This is my design for a bike lock that is unlocked with a fingerprint sensor. The locking mechanism is controlled by a solenoid and a relay. When the sensor successfully detects a correct fingerprint with sufficient confidence the arduino will trigger the relay, causing the solenoid to retract. The solenoid is equipped with a tip similar to a door lock, so power is only needed to unlock the bike lock. The system is currently powered by a rechargeable 9v battery, but a future system would feature a simpler power system and a sleep/wake system to ensure long term operation. This project was developed to improve the overall biking experience at Pitt. By creating convenience for the user the product adds value over current common solutions. 

The code is mostly from an example sketch written by Adafruit Industries.

 Some changes were made to implement the relay control and fingerprint sensor lighting. 

/***************************************************

  This is an example sketch for our optical Fingerprint sensor

  Designed specifically to work with the Adafruit BMP085 Breakout

  ----> http://www.adafruit.com/products/751

  These displays use TTL Serial to communicate, 2 pins are required to

  interface

  Adafruit invests time and resources providing this open source code,

  please support Adafruit and open-source hardware by purchasing

  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit Industries.

  BSD license, all text above must be included in any redistribution

 ****************************************************/

#include <Adafruit_Fingerprint.h>

#if (defined(__AVR__) || defined(ESP8266)) && !defined(__AVR_ATmega2560__)

// For UNO and others without hardware serial, we must use software serial...

// pin #2 is IN from sensor (GREEN wire)

// pin #3 is OUT from arduino  (WHITE wire)

// Set up the serial port to use softwareserial..

SoftwareSerial mySerial(2, 3);

#else

// On Leonardo/M0/etc, others with hardware serial, use hardware serial!

// #0 is green wire, #1 is white

#define mySerial Serial1

#endif

Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);

void setup()

{

  Serial.begin(9600);

  while (!Serial);  // For Yun/Leo/Micro/Zero/...

  delay(100);

  pinMode(4,OUTPUT); //new code

  Serial.println("\n\nAdafruit finger detect test");

  // set the data rate for the sensor serial port

  finger.begin(57600);

  delay(5);

  if (finger.verifyPassword()) {

    Serial.println("Found fingerprint sensor!");

  } else {

    Serial.println("Did not find fingerprint sensor :(");

    while (1) { delay(1); }

  }

  Serial.println(F("Reading sensor parameters"));

  finger.getParameters();

  Serial.print(F("Status: 0x")); Serial.println(finger.status_reg, HEX);

  Serial.print(F("Sys ID: 0x")); Serial.println(finger.system_id, HEX);

  Serial.print(F("Capacity: ")); Serial.println(finger.capacity);

  Serial.print(F("Security level: ")); Serial.println(finger.security_level);

  Serial.print(F("Device address: ")); Serial.println(finger.device_addr, HEX);

  Serial.print(F("Packet len: ")); Serial.println(finger.packet_len);

  Serial.print(F("Baud rate: ")); Serial.println(finger.baud_rate);

  finger.getTemplateCount();

  if (finger.templateCount == 0) {

    Serial.print("Sensor doesn't contain any fingerprint data. Please run the 'enroll' example.");

  }

  else {

    Serial.println("Waiting for valid finger...");

      Serial.print("Sensor contains "); Serial.print(finger.templateCount); Serial.println(" templates");

  }

}

void loop()                     // run over and over again

{

  getFingerprintID();

  delay(50);            //don't ned to run this at full speed.

}

uint8_t getFingerprintID() {

  uint8_t p = finger.getImage();

  switch (p) {

    case FINGERPRINT_OK:

      Serial.println("Image taken");

      break;

    case FINGERPRINT_NOFINGER:

      Serial.println("No finger detected");

      return p;

    case FINGERPRINT_PACKETRECIEVEERR:

      Serial.println("Communication error");

      return p;

    case FINGERPRINT_IMAGEFAIL:

      Serial.println("Imaging error");

      return p;

    default:

      Serial.println("Unknown error");

      return p;

  }

  // OK success!

  p = finger.image2Tz();

  switch (p) {

    case FINGERPRINT_OK:

      Serial.println("Image converted");

      break;

    case FINGERPRINT_IMAGEMESS:

      Serial.println("Image too messy");

      return p;

    case FINGERPRINT_PACKETRECIEVEERR:

      Serial.println("Communication error");

      return p;

    case FINGERPRINT_FEATUREFAIL:

      Serial.println("Could not find fingerprint features");

      return p;

    case FINGERPRINT_INVALIDIMAGE:

      Serial.println("Could not find fingerprint features");

      return p;

    default:

      Serial.println("Unknown error");

      return p;

  }

  // OK converted!

  p = finger.fingerSearch();

  if (p == FINGERPRINT_OK) {

    Serial.println("Found a print match!");

  } else if (p == FINGERPRINT_PACKETRECIEVEERR) {

    Serial.println("Communication error");

    return p;

  } else if (p == FINGERPRINT_NOTFOUND) {

     finger.LEDcontrol(FINGERPRINT_LED_FLASHING, 25, FINGERPRINT_LED_RED, 10);

  delay(1000);  // keep on for 1 second

  finger.LEDcontrol(FINGERPRINT_LED_OFF, 0, FINGERPRINT_LED_RED);

    return p;

  } else {

    Serial.println("Unknown error");

    return p;

  }

  // found a match!

  Serial.print("Found ID #"); Serial.print(finger.fingerID);

  Serial.print(" with confidence of "); Serial.println(finger.confidence);

  finger.LEDcontrol(FINGERPRINT_LED_ON, 0, FINGERPRINT_LED_BLUE);

  digitalWrite(4, HIGH);

  delay(1000);  // keep on for 1 second

  finger.LEDcontrol(FINGERPRINT_LED_OFF, 0, FINGERPRINT_LED_BLUE);

  digitalWrite(4, LOW);

  return finger.fingerID;

}

// returns -1 if failed, otherwise returns ID #

int getFingerprintIDez() {

  uint8_t p = finger.getImage();

  if (p != FINGERPRINT_OK)  return -1;

  p = finger.image2Tz();

  if (p != FINGERPRINT_OK)  return -1;

  p = finger.fingerFastSearch();

  if (p != FINGERPRINT_OK)  return -1;

  // found a match!

  Serial.print("Found ID #"); Serial.print(finger.fingerID);

  Serial.print(" with confidence of "); Serial.println(finger.confidence);

  return finger.fingerID;

}