Servo Motor Controlled Wireless Light Switch

4. Servo control with Arduino program

For Arduino, there are roughly two ways to control the servo motor.

PWM (Pulse Width Modulation) is a method of controlling the motor by turning on and off the pulse signal. It’s possible to achieve discrete movement by controlling the servo motor directly using PWM, but for more complex projects, you can take advantage of servo motor library included in Arduino IDE.

Arduino IDE → [File] → [Examples] → [10.StarterKit BasicKit] → [p05_ServoMoodindicator]

This program can change the angle of the servo motor based on the input value of the analog 0 pin (A0). By using a variable resistor such as potentiometer or an optical sensor for the analog pin, try moving the servo motor when the value changes.

Servo motor library function

Servo motor library is based on two types of commands: 1) specifying the pin number of the control signal to be sent to the servo motor and 2) specifying the angle when moving the servo motor.

Code-Example

myServo.attach(9); //Specify the servo motor's signal pin

1	myServo.attach(9); //Specify the servo motor's signal pin

Code-Example

myServo.write(angle); //Move the servomotor to a specific angle

1	myServo.write(angle); //Move the servomotor to a specific angle

The following circuit is an example using FEETECH FS90 micro servo. The operating voltage of this servo motor is 6V. Since the current at the time of operation is 200 mA, the servo motor is powered by four AA batteries connected in series (6V).

Figure 6. Example sketch circuit

Figure 7. Servo motor control circuit

Figure 8. p05_ServoMoodIndicator

Code-Example

/*
Arduino Starter Kit example
Project 5 - Servo Mood Indicator
 
This sketch is written to accompany Project 5 in the
Arduino Starter Kit
 
Parts required:
servo motor
10 kilohm potentiometer
2 100 uF electrolytic capacitors
 
Created 13 September 2012
by Scott Fitzgerald
 
http://www.arduino.cc/starterKit
 
This example code is part of the public domain
*/
 
// include the servo library
#include &lt;Servo.h&gt;
 
Servo myServo; // create a servo object
 
int const potPin = A0; // analog pin used to connect the potentiometer
int potVal; // variable to read the value from the analog pin
int angle; // variable to hold the angle for the servo motor
 
void setup() {
myServo.attach(9); // attaches the servo on pin 9 to the servo object
Serial.begin(9600); // open a serial connection to your computer
}
 
void loop() {
potVal = analogRead(potPin); // read the value of the potentiometer
// print out the value to the serial monitor
Serial.print("potVal: ");
Serial.print(potVal);
 
// scale the numbers from the pot
angle = map(potVal, 0, 1023, 0, 179);
 
// print out the angle for the servo motor
Serial.print(", angle: ");
Serial.println(angle);
 
// set the servo position
myServo.write(angle);
 
// wait for the servo to get there
delay(15);
}

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/*

Arduino Starter Kit example

Project 5 - Servo Mood Indicator

This sketch is written to accompany Project 5 in the

Arduino Starter Kit

Parts required:

servo motor

10 kilohm potentiometer

2 100 uF electrolytic capacitors

Created 13 September 2012

by Scott Fitzgerald

http://www.arduino.cc/starterKit

This example code is part of the public domain

*/

// include the servo library

#include <Servo.h>

Servo myServo; // create a servo object

int const potPin = A0; // analog pin used to connect the potentiometer

int potVal; // variable to read the value from the analog pin

int angle; // variable to hold the angle for the servo motor

void setup() {

myServo.attach(9); // attaches the servo on pin 9 to the servo object

Serial.begin(9600); // open a serial connection to your computer

}

void loop() {

potVal = analogRead(potPin); // read the value of the potentiometer

// print out the value to the serial monitor

Serial.print("potVal: ");

Serial.print(potVal);

// scale the numbers from the pot

angle = map(potVal, 0, 1023, 0, 179);

// print out the angle for the servo motor

Serial.print(", angle: ");

Serial.println(angle);

// set the servo position

myServo.write(angle);

// wait for the servo to get there

delay(15);

}

5. What can be done with a servo motor?

Let’s briefly review what you can be done with a servo motor. The following two are the typical operations:

I. Pressing the button

The servo motor can control the angle of its motion. This is why a servo motor is best for developing a mechanism that pushes buttons. You can make interesting devices like in the video below, and you can develop a variety of things just by pressing a button, switch in a room, etc.

II. Moving things

In Use Arduino to Control a Motor Part 3 – Making an RC Car Using a Servo Motor for the Steering, we made an RC car using LEGO. We mounted the steering part using a servo motor. Servo motors can be used for various applications, but it’s commonly used for “moving” parts/objects, whether it be moving the robot car or robot arm.