GMU:Printed Circuit Board Art/mxkllmnn: Difference between revisions

At this point, the switching mechanism has already been fully developed and all components were in place, although only on a breadboard. As the project is rooted in the smart home milieu, the decision on a microcontroller was easy: An ESP12 module based on the famous ESP8266 chip by espressif is the heart of the application. As mentioned before, GUIs can be altered by simply changing bits from zero to one or vice versa. Altering objects of the physical world requires kinetic energy. Therefore an electromechanical transducer is necessary. After many experiments, the decision was finally made in favour of a 12V DC brushed gearmotor. To control it with a microcontroller the L9110S H-bridge driver IC has been chosen. As the ESP runs on 3.3V a regulator IC (12V to 3.3V) was also to be installed as well as a couple of resistors, capacitors, and buttons.

The design was very much influenced by the early thoughts on the topic of "capacitive touch". I would have installed all the technical components in a [https://www.instructables.com/Dead-Bug-Prototyping-and-Freeform-Electronics/ dead bug] fashion, disappearing into the flush socket of the wall, if it hadn't been for the idea of realising the entire backend as a PCB in the front, with touchpads on its rear. When the idea of touch input gestures was dropped (because this contrasted with highlighting mechanical devices), all that was left were components that logically belong to the backend. Yet, having everything fit tightly into the cover of the switch makes debugging very easy. By removing it, all the connections are accessible. So the transfer from breadboard to a PCB was the only logical consequence. To achieve this several steps have to be taken.  

An intermediate step is a hand-soldered prototype. As common switches come with a cover, the base plate already existed. But I did not start soldering right away. The first thing I did was a rough sketch of all components and their respective connections on a piece of paper. Only then I made my first attempts at this design in KiCAD. Since I did not want to spoil my option of revisiting capacitive touch gestures at a later stage, it was my personal challenge to realise everything on just one side of a PCB with no viases or through-hole components. Of course, this also meant that all elements had to be placed so that there is no intersection of a single trace, which has been hard before I got to know the practice of ground areas (across the entire PCB). Before the final layout was finished, it was an eternal back and forth between different media (KiCAD, paper, Fusion, soldering iron, and back again).