Roll Your Own Presence Sensor [Hackaday]

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[Mellow_Labs] wanted an Everything Presence Lite kite but found it was always out of stock. Therefore, he decided to create his own. The kit uses a millimeter wave sensor as a super-sensitive motion tracker for up to three people. It can even read your heart rate remotely. You can see a video of the project below.

There are a few differences from the original kit. Both use the C4001 24 GHz human presence detection sensor. However, the homebrew version also includes a BME680 environmental sensor.

If you haven’t seen a millimeter wave sensor—often written mmwave—before, it is essentially a tiny radar that can measure movement, acceleration, and angles very accurately. They are available at different microwave wavelengths and have onboard processing to easily provide useful information for a processor like the one in this project. The processor on board is an ESP32, which works well with [Mellow_Labs’] home automation system.

A 3D-printed case rounds everything out. Circuit-wise, there isn’t much going on since everything is on a module PCB. You essentially just have to connect everything together.

These sensors can do a lot of things. For example, inspecting pipelines. Another common way to detect people is to use a specialized camera.