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Picool

A Raspberry Pi Zero controller for a refrigerator compressor. Also includes configuration for Telegraf to send data to Azure Monitor Metrics (which can be displayed with Grafana or Azure Monitor Workbooks).

screenshot of grafana temperature dashboard

screenshot of systemd status output

Setup Pi Zero W Hardware

  • Wire all DS18B20 temperature sensors with DAT line on GPIO4.
  • Wire refrigerator relay VCC to GPIO17.

Setup OS

  • Install Raspberry Pi OS Lite to SD Card.
  • In /boot:
    • Add empty ssh file.
    • Add wpa_supplicant.conf with wifi SSID and PSK.
    • Add dtoverlay=w1-gpio to config.txt.
  • Boot Pi and SSH in with default user pi password raspberry.
  • Change password and add authorized ssh key.

Setup Picool

  • Install Telgraf
    • Add a resource_id to attach metrics in telegraf.conf copy it to /etc/telegraf.
    • Fill in azuremonitor.env and copy it to /etc/telegraf.
      • The service principal needs "Monitoring Metrics Publisher" role on the resource in resource_id above.
      • Run chmod 600 azuremonitor.env.
    • Copy 10-azuremonitor.conf into new directory /etc/systemd/system/telegraf.service.d.
    • Run sudo systemctl enable telegraf, sudo systemctl start telegraf.
  • Install Picool
    • Copy picool binary and influx_temps.sh into new directory /opt/picool and chmod 755 them.
    • Fill in picool.env and copy it into /etc.
    • Copy picool.service into /etc/systemd/system.
    • Run sudo systemctl daemon-reload, sudo systemctl enable picool, sudo systemctl start picool.

Building for Raspberry Pi Zero

sudo apt install gcc-arm-linux-gnueabi
rustup target add arm-unknown-linux-gnueabi
cargo build --target arm-unknown-linux-gnueabi --release

Running

Assumes a temperature sensor and a relay for the compressor power is connected.

# picool <PATH TO TEMPERATURE FILE>                          <RELAY CONTROL GPIO PIN>
./picool "/sys/bus/w1/devices/28-00112233445566/temperature" 17

Demo Mode

Run cargo run --features demo-mode. This does not do any actual I/O and simulates the sensor.