Overview

Build a complete weather station that reads temperature, humidity, pressure, and light level from I2C sensors. Data is published to MQTT for real-time consumption, stored in InfluxDB for historical analysis, and visualized with Grafana dashboards. This intermediate project teaches I2C sensor communication, MQTT publishing, and time-series data management.

Intermediate

Difficulty

Nodes Used

~30 min

Setup Time

I2C Bus

Interface

What You'll Need

Hardware

* Raspberry Pi (any model with I2C)
* BME280 sensor module (temp + humidity + pressure)
* BH1750 light sensor module
* Jumper wires (4 wires per sensor, shared I2C bus)

Software

* EdgeFlow installed on your Pi
* MQTT broker (Mosquitto recommended)
* InfluxDB 2.x installed (local or cloud)
* Grafana (optional, for dashboards)

Wiring Diagram

Both sensors share the same I2C bus (SDA/SCL). They use different I2C addresses so there is no conflict.

BME280 (addr: 0x76)

VCC → 3.3V (Pin 1)

GND → GND (Pin 9)

SDA → GPIO2 / SDA1 (Pin 3)

SCL → GPIO3 / SCL1 (Pin 5)

Some BME280 modules default to 0x77. Check your module and adjust in the node config.

BH1750 (addr: 0x23)

VCC → 3.3V (Pin 1)

GND → GND (Pin 9)

SDA → GPIO2 / SDA1 (Pin 3)

SCL → GPIO3 / SCL1 (Pin 5)

ADDR pin LOW = 0x23, ADDR pin HIGH = 0x5C. Leave floating for 0x23.

Enable I2C on Your Pi

I2C must be enabled before the sensors will work. Run these commands:

# Enable I2C interface
sudo raspi-config nonint do_i2c 0

# Verify I2C is enabled
ls /dev/i2c-*

# Scan for connected devices (should show 0x23 and 0x76)
sudo apt install -y i2c-tools
i2cdetect -y 1

You should see addresses 23 and 76 in the i2cdetect output grid.

Importable Flow JSON

Copy this JSON and import it via Menu → Import in the EdgeFlow editor.

{
  "name": "Complete Weather Station",
  "nodes": [
    {
      "id": "bme280_1",
      "type": "bme280",
      "name": "BME280 Sensor",
      "address": "0x76",
      "interval": 30,
      "x": 120,
      "y": 160
    },
    {
      "id": "bh1750_1",
      "type": "bh1750",
      "name": "BH1750 Light",
      "address": "0x23",
      "interval": 30,
      "mode": "continuous_high",
      "x": 120,
      "y": 320
    },
    {
      "id": "join_sensors",
      "type": "join",
      "name": "Combine Data",
      "mode": "custom",
      "count": 2,
      "build": "object",
      "propertyType": "msg",
      "property": "topic",
      "x": 340,
      "y": 240
    },
    {
      "id": "format_weather",
      "type": "function",
      "name": "Format Weather Data",
      "func": "var bme = msg.payload.bme280 || {};\nvar light = msg.payload.bh1750 || {};\nmsg.payload = {\n  temperature: Math.round(bme.temperature * 100) / 100,\n  humidity: Math.round(bme.humidity * 100) / 100,\n  pressure: Math.round(bme.pressure * 100) / 100,\n  light_lux: Math.round(light.lux || 0),\n  timestamp: Date.now(),\n  station: 'weather-pi-01'\n};\nreturn msg;",
      "x": 540,
      "y": 240
    },
    {
      "id": "mqtt_weather",
      "type": "mqtt-out",
      "name": "MQTT Publish",
      "broker": "localhost",
      "port": 1883,
      "topic": "home/weather",
      "qos": 1,
      "retain": true,
      "x": 760,
      "y": 180
    },
    {
      "id": "influx_write",
      "type": "influxdb",
      "name": "Store in InfluxDB",
      "url": "http://localhost:8086",
      "org": "edgeflow",
      "bucket": "weather_data",
      "measurement": "weather",
      "token": "YOUR_INFLUXDB_TOKEN",
      "x": 760,
      "y": 300
    },
    {
      "id": "mqtt_temp",
      "type": "mqtt-out",
      "name": "MQTT Temperature",
      "broker": "localhost",
      "port": 1883,
      "topic": "home/weather/temperature",
      "qos": 0,
      "x": 760,
      "y": 120
    },
    {
      "id": "split_topics",
      "type": "function",
      "name": "Split to Topics",
      "func": "var data = msg.payload;\nvar msgs = [];\nmsgs.push({ payload: data.temperature, topic: 'home/weather/temperature' });\nmsgs.push({ payload: data.humidity, topic: 'home/weather/humidity' });\nmsgs.push({ payload: data.pressure, topic: 'home/weather/pressure' });\nmsgs.push({ payload: data.light_lux, topic: 'home/weather/light' });\nreturn [msgs];",
      "outputs": 1,
      "x": 540,
      "y": 120
    },
    {
      "id": "debug_weather",
      "type": "debug",
      "name": "Weather Monitor",
      "x": 760,
      "y": 380
    }
  ],
  "connections": [
    { "from": "bme280_1", "to": "join_sensors" },
    { "from": "bh1750_1", "to": "join_sensors" },
    { "from": "join_sensors", "to": "format_weather" },
    { "from": "format_weather", "to": "mqtt_weather" },
    { "from": "format_weather", "to": "influx_write" },
    { "from": "format_weather", "to": "split_topics" },
    { "from": "format_weather", "to": "debug_weather" },
    { "from": "split_topics", "to": "mqtt_temp" }
  ]
}

Step-by-Step Walkthrough

Enable I2C and Wire Sensors

Enable I2C via raspi-config, then wire both sensors to the same I2C bus (SDA on GPIO2, SCL on GPIO3). Both sensors can share the same 3.3V and GND connections. Run i2cdetect -y 1 to verify both addresses appear.

Install and Configure Mosquitto MQTT Broker

sudo apt install -y mosquitto mosquitto-clients
sudo systemctl enable mosquitto
sudo systemctl start mosquitto

# Test with a quick subscribe/publish
mosquitto_sub -t "test" &
mosquitto_pub -t "test" -m "hello"
# You should see "hello" printed

Install InfluxDB 2.x

# Install InfluxDB on Raspberry Pi
wget https://dl.influxdata.com/influxdb/releases/influxdb2_2.7.1-1_arm64.deb
sudo dpkg -i influxdb2_2.7.1-1_arm64.deb
sudo systemctl enable influxdb
sudo systemctl start influxdb

# Open http://YOUR_PI_IP:8086 to complete setup
# Create org: "edgeflow", bucket: "weather_data"
# Copy the generated API token

Import Flow and Configure Credentials

Import the flow JSON above into EdgeFlow. Then double-click the InfluxDB node and paste your API token, org name, and bucket name. If your MQTT broker uses authentication, update the MQTT nodes with username and password.

Deploy and Verify Data Flow

Click Deploy. Monitor the Debug panel for combined weather readings every 30 seconds. Verify MQTT messages arrive using a subscriber:

mosquitto_sub -t "home/weather/#" -v

Add Grafana Dashboard (Optional)

Install Grafana, add InfluxDB as a data source, and create panels for each measurement. A sample Flux query for the temperature panel:

from(bucket: "weather_data")
  |> range(start: -24h)
  |> filter(fn: (r) => r._measurement == "weather")
  |> filter(fn: (r) => r._field == "temperature")
  |> aggregateWindow(every: 5m, fn: mean, createEmpty: false)

Configuration Details

Parameter	Value	Description
BME280 Address	0x76	I2C address (some modules use 0x77)
BH1750 Address	0x23	I2C address (ADDR pin LOW)
Poll Interval	30 seconds	Both sensors read simultaneously
MQTT Topic	home/weather	Combined JSON payload; subtopics for individual values
MQTT QoS	1 (at least once)	Guaranteed delivery for the combined topic
InfluxDB Bucket	weather_data	Measurement name: "weather"

MQTT Topic Structure

home/weather              ← Combined JSON (all readings)
home/weather/temperature  ← Float: 22.45
home/weather/humidity     ← Float: 58.3
home/weather/pressure     ← Float: 1013.25
home/weather/light        ← Integer: 4520

Expected Output

The formatted weather data published to MQTT and stored in InfluxDB:

{
  "temperature": 22.45,
  "humidity": 58.3,
  "pressure": 1013.25,
  "light_lux": 4520,
  "timestamp": 1707750000000,
  "station": "weather-pi-01"
}

InfluxDB stores each field as a separate column in the "weather" measurement: