KNX protocol
This article expresses the private opinion of an automation specialist (not a KNX integrator), does not have an advertising nature and does not aim to excessively criticize the equipment.
The content of the article:
1. What is KNX, what is it for, how does it work, who is the main buyer of such a solution.
2. Stand of five devices. Assembly scheme, cable type, KNX bus, network topology.
3. ETS5 program for network configuration with EiB/KNX equipment. How it is installed and how it works.
4. Parameterization of the stand with devices through the ETS5 program.
5. Equipment cost.
6. More about the equipment.
What is KNX, what is it for, how does it work, who is the main buyer of such a solution
KNX is the name of a standard, technology and communication protocol (event protocol) used in most buildings in Europe, which provides information exchange between devices in residential and office buildings. In the EU countries, KNX equipment has an acceptable cost, which ensures its mass use. In addition, the presence of automated systems based on the KNX protocol allows consumers to significantly save on mandatory insurance premiums, which also affects the safe use of home automation.
In Russia, equipment with this standard is used in elite solutions that provide distributed control, where it is necessary to use light switches with increased requirements for design and nested functions, and allows you to create reliable solutions for connoisseurs of aesthetics and comfort.
The KNX protocol (if we mean the twisted-pair exchange protocol itself) is an event protocol, that is, sending a telegram to a common network does not occur cyclically and not in bulk, but only when it is specified in the configuration of interconnected devices. This allows, at an exchange rate of 9600 baud, to ensure a fast (up to 60ms) signal passage from the light switch to the relay unit or dimmer to turn on the desired lamp or group of light sources. This exchange rate between devices is achieved due to eventfulness, that is, the line is “silent” most of the time and reproduces some action strictly according to a configured event (for example, pressing a button). When a broadcast telegram is given, those devices that are logically connected to it react.
Let's say there are two buttons from different switches. Let's assume that they will be pressed "at the same time" (with a difference of a few milliseconds). What will happen on the bus?
Most likely, a situation will occur when one of the devices will miss the telegram and will not be able to respond to the received request. However, the device will still work, since any telegram in the protocol is waiting for confirmation, and if it is not received, it will resend.
There can be hundreds of devices in a building that are on a single network. In this case, the probability of simultaneous submission of commands is high. To do this, the KNX standard provides for routers that are designed to mask certain logical addresses. This allows you to create large distributed KNX networks and avoid collisions.
Stand of five devices. Assembly diagram, cable type, network topology
Wired standard KNX four-wire, two twisted pairs with screen. Two wires (red/black) carry out digital exchange between devices, two additional wires (white/black) provide additional power to devices (optional). The KNX gateway is not an ordinary USB-RS485 interface. It is important to understand that not only telegrams pass through the digital bus (red / black), but also a voltage of 30V is transmitted, which is necessary to power the devices themselves located on the bus.
It is worth noting an important "feature" of this protocol - these are connectors. They are self-locking. These chips are removed, which allows you to unscrew the monolithic conductors for disconnection. In this regard, you should not use cable products that are not intended for use in KNX solutions.
Network topology. There are no special restrictions for branching a KNX network. There is a limitation on segment lengths, and if these parameters are exceeded, an additional power supply unit is installed.
This stand is built according to the "BUS" topology.
From left to right: KNX power supply, dimmable module, air quality sensor, smart touch panel.
ETS5 program for network configuration with EiB/KNX equipment. How it is installed and how it works
The demo version of ETS5 was used for bench parameterization. For the full use of this program in order to integrate various solutions on a professional basis, you must purchase a Dongle (key version) and take the appropriate courses, have the appropriate certificate.
What to do in the event that all this is not there, but it is necessary to conduct an experiment with the stand?
The best thing to do would be to limit yourself to working with a small number of devices (up to five), download EKB training courses, connect the devices with a special cable and then start programming the devices.
The "Overview" tab contains a list of user projects. The project contains programmed device connections, and also allows you to sequentially parameterize each of the devices and prescribe logical connections (group addresses) in them.
The "System Bus" tab is designed to work with a gateway (USB interface), which will be needed to communicate with any device within the network.
It should be noted that almost all devices and manufacturers known at the time of the release of the ETS5 program are presented in these catalogs. This catalog is automatically updated when you have access to the Internet. You can also add devices yourself through the import tab if the desired device is not available. Knowledgeable people suggested that if you choose the localization of this program in Germany, then the composition of the equipment in the catalogs will be more relevant.
The "Settings" tab is used for finer settings of the ETS5 program. This issue is discussed in more detail in the course. In this task, everything was exposed by default.
Parameterization of the stand with devices via the ETS5 program
At this stage, the stand is already physically assembled, all segments are connected, the wires are inserted into the connectors in accordance with the polarity.
