Arduino - Rain Sensor - Relay

We are going to learn how to:

By connecting relay to light bulb, led strip, motor or actuator... We can use the rain sensor to control light bulb, led strip, motor or actuator...

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Rain Sensor
1×Jumper Wires
1×(Optional) Solenoid Lock
1×(Optional) 12V Power Adapter
1×(Optional) DC Power Jack
1×(Optional) 9V Power Adapter for Arduino
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Relay and Rain Sensor

If you do not know about relay and rain sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

Arduino Rain Sensor Relay Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code

/* * Created by * * This example code is in the public domain * * Tutorial page: */ #define RAIN_SENSOR_PIN A0 // Arduino pin connected to the OUTPUT pin of rain sensor #define RELAY_PIN A2 // Arduino pin connected to the IN pin of relay int rain_state = LOW; // current state of rain sensor's pin int prev_rain_state = LOW; // previous state of rain sensor's pin void setup() { Serial.begin(9600); // initialize serial pinMode(RAIN_SENSOR_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { prev_rain_state = rain_state; // store old state rain_state = digitalRead(RAIN_SENSOR_PIN); // read new state if (prev_rain_state == LOW && rain_state == HIGH) { // pin state change: LOW -> HIGH Serial.println("Rain detected!"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (prev_rain_state == HIGH && rain_state == LOW) { // pin state change: HIGH -> LOW Serial.println("Rain stopped!"); digitalWrite(RELAY_PIN, LOW); // turn off } }

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
Arduino IDE Upload Code
  • Move your hand in front of sensor
  • See the change of relay's state

Code Explanation

Read the line-by-line explanation in comment lines of source code!

Video Tutorial

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