The more tinkering with the Raspberry Pi, the more circuits you get. If you want to use your Raspi parallel productive 24/7 – e. g. as a Smarthome Server – you get constant problems with customizing and extending existing constructions and errors can be anywhere! How that works better, read here.
In my case, I use the Raspberry with different sensors for my Smarthome applications. For that I mostly use switches or reed contacts that are connected through GPIO pins. The necessary components (resistors, capacitors) are connected on a circuit board with a 40 pin header connector and a flat cable with the Pi.
Over time, new additional functions are always to come. And so every time the same painstaking process of expanding:
De-wiring everything, label it, go to the basement, solder, test, install again, re-wire everything.
Then hope that everything works without error. Otherwise, again through everything. The desire to change something or expand it got smaller and smaller. After the fifth enlargement, I did not want to go that way.
There had to be a solution that allows expansion or modification, but not always the whole system has to be switched off or can fall into error.
I have chosen a two-part system:
The base board must be universal, while providing full access to all GPIO pins. In order to implement, I have decided to use on a solution with screw connectors. A suitable shield I didn’t found. Maybe a possibility is a „GPIO Expansion Board“.
For me best is a homemade version.
- Dot matrix pcb
- 40-pin connector socket
- 20 pcs 2-terminal-screw
With this you can easily access any GPIO. However, the soldering takes you a while, about one hour.
The advantages of the base board come through the individual modules. There may be a new module or an existing can be extended for any area, any application or any extension. The decision is then up to you. Most importantly, the other modules can continue to operate without modification.
To wire the module with the base board I use little connectors with parts of an old pcb. So there is always the possibility of simply unplug the board without affecting the functions of other modules. I like to work here with a dot matrix pcb 7 x 5 cm.
- Dot matrix pcb 7 x 5 cm
- Pin plugs
- Pin sockets
If several modules are used, it turns very quickly the question of how and where they are best mounted. Come in a case? Will you put a shield on the Raspberry or the main board?
In this consideration, the old computer systems are somehow stayed in my memory. Huge boards are packed into even larger cabinets. I also wanted to do it in that way.
I have implemented it with a board holder from the 3D printer. In the blank holder, a module (pcb) can be inserted. Additionally, there are side holes to secure the circuit board when mounted vertically against falling out. The board holder itself can be easily fixed with screws.
An example is my Raspberry Pi with several sensors for my Smarthome solution. At the moment I use 4 modules.
- Module: 433 Mhz radio transmitter
- Module: recognition doorbell (project Telekom T-Concept X311 with Doorline at Raspberry)
- Module: Rabbit console (project Rabbits, Buttons and Lean-Management)
- Module: garage door state and control
In this picture you can see a the basic structure with an attached module.
The Raspberry Pi, the base board and the modules are screwed on a sheet of plywood. With each change or additional expansion I am now able to run the Pi without stop. Now it is much easier to continue improving or expanding my system.
And if something does not work, the module is thrown out.
3D model of the holder as STP file
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