OK. Opening the case was an easy task. Here is what is inside:
This Tuya Sensor is based on LD2410C mmWave sensor. Just in case here is an Amazon link:
https://www.amazon.com/dp/B0C8H7ZBRS?psc=1&ref=ppx_yo2ov_dt_b_product_details
I bought few LDs and playing DIY based on ESP Home project. It actually works more or less OK.
My DIY project is on a left.
The heating comes from mmWave chip itself. After power on it becomes noticeably worm
even in free air. It is wormer in the closed case.
