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Arduino - Keypad - Servo Motor
In this tutorial, we are going to learn how to use a keypad, servo motor, and Arduino together:
- If a user inputs an authorized password on the keypad, Arduino rotates the servo motor to 90°.
- After a period of time, the Arduino rotates the servo motor back to 0° without using delay() function.
- The Arduino code also supports multiple passwords.
Hardware Required
Or you can buy the following sensor kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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About Keypad and Servo Motor
If you do not know about keypad and servo motor (pinout, how it works, how to program ...), learn about them in the following tutorials:
- Arduino - Keypad tutorial
- Arduino - Servo Motor tutorial
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
Arduino Code - rotates Servo Motor if the password is correct
The below code turns the servo motor to 90° for 5 seconds if the password is correct. After 5 seconds, it turns the servo motor to 0°.
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-keypad-servo-motor
*/
#include <Keypad.h>
#include <Servo.h>
#define ROW_NUM 4 // four rows
#define COLUMN_NUM 4 // four columns
#define SERVO_PIN A0 // // the Arduino pin, which connects to the servo motor
Servo servo; // servo motor
char keys[ROW_NUM][COLUMN_NUM] = {
{'1', '2', '3', 'A'},
{'4', '5', '6', 'B'},
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};
byte pin_rows[ROW_NUM] = {9, 8, 7, 6}; //connect to the row pinouts of the keypad
byte pin_column[COLUMN_NUM] = {5, 4, 3, 2}; //connect to the column pinouts of the keypad
Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );
const String password_1 = "ABC1234"; // change your password here
const String password_2 = "5642B"; // change your password here
const String password_3 = "9765"; // change your password here
String input_password;
int angle = 0; // the current angle of servo motor
unsigned long lastTime;
void setup() {
Serial.begin(9600);
input_password.reserve(32); // maximum password size is 32, change if needed
servo.attach(SERVO_PIN);
servo.write(0); // rotate servo motor to 0°
lastTime = millis();
}
void loop() {
char key = keypad.getKey();
if (key) {
Serial.println(key);
if (key == '*') {
input_password = ""; // reset the input password
} else if (key == '#') {
if (input_password == password_1 || input_password == password_2 || input_password == password_3) {
Serial.println("The password is correct, rotating Servo Motor to 90°");
angle = 90;
servo.write(angle);
lastTime = millis();
} else {
Serial.println("The password is incorrect, try again");
}
input_password = ""; // reset the input password
} else {
input_password += key; // append new character to input password string
}
}
if (angle == 90 && (millis() - lastTime) > 5000) { // 5 seconds
angle = 0;
servo.write(angle);
Serial.println("Rotating Servo Motor to 0°");
}
}
Quick Steps
- Connect Arduino to PC via USB cable
- Open Arduino IDE, select the right board and port
- Navigate to the Libraries icon on the left bar of the Arduino IDE.
- Search “keypad”, then find the keypad library by Mark Stanley, Alexander Brevig
- Click Install button to install keypad library.
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Press 12345#
- Press 5642B#
- See the result on Serial Monitor and the state of servo motor
COM6
The password is incorrect, try again
The password is correct, rotating Servo Motor to 90°
Rotating Servo Motor to 0°
Autoscroll
Clear output
9600 baud
Newline
Code Explanation
Authorized passwords are pre-defined in the Arduino code.
A string is used to store the password inputted by users, called input_password. In keypad, two keys (* and #) are used for special purposes: clear password and terminate password. When a key on keypad is pressed:
- If the pressed key is not one of two special keys, it is appended to the input_password
- If the pressed key is *, input_password is clear. You can use it to start or re-start inputing the password
- If the pressed key is #:
- The input_password is compared with the pre-defined passwords. If it matched with one of the pre-defined passwords, rotate the servo motor to 90°.
- Regardless the password is correct or not, the input_password is clear for the next input
Video Tutorial
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