Hello
This is my first post, although I’ve been following the forum for quite some time. Let’s get straight to the point.
I’m an automation engineer and am currently setting up a smart home system in my own house, so I’d like to share a few insights.
When planning the installation in my home, I divided the whole process into two basic stages:
Stage I. Determining what is to be controlled and how
Looking at the building plan, I identified the elements I want to include in the control system and, in the form of a table, listed the control signals they require.
Controlled circuits and system functions
- lighting – divided into overhead (ceiling) lighting and wall lights, as well as lighting that is simply switched on and off, and lighting fitted with dimmers
- roller blinds
- power socket circuits – in most cases, one circuit covers all sockets in a given room; for rooms with a larger number of sockets, the system is divided into 2–3 circuits, and separate circuits are provided (e.g. for a washing machine)
- integration with the alarm system – use of the alarm system’s detectors and reed switches (two reed switches per window sash to detect when a window is opened or tilted)
- heating – control of valves on the manifold, integration with the heat pump and solar collectors (in the future)
- reading of indoor and outdoor temperatures
- setting up a weather station (measuring pressure, temperature, humidity, sunlight, wind, twilight sensor, etc.)
- control of outdoor lighting, garden watering, the entrance gate, septic tank level, and heating of the entrance and driveway
- building visualisation on the control panel and on a computer
- radio control capability
- Internet access
- home cinema screen
- creation of lighting scenes
- presence simulation
- support for outdoor cameras
Ultimately, it was decided that the system should support:
- approximately 200 digital inputs
- approximately 170 digital outputs
- 16–20 analogue inputs
- 8 – 16 analogue outputs
Stage II. Selection of components
We started ambitiously with EIB, LCN or some other smart building system. Unfortunately, after reviewing the capabilities and prices, we quickly had to reassess.
The prices of these systems were, to put it mildly, prohibitive; there were also potential technical issues relating to memory, communication between devices, as well as more mundane concerns such as the availability of software to programme the system.
The second approach involved using a PLC. After carrying out some analysis, I finally opted for the Siemens S7-300. Some might say there are plenty of other, perhaps better and cheaper, PLCs, but I chose this one because:
- I’ve been working with Siemens for 7 years and know it well
- I have access to the hardware and software
- it is a reliable and popular controller that can be easily obtained, for example by buying it ‘second-hand’ on eBay or Allegro.
The downside of the PLC solution is that, to a greater or lesser extent, this is a centralised system, i.e. there’s always a central unit somewhere, whereas, for example, EIB is a distributed system.
So much for the theory – but what about in practice?
As of today, I’m finishing off the electrical installation. So far, I’ve laid nearly 4 km of various types of cable: Profibus DP bus cable, twisted pair, alarm cable, standard 4x1.5, 3x2.5, 20x0.5 multi-core cable and a few others. The three of us laid the entire installation working only at weekends, and even so it took 7 months. I’d rather not think about how much a professional firm would charge for this and how they would go about it.
When planning such a system, you need to factor in the costs of cabling (which are not insignificant) and the labour costs for installation (which are even higher).
The second issue, which is generally not mentioned by anyone, is the size of the electrical distribution board. With a system like this, the number of cables increases dramatically, and consequently so does the number of terminals in the distribution board to which these cables need to be connected. Added to this are the components of the automation system, protection devices, power supplies, etc.
In my case, I ended up with two switchboards; the one on the ground floor is the size of a cupboard, namely 1200 mm x 1800 mm x 400 mm (W x H x D). I don’t yet know the dimensions of the second one in the loft, but I estimate it will be 1000 x 1000 x 300 mm.
At present, my controller consists of an S7-300 CPU315-2DP central processing unit with a 512 kB memory card, a 32 DI digital input module, a 32-channel digital output (DO) module, an analogue input module, a PC interface card and a 5.6” touchscreen.
I got some of these components for free from the company, whilst others I bought at online auctions.
Naturally, this configuration will be gradually expanded until it ‘reaches full operational capacity’.
Nevertheless, I reckon that the total cost of the installation, as I see it, will be half the price I’d have to pay for the components in an EIB system alone
That’s all for now, but I still have a long way to go. My wife looks at me as if I’m mad and just shakes her head
I don’t know if the costs are lower, as it’s a new house and I have nothing to compare it with. Let me put it this way, though: if I’d put the money I spent on the EIB into a savings account and stuck with traditional installations, the interest would certainly have covered the difference in running costs – and there’d probably have been some left over!
