Fingerprint Sensor: The Beginner’s Ultimate Guide

A fingerprint sensor circuit is a perfect project idea for an engineer or designer to create a security application. 

Since fingerprints are unique to each individual, the sensor adds an extra layer of security for any security system you plan to build. 

No doubt, the building fingerprint sensor sounds complex, especially if you’re a newbie engineer. But it’s not rocket science. 

This article will show you how fingerprint sensors work, their applications, and how to install them on your devices.

What is a Fingerprint Sensor?

People tend to lean towards biometrics when there’s a high demand for security. Plus, it provides advanced security levels when paired with other forms of protection–like passwords.

So, the finger sensor is a biometric system that can capture and recognize a human fingerprint. As we mentioned earlier, each person has a unique fingerprint that helps easy identification. Fingers have ridges that create up to five types of prints, including whorl, left loop, right loop, arch, and tented.



Fingerprint sensors primarily work for devices that require better performance and accuracy than regular passwords.

Hence, you don’t have to worry about problems with similar fingerprints. Fingerprint sensors come with built-in fingerprint detection modules that distinguish fingerprints. And it achieves it by discovering the ends of a finger’s ridge.

In addition, fingerprint sensors offer a more accessible and safer way to lock and unlock devices. Also, fingerprints can serve as digital passwords that you can’t forget. 

Device Safety

Device Safety

How Does a Fingerprint Sensor Work?

Enrollment and matching are the two main factors forming a fingerprint sensor’s working principle. Before using any fingerprint sensor, you’d have to enroll your print into the device’s database. 

Let’s say you bought a new mobile phone with a fingerprint sensor and want to activate your biometrics security. Now, the device will ask you to place your finger on the sensor multiple times to successfully enroll your fingerprint on the device. 

But that’s only what happens on the surface. While enrolling, the sensor generates a fingerprint pattern based on your finger and stores it in code form for matching.

Once you’ve successfully enrolled, the sensor will scan and turn your scanned fingerprint into a code. Then, it matches the code to the one stored in its database. Afterward, it automatically unlocks the device or system. If it doesn’t fit, it will deny access.

Three Scanning Methods of a Fingerprint Sensor

Additionally, a fingerprint sensor can use three scanning methods to enroll and match fingerprints. So they include optical, capacitive, and ultrasonic scanning.

Optical Scanners

Optical scanners shine a bright light over your finger to take high-resolution digital photos of your fingerprint. Plus, it’s similar to placing your hand on a photocopy machine.

But, instead of capturing a dark photocopy, it sends your captured print to a device for storage.

Optical scanners

Optical scanners

Also, optical scanners use light-sensitive microchips to create visual images. These light-sensitive microchips can be either CCD or CMOS sensors. 

Afterward, the device connected to the optical sensor does three things:

  • Analyzes the image 
  • Selects only the fingerprint
  • Turns the fingerprint into a code with advanced pattern-matching software

Capacitive Sensors

Once you place your finger on any surface, your fingerprint ridges make contact with the surface, while the hollows between the banks don’t precisely touch the surface. In contrast, capacitive sensors use an electrical current to measure your finger.

Hence, there are different distances between the parts of your finger and the surface you’re touching. Again, this distance is what a capacitive sensor measures to generate an image of your fingerprint. Also, capacitive scanners are similar to phone touchscreens and don’t work well with moist fingers. 

Though capacitive sensors are more secure and faster than optical sensors, you can damage them with static electricity. And that’s if you use them continuously with wet fingers.

Ultrasonic Fingerprint Scanners

Alternatively, the ultrasonic fingerprint sensor uses ultrasound instead of electricity or light to analyze your fingerprints. Hence, you can find ultrasonic scanners on new-model smartphones. Plus, ultrasound sensors scan fingerprints in 3D–making them more secure than optical scanners. However, ultrasonic scanners are usually slower than capacitive sensors.

How Do You Install a Fingerprint Sensor?

You can either install a USB-powered fingerprint sensor” on your device or install it with an Arduino. LLet’stake a closer look at both.

USB Fingerprint Sensor

First, connect your fingerprint scanner to your device via a USB port. If it works, your computer will recognize the device. Next, install the software for your reader. You can either use the installation disk with the reader or download the matching software online.

After installing the software, you can use your fingerprint sensors. Then, try pressing your finger on the sensor and registering your fingerprint. If it works, then your connection is successful. However, some models may require you to configure additional settings. 

Afterward, you can start using your fingerprint to unlock your device.

Fingerprint Sensor with Arduino

You only need a few components for connecting the fingerprint sensors to Arduino. These components include:

  • A fingerprint sensor module
  • Breadboard
  • Power bank
  • Connecting wires 
  • TFT display 
  • Arduino board

Step 1: The pins of the fingerprint sensors include a DNC, VCC, TX, RX, and GND pin. Hence, use a white wire to connect the DNC pin, red for VCC, blue for TX, green for RX, and black for GND. 

Step 2: To connect the fingerprint sensors to the Arduino, join the black wire to the GND pin, red to the 5V pin, green to pin 2, and white to pin 3.

Step 3: You can also connect the display to the Arduino by clicking the following order:

  1. Link the VCC of the TFT display to the 5v pin of the Arduino
  2. GND to GND
  3. CS pin to digital pin 10
  4. RST pin to digital pin 9
  5. A0 pin to digital pin 8
  6. SDA pin to digital pin 11
  7. SCK pin to digital pin 13 
  8. And the LED pin to 3.3v pin

After the following connections, upload the code below using the Adafruit fingerprint library for the sensor. And the Adafruit GFX and Sumotoy libraries for the display.

Arduino Code

Arduino Code

Arduino Code

Arduino Code

Not Working

If your fingerprint sensor is not working after a successful connection, you can either troubleshoot for problems or replace it. Plus, you can check the manual for troubleshooting options.

If using an Arduino connection, ensure you connect all pins properly or check if you have faulty equipment.


Fingerprint sensors primarily work for security applications. Hence, you can use them to secure your phone’s computers, access buildings, and even capture data.

Fingerprint Access

Fingerprint Access

Source: Pixabay

Closing Words

Fingerprint Scanning

Fingerprint Scanning

Fingerprint sensor scanning is more popular than any other form of biometric security. One of the advantages of using fingerprint scanning is protecting your device, information, or property from criminals or intruders. Plus, it’s easy to use and store data securely.

Hence, if you need a better way to secure your private information, you should use a fingerprint sensor. You won’t have problems like forgetting your password or your keys again.

If you have any more questions about fingerprint sensors not covered here, don’t he’s it ate to reach us.

Avatar photo
Emma Lu
Our professional engineering support saves our customers a lot of trouble and loss. >>>>>> After you place the order, our engineer will conduct technical reviews to make sure the parts can be mounted well/correctly on the boards. We will check if the component packages match well with the Gerber footprints, if the part numbers you provided match well with the descriptions, and if the polarity is clearly marked. >>>>> When your design is ready, please send your Gerber and BOM so we can quote and start!