This example shows how to use Simulink Support Package for Arduino Hardware to control a standard servo motor.
The Simulink Support Package for Arduino Hardware enables you to create and run Simulink models on an Arduino Mega 2560 board. The target includes a library of Simulink blocks for configuring and accessing Arduino sensors, actuators, and communication interfaces.
In this example, you will learn how to create a Simulink model that controls a standard servo motor. In a standard servo motor, the shaft position can be precisely set, usually between 0 and 180 degrees. Servo motors are used in many industrial, military, and consumer applications and products.
We recommend completing the Getting Started with Arduino Mega 2560 Hardware example.
To run this example, you will need the following hardware:
- Arduino Mega 2560 board
- USB cable
- Standard servo motor
- CdS photocell
- 10 kOhm resistor
- Breadboard wires
- Small breadboard (recommended)
In this task, you will connect your motor to the Arduino board. Servo motors have three wires: power, ground, and signal. Connect them as described below.
1. Connect the power wire (usually red) to the 5V pin.
2. Connect the ground wire (usually black) to the ground pin.
3. Connect the signal wire (usually orange) to digital pin 4.
In this task, you will set the position of the servo motor shaft using an internal source. The shaft angle will vary between 0 and 180 degrees, up and down.
1. Open the model included in the Support Package called
2. Notice the Standard Servo Write block. The block sets the new angle of the servo motor shaft every 0.01 second.
3. In your Simulink model, select Tools > Run on Target Hardware > Run.
4. When the model starts running on the Arduino Mega 2560 board, observe the motor shaft position sweeping between 0 and 180 degrees.
In this task, you will set the position of the servo motor shaft manually, using a potentiometer. Connect the outer potentiometer terminals to the 5V and GND pins on your Arduino Mega 2560 board. Connect the middle terminal to analog input pin 0. As your rotate the potentiometer, its resistance changes. As a result, the voltage at the analog input pin changes as well. Your task is to set the servo motor angle proportional to this voltage.
1. In MATLAB, select HOME > New > Simulink Model.
2. Enter simulink at the MATLAB prompt. This opens the Simulink Library Browser.
3. In the Simulink Library Browser, navigate to Simulink Support Package for Arduino Hardware.
4. Drag the Analog Input block into the model. Double-click the block and set the Pin number to 0, and the Sample time to 0.01 second.
5. Drag the Standard Servo Write block into the model. Double-click the block and set the Pin number to 4.
6. Connect the Analog Input and the Standard Servo Write blocks.
7. From Simulink Math Operations library, drag the Gain block into the model and drop it on the line connecting the Analog Input and the Standard Servo Write block. Double-click the Gain block and set its value to 0.1760 (maximum servo motor displacement in degrees divided by analog input digital resolution; i.e., 180/1023).
8. In your model, select Tools > Run on Target Hardware > Prepare to Run….
9. Review the parameters in the resulting dialog box. Unless already set, set the Target hardware parameter to Arduino Mega 2560.
10. In the model, select Tools > Run on Target Hardware > Run.
11. When the model starts running on the Arduino Mega 2560 board, observe the motor shaft sweeping between 0 and 180 degrees.
In this task, you will create a model that sets the position of the servo motor according to light intensity detected by a photocell. In a dark room, the motor shaft should be positioned at 0 degrees, while in a bright room it should be positioned at 180 degrees.
Use a photocell and a resistor instead of the potentiometer you used in Task 3. Connect one end of the photocell to the 5V pin on the Arduino Mega 2560 board. Next, connect one end of the resistor to the GND pin on the board. Connect the other ends of the photocell and the resistor together and then to the analog input pin 0 on the board.
The model will be similar to the one used in Task 3.
Experiment with other blocks in the Arduino block library. For example:
- Use the Digital Input block to adjust the motor shaft position depending on the external control signal or signals.
- Use the Standard Servo Read block to read the motor shaft position and compare it with the desired position.
This example showed you how to use the Simulink Support Package for Arduino Hardware to control a standard servo motor. In this example, you learned that:
- The Standard Servo Write block allows you to set the servo motor shaft position, usually in the range from 0 to 180 degrees.
- The Analog Input block measures the voltage applied to an Arduino analog input pin. A variety of sensors can be attached to analog pins.