Example 19: DHT11 Temperature and Humidity Sensor

Experiment Overview

DHT11 is a commonly used digital temperature and humidity sensor, measurement range: temperature 0~50°C (±2°C), humidity 20~90%RH (±5%RH). FastBee has a built-in SENSOR_GENERIC generic sensor type (type: 38) that directly supports DHT11/DHT22.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
DATA	GPIO27	DHT11 data pin

DHT11 three-wire connection: VCC→3.3V/5V, GND→GND, DATA→GPIO (module has built-in pull-up resistor).

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "dht_01",
      "name": "DHT11 Temp/Humidity",
      "type": 38,
      "enabled": false,
      "pins": [27],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario 1: Periodic Temp/Humidity Acquisition (Timer Trigger)

Function: Read temperature and humidity data every 5 seconds

Web Interface Configuration Steps

Step 1: Create Rule

1. Click Peripheral Execution in the left menu
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: DHT Temp/Humidity Acquisition
   • Report Data: ✅ Enable (report to cloud platform after reading)
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Timer Trigger	Execute at time intervals
   Timer Mode	Select Interval Timer	Execute every X seconds
   Interval Seconds	5	Acquire every 5 seconds

Step 3: Configure Action

1. Click Add Action button

2. Fill in action configuration:

   Field	Value	Description
   Action Type	Select Sensor Read	Read sensor data
   Target Peripheral	Select dht_room	Sensor to read
   Data Field	temperature	Read temperature (or humidity)

3. Click Save button

Execution Flow:

Every 5 seconds
  ↓
Read dht_room sensor
  ↓
Get temperature value
  ↓
Report to cloud platform (if reporting enabled)

💡 Tip: DHT11 minimum sampling interval is 1 second, recommend 2 seconds or more to avoid read failures

---

Scenario 2: Low Humidity Alarm (Poll Trigger)

Function: When humidity drops below 30%, start humidifier (relay control)

Web Interface Configuration Steps

Step 1: Create Rule

1. Click New Rule
2. Fill in basic configuration:
   • Rule Name: Low Humidity Alarm
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Poll Trigger	Periodically detect humidity
   Target Peripheral	Select dht_room	Temp/humidity sensor
   Poll Interval	10 seconds	Check every 10 seconds
   Comparison Operator	Select Less Than	Lower limit alarm
   Comparison Value	30	Humidity threshold 30%

Step 3: Configure Action

1. Click Add Action button

2. Fill in action configuration:

   Field	Value	Description
   Action Type	Select HIGH Level	GPIO output HIGH
   Target Peripheral	Select relay_humidifier	Humidifier relay

3. Click Save button

Execution Flow:

Every 10 seconds
  ↓
Read dht_room humidity value
  ↓
Check: humidity < 30 ?
  ↓ Yes
Start humidifier (relay closes)

⚠️ Note: This rule only has start function, no stop function. Recommend adding another rule: turn off humidifier when humidity > 50%

---

Scenario 3: Display Temp/Humidity on OLED (Timer Trigger + Multi-Action)

Function: Display current temperature and humidity on OLED screen every 3 seconds

Prerequisites

Need to configure OLED display peripheral (type: 36) first, assuming ID is oled_display

Web Interface Configuration Steps

Step 1: Create Rule

1. Click New Rule
2. Fill in basic configuration:
   • Rule Name: Temp/Humidity Display
   • Report Data: ❌ Disable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Timer Trigger	Periodically refresh display
   Timer Mode	Select Interval Timer	Execute every X seconds
   Interval Seconds	3	Refresh every 3 seconds

Step 3: Configure Actions (3 actions needed)

Action 1: Read Temperature

1. Click Add Action button
2. Fill in:
   • Action Type: Select Sensor Read
   • Target Peripheral: Select dht_room
   • Data Field: temperature

Action 2: Read Humidity

1. Click Add Action button again
2. Fill in:
   • Action Type: Select Sensor Read
   • Target Peripheral: Select dht_room
   • Data Field: humidity

Action 3: Display on OLED

1. Click Add Action button a third time

2. Fill in:

   • Action Type: Select OLED Display
   • Target Peripheral: Select oled_display
   • Display Content:

     Temp: ${dht_room.temperature}°C
     Humidity: ${dht_room.humidity}%

   • Execution Mode: Select Synchronous

3. Click Save button

Execution Flow:

Every 3 seconds
  ↓
Read temperature value
  ↓
Read humidity value
  ↓
Display two lines on OLED:
  Line 1: Temp: 25.3°C
  Line 2: Humidity: 65%

💡 Variable Substitution: ${dht_room.temperature} will be automatically replaced with the actual temperature value read

Notes

1. Sampling Interval: DHT11 minimum sampling interval is 1 second, recommend 2 seconds or more
2. DHT22 Compatible: DHT22 (AM2302) uses the same configuration, with higher precision
3. Power Supply: Both 3.3V and 5V work, 5V for longer transmission distance
4. First Read: First read after power-on may fail, second read is normal
5. Wire Length: Data line should not exceed 20m, longer distances need increased pull-up resistance