This is the use for presence sensors.
You have to translate it and see it.
https://blog.naver.com/ispark0114/222832624821
All products that look like this are the same. You can find a cheap product.
https://ko.aliexpress.com/item/1005004147995775.html?spm=a2g0o.order_list.0.0.4f16140fB5JklV&gatewayAdapt=glo2kor
Please refer to this
