Getting started with data logging on the Raspberry Pi

I've got a friend who just got a Raspberry Pi and wants to try doing some projects. One of the first things that he wants to do is track temperature and humidity in his house, which is a really good place to start because it's not TOO difficult. Great place to get your feet wet playing with "physical computing".

So, he got the Pi, got an OS on it, got it booted up, and then said "I have no idea what to do with it." So I thought a little, and realized, if the goal is temp logging, there's a really, really easy place to start.

I sent him this:

Open a terminal and copy this into a file called "log-cpu-temp": (do you know vi? if not, use nano)

#!/bin/bash

eval $(date +'now=%s date=%y%m%d')

echo "cpu.temp,$(< /sys/class/thermal/thermal_zone0/temp),$now" > \
    $HOME/cputemp-$date.csv

Then, make it executable:

chmod +x log-cpu-temp

Test it by running it:

./log-cpu-temp

It should create a file in your home directory cputemp-151223.csv containing the current CPU temperature in millideg C - something along the line of "35780" which means 35.780 deg C.

Once it's running, then add it to your crontab:

crontab -e

and add to the bottom:

* * * * * /home/pi/log-cpu-temp

Once you save and exit, it'll log the CPU temperature to the CSV file every minute.

Welcome to data logging!