TLDR

What is this?

As a hobby project, I have created a "smart home" system to make my home more comfortable and energy efficient. The entire thing runs off a Tecomat Foxtrot CP-1000 PLC. This is the Structured Text source code as well as all required MOSAIC IDE configuration files to reproduce my project.

Why is this on GitHub?

Although I have experience in software as well as a degree in embedded engineering, setting up the project was a pain due to the lack of documentation and available examples compared to mainstream languages like Java or C++. I hope providing a working, although far from perfect example will help other PLC projects to gain more motion.

"I'm going to hack your home!"

Nothing is exposed on the public internet and all systems included run on wired connection. I hope that is a high enough bar, but if isn't let me know!

Details

Hardware overview

This system have been fitted to a new construction home. Therefore, all sensors, inputs and actuators are wired.

• Each room has bunch off Cat6 outlets wired to a central patch panel in star topology. Apart from the regular TCP/IP network, this is the backbone of the alarm system, the analogue sensors and some other digital connections (ModBUS, RS232, OpenTherm). Wires are unshielded.
• Inputs are push button light switches wired in start topology to a central terminal block. They operate on 24V DC.
• Heating and domestic hot water is provided by a Vaillant boiler. It's communicating over OpenTherm using VR33 module
• Heating is fully underfloor with Siemens STP23 thermo electric valve controlled zones for every room.
• There's a Paradox alarm system equipped with a PRT3 Integration Module so it can talk to other systems over RS232.
• There are analogue PT-1000 temperature sensors all over the place. It's an SMD component fitted to a PCB so small that it hides in the belly of a RJ45 connector and is wired to its pins.
• The brain of the system is a Tecomat Foxtrot CP-1000 PLC. --It has several extension modules, so it talks over OpenTherm and ModBus on RS232 and RS485. --It interfaces with PT-1000 temperature sensors and reads temperature with approx 0,25 Celsius resolution. --It has relay modules those switch lighting and some programmable electric outlets. --It has contact inpts reading the signals from push buttons. --Features a built in webserver to serve as a UI. --It doesn't have SSL or any meaningful security measure, but it's easy to drag and drop a handy UI, so I use it on the internal newtork instead of spinning up a proper server.

Software overview

The code is entirely written in Structured Text using the Tecomat brand provided MOSAIC IDE. It requires a license and runs only in a very limited mode without it. My license is tied to my physical device I program.

There is significant project configuration (e.g. naming and mapping physical ports on the PLC) that's done over the MOSAIC UI, but is not actual code. I have added all the data files generated by MOSAIC which contains those project configuration to git. Maybe even more than what's needed. But I need a repo where after any change (that screws up my home) I can just roll back and reinstantiate previous functionality.

There is also autogenerated code for

• The WEB UI
• The built in data logger (that I use for a historic track of building temperatures and motion activity hoping that one day I'll just bump the entire thing to a magic neural network that will add some value to the thing).

The Structured Text code itself falls to 2 main categories:

• Generic data types and convenience functions. -- In normal systems, these would be user libraries, but creating and managing user libraries in MOSAIC isn't more convenient than source copy, so I don't do it.
• Functional modules -- Lighting -- Heating -- Alarm -- Persisting (data to an SD card in the PLC to save user settings)

Functional code usually follows the structure of having a module in 3 files:

• Globals, declaring variables that will be used across other modules or by the WEB UI
• Init, that maps inputs and outputs or more generically, data flow
• Actual logic that iterates over the data structures and does the actual trick

Contribution

This is the live system of my home and frankly, I have doubts that anyone would like to contribute to the code. Still, suggestions are warmly welcome and I'm happy to merge changes that improve code quality.

Things I would do differently next time

For sure

• Making shutters electric and controlling them centrally as well -- It doesn't even need more input, just control it by pressing the light switches longer or multiple times -- They are important part of heat regulation
• Using soil moisture sensors in the garden for more efficient watering

Maybe

• Thinking about KNX to make the system decentralised with no single point of failure like the central PLC unit