How to use the multiple passwords for keypad?

How can I use two passwords, three passwords, four passwords, or more with keypad and Arduino?
Answer

The below Arduino code uses three passwords for keypad. you can easily modify it for two passwords, four passwords, or more.

#include <Keypad.h> const int ROW_NUM = 4; //four rows const int COLUMN_NUM = 3; //three columns char keys[ROW_NUM][COLUMN_NUM] = { {'1','2','3'}, {'4','5','6'}, {'7','8','9'}, {'*','0','#'} }; 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}; //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 = "1234"; // change your password here const String password_2 = "5642"; // change your password here const String password_3 = "4545"; // change your password here String input_password; void setup(){ Serial.begin(9600); input_password.reserve(32); // maximum input characters is 33, change if needed } 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("password is correct"); // DO YOUR WORK HERE } else { Serial.println("password is incorrect, try again"); } input_password = ""; // reset the input password } else { input_password += key; // append new character to input password string } } }

The wiring diagram for above code:

Arduino Keypad Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

Hardware for above code

1 × Arduino UNO Buy on Amazon
1 × USB 2.0 cable type A/B Buy on Amazon
1 × Keypad 3x4 Buy on Amazon
1 × Keypad 4x4 (optional) Buy on Amazon
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See Also

The Best Arduino Starter Kit

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