SmartPot is a small IoT project designed to monitor the fill level of coffee pots in an office kitchen. The project was created together with a student intern with the goal of making it possible to see at any time whether coffee is still available or if it’s time to brew a new pot.
For this purpose, a 3D-printed base was developed to house the electronics and integrate load cells that measure the weight of the coffee pot. The analog signals from the load cells are digitized using an HX711 with a high-resolution 24-bit ADC and processed by an ESP microcontroller.
The ESP then transmits the measurement data as a BTHome advertising packet via Bluetooth. A Raspberry Pi 4 running Home Assistant receives this data and displays the current fill level on the network.
Alternatively, the data packets can be received directly using the Windows application CoffeePotReceiver. This is particularly useful for debugging and development.
This allows everyone in the office to see at any time:
- whether there is still coffee available
- whether it’s worth going to the kitchen
- or whether fresh coffee has just been brewed ☕
- ESP32-C3 or Seeed Studio XIAO ESP32-C3
- HX711 – 24-bit ADC for load cells (Avia Semiconductor)
- 2 × load cells (50 kg each)
- 3 × AA batteries
- Raspberry Pi 4 running Home Assistant
- 3D-printed base to house the electronics
The ESP was programmed using the Arduino IDE. The following libraries were used:
- BTHome Library – https://github.com/Chreece/BTHomeV2-ESP32-example.git
- HX711 Library – https://github.com/RobTillaart/HX711.git
The debugging application CoffeePotReceiver can directly receive and display the Bluetooth advertising packets.Requirements:
- Qt 6 / Qt Creator
- MSVC 2022 (required for Bluetooth Low Energy support under Windows)
- Load cells measure the weight of the coffee pot
- HX711 digitizes the sensor signal
- ESP32 processes the measurement data
- ESP32 transmits the data as BTHome BLE advertising
- Home Assistant on the Raspberry Pi receives and visualizes the data
A simple, battery-powered system that makes the fill level of coffee pots in the office visible without requiring additional infrastructure. Fewer empty pots – more coffee. ☕