Arduino - Keypad - Relay
In this tutorial, we are going to learn how to use a keypad, relay, and Arduino together. In detail, If a user inputs the password on the keypad correctly, Arduino turns the relay on.
The tutorial also provides the code that turns on a relay in a period of time and then turns off without using delay() function. The Arduino code also supports multiple passwords.
|1||×||Arduino UNO or Genuino UNO|
|1||×||USB 2.0 cable type A/B|
About Keypad and Relay
If you do not know about keypad and Relay (pinout, how it works, how to program ...), learn about them in the following tutorials:
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Arduino Code - turn relay on if the password is correct
The below codes turn a relay on if the password is correct
- Connect Arduino to PC via USB cable
- Open Arduino IDE, select the right board and port
- On Arduino IDE, Go to Tools Manage Libraries
- Search “keypad”, then find the keypad library by Mark Stanley, Alexander Brevig
- Click Install button to install keypad library.
- Search “ezOutput”, then find the ezOutput library by ArduinoGetStarted
- Click Install button to install ezOutput library.
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Press 1234 keys and press #
- Press 9765 keys and press #
- See the result on Serial Monitor and the state of relay
Authorized passwords are pre-defined in the Arduino code.
A string is used to store the password inputted by users, called input string. 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 two special keys, it is appended to the input string
- If the pressed key is *, input string is clear. You can use it to start or re-start inputing the password
- If the pressed key is #:
- The input string is compared with the pre-defined passwords. If it matched with one of the pre-defined passwords, the relay is turned on.
- No matter the password is correct or not, the input string is clear for the next input
Arduino Code - turn a relay on in a period of time if the password is correct
The below code turns the relay on for 5 seconds if the password is correct. After 5 seconds, the relay is turned off.
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