Sense HAT data logger 01

OK it is day two with my Raspberry Pi Sense HAT and here is my first attempt at a data logger program.  You can read about my first day with Sense HAT and the problems I have encountered so far.

This program simply logs the time, temperature, humidity and air pressure every six seconds.  The data is saved into a text file for later inspection.

Is it getting hot in here? Actually this is the temperature of the air just near the CPU (I am actually really cold right now in my hovel - please send warm jumpers).

I have read the output file over my home server and produced this graph in Windows 10.

# Data Logging App
# Logs the time, temperature, humidity and air pressure
# Tim Street
# 2015-01-14
# version history
# ---------------
#   logger class with time, temp, humidity and pressure

from datetime import datetime
import time
from sense_hat import SenseHat

FILE_PATH = "log.csv" # file path used to log data

class logger:
    """ A logger provides methods for reading the sensor values and saving to a file """
    def __init__(self, filepath):
        self.__time = 0
        self.__temp = 0
        self.__humidity = 0
        self.__pressure = 0
        self.__sense = SenseHat()
        self.__savepath = filepath

    def __str__(self):
        """ String representation of logger """
        return "Time:\t\t"+str(self.getTime())+"\nTemp:\t\t"+str(self.getTemp())+"C\nHumidity:\t"+str(self.getHumidity())+"%\nPressure:\t"+str(self.getPressure())+"mb"

    def __toCSV(self):
        """ Retuns a CSV file line """
        return str(self.getTime())+","+str(self.getTemp())+","+str(self.getHumidity())+","+str(self.getPressure())+",\n"

    def __setTime( self ):
        """ sets log to current date and time """
        self.__time =

    def getTime(self):
        """ returns the date and time from the log """
        return self.__time

    def __setTemp(self):
        """ logs the current temperature """
        self.__temp = self.__sense.get_temperature()

    def getTemp(self):
        """ returns the temperature """
        return self.__temp

    def __setHumidity(self):
        """ logs the current humidity """
        self.__humidity = self.__sense.get_humidity()

    def getHumidity(self):
        """ returns the humidity """
        return self.__humidity

    def __setPressure(self):
        """ logs the current air pressure """
        self.__pressure = self.__sense.get_pressure()

    def getPressure(self):
        """ returns the pressure """
        return self.__pressure

    def update(self):
        """ updates all sensors """

    def save(self):
        file = open(self.__savepath, 'a')
        file.write( self.__toCSV() )

log = logger( FILE_PATH )
while True:

The program needs to append a comma separated file "log.csv" which you can create yourself, or run the script below to create it automatically.

# creates a new output file
file = open("log.csv", "w")
file.write("time,temp /C,humidity /%,pressure /mb\n")

Features I intend to implement next:
  • Command line interface
  • Multiple logs by name
  • Option to toggle sensors on off
  • Variable log sleep time
  • LED matrix icons for each state - 'ready', 'sensing', 'writing', 'sleeping'
Well that's it for now, but do check back soon!

#raspberrypi #pi #sensehat #python #datalogging