Remote Controlled Door Lock Using a Fingerprint Sensor & Adafruit IO

Let's now see the sketch that we'll use for this part of the project. Again, as the sketch is quite complex,I'll only show you the most important parts here.

It starts by including the right libraries:

#include <ESP8266WiFi.h>
#include "Adafruit_MQTT.h"
#include "Adafruit_MQTT_Client.h"

Then, you need to set your WiFi settings:

#define WLAN_SSID       "your_wifi_ssid"
#define WLAN_PASS       "your_wifi_password"
#define WLAN_SECURITY   WLAN_SEC_WPA2

And also your Adafruit IO settings, just as in the previous project:

#define AIO_SERVER      "io.adafruit.com"
#define AIO_SERVERPORT  1883
#define AIO_USERNAME    "adafruit_io_username"
#define AIO_KEY         "adafruit_io_key"

We also define on which pin we'll connect the LED (and later the lock, or a relay for example):

int relayPin = 5;

We also define a new feed to the lock:

const char LOCK_FEED[] PROGMEM = AIO_USERNAME "/feeds/lock";
Adafruit_MQTT_Subscribe lock = Adafruit_MQTT_Subscribe(&mqtt, LOCK_FEED);

In the setup() function of the sketch, we set the pin of the LED as an output:

pinMode(relayPin, OUTPUT);

We also subscribe to the lock feed that we just defined earlier:

mqtt.subscribe(&lock);

In the loop() function of the sketch, we first check if we are connected to Adafruit IO:

MQTT_connect();

Then, we check what's coming from the lock feed we subscribed to. If the message is '1', we activate the pin we defined earlier, that is connected to the LED. If we receive a '0', we just put this pin to a low state again:

Adafruit_MQTT_Subscribe *subscription;
while ((subscription = mqtt.readSubscription(1000))) {
  if (subscription == &lock) {
    Serial.print(F("Got: "));
    Serial.println((char *)lock.lastread);
     
    // Save command to String
    String command = String((char *)lock.lastread);
    command.trim();
          
    if (command == "0") {
      digitalWrite(relayPin, LOW);
    }
    if (command == "1") {
      digitalWrite(relayPin, HIGH);
    }
  }
}

Note that you can find the latest version of the code on the GitHub repository of the project:

https://github.com/openhomeautomation/lock-control-fingerprint

It's now time to test the project! Use the Arduino library manager to download all the required libraries of this project.

Also make sure that you modified the code with your settings, like your Adafruit IO settings & your WiFi network credentials.

To program the ESP8266 chip, I used a simple USB-FTDI board. To learn more about how to program the Adafruit ESP8266 breakout board, I recommend this excellent guide:

https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout

Finally, upload the code to the board. Also open the Serial monitor. You basically just want to check for now that the project can indeed connect to Adafruit IO: we'll test the other functionalities in the next page.

Testing the Project

It's now time to finally test our project! First, go to your Adafruit IO dashboard, in the Feeds section. You need to check that the fingerprint & lock feeds have been created by your sketches:

If that's not the case, you'll need to create them manually.

Then, we still need a way to link the fingerprint feed, and the lock feed. We want the lock feed to take the '1' value when the fingerprint feed goes to 1, and vice-versa. 

For that, we'll use a very powerful feature of Adafruit IO: triggers. Triggers are basically conditions that you can set on your feeds, for example to link two feeds.

We'll define a new reactivr trigger from the Triggers section of Adafruit IO, linking our fingerprint & lock feeds:

Here is how it should look like with both triggers in the Adafruit IO dashboard:

Once that's done, you can actually test the project! Make sure that both parts of the project are working correctly. Then, put the finger that you enrolled before on the fingerprint sensor.

You should see a little light coming up on the Arduino board, meaning that data was transmitted to Adafruit IO. Then, very shortly after, you should see blinking light on the ESP8266 board, meaning data was received via MQTT. The LED should also light up immediately. 

After the delay you set in the code (10 seconds by default), you should see that the LED will go off again. Congratulations, you are now able to control the LED with your fingerprint, even if both projects were on the other side of the world!

Setting up th Electronic Door Lock

It's now time for the last part of the project: actually connecting the electronic lock. This is quite complex, and you could perfectly use the project as it is, for example by connecting a relay instead of the LED.

To actually connect the door lock, you'll need a bunch of additional components. You will first need a 12V power supply, and a breadboard-friendly DC barrel jack. 

You will also need a power transistor (I used an IRLB8721 power MOSFET, but you can also use a TIP102 bipolar transistor for example.) You'll also need a 1K Ohm resistor in case you are using a bipolar transistor. Finally, you will need a rectifier diode.

For the assembly of all these components to the ESP8266 board, it's better to look at this schematic:

Note that if you are using a MOSFET transistor, you don't need the resistor between the pin number 5 of the ESP8266 board & the transistor.

This is the completely assembled project:

When the project is assembled, power up again the ESP8266 using the FTDI module for example, and then connect the 12V DC power supply. You don't need to change anything in the code: it should work out of the box, as it's using the same pin as before.

Now, try again placing your finger on the fingerprint sensor: you should see the lock reacts nearly immediately.

How to go Further

In this project, we built a remotely controled door lock, that can be controled using your fingerprint. Thanks to Adafruit IO, it was also really easy to connect the two parts of the project wirelessly.

You can now experiment with this project, and of course modify it at your convenience. You can for example replace the door lock by anything you want: a simple relay, or a PowerSwitch Tail Kit to control an electrical appliance.

You could also imagine controlling several devices at once in your home just by placing your finger on the sensor once. For example, you could have all the doors in your home connected to such a project, and locking them all at once.