Luxsmart - The Smart House System

Written by Marko Jankovec on March 3, 2016

A students' hobby project that evolved into a commercial product.

It all started as a students' hobby project...

A few years ago, a group of three electronics master's students at the Faculty of Electrical Engineering (University of Ljubljana) started a hobby project with the goal of developing a system able to control blinds in an ordinary house over the web. They quickly managed to develop and build a prototype, and installed it in a house where it proved to work as supposed.

The students were, of course, pleased with their achievement and as their faculty supervisor I encouraged them to continue developing the system after they finished the course as I quickly recognized the project's potential. The students were then asked to joined the MULTILUX team and I am most glad they accepted it.

Defining system specifications

Most projects that begin with incomplete specifications are doomed to failure. So when devising the system, we took enough time for thinking, drawing, drinking coffee, brainstorming... Funny though, it helps a lot if you have someone in the team that does not have a clue about the subject. Such a person may give you the craziest ideas - so crazy that they might even work. Well, we weren't that lucky to have such a person in our team. Nevertheless, we managed to come up with specs of a new smart home system anyway, and we can summarize its core functionality using the following sentence: a web-connected system that centrally manages heating, air conditioning and all other internal and external energy sources of the house based on measurements with the aim of predicting the overall energy balance of the house.

And controlling the blinds was just one of the tasks that had to be mastered.

Designing the system hierarchy

Hierarchy is important and although it can and sometimes should be violated in real life, it most certainly has to be obeyed in electronics. The first role of MULTILUX here was to firmly support the team to define the system hierarchy to reach robustness of operation on one side and scalability on the other.

This awareness led us to the following hierarchical design:

  • Hierarchical system design based on a main controller with additional slave modules.
  • Main controller is an SBC that runs Linux and is connected to the web.
  • Slave modules:
    • blinds controller,
    • heating&cooling controller.
  • Slave modules execute tasks independently to achieve higher reliability.
  • Main controller has the role of a system coordinator.
  • A robust master−slave communication protocol exists between modules.

And these are the system's main functionalities:

  • weather monitoring (solar irradiance, temperature, wind speed, relative humidity),
  • room temperature and relative humidity monitoring,
  • advanced controlling of pumps, mixing valves, ventilation systems with heat recovery,
  • independent position and inclination control of blinds with real-time feedback,
  • advanced algorithms for calculating irradiation through windows in each room,
  • awareness of the weather forecast, acquired through online services,
  • secure web access to the system user interface from anywhere,
  • storage of all measured parameters for user analysis, system fault inspection or auditing,
  • as the icing on the cake, an alarm functionality was added with email notifications of any extraordinary events.

Although appetites were huge, we stayed modest and started developing the system from scratch, most essential things first, but keeping lots of room for candies.

Making it real

Many ideas stay on the drawing board due to insufficient knowledge for their realization. Having some of the best students in the class, the lack of knowledge was certainly not an issue. Nevertheless, freshmen, although packed with theory are still far from the experienced engineer with 10+ year practice which masters all the tips & tricks of a robust design, specific electronic component flaws, issues of system manufacturability and so on. But as young wannabe engineers are quick learners, after several design steps and a few prototypes with some wire reworks, the PCBs were ready for production of a pilot series. Microcontrollers, chips and corresponding circuits were not a big issue, thanks to many available application notes. One of the issues for instance was defining the right shape and mounting of the PCB, selecting the type of connectors and arrange them to perfectly fit the case.

It's alive!!

One of classic lines in horror movies can turn into a scream of delight of every engineer, when a LED starts to blink after the power-up of a board with a Blinky loaded into the microcontroller. Blinky is basic code, usually containing only the essential microcontroller startup and initialization routines, which finally indicates successful boot-up by blinking a LED. Encouraged by the steady heartbeat of the electronics, a few following weeks of coding and debugging were a piece of cake. Software was developed in three levels:

  • embedded code in microcontrollers of each module,
  • main controller code, running on Linux,
  • code of the web GUI, running on Linux.

A custom Linux image was compiled using Linux From Scratch (LFS), containing just essential components not only to achieve quickest possible boot time and smallest possible footprint but mainly to ensure smallest possible security fingerprint. Number of possible vulnerabilities and bugs can be greatly reduced when all unneeded software modules are removed. System reliability and lifetime were additionally improved by lowering the SD card I/O operations to minimum using tweaks of the appropriate driver parameters and software configurations. At this point, all advantages of having a most heterogeneous group of developers showed up, having an excellent embedded programmer on one side, a Linux geek on the other side and versatile HW/SW developers presenting a firm bridge between the two.

Making it legal

Engineers tend to be attracted by barely legal stuff. I know what you are thinking just now and I can assure you: it's not that. The point here is that electronics has to comply with several standards to be allowed being legally put to the market. MULTILUX engineers always apply good engineering practice already in the early design stage in our strive to achieve compliance with standards. We are very aware that by such approach we can avoid lots of problems that might occur later when repairing design flaws might be much more expensive. Spectrum analyzer with near field probes and conductive interference noise couplers are part of our standard test equipment. We also perform tests by either placing devices in a TEM cell and pinpoint the possible sources of radiation by using an EMC scanner, which is something we have of course done with this system as well.

First application of the Luxsmart system

There is always an awkward feeling when deploying a new system to the first customer. And our first customer was not a small fish in the pond. A three-floor house with 32 window blinds, a complex heating system combining wooden pellet stove, solar heat collectors and a fireplace in a living room, all together heating water in a big water storage tank, Finnish and Turkish sauna, not to mention electric floor heating of the front yard to melt the snow in the winter. Thanks to the flexibility of our system we managed to handle all that and added some creme on the top such as automatic lawn watering and remote control of saunas.

After this successful installation we have installed many systems in houses with different configurations. Thanks to the versatility and scalability of the system design we were always able to tailor the solution to the customers wishes.

Endless possibilities

Smart house systems are slowly gaining on popularity and more and more people are deciding to apply some kind of a smart house control system to their homes. One of the really nice features of our system is data logging for further analyses. We present some typical scenarios to illustrate the system capabilities.

This picture shows temperatures of the solar heat system in a house on a sunny spring day. Noise on the solar hat collector temperature in the afternoon is due to rapid on/off switching of the pump to assure a preset temperature difference between the energy source and sink. Temperature in the living room is stable despite large outside temperature variations showing maximum solar energy utilization thorugh the windows and solar heat collectors.

This graph shows temperatures in summertime during continuously hot period in July. The system despite high external temperature variations manages to stabilize daily room temperature variations in the range of 1°C and the rise average temperature of the house below 1°C in two weeks by help of intelligent room shading, air recuperation control and passive cooling by extensively ventilating the house during the night time.

Additional feature is fault detection and alarming capabilities. In this picture, some air bubbles were formed in a solar heat medium preventing adequate circulation. For that reason, solar heat collectors were overheated, the alarm was trigger and an email was sent to the owner of the house.

Finally, an example of the air recuperation unit is shown, where all four temperatures are monitored continuously. From the results a recuperation efficiency is estimated. In this case, one of the fans stopped working and consequently the internal air pressure in the house changed. Consequently, only a small portion of the air exchanged through the recuperation unit, while all the rest came to the house through other available openings. This anomaly was also detected by the help of our software.

The Luxsmart system has been not only tested but also deployed into production on several customers and they recognized many of its benefits. They also proposed some improvements. We have already implemented some of them, while others are queued and picked by our engineers when they are not busy with custom R&D projects for our customers.

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