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readme.md

Arduino Scales

More information available here.

Theory

The idea was to modify existing bathroom scales to output its result to the internet. The scales themselves should still work as before.

PCB

The PCB uses an XRF radio, along with a MCP3421 18bit ADC, the Wheatstone bridge made up of 4 strain gauges can be measured accurately (~90g per step).

A single gate 74AHC inverter takes the LCD backlight signal and uses it to wake the Atmega328 chip from deep sleep.

Parts list

  • Various 0805 resistors and capacitors
  • SMD crystal - 16 Mhz TXC 7B-16.000MAAJ-T - Farnell no: 1841977
  • ATMEGA328P-AU - TQFP-32 package - Farnell no: 1715486
  • Microchip MCP3421A1T-E/CH - Farnell no: 1605568
  • NXP 74AHC1G04GW/T1 - Single gate SOT-353 inverter - Farnell no: 1085239
  • TI TPS73133DBVTG4 - 0.15A 3.3v voltage regulator - Farnell no: 1207341