the current or we can change the orientation of the coil.

Note that the coils in the motor are in opposite directions, this creates opposite polarities. By making the motor stronger we know that the magnets interact by pushing and pulling, we can use them to cause rotation, we can control the coils to precisely control the rotation, so if we energize one phase it will push and pull the magnets in the rotor at multiple points. causing rotation and giving us a very powerful motor the controller receives a pulse width modulation signal, this means that the voltage is sent pulses through the wire, the width of the pulse can be varied, this is similar to when we press a switch to turn on a light for a longer time.

We press the switch, the longer the pulse will be, these pulses are sent every 20 milliseconds, so it sends them 50 times per second. We can see the pulse by connecting the device to an oscilloscope. If I zoom in, we can see that the pulse width varies. as I turn the dial that's why it's called pulse width modulation, if I change the voltage we see the pulse getting higher but it doesn't change the width of the pulse, the internal driver receives these pulses and it will open and close the mosfets . in a certain order to energize the coils in the stator, the speed at which it does so depends on the width of the pulse received, this causes a rotating electromagnetic field which occurs in six stages, there are only three sets of coils, so the direction of the current is reversed each time.

It is energized and therefore the polarity also alternates the faster the mosfets open and close the faster the rotation will be. We can see using this oscilloscope that as the width of the poles increases, the motor spins faster, so the width of the pulse determines the speed of the mosfets turn on and off, which changes the speed of the motor. The speed controller needs to know the orientation of the motor. Some motors use a Hall effect sensor that detects the change in the polarity of the magnets and from this generates a unique pattern that the controller can map to the position of the rotor, however, most hobby motors like this do not use Hall effect sensors, but the speed controller measures the back electromotive force.

We know that when we pass a current through a coil, it generates an electromagnetic field that can move another magnet but equally. If we move a magnet past a coil, the coil will generate a voltage. The speed controller does not energize all coils at the same time. When the magnets pass over an unenergized coil, it induces a voltage in that coil which is sent back to the controller. We call it back emf, so the speed controller monitors the coils to know when electricity is supplied or electricity is generated from From this, it creates a unique pattern and determines the position of the rotor when the engine starts, makes some noises and spins small amounts.

This is to determine the orientation, so now let's build this circuit and learn how to control a brushless motor with an arduino. We are going to learn how to control a brushless motor with an arduino and a potentiometer. For that we need an arduino and a brushless motor. a potentiometer a speed controller a power supply and some cables first we need to connect the brushless motor to the speed controller then connect the white signal wire of the speed controller to port 9 of the arduino the arduino will send a width modulation signal pulse to the speed controller through this wire, then connect the red wire from the speed controller to the positive rail of the breadboard, this will provide around 5 volts to the breadboard, then connect a red wire from the positive rail to the 5 volt port of the arduino, this will power Then the arduino connects a black wire from the ground port of the arduino to the ground rail of the board and then connects a black wire from the ground rail to the ground port of the speed controller.

Next we will need to connect the potentiometer to connect the left side to the positive rail and then the right side to the negative rail finally we connect the center pin to the a0 port of the arduino now connect your arduino to the computer to start writing the program you can download my arduino code for free with the links below for that, then write this code, this tells the arduino to use the pre-built servo instruction library. A servo is a different type of motor, but it will work well for this project. If you want to learn how that motor works, you can find a link in the video description.

Below we write this which creates an object called esc, although you can call it whatever you want, then we write this line of code which creates a variable integer called speed, then we write this line of code which tells the arduino that the object is called esc is connected to pin 9. it will send a pulse width modulation signal from pin 9. the pulses will have a duration between 1 millisecond and 2 milliseconds, the motor will continue to rotate without this last part, but the motor will stop when the potentiometer is at is maximum, so we'll include this in the code, then we write this, this takes a voltage reading from thepotentiometer on port a0 and associate it with a variable we created called speed, we are sending 5 volts through the potentiometer and reading the voltage we get. behind this, which varies depending on the position of the potentiometer, the arduino receives this and converts the voltage into a number between 0 and 1023 when it receives 5 volts it is and twenty-three when it is zero volts it is zero the servo library we are using no understands these numbers, it only understands values ​​between zero and one hundred and eighty, so we are creating a scale here to convert between them, then the final part of the code takes this value and sends it as a pulse whip modulation signal to the controller of speed, then we send this code to the arduino, then we disconnect the USB cable and connect the power supply to the speed controller, the motor will create some beeps while setting up and after a while we can start controlling the speed. of the motor using the potentiometer watch one of these videos on screen now to continue learning about electronic engineering and I will see you there for the next lesson.