Tag Archives: Cron

Raspberry Pi Thermal Probe

How to read a temperature probe, save the value to a MySQL database and then show the value on a webpage or just show the value with no database.

 

See this link for how to setup a DS18B20+ thermal probe with a Raspberry Pi, these instructions  are the best that i have come across for this and will cover the bullet points below :

  • Enabling the 1 wire features in the Raspbian OS
  • Physically connecting the probe via a resistor to the RPi
  • Instructions on how to read the probe and a script example

https://www.modmypi.com/blog/ds18b20-one-wire-digital-temperature-sensor-and-the-raspberry-pi

Once you have followed the above steps you should have a working temperature probe, that’s great.. but what can you do with it now!?

For the piTank/piGrow projects,  I started off by just using the script provide in the instructions above, modifying it slightly and using that to display the temperature value on the piTank web-page. Using some JavaScript you can make the box’s refresh every x seconds, running the probe read script and showing a new value without the need for a page reload.  I call this a ‘live’ reading.

Continue reading Raspberry Pi Thermal Probe

Raspberry Pi Enable Cron

By default,  Cron is disabled meaning anything entered into  ‘crontab’ wont be run.

To enable this function, follow the steps below:

Once logged into the Pi use the below command to open up the ‘rsyslog.conf’ file in the Nano editor

cd/etc
sudo nano rsyslog.conf

Once the rsyslog is loaded into nano, navigate to the below section and un-comment the ‘cron’ option

#
# First some standard log files.  Log by facility.
#
auth,authpriv.*              /var/log/auth.log
*.*;auth,authpriv.none          -/var/log/syslog
cron.*                          /var/log/cron.log
daemon.*                        -/var/log/daemon.log
kern.*                          -/var/log/kern.log
lpr.*                           -/var/log/lpr.log
mail.*                          -/var/log/mail.log
user.*                          -/var/log/user.log

Save the document by pressing CTRL + O and then CTRL+X  close the editor.

Reboot the Raspberry Pi:

sudo reboot