Security and accessibility is the main concern in today's world. We always try to keep our house secure and at the same time we want to make our home devices easy accessible even from the remote location. Think, you have a guest waiting at your front door and you are outside of the home. But you want to allow him inside your house. Or you are doing a very important task on your desk and want to know who came at the front door without leaving your seat. Just imagine! Alexa can do everything for you!!

What it does

Yes, I made an intelligent door lock which can recognize a guest, greet the guest with name, notify the owner about the guest and remember an unknown guest. House owner can know the name of the guest by asking Alexa like "Alexa, who is at the front door?" You can also ask Alexa to open or close the door. I made a custom Alexa Skill for this. Using the skill you can know your guest and welcome him inside your house without leaving your seat.

My skill is live at Amazon Store (Skill ID: amzn1.ask.skill.4ba64998-cb8f-461d-8712-16c5dfcfc9d3)


How I built it

Step by step instructions In this tutorial, I will show you how you can make such an intelligent device yourself. I am assuming you have some previous experience with Arduino & Raspberry Pi and some basic knowledge in Python programming.

In this project, I used several AWS services (e.g. IoT, Lambda, Bucket, Polly, SNS). So, you will be required an Amazon AWS account.

Before going into detail instructions let me first explain how it works. I am calling this device Intelligent Door Lock and for making the device I used a Raspberry Pi with the official camera module and an Arduino with a servomotor for controlling the lock.

When a guest comes to your door and press the calling button, Raspberry Pi performs three tasks:

  1. It takes a picture of the guest and uploads it to AWS S3 Bucket and S3 Bucket trigger an SNS notification to a specific topic.
  2. It sends an email with the photo to the house owner.
  3. It sends a greeting text to AWS Polly and then plays the audio greeting for the guest returned by the Polly. After getting the notification from AWS SNS or the email house owner can ask Alexa to introduce the guest by invoking the custom skill "Door Guard" and saying:

Alexa, ask door guard who is at the front door? or

Alexa, ask door guard who came?

Alexa triggers a Lambda function and Lambda function does the following jobs:

  1. Read the image uploaded to the S3 Bucket.
  2. Sends a face search request for the image to AWS Rekognition.
  3. After getting face matches result return by Rekognition, Lambda search for the name to AWS DynamoDB and return the name to the Alexa if found. Alexa provides the name to the house owner and house owner again call the Alexa to open the door for the guest. In this case, Lambda sends an open door command to AWS IoT to a specific topic. Raspberry Pi receives this command and sends to Arduino using the serial port. Arduino controls the lock accordingly. The following block diagram can help for better understanding. Block Diagram

Work Flow

-->Preparing Raspberry Pi (installing required libraries) -->Writing program for Raspberry Pi (for capturing image on button press, uploading the image to S3, sending email to -->the owner, receiving message from mqtt broker, greeting guest, sending control signal to Raspberry Pi) -->Setting AWS Services (AWS S3 Bucket, AWS DynamoDB, AWS Lambda, AWS SNS, AWS Rekognition) -->Writing program for uploading Images of knows persons and storing Face Index in the DinamoDB table. -->Making Custom Alexa Skill and writing code for Lambda function. -->Writing code for Arduino. -->Connecting all the hardware. -->Testing & Debugging.

Setting up the Raspberry Pi

Prepare your Raspberry Pi with the latest Raspbian operating system and get ready to do some programming. If you are new in Raspberry Pi read this how to get started using Raspberry Pi guide. You can plug a mouse, keyboard, and monitor into your Pi or access it using SSH client like PuTTY. To know how to connect with PuTTY you may read this tutorial.

Install python serial module using the command: sudo apt-get install python-serial

Install AWS IoT SDK using following command: sudo pip install AWSIoTPythonSDK

Details of AWSToTPythonSDK is here.

Installing & Configuring AWS CLI

The AWS Command Line Interface (CLI) is a unified tool that allows you to control AWS services from the command line. AWS CLI helps you creating any AWS object from command line without using GUI interface. If you already have pip and a supported version of Python (integrated with latest Raspbian OS), you can install the AWS CLI with the following command:

pip install awscli --upgrade --user

You need to configure AWS CLI with Access Key ID, Secret Access Key, AWS Region Name and Command Output format before getting started with it.

Follow this tutorial for completing the whole process.

Setting up Amazon S3 Bucket, Amazon Rekognition and Amazon DynamoDB

Amazon Rekognition is a sophisticated deep learning based service from Amazon Web Services (AWS) that makes it easy to add powerful visual search and discovery to your own applications. With Rekognition using simple APIs, you can quickly detect objects, scenes, faces, celebrities and inappropriate content within images. Amazon Rekognition also provides highly accurate facial analysis and facial recognition. You can detect, analyze, and compare faces for a wide variety of user verification, cataloging, people counting, and public safety use cases.

Amazon Rekognition is based on the same proven, highly scalable, deep learning technology developed by Amazon’s computer vision scientists to analyze billions of images and videos daily, and requires no machine learning expertise to use. Amazon Rekognition is a simple and easy to use API that can quickly analyze any image or video file stored in Amazon S3.

Amazon Rekognition can store information about detected faces in server-side containers known as collections. You can use the facial information stored in a collection to search for known faces in images, stored videos and streaming videos. Amazon Rekognition supports the IndexFaces operation, which you can use to detect faces in an image and persist information about facial features detected into a collection.

The face collection is the primary Amazon Rekognition resource, each face collection you create has a unique Amazon Resource Name (ARN). You create each face collection in a specific AWS Region in your account.

We start by creating a collection within Amazon Rekognition. A collection is a container for persisting faces detected by the IndexFaces API. You might choose to create one container to store all faces or create multiple containers to store faces in groups. You can use AWS CLI to create a collection or use the console. For AWS CLI, you can use the following command:

aws rekognition create-collection --collection-id guest_collection --region eu-west-1

The above command creates a collection named as guest_collection.

The user or role that executes the commands must have permissions in AWS Identity and Access Management (IAM) to perform those actions. AWS provides a set of managed policies that help you get started quickly. For our example, you need to apply the following minimum managed policies to your user or role:

  1. AmazonRekognitionFullAccess

  2. AmazonDynamoDBFullAccess

  3. AmazonS3FullAccess

  4. IAMFullAccess

Next, we create an Amazon DynamoDB table. DynamoDB is a fully managed cloud database that supports both document and key-value store models. In our example, we’ll create a DynamoDB table and use it as a simple key-value store to maintain a reference of the FaceId returned from Amazon Rekognition and the full name of the person.

You can use either the AWS Management Console, the API, or the AWS CLI to create the table. For the AWS CLI, use the following command:

aws dynamodb create-table --table-name guest_collection \ --attribute-definitions AttributeName=RekognitionId,AttributeType=S \ --key-schema AttributeName=RekognitionId,KeyType=HASH \ --provisioned-throughput ReadCapacityUnits=1,WriteCapacityUnits=1 \ --region eu-west-1

For the IndexFaces operation, you can provide the images as bytes or make them available to Amazon Rekognition inside an Amazon S3 bucket. In our example, we upload the images (images of the known guest) to an Amazon S3 bucket.


Again, you can create a bucket either from the AWS Management Console or from the AWS CLI. Use the following command:

aws s3 mb s3://guest-images --region eu-west-1

Although all the preparation steps were performed from the AWS CLI, we need to create an IAM role that grants our function the rights to access the objects from Amazon S3, initiate the IndexFaces function of Amazon Rekognition, and create multiple entries within our Amazon DynamoDB key-value store for a mapping between the FaceId and the person’s full name.

To get the access use the following code snippet and save as access-policy.json

    "Version": "2012-10-17", 
    "Statement": [ 
             "Effect": "Allow",
             "Action": [ 
                "Resource": "arn:aws:logs:*:*:*"
             "Effect": "Allow", 
             "Action": [ 
                "Resource": [
            "Effect": "Allow", 
            "Action": [
            "Resource": [ 
            "Effect": "Allow", 
            "Action": [ 
            "Resource": "*"

For the access policy, ensure you replace aws-region, account-id, and the actual name of the resources (e.g., bucket-name and family_collection) with the name of the resources in your environment.

