Raspberry Pi Sensehat weatherstation

A Raspberry Pi Weather Station using the Sense HAT that stores all captured data in a local SQLite DB. You will need a sense HAT and a few other bits of equipment to be able to get this to work.

Things needed:

• Raspberry Pi 2 or 3
• Micro SD Card or a SD card if you’re using an old version of the Pi.
• Power Supply
• Sense HAT
• Ethernet Cable or WiFi Dongle (The Pi 3 has WiFi inbuilt)

Getting started with the Sense HAT:

This weatherstation consists of two parts. A python script that reads out all the data from the Sense Hat and persists it into a SQLite databse, and a Node.js part that executes the py script, and displays the retrieved data on a webpage.

The Python part

1. Make sure the Pi has the latest updates and software.

   $sudo apt-get update
   $sudo apt-get upgrade
   

2. Install the Sense Hat software package, which provides all the libraries to interact with the Sense Hat.

   $sudo apt-get install sense-hat
   $sudo reboot
   

3. Create the following python script and save it as weatherstation.py

   from timer import Timer
   from sense_hat import SenseHat
   from time import sleep
   import os
   import sqlite3
   import time, datetime
   
   sense = SenseHat()
   
   def persistData ():
   
      temp = round(sense.get_temperature(),1)
      cpu_temp = round(get_cpu_temp(), 1)
      temp_calibrated = temp - ((cpu_temp - temp)/5.466) # Temperature correction due to cpu heat
   
      pressure = round(sense.get_pressure(), 1)
      humidity = round(sense.get_humidity(), 1)
      date = datetime.datetime.now().strftime("%Y-%m-%d %H:%M") 
   
      # This creates or opens up a DB
      db = sqlite3.connect('./db/weatherstation.db')
      cursor = db.cursor()
      cursor.execute('INSERT INTO pidata(pressure, temperature, humidity, datum) VALUES(?,?,?,?)', 
          (pressure, temp_calibrated, humidity, date))
      db.commit()
      db.close()
   
   
   def get_cpu_temp():
   
      res = os.popen("vcgencmd measure_temp").readline()
      t = float(res.replace("temp=","").replace("'C\n",""))
      return(t)
      
   # Persist wheater data every 15 mintues
   rt = Timer(900, persistData) 
   

4. Test and run your python script

   $sudo python3 weatherstation.py
   

The Node.js part

1. Add a weathercontroller.js

   module.exports = function(app, db, jsonParser){
   
       var fields = ["ID",  "pressure", "temperature", "humidity", "datum"];
   
       //  api/weatherdata
       app.get('/api/weatherdata', function(req, res){ 
           db.all("SELECT " + fields.join(", ") + " FROM pidata", function(err, rows) {
               res.json(rows); 
           });                       
       });
   
       //  api/weatherdata/trend/pressure  - Select last 7 days and every nth row (ID % 4 = 0), four in this case
       app.get('/api/weatherdata/trend/pressure', function(req, res){ 
           db.all("SELECT pressure, time(datum) AS datum FROM pidata WHERE datum > (SELECT DATETIME('now', 'localtime', '-7 day')) AND ID % 4 = 0", function(err, rows) {
               res.json(rows); 
           });                       
       });
   
       //  api/weatherdata/trend/pressure/today
       app.get('/api/weatherdata/trend/pressure/today', function(req, res){ 
           db.all("SELECT pressure, time(datum) AS datum FROM pidata WHERE  datum >= (SELECT DATETIME('now', 'localtime', '-1 day')) AND datum <=  (SELECT DATETIME('now', 'localtime'))", function(err, rows) {
               res.json(rows); 
           });                       
       });
   
       //  api/weatherdata/trend/temperature/today
       app.get('/api/weatherdata/trend/temperature/today', function(req, res){ 
           db.all("SELECT temperature, time(datum) AS datum FROM pidata WHERE  datum >= (SELECT DATETIME('now', 'localtime', '-1 day')) AND datum <=  (SELECT DATETIME('now', 'localtime'))", function(err, rows) {
               res.json(rows); 
           });                       
       });
   }
   

2. And finally the server.js file:

   var express = require('express');
   var app = express();
   
   var bodyParser = require('body-parser');
   var jsonParser = bodyParser.json()
   var urlencodedParser = bodyParser.urlencoded({ extended: false })
   
   var path = require('path')
   var dbPath = path.resolve(__dirname, 'db/weatherstation.db')
   var www = path.resolve(__dirname, 'www')
   var python = path.resolve(__dirname, 'python/weatherstation.py')
   
   
   var sqlite3 = require('sqlite3'); //.verbose();
   var db = new sqlite3.Database(dbPath);
   
   // Add restful controller
   require('./controllers/weathercontroller')(app, db, jsonParser);
   
   
   // Start the weatherstation.py script
   var child_process = require('child_process');
   
   child_process.exec('python3 ' + python, function (err){
      if (err) {
          console.log("child processes failed with error code: " + err.code);
      }
   });
   
   
   // Serve static files
   app.use(express.static(www))
   app.listen(9999);
   
   

3. Run your node script

   $node server.js
   

4. Access the retrieved data

   Overview with charts:                 localhost:9999
   
   json results:
   
   All data:                             localhost:9999/api/weatherdata
   Pressure data for the last 7 days:    localhost:9999/api/weatherdata/trend/pressure
   Pressure data today:                  localhost:9999/api/weatherdata/trend/pressure/today
   Temperature data today:               localhost:9999/api/weatherdata/trend/temperature/today