BornHack is an annual hackercamp in Denmark. A ticket to this camp includes a badge which you can hack on. This year (2021) The badge was half and half throughhole and SMD prototype board from which you could build your own badge in the Hardware village. Since I brought some of my bubble prototypes I decided to make it into a bubble badge. The end result is a badge that can inflate, change color via NeoPixel and is programmable in CircuitPython.
BornHack 2021 badge/PCB
CircuitPython capable microcontroller with small form factor
single ws2812 on PCB
Discrete Semiconductors / Power Transistors and MOSFET
These pcb NeoPixels have pads on their underside, therefore making it impossible to solder them to the flat service of the badge. To circumvent this solder some metal rods to the pads. Make wires a little longer to cut to size later for easier placement.
Place the NeoPixel on the SMD part of the badge so it is as much center as possible. Though this also doesn't need to be perfect since the bubble goes on top and will diffuse the light anyway.
Add presure sensor module
Add the pressure sensor. Take the following into account, we need as much space as possible for both the other components as well as the bubble. Therefore we solder it portruding out of the badge. The connector for the tube needs to face the front otherwise the tube might cause the badge to tilt/spin. The headers on the module will point quite far in the direction your chest will be on the finished badge. Desolder them and flip them around so the short end faces down.
The regidity of this construction will be from the small overlaps of the module and the badge combined with the fact that the module lays very flat on the badge. There is no planned mechanical strain on the module. Though it still might be a weak point to be carefull about.
Place the 2 TIP120's in the second row of the prototype board (first row has qwic and SAO breakouts). Bend the leads in such a way that the transistor can lay flat on the badge, don't push the leads too far in so bending is easier. Solder the them in place.
On the back add the resistors and diodes between the pins of the transistor based on the schematic below. (The resistors are different values and we don't use the ceramic cap, diagram is more as illustration).
The GND will be connected to the microcontroller in a later step.