Example 18: DS18B20 Temperature Sensor

Experiment Overview

DS18B20 is a one-wire digital temperature sensor with a measurement range of -55°C~+125°C and ±0.5°C accuracy. FastBee has a built-in ONE_WIRE peripheral type (type: 44) that directly supports DS18B20.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
DATA	GPIO4	DS18B20 data line (requires 4.7kΩ pull-up resistor)

DS18B20 three-wire connection: VCC→3.3V, GND→GND, DATA→GPIO + 4.7kΩ pull-up to VCC.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "ds18b20_01",
      "name": "DS18B20 Temperature",
      "type": 44,
      "enabled": false,
      "pins": [4],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario 1: Periodic Temperature Acquisition (Timer Trigger)

Function: Read DS18B20 temperature 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: Temperature Acquisition
   • 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 Timer Trigger	Periodic acquisition
   Timer Mode	Select Fixed Interval	By millisecond interval
   Interval Time	5000	5 seconds

Step 3: Configure Action

1. Click Add Action button

2. Fill in:

   • Action Type: Select Read Sensor
   • Target Peripheral: Select ds18b20_01
   • Data Field: temperature

3. Click Save button

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Scenario 2: Temperature Over-Limit Alarm (Poll Trigger)

Function: Check temperature every 5 seconds, trigger buzzer alarm when temperature exceeds 40°C

Web Interface Configuration Steps

Step 1: Ensure buzzer peripheral is configured

• Peripheral ID: buzzer_gpio
• Type: GPIO Output

Step 2: Create Rule

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

Step 3: Configure Trigger (Poll Trigger)

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Poll Trigger	Periodically detect condition
   Target Peripheral	Select ds18b20_01	Temperature sensor
   Poll Interval	5000	5 seconds
   Condition Expression	temperature > 40	Temperature greater than 40°C

Step 4: Configure Actions (2 actions needed)

Action 1: Buzzer Alarm

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

Action 2: Send Alarm Event

1. Click Add Action button again

2. Fill in:

   • Action Type: Select Send Event
   • Event Type: alarm
   • Event Message: Temperature too high

3. Click Save button

DS18B20 Features

Feature	Parameter	Description
Measurement Range	-55°C ~ +125°C	Wide temperature range
Accuracy	±0.5°C	High precision
Resolution	9-12 bit adjustable	Default 12 bit
Conversion Time	750ms (12 bit)	Auto wait
Bus Type	OneWire	Can mount multiple devices

Notes

1. Pull-up Resistor: Must connect 4.7kΩ resistor between data line and VCC
2. Bus Length: Short distance (<5m) uses 4.7kΩ, longer distances need lower resistance
3. Multi-Device: Multiple DS18B20 can be mounted on the same bus (each has a unique 64-bit ID)
4. Conversion Time: ~750ms at 12-bit precision, FastBee handles waiting internally
5. Parasitic Power: Supports two-wire (DATA+GND) parasitic power mode, but three-wire is recommended
6. Waterproof: Waterproof DS18B20 probes in stainless steel housing are available