Design kitchen scale based on arduino

Since Thingiverse is not able to provide all 3D files correctly, here you may download the complete stl and Obj. file set in one zip file:

http://bechele.de/images/attach/155-table_scale.zip

Because the project is powerd by a 9V battery, every mA of current plays a role. By default the display background illumination is quite bright. that cost about an extra of 15 mA of current. By replacing the jumper of the display illumination by a resistor (in my case 1KOhms) the current dropped a lot. So the display was still bright enough to read the text. Also I removed the Power LED on the Arduino Pro mini. This saved me another 5 mA. Finally the Scale takes in operation about 55mA of current from the 9V battery.

During the build of the project i noticed that the scale values were drifting quite a lot. After a deep investigation into the problem it showed that the resistance of some of the used SMD parts on the controller are very sensitive. Even by breathing over the electronicss slightly the values drifted dramatically. So I decided to cover the electronics with some transparent varnish. The varnish after it was dry caused the drift of the controller to drop to almost zero. So my recommendation is to put some varnish onto the complete board after soldering everything together.

Meanwhile I ordered a few new weight cells to build more units and i noticed the weight cells had suddenly a different size. Though the article image was correct the delivery was different.

Instead of a lenghth of 80 mm the delivered once had only 75 mm and also the distance in between the mounting threads  changed from 15 to 10 mm, so I re- desigend both the scale stand an also the scale dish. Now you will find two different parts of each for download on Thingiverse.