SENSORS/ACTUATORS

Raspberry Pi - Rain Sensor

The rain sensor detects and measures rain/snow levels, offering both digital (LOW/HIGH) and analog outputs. This tutorial guides you in using a Raspberry Pi and a rain sensor to detect and measure rain, covering:

Connecting the rain sensor to a Raspberry Pi.
Programming the Raspberry Pi to detect rain by reading the digital signal from the sensor.
Programming the Raspberry Pi to measure rain levels by reading the analog signal from the sensor.

You can then customize the code to activate a motor or warning when rain/snow is detected.

Hardware Preparation

1	×	Raspberry Pi 4 Model B
1	×	Rain Sensor
1	×	Jumper Wires
1	×	(Optional) Screw Terminal Adapter for Raspberry Pi

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you. We appreciate your support.

Overview of Rain Sensor

The rain sensor serves to detect rain presence or measure water level from rainfall. It offers options through a digital output pin and an analog output pin.

Components of the rain sensor include: sensing pad and electronic module

image source: diyables.io

The sensing pad

The sensing pad, positioned outdoors to encounter rain/snow (e.g., on the roof), features exposed copper traces divided into two groups: power traces and sense traces. These traces remain unconnected unless bridged by water or snow. Power and sense traces are interchangeable, allowing you to designate one as the power trace and the other as the sense trace.

The electronic module

The electronic module of the rain sensor transforms signals from the sensing pad into analog or digital values readable by the Raspberry Pi. It includes four pins:

VCC pin: Connects to VCC (3.3V to 5V).
GND pin: Connects to GND (0V).
DO pin: Digital output pin; it is HIGH when rain is not detected and LOW when detected. The rain detection threshold is adjustable with a built-in potentiometer.
AO pin: Analog output pin; the value decreases with increased water on the sensing pad and increases as water decreases.

Furthermore, it features two LED indicators:

PWR-LED indicator: Indicates power status.
DO-LED indicator: Represents the rain state on the DO pin, illuminating when rain is present.

How It Works

Regarding the DO pin:

The module is equipped with a built-in potentiometer to set the sensitivity threshold.
When the intensity surpasses the threshold, rain is detected, the sensor's output pin is LOW, and the DO-LED illuminates.
When the intensity falls below the threshold, no rain is detected, the sensor's output pin is HIGH, and the DO-LED turns off.

Concerning the AO pin:

The AO pin's reading is inversely proportional to the water level in the sensing pad.
More water results in a lower AO pin value, while less water leads to a higher AO pin value.

Note: The potentiometer does not influence the value on the AO pin.

Wiring Diagram

As previously noted, connecting the VCC pin of the sensor directly to the 3.3V or 5V pins on the Raspberry Pi can reduce the sensor's lifespan due to electrochemical corrosion. A recommended alternative is to connect the VCC pin of the rain sensor to an output pin on the Raspberry Pi. By programming that pin, the rain sensor can be powered only during readings, effectively minimizing the impact of electrochemical corrosion.

This image is created using Fritzing. Click to enlarge image

Raspberry Pi Code

Detailed Instructions

Make sure you have Raspbian or any other Raspberry Pi compatible operating system installed on your Pi.
Make sure your Raspberry Pi is connected to the same local network as your PC.
Make sure your Raspberry Pi is connected to the internet if you need to install some libraries.
If this is the first time you use Raspberry Pi, See how to set up the Raspberry Pi
Connect your PC to the Raspberry Pi via SSH using the built-in SSH client on Linux and macOS or PuTTY on Windows. See to how connect your PC to Raspberry Pi via SSH.
Make sure you have the RPi.GPIO library installed. If not, install it using the following command:

sudo apt-get update sudo apt-get install python3-rpi.gpio

Create a Python script file rain_sensor.py and add the following code:

# This Raspberry Pi code was developed by newbiely.com # This Raspberry Pi code is made available for public use without any restriction # For comprehensive instructions and wiring diagrams, please visit: # https://newbiely.com/tutorials/raspberry-pi/raspberry-pi-rain-sensor import RPi.GPIO as GPIO import time POWER_PIN = 12 # GPIO pin that provides power to the rain sensor DO_PIN = 7 # GPIO pin connected to the DO pin of the rain sensor def setup(): GPIO.setmode(GPIO.BCM) GPIO.setup(POWER_PIN, GPIO.OUT) # configure the power pin as an OUTPUT GPIO.setup(DO_PIN, GPIO.IN) def loop(): GPIO.output(POWER_PIN, GPIO.HIGH) # turn the rain sensor's power ON time.sleep(0.01) # wait 10 milliseconds rain_state = GPIO.input(DO_PIN) GPIO.output(POWER_PIN, GPIO.LOW) # turn the rain sensor's power OFF if rain_state == GPIO.HIGH: print("The rain is NOT detected") else: print("The rain is detected") time.sleep(1) # pause for 1 second to avoid reading sensors frequently and prolong the sensor lifetime def cleanup(): GPIO.cleanup() if __name__ == "__main__": try: setup() while True: loop() except KeyboardInterrupt: cleanup()

Save the file and run the Python script by executing the following command in the terminal:

python3 rain_sensor.py

Drop some water to the rain sensor
Check out the result on the Serial Monitor.

PuTTY - Raspberry Pi

The rain is NOT detected The rain is NOT detected The rain is NOT detected The rain is detected The rain is detected The rain is detected The rain is detected The rain is detected The rain is NOT detected The rain is NOT detected The rain is NOT detected

Please keep in mind that if you notice the LED status remaining on constantly or off even when the sensor faces to a rain, you can adjust the potentiometer to fine-tune the sensitivity of the sensor.

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