How to create real time graphs of CPU temperature on a Raspberry Pi

3 November 2015 by marty RaspberryPi

Probably heavily linked with my inner analyst, for a while now I've wanted to create some real-time graphing of some of my raspberry pi stats. I've had a couple of stabs at it but getting it to actually work has eluded me until now.

The below example guides you through how to plot your CPU temp as a graph to an image file, the code is in my github repository where I'll hopefully add further functionality in the future.

How to guide

First off you need to install Python3

sudo apt-get install python3
sudo apt-get install python-setuptools
sudo apt-get install python3-pip

Next install GNUPlot

sudo apt-get install gnuplot-x11

Then we need to setup a working directory:

cd ~
mkdir plottemp
cd plottemp

create the necessary files:

nano datagen.py

Paste in the following code:

#!/usr/bin/env python

import sys, os, logging, urllib, datetime

def fetchtemp():
	cmd = '/opt/vc/bin/vcgencmd measure_temp'
	line = os.popen(cmd).readline().strip()
	output = line.split('=')[1].split("'")[0]#+' C'
	return output 

format = "%Y-%m-%d,%H:%M:%S" 
today = datetime.datetime.today()
s = today.strftime(format)
output = s+' '+fetchtemp()+'\n'

print(output)

with open('/home/pi/plottemp/tempdata.dat', 'a') as f:
	f.write(output)

Create this also

nano plottemp.sh

and paste the following:

#!/bin/bash
echo "set terminal png size 900, 300
set xdata time
set xrange [ time(0) - 86400 : time(0) ]    # 86400 sec = 1 day
set timefmt '%Y-%m-%d,%H:%M:%S'
set format x '%H:%M'
set output '/home/pi/plottemp/tempplot.png'
plot '/home/pi/plottemp/tempdata.dat' using 1:2 with lines" | gnuplot

make it executable

chmod +x plottemp.sh

next all we have to do is to run the script every 5 minutes (or whatever interval you choose) with cron:

crontab -e

and add this line:

*/5 * * * * python3 /home/pi/plottemp/datagen.py && /home/pi/plottemp/plottemp.sh &> /dev/null

and there we have it, it will generate a file called:

plottemp.png

The result

If you have successfully implemented the instructions you should get something like this:

How it works

I'll very briefly walk you through how it works - there's a cron job running every five minutes which firstly runs a command line function which reports the CPU temp and saves it to a log file. Upon completion it then runs a GNUPlot command to generate a graph of the last 24 hours logging.