Arduino - Keypad - Electromagnetic Lock
In this tutorial, we are going to learn how to use a keypad, electromagnetic lock, and Arduino together. In detail, If a user inputs the password on the keypad correctly, Arduino turns the electromagnetic lock on.
The tutorial also provides the code that turns on a electromagnetic lock in a period of time and then turns off without using delay() function. The Arduino code also supports multiple passwords.
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About Keypad and Electromagnetic Lock
If you do not know about keypad and Electromagnetic Lock (pinout, how it works, how to program ...), learn about them in the following tutorials:
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Arduino Code - turn electromagnetic lock on if the password is correct
The below codes turn a electromagnetic lock on if the password is correct
- 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 8123 keys and press #
- Press 1234 keys and press #
- See the result on Serial Monitor and the state of electromagnetic lock
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 electromagnetic lock is turned on.
- No matter the password is correct or not, the input string is clear for the next input
Arduino Code - turn a electromagnetic lock on in a period of time if the password is correct
The below code turns the electromagnetic lock on for 5 seconds if the password is correct. After 5 seconds, the electromagnetic lock is turned off.
Please note that, the above code use ezOutput library, which makes it easy to manage time in non-blocking maner. You can refer to ezOutput Library Installization Guide
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