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Power Price Monitor

IoT device that monitors power prices and displays the current price as a color of light using an RGB LED on the ESP32.

It connects to a Philips Hue bridge to control grouped lights based on the power price.

In essence every light you put in a predefined room, the color changes according to the price

Color Indications

  • Purple: No WiFi connection if it is stuck on this color
  • Blue/Red: Flashing 250ms apart, press button on Hue Bridge
  • Blue/Red: Flashing slowly for longer period of time, something is wrong, check if access point is setup correctly

Default colors for prices

  • Red: High power price
  • Yellow: Moderate power price
  • Green: Low power price
  • White: Extremely low price

This is my first time in years programming in c++, so be very careful about blindly copying my code. Especially in terms of good practices and security, I still have a lot to learn.

This version does not yet use HTTPS for the Hue, only for the call to the price portal (API) I also had to remove it for the price portal as the certificate changed, and as I don't control the API, I don't want the hassle og changing the certficate every time. Signify (Former: Philips lighting) strongly recommends HTTPS. You can see the excellent documentation here: https://developers.meethue.com/develop/application-design-guidance/using-https/

It does require a login, but you can register for free and it is worth it. The documentation is very to the point and easy to follow with great examples.

Table of Contents

Hardware Requirements

  • ESP32 board, made for FireBeetle 2 ESP32-E IoT, but any other board should do. You need to change the neopixel RGB led pin from D8 to your relevant GPIO
  • RGB LED (Neopixel, built in on the Firebeetle)
  • Philips Hue bridge
  • Push button (for resetting WiFi credentials and custom values for colors and prices, built in on GPIO27 on the Firebeetle)

Software Requirements

  • PlatformIO IDE (or you might change main.cpp to main.ino and get lucky with the Arduino IDE)
  • ESP32 board library (Beware Espressif changed the WifiSecureClient.h in 3.x, but I set a specific version dependency for 2.x, so if you update it will need to be updated to the new NetworkSecure.h or whatever it is called)
  • FastLED library
  • ArduinoJson library
  • ESP32mDNS
  • Other basic libs...

File Descriptions

Main Files

  • main.cpp: Main file that initializes the device, connects to WiFi, and starts the main loop.

Helper Files

  • RGBControl.hpp/cpp: Contains functions for setting up and controlling the RGB LED (neopixel).
  • TimeHandler.hpp/cpp: Handles time synchronization with an NTP server.
  • ElprisenRESTReader.hpp/cpp: Fetches the current power price from elprisenligenu.dk.
  • ConfigService.hpp/cpp: Manages saving and loading WiFi credentials and API keys from non-volatile storage.
  • HueService.hpp/cpp: Discovers and fetches IP address and port of the Philips Hue bridge.
  • HueLightService.hpp/cpp: Controls the lights connected to the Philips Hue bridge.
  • HueEventService.hpp/cpp: Handles events from the Philips Hue bridge. (Currently not integrated, but does work. Needs more work and integration with main.cpp not straightforward)
  • WiFiSetupService.hpp/cpp: Sets up the device as a WiFi access point to capture WiFi credentials and custom setup of colors and prices using Captive Portal
  • WifiSetup.html.hpp: Used by the WifiSetupService. An html file wrapped as a header file. I am not really sure why I did it like this. It was easy though. Should probably properly load it from NVS as a blob.
  • WiFiUtils.hpp/cpp: Simply connects to the Wifi, keeps trying forever

Setup Instructions

  1. Clone the Repository

    git clone https://github.com/jeppeml/power-price-monitor.git
cd power-price-monitor

  2. Install Required Libraries Open PlatformIO and make sure following libraries are installed (they should already be in the ini file for Platform.io):

    • FastLED
    • ArduinoJson
    • ESP32mDNS

  3. Upload

    • Connect your ESP32 board to your computer
    • Select the appropriate board and port from the Tools menu
    • Upload the sketch to the ESP32

  4. Setup

    • Upon first boot, the device will start as an access point named PowerPriceMonitor.
    • Connect to this access point using a phone or computer.
    • You will be redirected to a setup page. Enter your WiFi SSID, password, and the name of the Philips Hue room. Change the colors and/or price ranges if you want.
    • The device will save everything and restart to connect to the provided WiFi network.

Usage

  • The device fetches the current power price every minute and updates the color of the RGB LED based on the price.
  • The Philips Hue lights in the specified room will also change color based on the power price.
  • If the button connected to GPIO27 is held for around 6 seconds while booting, the device will reset the WiFi credentials and settings, and restart with setup.

Contributing

Contributions are welcome! Please fork the repository and use a feature branch. Pull requests are welcome.

TODO

WiFi setup should include setting up the price points for high, medium, low, very low WiFi setup should include setting up the colors for price points

  • HTTPS should be enabled for the Hue bridge connection
  • "Nice to have", would be instead of polling changes in the room, to listen for changes through events. I have a working service for this HueEventService, however it needs some work to properly filter events and be integrated with the main.cpp would require some work, because of the async nature of events. The max polling is 1 light change per second according to the documentation, and right now I set it up to 1 minute... so this shouldn't be a problem