This is a customizable support for electronic cards. It can be adjusted to fit almost any board, with screws fitting or just sitting in a notch.
I made two board, one with an external power supply with rectifier, voltage regulator, volt and amps gauge, a little voltage booster, temperature gauge, a big breadboard and a Uno, and another with the Uno, a little voltage booster, volt and amps gauge, 1602 display and a little breadboard. I fixed some of the boards with screws and some that have no fixing points with a drop of hot glue.

In the customizer you can add as much as 10 boards, in case you need more you have to do some copy and paste...

I used some boards stl files as a reference in the examples, and if you want them you can find them at the following links:

Arduino uno: https://www.thingiverse.com/thing:253463
Mega 2560: https://www.thingiverse.com/thing:739959
Raspberry Pi A+ : https://www.thingiverse.com/thing:566520
Raspberry Pi B+: https://www.thingiverse.com/thing:402498
Raspberry zero: http://www.thingiverse.com/thing:1323037

Most of the stl files are rendered and exported in different positions respect axis centers.
This is a preferences of designers, and will not bug the slicers, but if you import them into another project and want them centered, you should to do it manually. To avoid that, I open the file with Cura, slice it without moving it on the plane, and save it again as stl. This will center the model in all 3 axis, and even correct it if there are any errors with it.

Unfortunately in Thingiverse customizer is not possible to implement external files (or at least I don't know how) and you will not be able to see the boards stl files but use the "show_box" option, otherwise you need to use OpenScad.

There are more modules and components in the groups:
https://www.thingiverse.com/groups/openscad-electronic-design/things
https://www.thingiverse.com/groups/electronic-cards/things

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I created these eBay links where you can find components, filaments and spare parts at the best prices. These are just links to eBay and Aliexpress items, where I normally buy spare parts and materials for my printer and projects. Clicking on these links will support a little bit these projects.

PCB perforated boards - Resistors eBay - Capacitors eBay - Diodes eBay - led - Wire terminals eBay - Arduino and modules eBay - Raspberry and modules

Prototype PCB board Aliexpress - Resistors Aliexpress - Capacitors Aliexpress - Diodes and LED Aliexpress - Arduino and modules Aliexpress - Raspberry and modules Aliexpress

PLA Filament - eBay - ABS Filament - eBay - TPU Filament - eBay - PET Filament - eBay

Complete extruders - eBay

Heat blocks and heaters - Aliexpress

Standard nozzles - eBay - Standard nozzles Aliexpress

Volcano nozzles - eBay - Volcano nozzles - Aliexpress

GT2 pulleys - eBay - GT2 pulleys - Aliexpress

GT2 belts - eBay - GT2 belts - Aliexpress

Linear bearings LM series - eBay - Linear bearings LM series - Aliexpress

NEMA 17 step motors - eBay - NEMA 17 step motors - Aliexpress

3d pen - eBay

100$-200$ 3D printers - eBay - 100$-200$ 3D printers - Aliexpress

200$-300$ 3D printers - eBay - 200$-300$ 3D printers - Aliexpress

300$-500$ 3D printers - eBay - 300$-500$ 3D printers - Aliexpress

500$-1000$ 3D printers - eBay - 500$-1000$ 3D printers - Aliexpress

1000$-2000$ 3D printers - eBay - 1000$-2000$ 3D printers - Aliexpress

2000$ - 5000$ 3D printers - eBay - 2000$-5000$ 3D printers - Aliexpress

Filament extruding machine - eBay -
Filament extruding machine - Aliexpress

Pellets for extruding machine