Scenario: DHT Temp/Humidity Sensor + Relay Linkage

Scenario Description

Configure DHT11/DHT22 temperature/humidity sensor for periodic environmental data collection. When temperature exceeds a set threshold, automatically turn on the relay (controlling fan/AC); when temperature returns to normal, automatically turn off. Also display real-time temperature/humidity data on an OLED screen.

Hardware List

Module	Model	Qty	Wiring
Temp/Humidity Sensor	DHT22	1	DATA→GPIO4
Relay Module	5V single channel	1	IN→GPIO15
OLED Display	SSD1306 128x64	1	SDA→GPIO21, SCL→GPIO22
(Optional) Buzzer	Active buzzer	1	IN→GPIO25

Complete Configuration Process

Method 1: Web Interface Configuration (Recommended)

This scenario requires first adding the temperature/humidity sensor, relay, and display, then using peripheral execution rules for collection, threshold evaluation, control, and display.

The temperature control scenario is broken down in a closed loop: DHT collects temperature/humidity, rule evaluates threshold, relay or display executes actions, MQTT or log records results.

Step 1: Configure Peripherals

Step 1: Open Peripheral Management Page

1. Open a browser and navigate to the ESP32 IP address
2. After logging in, click Peripheral Configuration in the left menu

Step 2: Add DHT22 Temperature/Humidity Sensor

1. Click the Add Peripheral button

2. Fill in the configuration:

   Field	Value	Description
   Peripheral ID	dht22_room	Room temp/humidity
   Name	Room Temp/Humidity	Display name
   Peripheral Type	Universal Sensor (type: 38)	DHT driver
   Pin Configuration	4	DATA connected to GPIO4
   Sensor Category	DHT	DHT series
   Sensor Model	DHT22	DHT22 has higher accuracy
   Collection Interval	5000	5 seconds

3. Click Save

Step 3: Add Fan Relay

1. Click the Add Peripheral button again

2. Fill in the configuration:

   Field	Value	Description
   Peripheral ID	relay_fan	Fan relay
   Name	Fan Relay	Display name
   Peripheral Type	GPIO Digital Output (type: 12)	Relay control
   Pin Configuration	15	IN connected to GPIO15
   Initial State	0	Default off

3. Click Save

Step 4: Add Alarm Buzzer (Optional)

1. Click the Add Peripheral button a third time

2. Fill in the configuration:

   Field	Value	Description
   Peripheral ID	buzzer_alarm	Alarm buzzer
   Name	Alarm Buzzer	Display name
   Peripheral Type	GPIO Digital Output (type: 12)	Buzzer control
   Pin Configuration	25	IN connected to GPIO25
   Initial State	0	Default off

3. Click Save

---

Step 2: Configure Peripheral Execution Rules

Rule 1: Timed Temperature/Humidity Data Collection

1. Click Peripheral Execution in the left menu

2. Click the Add Rule button

3. Fill in basic configuration:

   • Rule Name: Timed Temp/Humidity Collection
   • Report Data: ✅ Enabled
   • Enable: ✅ Enabled

4. Configure trigger:

   • Trigger Type: Select Timer Trigger
   • Timer Mode: Select Fixed Interval
   • Interval Time: 30 (30 seconds)

5. Configure actions (3 actions needed):

   • Action 1: Select Sensor Read, target dht22_room, field temperature
   • Action 2: Select Sensor Read, target dht22_room, field humidity
   • Action 3: Select OLED Display, target oled1 (must be configured in advance), template:

     # Env Monitor
     Temp: ${dht22_room.temperature}°C
     Humidity: ${dht22_room.humidity}%

6. Click Save

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Rule 2: Temperature Exceeds Threshold - Turn On Fan

1. Create rule, name: High Temp Turn On Fan

2. Trigger configuration:

   • Trigger Type: Select Event Trigger
   • Event ID: Enter ds:dht22_room_temperature
   • Operator: Select Greater Than (>)
   • Threshold: 30 (30°C)

3. Action configuration:

   • Action Type: Select High Level
   • Target Peripheral: Select relay_fan

4. Click Save

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Rule 3: Temperature Recovers - Turn Off Fan

1. Create rule, name: Temp Normal Turn Off Fan

2. Trigger configuration:

   • Trigger Type: Select Event Trigger
   • Event ID: Enter ds:dht22_room_temperature
   • Operator: Select Less Than or Equal (<=)
   • Threshold: 26 (26°C)

3. Action configuration:

   • Action Type: Select Low Level
   • Target Peripheral: Select relay_fan

4. Click Save

💡 Tip: Turn on at 30°C, turn off at 26°C, forming a 4°C hysteresis band to prevent frequent switching

---

Rule 4: High Temperature Alarm (Exceeds 35°C)

1. Create rule, name: High Temperature Alarm

2. Trigger configuration:

   • Trigger Type: Select Event Trigger
   • Event ID: Enter ds:dht22_room_temperature
   • Operator: Select Greater Than (>)
   • Threshold: 35 (35°C emergency alarm)

3. Action configuration (2 actions needed):

   • Action 1: Select Flash, target buzzer_alarm, interval 500 (500ms)
   • Action 2: Select Trigger Event, event ID high_temperature

4. Click Save

---

Method 2: JSON Configuration File Import

Workflow Diagram

┌──────────────┐    Every 30s   ┌────────────────┐
│ Timer Trigger │──────────────>│ Read DHT22 Temp │
└──────────────┘               │ Read DHT22 Humi │
                               │ OLED Display    │
                               └───────┬────────┘
                                       │ Collection results cached as
                                       │ ds:dht22_room_temperature
                                       │ ds:dht22_room_humidity
                                       ▼
                               ┌────────────────┐
                               │ Event Trigger Rule Matching │
                               └───┬────┬───┬───┘
                                   │    │   │
                     Temp>30°C ────┘    │   └───── Temp>35°C
                          │             │              │
                          ▼             ▼              ▼
                   ┌──────────┐  ┌──────────┐  ┌──────────────┐
                   │ Fan ON   │  │ Fan OFF  │  │ Buzzer Alarm │
                   │ (Relay HIGH)│ │ (Relay LOW)│ │ + Event Report│
                   └──────────┘  └──────────┘  └──────────────┘
                                 Temp≤26°C

Parameter Adjustment Recommendations

Parameter	Recommended Value	Description
Collection Interval	30s	Indoor environment changes slowly; 30s is sufficient
Fan ON Threshold	30°C	Adjust based on actual needs
Fan OFF Threshold	26°C	4°C below fan ON threshold, forming hysteresis anti-jitter
Alarm Threshold	35°C	Emergency alarm, above normal control threshold
Buzzer Flash Interval	500ms	0.5s interval alert tone

Hysteresis Control Explanation

The 4°C difference between the ON threshold (30°C) and OFF threshold (26°C) forms a hysteresis band, preventing rapid relay switching (jitter) when temperature fluctuates near the threshold, extending relay lifespan.

Extension Suggestions

1. Multi-level Temperature Control: Add intermediate temperature ranges, use PWM to control fan speed
2. Humidity Linkage: Turn on dehumidification equipment when humidity is too high
3. Time-based Control: Use different thresholds for day/night (via daily time point trigger to switch rule enable states)
4. Remote Override: Keep platform trigger to allow IoT platform remote forced control