Thanks for your reply it really helps the video’s you linked I already found. and found that they where really helpful for understanding. Together with your experience I am probably going to experiment a little to(I like to make my own stuff to so not looking nice is less of a concern as long as it works). Thanks for explaining the few details I didn’t understand. I feel like they are a perfect tool for presence detection that together with something else are exactly what I need. Once again thank you for sharing your experience and knowledge

Interference never though about that good to know might go 60ghz then and get 3 for 180 degree coverage. Also they can look through walls? Also trough wood or concrete or only the american paper walls? As this would be amazing for my hallway where there is a staircase kind of in the way.

Also what do you mean by fast detection are the radars not enough for someone walking by?