ESP32 + Attiny85 sensor for HomeAssistant to track Gaz consumption by using data port located on the french Gazpar energy meter.
The Gazpar meter provided by GRDF has a 2 pin connector on its left side, which sends an electrical pulse for every 10 liters of gas consumed. This project's goal is to leverage this port to integrate Gaz consumption into HomeAssistant, with the help of an MQTT broker.
This setup will be located in my utility closet, outside of my apartment, without an AC outlet. So, we will need battery power, and thus a low-power design. More on that in the next chapter!
To lower the power consumption, we won't be running the ESP32 all the time, as its normal run mode draws around 80mA. We use 18650 lipo cells, with a capacity in the 2800mAh-4000mAh range, which translates to a battery run time of 2-3 days, which is unacceptable.
To solve this, we use an Attiny85, which draws a much more reasonable 2mA during normal operations, and wake up the ESP32 every couple of hours to transmit the data.
TODO: after a couple of runs, report back the battery life here!
The ESP32 runs a very simple routine:
- Boot
- Connect to WiFi
- Connect to MQTT
- Wait for the retained value from HASS
- Fetch the new number of pulses from the Attiny
- Adds the old value and the new value
- Publish the new value to the MQTT broker
- Go to sleep
TODO
To set up the sensor in HomeAssistant, start by installing an MQTT broker if you don't already have one: https://github.com/home-assistant/addons/tree/master/mosquitto. The MQTT integration also needs to be installed, enabled, and set up correctly.
Then, edit the configuration.yml file, and add the following:
sensor:
- platform: mqtt
state_topic: "energy/gaz_pulse_10_liters"
device_class: gas
state_class: total_increasing
name: Consomation de Gaz
unit_of_measurement: "m³"
value_template: "{{ value | multiply(0.01) }}"Note: the value_template attribute is used here because our input is 1 pulse per 10L, and we want cubic meters. There are 100 times 10 liters in a cubic meter, so we need to multiply by 0.01 (yay for metric !)