Overview

The 1-wire node enables communication with 1-Wire protocol devices. This protocol allows multiple devices to share a single data line, making wiring simple. Most commonly used with DS18B20 temperature sensors.

Data Wire

100+

Devices Per Bus

100m

Max Wire Length

64-bit

Unique ID

Enable 1-Wire on Raspberry Pi

1. Edit /boot/config.txt

# Add this line (default GPIO 4)
dtoverlay=w1-gpio

# Or specify different pin
dtoverlay=w1-gpio,gpiopin=17

2. Reboot and Verify

sudo reboot

# Check devices are detected
ls /sys/bus/w1/devices/

# Example output:
# 28-00000abcdef1
# w1_bus_master1

Wiring Diagram

DS18B20 Wiring

VCC (Red) → 3.3V

GND (Black) → GND

DATA (Yellow) → GPIO 4 (Pin 7)

Important: Add 4.7kΩ pull-up resistor between DATA and VCC

Multiple Sensors

All sensors share the same 3 wires. Each has a unique 64-bit address.

VCC → 3.3V (all)

GND → GND (all)

DATA → GPIO 4 (all, parallel)

Pull-up: Single 4.7kΩ for all

Properties

Property	Type	Required	Default	Description
deviceId	string	No	""	Specific device ID or empty for all
command	string	No	"read"	"read", "list", or "search"
family	string	No	""	Filter by family code (e.g., "28" for DS18B20)

Inputs

Read Specific Device

{
  "payload": {
    "command": "read",
    "deviceId": "28-00000abcdef1"
  }
}

List All Devices

{
  "payload": {
    "command": "list"
  }
}

Outputs

Temperature Reading

{
  "payload": 23.5,
  "deviceId": "28-00000abcdef1",
  "family": "28",
  "type": "DS18B20",
  "raw": "23500",
  "unit": "°C"
}

Device List

{
  "payload": [
    "28-00000abcdef1",
    "28-00000abcdef2"
  ],
  "count": 2
}

Common 1-Wire Devices

Device	Family	Type	Notes
DS18B20	28	Temperature	-55°C to +125°C, ±0.5°C
DS18S20	10	Temperature	Older, 9-bit resolution
DS2438	26	Battery Monitor	Voltage, current, temp
DS2413	3A	GPIO Switch	2-channel I/O

Example: Multi-Sensor Temperature Logger

Read all DS18B20 sensors every 10 seconds and store in database.

inject (10s) → 1-wire (list) → split → 1-wire (read) → sqlite

[
  {
    "id": "trigger",
    "type": "inject",
    "repeat": "10",
    "payload": "{ "command": "list", "family": "28" }",
    "payloadType": "json"
  },
  {
    "id": "list-sensors",
    "type": "1-wire",
    "command": "list"
  },
  {
    "id": "split-devices",
    "type": "split"
  },
  {
    "id": "read-temp",
    "type": "1-wire",
    "command": "read"
  },
  {
    "id": "store-db",
    "type": "sqlite",
    "sql": "INSERT INTO temperatures (device_id, value, timestamp) VALUES (?, ?, ?)"
  }
]

Troubleshooting

No devices found

Check /boot/config.txt has dtoverlay=w1-gpio
Verify 4.7kΩ pull-up resistor is connected
Check wiring (VCC, GND, DATA)
Ensure you've rebooted after config changes

Reading 85°C constantly

85°C is the power-on reset value. This indicates:

Insufficient power - use powered mode, not parasitic
Reading too quickly after conversion started
Loose connection or damaged sensor

CRC errors

Try a lower value pull-up resistor (2.2kΩ)
Reduce wire length or use shielded cable
Add decoupling capacitor (0.1µF) at sensor

Related Nodes

ds18b20

Dedicated DS18B20 node

i2c

I2C bus communication

sqlite

Store readings locally