Example 30: Rain Sensor

Experiment Overview

A raindrop sensor outputs both analog and digital signals by detecting water droplets on its board surface. The analog output reflects humidity levels, while the digital output indicates whether a threshold has been reached. Suitable for smart clotheslines, automatic rain awnings, and similar applications.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
AO	GPIO34	Rain sensor analog output
DO	GPIO4	Rain sensor digital output

The module includes a potentiometer to adjust the digital output threshold.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "rain_analog",
      "name": "Rainfall - Analog",
      "type": 15,
      "enabled": false,
      "pins": [34],
      "params": {}
    },
    {
      "id": "rain_digital",
      "name": "Raindrop - Switch",
      "type": 11,
      "enabled": false,
      "pins": [4],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario: Rain Alarm (Polling Trigger)

Feature: Check raindrop switch every 1 second; trigger buzzer alarm when rain is detected

Web UI Configuration Steps

Step 1: Ensure Buzzer Peripheral is Configured

• Peripheral ID: buzzer_gpio
• Type: GPIO Output

Step 2: Create Rule

1. Click Peripheral Config in the left menu → Switch to Peripheral Execution tab
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Rain Alarm
   • Report Data: ✅ Enabled
   • Enable: ✅ Enabled

Step 3: Configure Trigger (Polling Trigger)

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Polling Trigger	Periodic condition check
   Target Peripheral	Select rain_digital	Raindrop switch
   Polling Interval	1000	1 second
   Condition Expression	value == 0	LOW = rain detected

Step 4: Configure Actions (2 actions required)

Action 1: Buzzer Alarm

1. Click Add Action button
2. Fill in:
   • Action Type: Select HIGH
   • Target Peripheral: Select buzzer_gpio

Action 2: Send Weather Event

1. Click Add Action button again

2. Fill in:

   • Action Type: Select Send Event
   • Event Type: weather
   • Event Message: Rain detected

3. Click Save button

Raindrop Sensor Value Reference

Status	Analog Value	Description
No Water	~4095	Dry condition
Light Rain	2000-3000	Few water droplets
Moderate Rain	1000-2000	More water droplets
Heavy Rain	<1000	Many water droplets

Notes

1. Corrosion: Prolonged exposure leads to sensor board corrosion; power off when not raining
2. Threshold Adjustment: Adjust digital output trigger sensitivity via the on-module potentiometer
3. Analog Value: Near 4095 when dry; decreases when wet — lower value means heavier rain
4. ADC2 Limitation: GPIO34 belongs to ADC1, unaffected during WiFi operation