This is a classic example of a well done hack, simply for the sake of hacking. [Jorge] wanted to be able to chart his weight changes.  His solution wasn’t to simply buy a scale that could be hooked to the computer. Those are available and aren’t really that expensive. He could have even used pencil and paper to chart it in a few seconds. Instead, [Jorge] started hacking. He took apart a digital scale he already had and installed his own circuit to display weight and write the values to a CSV. The CSV resides on a removable card which can then be put in his computer to chart the data in openoffice.

[John Peterson] created this postal scale device for a Renesas design contest. The Weasure not only calculates the package’s total weight but the dimensions as well. He built it using a SKP16C62P evaluation board that had an LCD, pushbuttons, and indicator LEDs. The original DigiWeigh parcel scale was modified to provide PWM output and tare control. He embedded photoresistors every inch along each axis. They were angle slightly upward and the surroundings were painted black to minimize reflection. The Weasure outputs everything via a serial connection so it can be used with shipping software to generate postage.

[David Steeman] sent us this project. He uses a consumer scale to measure rocket engine thrust. He wanted to be able to map the thrust curve of his homemade rocket motors to determine whether they are meeting the design goals. It does this by measuring the force applied by the rocket engine via a microcontroller that records it in a text file on a computer. He then analyzes this data in an Excel spreadsheet.

The sensors were harvested from a consumer scale while the rest of the electronics were built by hand. He’s using a PIC 18F2550 microcontroller which has a built in USB interface. He has breakdowns of each piece with detailed information on how it works as well as some nice pictures. There is also a list of future improvements that he would like to do such as increasing sample speed, integrating it with the ignition, and decreasing the physical size. Files for the schematic, firmware, and excel spreadsheet are available for download at the bottom of the page, so keep scrolling down.