First you need to deal with addressing. All devices included in the stand either have addresses that do not match the project, or are the same. You will need to download a different KNX address to each device on the network. Usually, each device has a physical button that allows you to put a specific KNX device into programming mode. When the device is switched to the programming mode, the red LED lights up and it becomes possible to download the current firmware and address from the ETS5 program, thus replacing any previous settings. It can be called programming very loosely. Rather, it is a binding of features or variables included in the device. It should be clarified that it is unacceptable to put two devices into programming mode at the same time, you should act sequentially, one at a time, otherwise there is a risk of getting two devices with the same addresses on the network, which will inevitably lead to disruptions in the network.
How to program devices
1. Setting the address for the gateway. We go to the tab "System bus" and set the necessary address there. According to established traditions, this is 1.1.255. There is a "Test" button that allows you to check the uniqueness of the assigned address. If it is not unique on the network and there are retries, the interface will not be usable.
2. On the "Overview" tab, create a new project and add devices from the catalog that are the most similar to ours in terms of models and firmware versions.
3. Next, by activating the device options we need, we parameterize them and load the initial program into them. Devices are transferred to the programming mode using a special button located on the case.
4. After all devices included in the KNX network have unique addresses, we begin to form a logical level or group addresses by dragging and dropping device options or functions inside group addresses into them (drag & drop). Thus, the cause (for example, a short press on the button) and the effect (turning on the relay on the dimmable module) are combined.
Using various combinations between the initiator of the command and the device that implements this command, we obtain a room control scheme in accordance with the terms of reference. After making changes, we do a partial download of the selected logic to the devices.
As a result, when Button1 is pressed, the OUTPUT A relay closes.
Let's take a specific example.
It is necessary to make it so that the CO2 level is displayed on the panel.
We parameterize the option associated with the air quality sensor and the CO2 parameter so that once every 10s the value is sent to the bus.
Also on the screen of the panel, you must parameterize the place for displaying this value. We connect both of these values in the group address, load and see the value on the panel.
CO2 value is displayed in the left corner of the panel
5. The ETS5 program has a convenient tool for diagnosing the passage of signals, each telegram and response can be seen in the exchange history.
It looked like the equipment issued for testing.
About cost
1. Exchange gateway with PC USB Interface BNUS-00/00.1 - 13132r
2. Touch panel with 6 physical buttons GVS series WaltzTouch - 39387r
3. Air quality sensor GVS Quality Sensor V2 - 33621r
4. 4-channel control module 1-10V GVS Dimming Actuator 4-fold - 16500r
5. Power supply KNX KP / D 30.640.1 - 17784r
This price was announced in November 2022 and may vary at the moment.
USB Interface BNUS-00/00.1This device is intended for configuring devices located on the KNX bus. Used as an entry point to the ETS5 program. Without such a gateway, it is impossible to start configuring KNX devices. It does not require any driver installation and connects to the system automatically.
An experiment was made to connect to the KNX bus through other software, namely SCADA PCVUE14, but unsuccessfully. It did not work out to pick up the device ID and the program simply did not see the gateway.
Touch panel with 6 physical buttons GVS series WaltzTouch
Aesthetically pleasing product. The buttons are backlit to indicate the group's power-on status (on or off). High contrast display with good resolution. You can place a lot of information, for example, air parameters. In fact, an ordinary six-button switch has been turned into a mini HMI to display current information and control lighting zones on an object.
Air quality sensor GVS Quality Sensor V2
An interesting smart device, according to the readings of which you can monitor five very different parameters. It has a monochrome display on the body of the device, where air quality indicators alternate.
The sensor has two connectors: power supply from the KNX bus + additional power connector.
During the connection, the following parameters were measured:
- Temperature (showed 25.4 C)
- Relative humidity (showed 38.2%)
- Indicator of harmful organics in the air VOC (showed 1.29 mg / M3)
- CO2 indicator (showed 1534 PPM)
- The content in the air of ultrafine particles PM2.5, less than 2.5 micrometers (showed 15 mg / M3)
Have you ever thought about the quality of the air in your living space?
1-10V GVS Dimming Actuator 4-fold
Unfortunately, it was not possible to fully understand this block. According to the diagrams, it was required to connect EVO dimmer blocks, they simply were not available. It also failed to control the 12VDC LEDs, since the unit itself is not active and does not output voltage. The relays worked great. Good strong screws and large sockets for conductor clamps.
It works well, the unit was not used in extreme modes.
I would like to express my gratitude to the Smart-balt company for the equipment provided.
#knxdevice, #knxnetwork, #knxaddress, #ets5program, #knxequipment, #knxbus, #eventprotocol
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