Raspberry Pi Sensor Data Transmission Sample

What We’ll Do

• Create a sample that sends data using a temperature and humidity sensor and creates graphs. For a simple sample code using temperature and humidity API, see here.

Required Items

• Raspberry Pi
• Power supply (AC adapter, etc.)
• Temperature and humidity sensor (DHT11, etc.)

Steps

1. Install OS on Raspberry Pi and verify startup
2. Connect/read temperature and humidity sensor
3. Run data transmission sample
4. Verify data transmission and create graphs
5. (Bonus) Persist as systemd service

1. Install OS on Raspberry Pi and Verify Startup

Install Raspberry Pi OS using Raspberry Pi Imager.

1. Download and install Raspberry Pi Imager
2. Insert SD card and launch Raspberry Pi Imager
3. Select OS (Raspberry Pi OS (64-bit) recommended)
4. Configure from settings (gear icon):
   • Enable SSH
   • Set username and password
   • Configure Wi-Fi (not needed for wired connection)
5. Execute write
6. Insert SD card into Raspberry Pi, connect power and boot
7. Connect via SSH and verify startup

ssh pi@raspberrypi.local
# or
ssh pi@<Raspberry Pi IP address>

2. Connect/Read Temperature and Humidity Sensor

Sensor Connection

Connect a temperature and humidity sensor such as DHT11.

DHT11 Connection Example:

• VCC → 3.3V (Pin 1)
• GND → GND (Pin 6)
• DATA → GPIO 4 (Pin 7)

Install Required Libraries

sudo apt update
sudo apt install -y python3-pip python3-dev
pip3 install Adafruit_DHT requests

Test Sensor Reading

Test if sensor values can be read with the following Python script.

import Adafruit_DHT

sensor = Adafruit_DHT.DHT11
pin = 4

humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)

if humidity is not None and temperature is not None:
    print(f'Temperature: {temperature:.1f}°C')
    print(f'Humidity: {humidity:.1f}%')
else:
    print('Failed to read from sensor')

3. Run Data Transmission Sample

Create a Python script to send data to Miniviz API.

Create Script

nano miniviz_sender.py

Write the following content (replace PROJECT_ID and TOKEN with actual values):

For details, see “3. Send Data (Device Side)” in Quick Start.

import os
import time
from datetime import datetime, timezone
import Adafruit_DHT
import requests

PROJECT_ID = "MINIVIZ_PROJECT_ID"
TOKEN = "MINIVIZ_API_TOKEN"
API_URL = "https://api.miniviz.net"
LABEL_KEY = "raspberry_pi_home"
SEND_INTERVAL = 90  # seconds

# DHT11 sensor configuration
DHT_SENSOR = Adafruit_DHT.DHT11
DHT_PIN = 4

def read_sensor():
    """Read temperature and humidity from sensor"""
    humidity, temperature = Adafruit_DHT.read_retry(DHT_SENSOR, DHT_PIN)
    return temperature, humidity

def send_data():
    """Send data to Miniviz API"""
    url = f"{API_URL}/api/project/{PROJECT_ID}?token={TOKEN}"
    timestamp_ms = int(datetime.now(timezone.utc).timestamp() * 1000)
    
    temperature, humidity = read_sensor()
    
    if temperature is None or humidity is None:
        print("Failed to read from sensor")
        return
    
    payload = {
        "timestamp": timestamp_ms,
        "label_key": LABEL_KEY,
        "payload": {
            "temperature": round(temperature, 1),
            "humidity": round(humidity, 1)
        }
    }
    
    try:
        response = requests.post(url, json=payload)
        if response.ok:
            data = response.json()
            print(f"Send successful (id={data.get('id')}) - Temperature: {temperature:.1f}°C, Humidity: {humidity:.1f}%")
        else:
            print(f"Send failed: {response.status_code} {response.text}")
    except Exception as e:
        print(f"Error: {e}")

if __name__ == "__main__":
    print("Starting Miniviz data transmission (press Ctrl+C to stop)")
    while True:
        send_data()
        time.sleep(SEND_INTERVAL)

Run Script

python3 miniviz_sender.py

If working correctly, data will be sent every 90 seconds and transmission results will be displayed on the console.

4. Verify Data Transmission and Create Graphs

Verify Data Transmission

1. Log in to Miniviz web interface
2. Check sent data from Database menu
3. Verify that temperature and humidity data is displayed

Create Graphs

1. Create graphs from Visualize menu
2. Select graph type (line chart recommended)
3. Select temperature and humidity as data sources
4. Verify that graphs are displayed correctly

For details, see “5. Create Charts” in Quick Start.

5. (Bonus) Persist as systemd Service

Configure as a systemd service to automatically start data transmission when Raspberry Pi boots.

Create Service File

sudo nano /etc/systemd/system/miniviz-sender.service

Write the following content (replace /home/pi/miniviz_sender.py with the actual script path):

[Unit]
Description=Miniviz Data Sender
After=network.target

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi
ExecStart=/usr/bin/python3 /home/pi/miniviz_sender.py
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

Enable and Start Service

sudo systemctl daemon-reload
sudo systemctl enable miniviz-sender.service
sudo systemctl start miniviz-sender.service

Check Service Status

sudo systemctl status miniviz-sender.service

Check Logs

sudo journalctl -u miniviz-sender.service -f

Now, data transmission will automatically start even after Raspberry Pi reboots.