This project is a collaboration with Younjin Song, Sairanjith Thalanki, and Andrew Ge. It was supported by Robotics@Berkeley as part of their annual DXM Robotics Competition.


  • Users name each platform in the app depending on the item it is tracking
  • To setup an item, Re.Stock takes a calibration reading of the platform while empty. Users then place on the item and specify how full it is
  • Users adjust the percent of the item left at which they receive a notification. Setting the level higher can account for the weight of the item's packaging
  • The app compares each reading to the empty platform calibration reading so it can ignore data taken when the item is not on the platform


  • Box and platforms built from birch plywood, finished with spray lacquer
  • Each platform is attached only to a load cell underneath
  • Load cells secured to wood using tee nuts and machine screws


  • Each load cell is connected to a HX711 amplifier board, which reads the voltage signal from the cell and converts it to a digital signal read by an Arduino
  • Amplifiers receive a 5V power supply, a shared ground, and a clock signal from the Arduino
  • Arduino takes periodic readings from the amplifiers and passes on the data to the ESP8266 WiFi Module
  • Entire system is powered off a 5V power supply connected to the Arduino


  • Data sent to ESP is passed on to a database hosted online using PHP
  • App uses HTML parser to pull data from the webpage