Those who own an outdoor cat or even several might run into the occasional problem of having to let them back in. Due to finding it annoying when having to constantly monitor for when his cat wanted to come inside the house, GitHub user gamename opted for a more automated system.

The solution gamename came up with involves listening to ambient sounds with a single Raspberry Pi and an attached USB microphone. Whenever the locally-running machine learning model detects a meow, it sends a message to an AWS service over the internet where it can then trigger a text to be sent. This has the advantage of limiting false events while simultaneously providing an easy way for the cat to be recognized at the door.

This project started by installing the AWS command-line interface (CLI) onto the Raspberry Pi 4 and then signing in with an account. From here, gamename registered a new IoT device, downloaded the resulting configuration files, and ran the setup script. After quickly updating some security settings, a new function was created that waits for new messages coming from the MQTT service and causes a text message to be sent with the help of the SNS service.

After this plethora of services and configurations had been made to the AWS project, gamename moved onto the next step of testing to see if messages are sent at the right time. His test script simply emulates a positive result by sending the certificates, key, topic, and message to the endpoint, where the user can then watch as the text appears on their phone a bit later.

The Raspberry Pi and microSD card were both placed into an off-the-shelf chassis, which sits just inside the house's entrance. After this, the microphone was connected with the help of two RJ45-to-USB cables that allow the microphone to sit outside inside of a waterproof housing up to 150 feet away.

Running on the Pi is a custom bash script that starts every time the board boots up, and its role is to launch the Python program. This causes the Raspberry Pi to read samples from the microphone and pass them to a TensorFlow audio classifier, which attempts to recognize the sound clip. If the primary noise is a cat, then the AWS API is called in order to publish the message to the MQTT topic. More information about this project can be found here in gamename's GitHub repository.

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This Smart Doorbell Responds to Meowing Cats Using Machine Learning and IoT - Hackster.io