Rain Sensor Complete Guide¶
Detect rainfall and automate your world
📖 Overview¶
The rain sensor detects water on its surface and measures rainfall intensity. Perfect for automatic window closing, irrigation control, and weather stations.
| Feature | Specification |
|---|---|
| Output type | Analog (0-4095) + Digital (LOW/HIGH) |
| Intensity range | 0% (dry) to 100% (heavy rain) |
| Response time | <1 second |
| Operating voltage | 5V (recommended) or 3.3V |
| Board compatibility | ESP32, ESP8266, Pico W |
🔌 Wiring Guide¶
ESP32¶
| Sensor Pin | ESP32 Pin |
|---|---|
| VCC | 5V |
| AO | GPIO34 (ADC) |
| GND | GND |
ESP8266¶
| Sensor Pin | ESP8266 Pin |
|---|---|
| VCC | 5V |
| AO | A0 |
| GND | GND |
Pico W¶
| Sensor Pin | Pico W Pin |
|---|---|
| VCC | 5V (pin 40) |
| AO | GP26 (pin 31) |
| GND | GND (pin 38) |
Note: Use 5V for best accuracy. 3.3V works but reduces sensitivity.
⚙️ Dashboard Configuration¶
- Go to Device Configuration
- Enable Rain Sensor
- Set threshold: 2000-3000 (ESP32/Pico) or 500-800 (ESP8266)
- Save and regenerate firmware
- Flash to your device
📊 How It Works¶
| Condition | ADC Raw | Intensity % | Digital Output |
|---|---|---|---|
| Dry (no rain) | 4095 | 0% | HIGH |
| Light drizzle | 3000 | 27% | HIGH |
| Light rain | 2000 | 51% | LOW |
| Heavy rain | 500 | 88% | LOW |
| Flood | 0 | 100% | LOW |
Formula: Intensity% = map(ADC_RAW, 4095, 0, 0, 100)
🤖 Automation Examples¶
Example 1: Automatic Window Closer¶
| Setting | Value |
|---|---|
| Sensor | Rain |
| Condition | Above |
| Threshold | 80% |
| Action | Turn ON |
| Target Relay | Relay 4 (Window) |
| Return value | 50% |
| Cooldown | 1 minute |
Behavior: Rain >80% for 60s → Window closes | Rain <50% → Window opens
Example 2: Pause Irrigation¶
| Setting | Value |
|---|---|
| Sensor | Rain |
| Condition | Above |
| Threshold | 30% |
| Action | Turn OFF |
| Target Relay | Relay 3 (Pump) |
| Return value | 10% |
Example 3: Heavy Rain Alert¶
| Setting | Value |
|---|---|
| Sensor | Rain |
| Condition | Above |
| Threshold | 90% |
| Action | Turn ON |
| Target Relay | Relay 5 (Buzzer) |
| Deactivation | Timer |
| Timer duration | 30 seconds |
🛡️ 60-Second Debounce Protection¶
All rain rules include automatic 60-second debounce: 1. Rain detected → Debounce STARTED 2. 60 seconds consistent → Debounce COMPLETE 3. Relay activates
Why? Prevents false triggers from single raindrops, splashing water, or sensor noise.
🔧 Calibration Guide¶
| Board | Dry Raw | Wet Raw | Recommended Threshold |
|---|---|---|---|
| ESP32 | 4095 | 500 | 2500 |
| ESP8266 | 1023 | 150 | 600 |
| Pico W | 4095 | 500 | 2500 |
🧪 Testing Your Sensor¶
- Pour water slowly on sensor
- Watch dashboard values change from 0% to 100%
- Serial Monitor shows:
Rain: 0% → 45% → 88%
⚠️ Troubleshooting¶
| Problem | Solution |
|---|---|
| Always 0% | Use 5V power, not 3.3V |
| Always 100% | Dry sensor, check for short circuit |
| No response | Check ADC pin: GPIO34 (ESP32), A0 (ESP8266), GP26 (Pico) |
| False triggers | Increase threshold to 3000 |
🧼 Maintenance¶
| Frequency | Action |
|---|---|
| After rain | Wipe dry |
| Monthly | Clean with alcohol |
| Yearly | Replace if corroded |
Pro tip: Mount sensor at slight angle so water runs off.
❓ FAQ¶
Q: Why 60-second debounce?
A: Prevents false triggers from single raindrops. Real rain lasts longer.
Q: Can I use digital output only?
A: Yes, but analog gives intensity percentage for better automation.
Q: How to test without rain?
A: Pour water slowly or use wet cloth.
🔗 Next Steps¶
✅ Your rain sensor is ready for weather automation!