Upgrade Your Door Lock With Fingerprint

In this tutorial, we’ll build a fingerprint-based door lock system using an Arduino Uno and a fingerprint sensor. The project combines convenience and security, allowing only registered fingerprints to unlock the door. Instead of carrying keys or remembering passwords, you can simply use your finger as the key.

We’ll cover the required components, wiring, and programming step by step, so even beginners can follow along. By the end, you’ll have a fully working biometric lock system that can be applied to home doors, lockers, or any project where security matters.

To make this fingerprint door lock, you will need the following components and hardware:

1. Tower Bolt – acts as the locking mechanism
2. Bond Set – for fixing parts securely in place
3. Nut and Bolt (6 mm / 7 cm long) – for mounting the tower bolt and other components
4. Arduino Uno – the main controller of the project
5. MG90 Servo Motor – to slide the tower bolt and lock/unlock the door
6. Fingerprint Sensor – for biometric authentication
7. 9V Battery – power supply for the system
8. Wood Ply

1. Take the 8 mm wood ply of size 15 cm × 10 cm.
2. Place the tower bolt at one corner of the ply in the desired position.
3. Using a pencil, mark the screw hole positions of the tower bolt on the wood ply.
4. Remove the tower bolt and, with a drill machine and 3 mm drill bit, drill 4 holes at the marked points.
5. Place the tower bolt back in position, aligning it with the drilled holes.
6. Insert the screws one by one and tighten them firmly using a screwdriver.

Now the tower bolt is securely fixed to the wood ply.

1) Take the Bond Set, which contains two cubes (resin and hardener).

2) Cut out equal quantities from both cubes.

3) Mix them thoroughly using your fingers until you get a uniform paste.

⚠️ Tip: You may apply a little oil or wear gloves to avoid sticking on fingers.

Once mixed, the adhesive starts setting, so use it quickly.

1) Apply the mixture to the nut and press it firmly onto the tower bolt handle.

2) Leave it undisturbed for 1–2 hours until the Bond Set hardens completely.

Now the nut is securely fixed on the tower bolt handle.

1) Take a small 8 mm wood block to create a platform for the servo motor.

2) Apply glue on the block and fix it at the top side of the tower bolt.

⚠️ Make sure the block is positioned firmly and level.

3) Once the block is fixed, apply glue on its surface.

4) Place the MG90 Servo Motor on the block and press gently so it sticks properly.

5) Allow the glue to dry completely before testing the motor movement.

Now the servo motor is mounted securely above the tower bolt.

1) Take an old pen body and cut a piece about 1 cm long.

1. This will act as a connector between the servo shaft and the bolt.

2) Insert one end of the cut pen piece onto the servo motor shaft.

3) Insert the other end onto the 6 mm bolt.

4) Apply a few drops of Fevikwik at both joints (shaft side & bolt side).

5) Hold it in place for a few seconds until the glue sets.

Now the servo motor shaft and 6 mm bolt are firmly connected through the pen connector.

1) Take the fingerprint scanner and cut the yellow and blue wires (not required for this project).

2) Now only 4 wires remain:

1. Red = Positive (VCC)
2. Black = Ground (GND)
3. Green = Pin 2 (Digital)
4. White = Pin 3 (Digital)

3) Place the fingerprint scanner firmly on the wood ply in a convenient position.

4) Place the Arduino Uno beside the scanner on the same wood ply so the wiring can be done easily.

Now both the fingerprint scanner and Arduino Uno are mounted and ready for wiring.

Wiring Fingerprint Scanner and Servo Motor with Arduino Uno

1. Fingerprint Scanner Wiring

1. Red → 5V (VCC)
2. Black → GND
3. Green → Pin 2
4. White → Pin 3

2. Servo Motor (MG90) Wiring

1. Red → 5V (VCC)
2. Black → GND
3. Orange → Pin 8

⚡ Make sure the power supply is stable (use external 5V if needed) because the servo and fingerprint scanner together may draw extra current.

Now both the fingerprint scanner and servo motor are connected to Arduino Uno and ready for programming.

Take a USB cable and connect the Arduino Uno to your laptop/PC.

Open the Arduino IDE software on your computer.

Install the required Fingerprint Sensor Library (e.g., Adafruit Fingerprint Sensor Library).

Use the enrollment sketch from the library examples to store fingerprints in the sensor’s memory.

Steps to Include Adafruit Fingerprint Library in Arduino IDE

1) Open Arduino IDE on your computer.

2) Go to the menu: Sketch → Include Library → Manage Libraries…

3) In the Library Manager window, type “Adafruit Fingerprint Sensor Library” in the search bar.

4) Find Adafruit Fingerprint Sensor Library in the results and click Install.

5) Wait for the installation to complete.

6) Close the Library Manager.

1) After Upload enroll sketch , open the Serial Monitor in the Arduino IDE.

2) Set the baud rate to 57600 (or as per your sketch).

3) In the Serial Monitor, type 1 and press Enter to start storing a fingerprint with ID 1.

4) Place the finger on the fingerprint scanner.

1. The Serial Monitor will display “Image taken”.

5) Lift your finger and place it on the scanner again.

1. This step ensures a second scan is captured for better accuracy.
2. This completes the fingerprint enrollment for ID 1.

✅ Now the fingerprint is stored successfully, and the sensor is ready to recognize this finger for unlocking the tower bolt.

1) After successfully storing the fingerprint, close the Serial Monitor in the Arduino IDE.

2) Open the main fingerprint sketch from the Adafruit Fingerprint Sensor Library.

3) Upload the sketch to the Arduino.

4) Once uploaded, the sketch will allow the fingerprint scanner to detect stored fingerprints and trigger actions, such as moving the servo motor to unlock the tower bolt.

✅ Your fingerprint door lock system is now ready for testing.

1) After uploading the sketch and testing via laptop, disconnect the Arduino Uno from the USB cable.

2) Take a 9V battery and connect it to the Arduino Uno’s power jack.

1. Ensure proper polarity: positive to +, negative to –.

3) Once connected, the Arduino, fingerprint scanner, and servo motor will run on battery power.

✅ Your fingerprint door lock is now fully functional and independent of the laptop.

Test the lock:

1. Place an enrolled finger on the scanner.
2. Servo motor should rotate and move the tower bolt to unlock and lock.
3. Non-enrolled fingers should not unlock the bolt.

✅ Your fingerprint door lock is now working.