Earlier in the week, I mentioned that I’d bought a new case to keep my Raspberry Pi cool. So that I can keep an eye on the CPU temperature, and hope that it doesn’t overheat again, I’ve added this as a sensor in Home Assistant.
Adding a CPU temperature sensor to Home Assistant isn’t as straightforward as most other integrations. It’s not included in the System monitor integration, for example. When I was searching for solutions, I found all sorts, including one which required installing several packages from Aptitude, a script, and an MQTT broker. To be fair, that was designed to monitor multiple Raspberry Pis remotely; all I needed was just to poll the CPU temperature of the device that Home Assistant was running on.
Command line integration
Whilst not as straightforward as adding an integration, there is a relatively simple way of adding a CPU temperature sensor using the Command line integration. Indeed, it’s one of the given usage examples, which I’ve copied below:
# Example configuration.yaml entry
command_line:
- sensor:
name: CPU Temperature
command: "cat /sys/class/thermal/thermal_zone0/temp"
# If errors occur, make sure configuration file is encoded as UTF-8
unit_of_measurement: "°C"
value_template: "{{ value | multiply(0.001) | round(1) }}"You’ll need to add this to your configuration.yaml file, and then restart Home Assistant. You should now have a ‘CPU Temperature’ entity, which you can add to a card to display on your home dashboard.
As well as running the command, the example code also adds the relevant units, and also reformats the numbers. If you open a terminal window and run the cat /sys/class/thermal/thermal_zone0/temp command on its own, you’ll get a value like ‘36511’. So, the value_template line divides the number by 1000 (or specifically multiplies it by 0.001, but the result is the same), and rounds it to one decimal place.
Once you’ve got the entity into Home Assistant, you can log your CPU temperature over time, and even display it as a graph if you want. You can also build automations, so that you can receive notifications when your CPU temperature is too high. For a Raspberry Pi, ‘too high’ is 85°C.
