FEATURE

This device is intended to be a DIY alarm system that can be built using Spresense and as many readily available components as possible. We envision this device to be used by people living in mountainous areas or on slopes in the foothills of the mountains, where it can be easily installed behind their homes or on their property.
The basic principle of operation of this device is to sense changes in the inclination of an erected pile.

Our research into existing technology shows that similar concepts already exist. However, since it is necessary to operate a large number of devices to detect predictive phenomena that can occur anywhere, a key issue is to further reduce the cost of the devices.
The main focus of this project was not to develop a multifunctional device, but to develop a device that is easy to operate and can be implemented as easily as possible by people with no knowledge of electronics or electricity.
The main functions of the device can be implemented by using common garden lights or by combining components that can be purchased in stores.

Main Functions and Features

In operation

Field test.

Field test #2

Smartphon Apps

Installation

When installing the device, simply plug the device into the location you wish to monitor, stand it up, and turn on the power. (0:04~)
When the power is turned on, the acceleration sensor measures the tilt of the device and memorizes the initial state, and the startup completion status is transmitted via Wi-SUN communication.
The LED for alarm indication flashes once when the system starts up, and flashes twice after successful Wi-SUN communication to confirm normal startup. (0:14~)
When startup is completed, the system enters Deepsleep.

When no abnormality is detected

By default, Deepsleep is released every hour to measure the tilt. In the above movie, Deepsleep is set to 3 seconds for operation check. If the difference from the initial tilt is less than the threshold value (5° by default), the system sends a "no abnormality" status and the value of the angle change, and enters Deepsleep again.

When an abnormality is detected

If the difference between the inclination of the device after the release of Deepsleep and the initial inclination is greater than the threshold value, the LED of the garden light flashes and an alert status is sent via Wi-SUN communication.

Receiver-side device (Raspberry Pi 4B)

A Raspberry Pi 4B is used as the receiving device, and a Wi-SUN USB dongle BP35C2 is used to receive Wi-SUN communications.
It also serves as an MQTT server and sends alarm data to the alarm display device or any device.

Alarm display device (M5Stack)

When alarm data is received from the receiving device, it displays the ID of the sensor terminal that detected the abnormality, and indicates the alarm with text, background color, and alarm sound. (0:45～)

System Configuration

The overall system configuration is as follows

Spresense is used as the controller for the sensor section to calculate the device's tilt from the BMI160's accelerometer values. The measurement results are sent to the receiving device via Wi-SUN communication.
The receiving device, a Raspberry Pi, uses python for Wi-SUN communication and data processing, and Node-RED for running the MQTT server and sending alarm information to Google Cloud and the display device.
Data sent to Google Cloud is edited by Google Apps Script and stored in Spreadsheets. Multiple terminals can be managed by using unique ID numbers for each terminal.
Information on each terminal can also be viewed on the smartphone application produced by Glide. Includes a function to display the location of the terminal on a map based on the coordinate information of the installation location in order to confirm the location of the terminal.
When the tilt of the sensor device exceeds the threshold value, the information is also sent to a dedicated display device created with M5Stack, and an alarm is displayed with sound and screen display. Since multiple dedicated display devices can be operated, they can be placed freely in the living room next to the TV, in the bedroom, or in a child's room.

Finally

The results of the field test confirmed that the system is capable of detecting signs of a landslide and issuing an alarm. However, power savings and battery capacity are still insufficient, and further improvements are needed.
As for the communication function, Wi-SUN communication alone has limitations in terms of communication area, and we feel that networking with a mother device using LoRa or other technologies would be effective, but this would require further study as it would complicate the system.
We would like to solve the issues identified in this project and develop the next version to further pursue its potential as an open source hardware that is useful to society.