Power Monitor

Firmware for ESP32-C3 SuperMini development board that reads GPIO5 pin which signals about availability of electricity at your home.

Board is connected and powered on UPS-DC-36W using HX12500-9Y connector. UPS pins to ESP32 pins:

• G to GND
• V to 3V3
• GN to GPIO5 (inverted)

GN pin sends inverted signal, means it set 3.3 volts when no power grid electricity, and send zero volts when electricity is available.

Setup

• Copy secrets.h.example to secrets.h
• Configure WiFi and Telegram credentials in secrets.h
• Figure out IP address of your board once connected (or assign IP to board MAC statically on your router which is recommended)

Home Assistant

In order to enable automation based on power availability Power Monitor can report binary_sensor to your Home Assistant.

Home Assistant Webhook API is used. First please configure your trigger and sensor by adding following configuration to Home Assistant's configuration.yml:

template:
  - trigger:
      - trigger: webhook
        webhook_id: {{ your-secret-webhook-ID }}
    binary_sensor:
      - name: "Power Monitor"
        unique_id: "binary_sensor.power_monitor"
        state: "{{ trigger.json.available }}"
        device_class: power

Don't forget to reboot Home Assistant instance.

Test it by using proper values from the config.

curl --location 'http://homeassistant.local:8123/api/webhook/{{ your-secret-webhook-ID }}' \
	--header 'Content-Type: application/json' \
	--data '{"available":true}'

You should see updates in your Home Assistant Settings / Devices / Entites and search for "Power Monitor".

Now configure secrets.h accordingly and flash updated firmware.

Wake On Lan

You may want to configure some of your device in LAN to start as soon as power comes online. To configure Wake On Lan update in secrets.h:

• WOL_MAC - the MAC address of your device (e.g AA:BB:CC:DD:EE:FF)
• WOL_ENABLED

Optionally you can update the WOL_DELAY in config.h to wait for specific amount of time before sending Wake On Lan (30 seconds by default). This may be useful if there is other devices without reserve power that needs to come up online between Power Monitor and your target device, like network switch.

Development

USB Serial

Comment line with monitor_port and add next config to platformio.ini to enable on boot USB serial:

monitor_rts = 0
monitor_dtr = 0
build_flags = 
	-DCORE_DEBUG_LEVEL=5
	-DARDUINO_USB_MODE=1
	-DARDUINO_USB_CDC_ON_BOOT=1

Remote Serial

Serial over Telnet can be enabled by installing TelnetSerial package. Next line should be added to platformio.ini (based on IP of your board):

monitor_port = socket://192.168.50.100:23

Then TelnetSerial.print output will be accessible over the network:

$ nc 192.168.0.10 23

OTA

Firmware upgrade (OTA) enabled by default using PlatformIO, keep next configs with IP address of your board

upload_protocol = espota
upload_port = 192.168.0.10

If you messed up with OTA codebase and it is no longer working - comment lines above and flash firmware via USB.

Credits

Thanks to @Akceptor for the original idea: https://github.com/Akceptor/esp32/blob/main/ElectricityMonitor.ino Thanks to @BootuzDinamontuz for the UPS-DC-36W pinout: https://www.youtube.com/watch?v=heOfX0curtU