ekm-meter-watcher

Script and Docker image for monitoring an EKM meter over GPIO and logging readings in SQLite.

Setup

1. Build the image:

docker build -t ekm-meter-watcher .

2. Create a docker-compose.yaml like this:

services:
  ekm-meter-watcher:
    image: ghcr.io/snoack/ekm-meter-watcher:latest
    restart: unless-stopped
    devices:
      - /dev/gpiochip4:/dev/gpiochip4
    # environment:
    #   EKM_GPIO: "27"
    #   EKM_TIMEOUT: "10"
    #   EKM_LOG_LEVEL: WARNING
    #   EKM_AGGREGATE_AFTER_WEEKS: "6"
    #   EKM_AGGREGATE_BY_SECONDS: "3600"
    volumes:
      - ./data:/data

These environment variables are optional; the commented values shown above are the defaults.

3. Start it:

docker compose up -d

The host still needs to expose the GPIO character device you map in devices.

Wiring

By default the watcher reads pulses from GPIO 27, which is physical pin 13 on the Raspberry Pi. If using a different GPIO pin set EKM_GPIO accordingly.

The EKM meter pulse output behaves like a switch that closes and opens 800 times per kWh used. Wire it like this:

1. Supply 3.3 V from the Pi to the meter.
2. Put a 1 kOhm resistor in series with the input GPIO pin to limit current.
3. Add a 10 kOhm pull-down resistor on the GPIO input, on the meter side of the 1 kOhm resistor.
4. Connect the meter pulse output to the GPIO input.

The script requests the GPIO line with bias disabled, so the external pull-down is required.