Research and test of possible presence sensors

[ClemensGruber]

GPTree should start a conversation when a human shows up before the tree or passes the tree.

Requirements:

• 2 to 8 m detections distance
• 3.3 V operation
• some RasPi code would be nice

Hardware

Should be a radar sensor working on high temperature environment and sunlight, see: https://www.youtube.com/watch?v=PNbAM9IhfBE (at 11:14)

A good overview gives Andreas Spiess in

Radar Switches: Vergleich und Tests https://www.youtube.com/watch?v=9WiJJgIi3W0&t=14s

Only the HFS-DC06 in this video is working at 3.3 V! All other radar modules need 5V. But also some 5 V sensors like the RCWL-0516 work at 3.3 V logic level, see https://randomnerdtutorials.com/esp32-rcwl-0516-arduino/ .

This video is around 6 years old, so it may be good to have a look on an update:

Radar Sensors from $3 to over $100: Which one is Best? https://www.youtube.com/watch?v=s-GzUTyIH9c

With a overview table under https://drive.google.com/drive/folders/1Tslck6CkSz_NcNoW2aIw0u0UAqh7oL49

Software

[ClemensGruber]

Only the HFS-DC06 in this video is working at 3.3 V! All other radar modules need 5V. But also some 5 V sensors like the RCWL-0516 work at 3.3 V logic level, see https://randomnerdtutorials.com/esp32-rcwl-0516-arduino/ .

I ordered this two HFS-DC06 Modules https://www.amazon.de/dp/B081J44XCK and tried it on an ESP32. Unfortuatelly is not working reliable at 3.3 V, but with 5 V! So I assume that at least this module needs 5 V for stable working. Sensor voltage level seems to be Vin level and is not limited -- at least not to 3.3 V, so a no go on the RasPi.

Perhaps there is an error in the video Radar Switches: Vergleich und Tests https://www.youtube.com/watch?v=9WiJJgIi3W0 from Andreas Spiess:

At the beginning it is said that the RCWL-0516 works with 3.3 V:

but in the table later on the HFS-DC06 is only listed as 3.3. V, something mixed up?

The tutorial ESP32 with RCWL-0516 Microwave Radar Proximity Sensor https://randomnerdtutorials.com/esp32-rcwl-0516-arduino/ from randomnerdtutorials indicates also that the table is not correct and the RCWL-0516 will work with 3.3 V, so I will order and test them!

[ClemensGruber]

Hint from Effective Ways To Detect People With Common Sensors https://www.youtube.com/watch?v=LNeSz5hfTLI Sensors like the mmWave Radar from DFRobot https://www.dfrobot.com/product-2282.html do not only detect movement but also presence. So also peple who stay on the tree can detected. And you can detect the absence of a person "Oh, you're leaving, what a pitty, I'd like to keep talk with you!" But 10x more expensive!

... DFRobot's mmWave Radar sensor ordered and have to be tested ...

[ClemensGruber]

Today I tested the RCWL-0516 with a RasPi and ESP32 and it works good. I tested it with 3.3 V and 5 V Vin and the module is working on both voltage levels, while digital output is still 3.3 V level! Data sheet says 4 V recommended at least.

As with many motion sensors, there is a delay of approx. 2-3 s if the sensor has detected "no movement", so it stays 2-3 s off even if there is movement before the sensor. And it seems to be a bit less sesitive than a PIR sensor; very slow movements don't trigger it.

Detection range (with 3.3 V) is about 4-5 m, but I have to test it more detailed in the field (not in the office).

OT: The pin with "3V3" lable on the module is juste a constant 3V3 source and does not change by movement or not, so not needed for us.