Hi-Link manufactures a number of different sensor modules with millimeter wavelength radars which are great to detect humans with.
Some time ago I read about these and they were did not cost much. I bought these from AliExpress. So I ordered some different ones. Recently I found some time to experiment with one of them, the LD2450 (The AliExpress item I bought). On the product page there is a link to a Google drive with documents and software for this module.
I had previously tried one of the others briefly but unsuccessfully. So this time I took a bit different path.
I read that several (maybe all?) of these has built in Bluetooth so I downloaded the HLKRadarTool (iOS or Android) to my phone and powered up the module and connected the phone to it. It worked directly and it was easy to evaluate how the device performed.
Once I know it worked well it was time to connect it to an ESP32. The manual made it easy to understand what pins to use on the radar module. I had some ESP32-C3 modules at home so I decided to use it. The model I had was Tenstar Robot Super Mini and the pinout made it easy to figure out how to connect RX and TX on the sensor to TX and RX on the ESP32.
I then used ESPHome device builder in Home Assistant and the information on the ESPHome LD2450 page to create and install a configuration for the sensor. And soon it appeared in Home Assistant.
After that I looked for a case and found a nice simple case that could easily be pointed in different directions but was not too bulky.
