DIY Solar‑Powered Weather Station with Raspberry Pi

This guide outlines how to build a lightweight, solar‑powered weather station using a Raspberry Pi and inexpensive sensors. The system records temperature, pressure, humidity, and can be extended to wind speed, direction, UV, and insolation.

Step 1: Hardware description

• Raspberry Pi A+ (any Pi model works)
• Bosch BMP180 temperature/pressure sensor
• HTU21D temperature/humidity sensor
• Wireless adapter
• Micro‑SD card
• 10 W solar panel (3 × 3.5 W modules)
• 7.2 Ah 12 V battery
• 12 V solar charge controller
• 5 V regulator (7805)
• Miscellaneous wiring and connectors (e.g., 4‑wire telephony cable)

Step 2: Setting up the basics

Install Raspbian on a fresh SD card. You can download the latest image from Raspberry Pi Downloads. If you have a pre‑configured card, simply clone the image to a new one.

For a quick start guide, see Raspberry Pi Quick‑Start Guide. If you prefer wireless connectivity, follow the instructions in Wireless Configuration.

Enable I²C on the Pi using the Adafruit tutorial: Configuring I²C.

Step 3: Installing required software

All software is installed via the command line. For the BMP180 sensor, install Adafruit’s library from Adafruit BMP085 Tutorial.

To read the HTU21D, download and install the Pigpio library from Pigpio Downloads. After installation, ensure Pigpio starts automatically on boot by adding sudo pigpiod to /etc/rc.local.

Step 4: Wiring the sensors

The BMP180 and HTU21D are I²C devices. Connect them to the Pi’s 3.3 V, GND, SDA, and SCL pins. A 4‑wire cable (e.g., telephone cable) is convenient for both sensors.

Each sensor has a unique I²C address, allowing multiple devices on the same bus.

Step 5: Main program

The core script is temp-monitor.py (or the updated temp-monitor-online.py). It runs on boot and uploads data to Weather Underground every two minutes.

Sample code excerpt:

import Adafruit_BMP.BMP085 as BMP085
import smbus
import os
import sys
import getopt
import sqlite3
import math
import pigpio
import time

# Functions to read temperature and humidity
# (implementation follows sensor datasheets)

# Upload command
cmd = (
    "curl 'https://weatherstation.wunderground.com/weatherstation/updateweatherstation.php?"
    "ID=YOUR_ID&PASSWORD=YOUR_PASSWORD&dateutc=now&tempf="
    + str((temp * 1.8) + 32)
    + "&humidity="
    + str(round(humidity, 2))
    + "&baromin="
    + str((pressure / 100) * 0.0295299)
    + "&action=updateraw'"
)

# Run script on boot
# Add the following line to /etc/rc.local:
# sudo python /usr/lib/cgi-bin/temp-monitor.py &

Replace YOUR_ID and YOUR_PASSWORD with credentials from your Weather Underground account. The & at the end ensures the script runs in the background.

Step 6: Solar power setup

For an autonomous outdoor deployment, use three 3.5 W modules in series to produce 18 V, suitable for a 12 V solar system. Connect the output to the 12 V battery via the charge controller, then power the Pi through a 5 V regulator.

While a 10 W panel and 7.2 Ah battery may seem generous for a Pi, it provides several days of operation during Ireland’s cloudy periods.

For detailed wiring diagrams and component specifications, consult the original project notes.

Additional Resources

• BMP180 datasheet: BMP180 Datasheet
• HTU21D datasheet: HTU21D Datasheet