See the following video to understand how to operate and calibrate the scale:
The scale mechanics has been designed with 3D print in mind. This means all parts of the scale can be printed on a standard size 3D FDM (Fused Deposition Modeling) printer without any extra support.
For the electronics I had in mind to use standard modules that are commonly used in the electronic maker scene, that can be purchased easily and cheap from the internet. Also I focused on low power consumption. Therefore I designed a zero power voltage supply that drops the power consumption to zero during off mode, though power on is realized by a key press. So I realized the Electronics with an Arduino pro mini and a weight cell and controller based on HX711. These parts can be usually purchased for less than 10€ all together from the internet. If you search for “HX711 module” and/or “arduino pro mini”, you will find plenty of offers.
For the software I had flexibility in mind and the possibility to use different range sensors and different weight units. Therefore weight calibration is not fixed in code, but flexibly adaptable and calibrateable via software. In other words with no changes in the arduino sketch you may calibrate your scale by software. And with very little changes in the parameter section of the sketch you may change weight range, number of digits after the point or the weight unit – g, KG, N, ounces or whatever unit you prefer – and much more.