Logging Temperatures with a Raspi and ds18b20 sensors(s)
Much credit to https://tutorials-raspberrypi.com/raspberry-pi-temperature-sensor-1wire-ds18b20/
Phsyically connecting to Raspi and initializing
Sensor data wire(s) should be connected to GPIO 4.
Also need to connect GND and 3.3-5V.
Initialize the sensors:
sudo modprobe w1-gpio
sudo modprobe w1-therm
Check that it worked:
lsmod
The modules should now be listed, if not, ensure GPIO pin 4 was used.
If yes, perhaps some error occurred while activating.
Might also check sudo raspi-config > interfacing options
"1 wire" needs to be enabled
To load the modules every time, we'll add them to /etc/modules
sudo echo >> w1_gpio /etc/modules
sudo echo >> w1_ther /etc/modules
Getting the ID(s) of the sensor(s):
If connecting several in parallel, it is best to connect one at a time.
Test each sensor individually, and make a note of it's ID.
Go to the w1 directory and list the files:
cd /sys/bus/w1/devices/
ls
Sensors might look like 10-000802b4ba0e, 28-0516803024ff, or something similar.
We'll need this ID we use to query the sensor (adjust ID to match your sensor)
Getting the output of sensor:
Use a command like this to get the output of a sensor
cat /sys/bus/w1/devices/10-000802b4ba0e/w1_slave
cat /sys/bus/w1/devices/28-0516803024f/w1_slave
Sample output, the value after t= is your temp in (in “mili-degrees °C”)
31 00 4b 46 ff ff 05 10 1c : crc=1c YES
31 00 4b 46 ff ff 05 10 1c t=24437
Divided by 1000, we'd get 24.437 °C.
For a bash example of transforming and showing these values:
See tempshow.sh
Consider making tempshow.sh executable chmod +x tempshow.sh
Also consider removing ".sh" and placing at /usr/bin/tempshow
For a bash example of logging these values to CSV:
See templog.sh
Same considerations as above apply.
For systemd service and timer examples see:
templog.service
templog.timer
which should be placed at /etc/systemd/system/
Use systemctl to enable | start | stop | disable | restart