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electronicdesign.com | 1/25/2021
What you’ll learn:
Origin Wireless takes a unique approach to home security. Instead of using cameras or motion sensors, the company employs Wi-Fi in its Home Security System (Fig. 1). The control device uses Wi-Fi to communicate with your network, but it also uses the technology to sense movement within an area such as rooms in a house. How so?
Well, the latest Wi-Fi 5 and 6 implementations employ multiple-input multiple-output (MIMO) antennas. A base station sends out multiple signals and the other end uses that combination to provide higher bandwidth and more reliable communications since alternate paths exist between the devices. Typically, the devices use this for sending and receiving data; they’re not concerned with the quality of the signals other than being sufficient for reliable communication.
The thing is, there’s variation in the signals that are affected by the position and construction of the objects in the environment from walls to people. Move an object and this will slightly affect multiple Wi-Fi signals. The trick is to detect the changes that require a similar but different set of sensors. A rough comparison would be an analog-to-digital converter (ADC) versus a digital circuit that’s based on fixed thresholds.
The other half of the challenge is analyzing the details. Here a digital signal processor (DSP) comes to the rescue. Some machine learning even might be mixed in there. The system considers all signal changes it receives. Even slight movements will affect some of the signals, which the system is able to detect. There are 10 adjustable sensitivity levels in terms of system response to movements.
The system consists of a command hub and multiple Hex Sense sensor units. The command hub is a standard Wi-Fi device that links to your local Wi-Fi network to communicate with the cloud. Of course, this is an Internet of Things (IoT) device. The Hex Home smartphone app provides feedback and security alerts (Fig. 2).
The sensor units plug directly into a wall socket while the command hub has an external power supply. The sensor units receive Wi-Fi signals from the command hub but communicate with it using a separate 2.4-GHz ISM channel. The DSP that handles the signal analysis is in each sensor. Essentially, the sensors track the standard Wi-Fi signals from the command hub and send the results back to the hub.
The system detects movement to determine if something is present in an area. It doesn’t detect an absolute position or distance from a point like radar or optical systems. The advantage is the ability to cover a large area with just a few sensors.
It’s possible to use the app to see the system in action while people are moving around. If everyone freezes, then the detected movement stops but a slight movement will still be detected.
The system also has 80-dB sirens. As with most home security systems, it can be set up to track, notify, or sound an alarm upon detection of unwanted motion. The system can’t be adjusted for height like some other sensor systems, but it’s possible to adjust sensitivity. The system also can selectively manage areas.
The system is trackable via the app. An optional professional monitoring service is in the works that’s similar to conventional security companies and sensing systems. The system can be tied to other devices, such as recording via a camera when movement is detected.
