{"id":600,"date":"2025-07-06T22:30:43","date_gmt":"2025-07-06T20:30:43","guid":{"rendered":"https:\/\/blog.bratfisch.net\/?p=600"},"modified":"2025-07-09T23:33:08","modified_gmt":"2025-07-09T21:33:08","slug":"a-beelogger-on-esp32-basis-part-7-test-setup-the-scale-part-2","status":"publish","type":"post","link":"https:\/\/blog.bratfisch.net\/index.php\/2025\/07\/06\/a-beelogger-on-esp32-basis-part-7-test-setup-the-scale-part-2\/","title":{"rendered":"A beelogger on ESP32 basis, part 7: Test setup: The scale part 2"},"content":{"rendered":"\n

I built four bee-hive scales according to the great instructions of the Beelogger project<\/a>.<\/p>\n\n\n\n

As the HX711-breakout-boards are not suitable for setups with 3.3V<\/a>, I’m trying it with a NAU7802-breakout-board now.
It doesn’t have problems when being driven with 3.3V and should be more precise than the HX711.
As an additional feature it has an internal temperature sensor which could help compensating the temperature drift, sadly its esphome-component doesn’t support it (yet).
According to the documentation it has an external calibration mode that may only be used without load, so it cannot be used for our use case.
It also has an internal calibration mechanism that can be used with load, it somehow uses the internal temperature sensors’ values, sadly the datasheet doesn’t say anything about how it really works.
The result of the internal calibration is getting read back by the esphome-component as it just sets the offset and the gain.<\/p>\n\n\n\n

The breakout-board I bought<\/a> only exposes one ADC channel, Adafruit has an updated version<\/a> since June 23rd, 2025 <\/strong>that exposes both channels, but sadly I couldn’t find any way to get it in Europe yet.
It’s also not supported by the esphome-component (yet).<\/p>\n\n\n\n


I connected it like this:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The code for the test setup:<\/p>\n\n\n\n

i2c:\n  sda: GPIO4\n  scl: GPIO5\n  frequency: 400khz\n  scan: true\n\nsensor:\n  - platform: nau7802\n    name: \"NAU7802 Weight\"\n    gain: 128\n    ldo_voltage: \"3.0V\"\n    update_interval: ${update_interval}\n    filters:\n     - calibrate_linear:\n          datapoints:\n          # measuring at 25 \u00b0C\n           -  64429 -> 0\n           -  166362 -> 4.58    # super with empty frames + tension belt\n           -  392628 -> 14.58   # super with empty frames + tension belt + 10kg\n           ...\nbutton:\n  - platform: template\n    name: \"Toggle Internal Calibration\"\n    on_press:\n      - logger.log: \"Internal calibration toggled\"\n      - nau7802.calibrate_internal_offset  <\/code><\/pre>\n\n\n\n
This code exposes the internal calibration via a button. The documentation says the internal calibration should be called on temperature or parameter changes, this is an open TODO as well as compensating the temperature drift.<\/p>\n\n\n\n
Additional new TODOs:<\/p>\n\n\n\n