The SparkFun OpenScale – IoT is an out-of-the-box, ESP32-powered smart scale for IoT applications, featuring open-source hardware and firmware for easy integration with load cells without needing to develop custom code from scratch for core functionalities.
The device utilizes the HX711 24-bit ADC for amplification, includes calibration and temperature compensation capabilities (via the onboard TMP102 sensor and an optional DS18B20 probe), and offers serial output and configuration through a straightforward text-based menu. It provides Wi-Fi connectivity for real-time data and OTA firmware updates, accessible via standard terminal tools and a web browser instead of specialized apps. Additionally, it includes a Qwiic I²C connector for attaching extra sensors or displays. Operating at 5 V with typical consumption of 80–100 mA, the board supports selectable data rates of 10 or 80 SPS and provides adjustable gain for precise long-term measurements.
Specifications of the SparkFun OpenScale – IoT include:
– Wireless module: ESP32-PICO-MINI, 2.4GHz WiFi, Bluetooth/BLE, PCB antenna
– Load Cell: HX711 ADC supporting 4- or 5-wire load cells
– Sensors: TMP102 digital (I²C); 3-pin terminal for DS18B20 sensor
– USB: Type-C for power and configuration (via CH340C converter)
– Expansion: SparkFun Qwiic connector
– Miscellaneous: LEDs, Reset and Boot buttons, external serial interface, selectable data rates
– Power: 5 V input, 80–100 mA consumption, onboard 3.3 V regulator
– Dimensions: 55.88 x 46.99 mm
The initial SparkFun OpenScale features an ATmega328P base for load cell operations but lacks wireless features, similar to another kit from 2017. The OpenScale IoT version can operate without custom Arduino code and allows Bluetooth/BLE or wired USB-C serial connections. It connects to a local Wi-Fi network for live data viewing and OTA updates. The design files and firmware are available on SparkFun’s GitHub.
The board is intended for industrial applications needing continuous weight monitoring. Other ESP32-based options exist, such as the TTGO T-Weigh board with LoRa connectivity. The SparkFun OpenScale IoT is priced at $44.95, while the original non-wireless version costs $34.95, and the LoRaWAN-enabled option is around $32 on AliExpress. A demonstration video with the original ATmega-based OpenScale board is provided.