Shield for Arduino that allows a complete electrically controlled lock which opens thanks to a code, always different, generated by an application to be installed on your smartphone based on an algorithm that consider the time.
The shield has a relay for to activate an external load (such as an electric lock) if the code inserted is correct; a buzzer to generate acoustic signals; Two LEDs (one red and the other green) to view the status of the lock; a Real Time Clock (with integrated DS1307 from Maxim / Dallas) to always have a current timestamp value and correct; a backup battery to power the RTC even if the card is not powered. At the shield to be connected to a membrane alphanumeric keypad for entering codes; a serial display to view the status of the lock and entered codes.

This project comes in kit. Some components have to be soldered to the included PCB.

N.B. Arduino Uno Rev3, the keypad and display are not included in the kit (see related products).

The sketch for Arduino can be downloaded below in the section "Documentation and useful links". You need to install three libraries: keypad; RTClib; TOTP Library.
All libraries can be installed through the Library Manager included in recent versions of the IDE of Arduino; from Sketch menu impart the command Includes Library -> Manage Libraries.

For to use the lock, the first thing you need to do is to install an application on your smartphone that can generate OTP codes with the choosed algorithm. For IOS and Android you can install the App "Google Authenticator", while for Windows Phone can be used " Authenticator+ ". All applications are free and you can find them in the link below, section "Documentation and useful links".

• Sketch and Library
• Google Authenticator per iOS
• Google Authenticator per Android
• Authenticator+ for Windows Phone