Arduino - Servo Motor
In this tutorial, we are going to learn how to use the servo motor with Arduino. In detail, we will learn:
- How servo motor works
- How to program Arduino to control servo motor
- How to program Arduino to control the speed of servo motor
- How to provide the extra power for high-torque servo motors.
|1||×||Arduino UNO or Genuino UNO|
|1||×||USB 2.0 cable type A/B|
|1||×||(Optional) 9V Power Adapter for Arduino|
|1||×||(Recommended) Screw Terminal Block Shield for Arduino Uno|
Or you can buy the following sensor kit:
|1||×||DIYables Sensor Kit 30 types, 69 units|
About Servo Motor
Servo motor is a component that can rotate its handle (usually between 0° and 180°). It used to control the angular position of the object.
The servo motor used in this example includes three pins:
- VCC pin: (typically red) needs to be connected to VCC (5V)
- GND pin: (typically black or brown) needs to be connected to GND (0V)
- Signal pin: (typically yellow or orange) receives the PWM control signal from an Arduino's pin.
How It Works
After connecting VCC pin and GND pin to 5V and 0V, respectively, we can control the servo motor by generating proper PWM signal to signal pin.
The angle is determined by the width of PWM signal.
Datasheet of the servo motor provides us the following parameters:
- Period of PWM (PERIOD)
- Minimum width of PWM (WIDTH_MAX)
- Maximum width of PWM (WIDTH_MIN)
These parameters are fixed in Arduino Servo library. We do NOT need to know the value of parameters.
The angle is determined as follows:
- If PWM's width = WIDTH_MIN, the servo motor rotates to 0°.
- If PWM's width = WIDTH_MAX, the servo motor rotates to 180°.
- If PWM's width is between WIDTH_MIN and WIDTH_MAX, the servo motor rotates to angle between 0° and 180° in proportion.
Arduino - Servo Motor
Some of Arduino pins can be programmed to generate PWM signal. We can control the servo motor by connecting the servo motor's signal pin to an Arduino's pin, and programming to generate PWM on the Arduino's pin.
Thanks to Arduino Servo library, controlling servo motor is a piece of cake. We even do NOT need to know how servo motor works. We also do NOT need to know how to generate PWM signal. We JUST need to learn how to use the library.
For the sake of simplicity, the above wiring diagram is used for the testing or learning purposes, and for small-torque servo motor. In practice, we highly recommend using the external power supply for the servo motor. The below wiring diagram shows how to connect servo motor to an external power source.
How To Program For Servo Motor
- Include the library:
- Declare a Servo object:
If you control more than one servo motors, you just need to declare more Servo objects:
- Set the control pin of Arduino, which connects to the signal pin of the servo motor. For example, pin 9:
- Lastly, rotate the angle of the servo motor to the desired angle. For example, 90°:
- Connect Arduino to PC via USB cable
- Open Arduino IDE, select the right board and port
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- See the result: Servo motor rotates slowly from 0 to 180° and then back rotates slowly from 180 back to 0°
Read the line-by-line explanation in comment lines of code!
How to Control Speed of Servo Motor
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Use the servo motor to do one of the following projects:
- The Servo library supports up to 12 motors on Arduino UNO and 48 on the Arduino Mega.
- Power from 5V pin of Arduino maybe NOT enough for servo motor in one of the following cases:
- Using a high-torque servo motor, which can carry a high-weight thing.
- Using many servo motors.
- Do not connect the positive pin of extra power source to 5V pin of Arduino.
- Must connect the negative pin of extra power source to the GND pin of Arduino.
In these cases, we may need to provide an extra power source for servo motors.
As we can see in the above diagram, the VCC pin of servo motor doest NOT connect to the 5V pin of Arduino. It connects to the positive pin of an extra power source.
Please note that: