Build a LoRaWAN weighing scale with TTGO T-Weigh ESP32 board, HX711 modules

Ever wanted to build your own LoRaWAN connected weighing scale? Me neither, but apparently those types of products already exist for logistics and inventory management, and LilyGO’s latest ESP32 board – the TTGO T-Weigh – is designed for this exact purpose with a Semtech SX1272 based LoRa module, and four HX711 24-bit ADC chips.

The board can handle up to four scales that transfer weight data over WiFi, Bluetooth or LoRaWAN, and should be useful in applications that require weighting goods or products where there are limited connectivity options including logistics, farming.

TTGO T-Weigh specifications:

  • Wireless modules
    • TTGO T-Micro32 module based on ESP32-PICO-D4 SiP with ESP32 dual-core processor, 4MB SPI flash, 2.4 GHz WiFi 4 and Bluetooth 4.2/5.x
    • TTGO LORA32 module based on Semtech SX1262 transceiver  (EU868/US915)with -22 dBm Tx power, -148 dBm sensitivity, up to 62.5 kbps LoRa bitrate, up to 300 kbps FSK bitrate
  • Antennas
    • WiFi/Bluetooth – Ceramic antenna or external antenna via u.FL connector
    • LoRa – u.FL connector
  • USB – 1x USB Type-C port for power and programming
  • Sensor interfaces – 4x 4-pin connectors for load cell to interface with the four on-board AVA Semiconductor HX711 24-Bit Analog-to-Digital Converter (ADC)
  • Misc – Reset & Boot buttons, power switch, 4-pin I2C header (unpopulated)
  • Power Supply – 5 to 12V DC via 2-pin terminal block
  • Dimensions – 57.8 x 50.1 x 15.8 mm

The company provides Arduino and Platform.io samples on Github to show how to measure the weight and transmit the data with WiFi or LoRa. The results can also be shown on one of LilyGO bracelets. You’d also need a load cell with the minimal configuration as shown below to measure weight.

If that seems a lot of work to come up with a complete scale, because there’s no enclosure and so on, it might be possible to hack the DIY digital scale kit (now on Ebay for $40) we covered a few years ago, and replace the 8-bit MCU board with TTGO T-Weigh, although getting the display and buttons to work should require an I2C IO expander. LilyGO should probably sell the board as part of a kit, or I don’t see many people buying this board, or maybe they already have commercial customers.

If you are interested in the board, you can purchase it on Aliexpress for about $20.5 with either an 868 MHz or 915 MHz antenna.

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5 Replies to “Build a LoRaWAN weighing scale with TTGO T-Weigh ESP32 board, HX711 modules”

    1. Yep. I misunderstood that part. The chip in the middle of the board appears to be the HX711 indeed. I’ve updated the post.

  1. I don’t think you can manage 4 weight scales, the HX711 has only 2 differential inputs.
    The Lilygo documentation is poor so it is impossible to conclude.
    This link shows the different topologies https://circuitjournal.com/50kg-load-cells-with-HX711
    Such affordable board is very interesting for beekeepers (like me) as it allows to monitor remotely the status of the hives, so I wouldn’t say it is useless.

    1. My mistake, from github pictures it seems the board has 4 HX711 at the back so indeed it can monitor 4 weight scales. They definitively need to publish more information’s or at least the schematics.

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