I found a small problem in the Hardware connect part of Case 05 Water Level Alarming.
In the picture, the water level sensor and relay are connected to the wrong pins.
Wrong:
Water level sensor → P1
Relay → P2
Correct:
Water level sensor → P2
Relay → P1
I marked the wrong connection with a red circle in the picture below.
This also matches the code in the tutorial. The code uses P2 to read the water level sensor and P1 to control the relay.
After I changed the connections, the project worked correctly.I hope this can help fix the hardware connection picture in the tutorial!
Tutorial: https://wiki.elecfreaks.com/en/microbit/wisdom-life/microbit-smart-home-kit/smart_home_case_05/