Hacking a milligram balance (scale) with a Parallax Propeller microcontroller

2013-02-25

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For an upcoming project, I'd like to develop a dispensing system that can measure out a desired mass of material. The idea would be to use a microcontroller, dispensing valve, and electronic balance to provide feedback. I already have an American Weigh Scales miniPro-100, and decided to hack it so that my microcontroller can discover how much mass is on the balance. It can then regulate the dispensing valve appropriately.

The balance contains a Cirrus CS5530 24-bit ADC. I tapped the clock and data lines and found bursts of data that occurred at 7.5Hz. The clock is about 150KHz. I used a Parallax Propeller running assembly in one of its cores to capture the data stream and load it into my main program.