OpenSprinkler › Forums › Hardware Questions › OpenSprinkler Pi (OSPi) › There is option to connect rain sensor ? › Reply To: There is option to connect rain sensor ? July 16, 2019 at 4:40 pm #61696 RayKeymaster Please, the pull up resistor needs to be connected to 3.3V, not 5V! Connecting it to 5V you will risk damaging your GPIO pin. This is basic knowledge of RPi — that is, GPIO pins are only 3.3V tolerant.