Now, attach the access policy to the role using the following command.

aws iam put-role-policy --role-name LambdaRekognitionRole --policy-name \ LambdaPermissions --policy-document file://access-policy.json

We can almost configure our AWS environment. We can now upload our images to Amazon S3 to seed the face collection. For this example, we again use a small piece of Python code that iterates through a list of items that contain the file location and the name of the person within the image.

Before running the code you need to install Boto3. Boto3 is the Amazon Web Services (AWS) Software Development Kit (SDK) for Python, which allows Python developers to write software that makes use of services like Amazon S3 and Amazon EC2. You can find the latest, most up to date, documentation at Read the Docs, including a list of services that are supported.

Install the Boto3 library using the following command:

sudo pip install boto3

Now, run the following python code to upload the images into S3 Bucket. Before running the code be sure that you keep all the images and the python file in the same directory.

import boto3
s3 = boto3.resource('s3')
images=[('afridi.jpg','Shahid Afridi'),
       ('sakib.jpg','Sakib Al Hasan'),
       ('kohli.jpg','Birat Kohli'),
       ('masrafi.jpg','Mashrafe Bin Mortaza'),
       ('ganguli.jpg','Sourav Ganguly')
for image in images:
   file = open(image[0],'rb')
   object = s3.Object('taifur12345bucket',image[0])
   ret = object.put(Body=file,

Now, add the Face Index to AWS DynamoDB with full name for every image using the following python code.

import boto3
from decimal import Decimal
import json
import urllib
BUCKET = "taifur12345bucket"
KEY = "sample.jpg"
IMAGE_ID = KEY  # S3 key as ImageId
COLLECTION = "family_collection"
dynamodb = boto3.client('dynamodb', "eu-west-1")
s3 = boto3.client('s3')
def update_index(tableName,faceId, fullName):
    response = dynamodb.put_item(
        'RekognitionId': {'S': faceId},
        'FullName': {'S': fullName}

def index_faces(bucket, key, collection_id, image_id=None, attributes=(), region="eu-west-1"):
    rekognition = boto3.client("rekognition", region)
    response = rekognition.index_faces(
            "S3Object": {
                "Bucket": bucket,
                "Name": key,
    if response['ResponseMetadata']['HTTPStatusCode'] == 200:
        faceId = response['FaceRecords'][0]['Face']['FaceId']
        ret = s3.head_object(Bucket=bucket,Key=key)
        personFullName = ret['Metadata']['fullname']
    return response['FaceRecords']
for record in index_faces(BUCKET, KEY, COLLECTION, IMAGE_ID):
    face = record['Face']
    print "Face ({}%)".format(face['Confidence'])
    print "  FaceId: {}".format(face['FaceId'])
    print "  ImageId: {}".format(face['ImageId'])


Once the collection is populated, we can query it by passing in other images that contain faces. Using the SearchFacesByImage API, you need to provide at least two parameters: the name of the collection to query, and the reference to the image to analyze. You can provide a reference to the Amazon S3 bucket name and object key of the image, or provide the image itself as a byte stream.

In the following example, I used the following code in Lambda function to search face by taking the image from S3 Bucket. In response, Amazon Rekognition returns a JSON object containing the FaceIds of the matches. Using the face ID it retrieves the full name.


Making Alexa skill & Creating Lambda Function

For making Alexa skill and creating Lambda Function follow my tutorial from here.

Making the Hardware

Raspberry Pi is connected with a camera module. Raspberry Pi sends data to Arduino using the serial cable. I short Arduino cable was used to connect Arduino with Raspberry Pi.


A test setup was made for primary testing either it is working perfectly or not.


After primary testing, I set up all the devices in a door using some hot glue. This setup is for demonstration purpose only. To make the demonstration easy I place all the components on the same side of the door. Practically the camera and the button switch will be the outer side of the door. Here, I did not attach any speaker. A speaker is required to play the greetings for the guest. The demo lock was printed using a 3D printer.



Special thanks to Mr. Christian Petters for his nice tutorial Build Your Own Face Recognition Service Using Amazon Rekognition. It was really helpful and I copied some instructions and commands directly from his writing.

This GitHub link also helped me to develop the program.

Demo Setup


VUI Diagram


Raspberry Pi Circuit

Raspberry Pi is equipped with a camera module, audio amplifier, and a button switch. image

Video of controlling the door lock using Alexa

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