KNX home control: lighting

    Hello! I will try to tell you how you can build a home control system using the KNX system. The main issues that I want to highlight are the approach to implementing the “smart home” on KNX, cost benchmarks, pitfalls. If the material "goes", I will continue. I don’t strive to cram nevpihuemoe: dimmers, control RGB and the like will remain outside the article - for now we just turn the lights on and off :)

    TL; DR: it’s not as expensive as it might seem at first glance and fairly reliable.

    An approach

    In my (and not only) opinion, “smart home” is a set of systems that simplify life. Ideally, the operation of most systems should be invisible to the end user — tuned and forgotten — this applies to lighting, heating and air-conditioning control systems. In contrast to the “classic” approach, I want to be able to fine-tune the process - not all Wishlist can be imagined at the design and commissioning stages.


    Why knx? Skipping marketing, I will note the main advantages of the system:

    • KNX is a decentralized system. This means that if necessary, you can replace any component, almost without affecting the rest. In particular, there is no centralized controller that controls everything and everyone. Of course, in the budget systems there are points of failure such as power supplies, but this can be tolerated.
    • The system, in fact, is not tied to a specific vendor - you can choose any equipment based on needs, budget and aesthetic preferences. If you want to have switches of one German manufacturer, the controllers are different and third, and thermostats - generally Italian - no one interferes. As a rule, the relationship between devices is prescribed without any problems. For example, I use MDT equipment , but anything can be in its place - the choice is huge .
    • From the preceding paragraphs another pleasant moment arises: at any moment the system can be expanded and improved. Conventionally, if the push-button switches were originally installed, if a need arises (and opportunities), you can replace them with touch ones. Or even hung with multifunctional screens.

    I must say that the system has one noticeable nuance - there is only one programming environment, with its advantages and disadvantages, called ETS and costs money - from 200 euros for a version with a limited number of devices in the project (up to 20 - for a small installation it is enough ) up to 1000 euros for a version with an unlimited number of devices. They say there is a version adapted for the Russian market somewhere on torrents - I have not met it.

    General Design Principles

    KNX is primarily a tire. Two-wire, but when installing it is necessary to use a four-wire cable - it is recommended that JY (St) Y 2x2x0.8 - the same as in fire alarm systems. Two cores are used - red and black, white with yellow - in reserve. Cable - shielded, not afraid of interference.

    Topologically, KNX is a tree, the main thing is not to allow rings. Terminating devices are required.

    The entire system is divided into actuators (actors - controlled relays of various purposes), sensors (buttons, switches, thermostats, weather stations) and system devices - power supplies, line connectors, and so on.

    Lighting control

    Suppose we need to organize the lighting control in a small house - let's say we have two floors, a staircase and several rooms - several bedrooms, an office, bathrooms and all kinds of walk-through rooms such as staircases, hallways and the like.

    In the simplest case, I want the following:

    1. Convenience. For example, if you come home late, you want to immediately light up the hallway, porch stairs and beyond. Another - turn on / off the light in the bathroom on the presence sensor.
    2. Fighting forgetfulness. Went to bed, and from under the door light comes from the corridor. Well, figs with him, let him go out after 10 minutes, for example.
    3. The ability to include emergency lighting - let's say we are in a bedroom on the second floor, and someone is ringing at the door - we’ll immediately light up the stairs, the corridor, the porch
    4. Ability to repay the entire house when leaving

    We calculate lighting groups, we throw switches on the plan, having estimated their roles: the number of keys depends on it. Many manufacturers make as many as eight-button switches in a single installation box - like this:

    This allows you to implement a bunch on just one switch, but it is not always convenient in terms of finding the right button.

    For lovers of the classic electrical installation, instead of the native KNX switches, you can use regular ones with signal transmission to the bus through a dry contact placed under the switch in the wiring box (in the picture is a rusk under the four-button switch):

    Based on the number of groups and their purpose, you can select a multi-channel relay (do not forget to take into account the load currents). They produce just about everything, but Gira, ABB, MDT, Zennio devices are common.

    Next is the wiring plan. From the shield to the switches, only the bus cable is fed, the same JY (St) Y 2x2x0.8. To loads (luminaires) - the corresponding electric cable (VVG, NYM - to taste). The number and location of shields - to taste. In a three-story townhouse, I made three storey shields - each with a multi-channel relay to control the light on the floor, so unwind less electrical cable.

    A nice bonus: free relay channels can be used to control sockets. However, since multichannels have, as a rule, small power (currents up to 10A), intermediate sockets of corresponding power should be used at sockets.


    So, all the wires are stretched, the devices are installed, the shields are connected. You can try all this run - you need the same ETS. I will skip the starting steps - creating the building topology in the project, adding devices, etc. If interested - ask in the comments, I will try to do the basic tutorial.

    In accordance with the Wishlist and the number of lighting groups, we plan multicast.
    A group is such an entity in a bus that actors attached to it listen to and which sensors of all kinds write to. Actor (for example, a relay channel) can be tied to several groups, the sensor will write to one group.

    For example: on the first floor there is a four-channel relay, from which we turn on / off the light on the porch, in the hallway, bathroom and living room.

    It is advisable to suggest the following groups (we use the three-level structure of group addresses, the first floor - 0, the lighting of the first floor - 0/0):

    0/0/0 - all the lights of the first floor, tied to all channels
    0/0/1 - the light on the porch, channel A
    0/0/2 - light in the hallway, channel B
    0/0/3 - light in the bathroom, channel C
    0/0/4 - light in the living room, channel D

    Here’s how it looks in the programming environment:

    Next, to the groups bind switches, in accordance with their location. Suppose we use two-button switches with LED status indicators, like this:

    For example, in the living room, the first button turns the light on / off (toggle) in the living room itself, and the second - forcibly turns off all the lights on the floor:

    Binding of light in the living room:

    Turning off all the lights on the floor:

    For switching (toggle), it is necessary to transfer their status from the relay channels to the bus so that the switch knows what value to pass to the bus.

    If necessary, we tie the diodes on the switches to the state of the corresponding relay channels - the meaning is the same, I will not load with pictures.

    We load the configuration into the devices and enjoy the effect :)

    Then we start playing with the project of the relay - shutdown delays, automatic light off functions, setting of switches in unlimited quantities and so on - until the desired effect is obtained.

    How much is it?

    The question is, in fact, multifaceted. You can go to a domestic online store and buy everything at an exorbitant price. You can order anywhere in Europe - I will quote German price tags (from which they gladly give a very nice discount) for the minimal installation that I just described:

    1. 320mA power supply: 110 euro
    2. Four-channel relay: 145 euro
    3. Four switches : 65 euros for each

    Total - 515 euros, 130 euros for the lighting channel. Do not forget about possible discounts and the fact that more capacious give lower cost channel lighting.

    For those who want to save - sometimes it makes sense to Avito wool - sometimes sweet remnants are sold there, the main thing is to monitor the price.

    What's next?

    1. You can choose a platform to control the lighting over the network (from a smartphone, for example).
    2. You can embed presence, light and so on sensors in the system, depending on your imagination (of course, wiring for them should be laid at the design stage)
    3. You can finally remember that KNX is not only light, but also climate and other amenities - but this is clearly beyond the introductory article :)

    Thanks for attention :)

    Also popular now: