Unlock a Door with your Fingerprint

We built a biometric fingerprint-controlled lock prototype. A fingerprint scanner is used to capture and store the fingerprints of authorized users. When the scanner recognizes a user, a solenoid plunger disengages and opens the lock.
Parts List:
The fingerprint scanner module is powered by an ARM Cortex M3 CPU, which controls the on-board optical sensor and fingerprint recognition. Fingerprints are stored and processed by the module, which supports a UART protocol for communicating with a host application. The solenoid is powered from Kinoma Create and controlled by a digital output pin.


Step 1: Wiring

Unlock a Door with your Fingerprint

The proto board is connected to the solenoid and Kinoma Create back header pins. The fingerprint scanner is also connected to the back header UART TX and RX pins.
Both front pin headers are configured for +5V and pin 51 is configured as a digital output. The application programmatically configures the front pins and displays the Pins Settings dialog.

Step 2: Proto board

The solenoid used to lock and unlock the door requires two additional bits of electronics: a transistor and a fly back diode. The transistor acts as a switch for the 5v power supply from Kinoma Create, allowing us to turn on and off that current to the solenoid using our 3.3v digital out pin. The diode helps to protect Kinoma Create from electrical surges generated by the solenoid, dissipating fly back energy as heat through the solenoid rather than as a power spike into the Kinoma Create’s digital output pin.

Step 3: Application Overview

The KinomaJS application opens to a screen that displays a list of registered fingerprints. Three buttons are provided at the bottom of the screen to interact with the scanner.

The Register button kicks off the fingerprint capture and registration flow. Once fingerprint registration is complete, the user associates his or her name with the fingerprint using the Kinoma Create on-screen keyboard. The registered fingerprint is added to the displayed list. The Authorize button is used to validate a fingerprint against the list of registered users. The door is unlocked and a success sound is played if the fingerprint scanned matches a registered user. If the fingerprint is not authorized, the door remains locked and the application plays a failure sound. The Clear button removes all registered fingerprints from the displayed list and clears the fingerprint scanner module storage.
For more detail: Unlock a Door with your Fingerprint

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