Publications

Slow revolution in system integration 2010 April
Modern building automation systems have to unite subsystems with different abilities and functionalities, and present a single system to the technical operation. Solutions on the market to this issue seem to resolve a similar manner, but the detailed examination shows, that there are no fundamental differences between long-term investment value protection and IT system security.
Author: Baán László

DDC systems, monitoring, information systems
Hungary in past short period of construction industry has undergone a huge development. Modern world class shopping centers, office buildings, apartment houses grew out of the ground one after another. These buildings, and building systems’ safe and efficient operation is unimaginable without modern IT systems. The advantage of computer network’s data management and information forwarding capability is used by connected object’s operation’s fire safety and building mechanical control and regulatory system.



DDC systems, monitoring, information systems
Hungary in past short period of construction industry has undergone a huge development. Modern world class shopping centers, office buildings, apartment houses grew out of the ground one after another. These buildings, and building systems’ safe and efficient operation is unimaginable without modern IT systems. The advantage of computer network’s data management and information forwarding capability is used by connected object’s operation’s fire safety and building mechanical control and regulatory system.

Installation of fire protection and security systems has been standards in larger buildings. Microprocessor based digital devices that are linked to some type of communication network accomplish these systems. The analog devices were replaced in the building regulatory and control systems as well. It became possible to integrate these devices to ensure the flow of the data between systems, and to log and archive data.
The rising energy prices and other costs of operation make renovation of the existing object reasonable, as the coordinated and supervised operation of mechanical equipment saves cost. Perhaps the most illustrative is the following; the security system keeps tracking whether is someone in the given room or not. If not, it sends a message to the engineering control, which has the effect of switching off the heating and lighting. In case of a building with several rooms, means substantial savings. The process outlined above and many others defined, over the years, forcing manufacturers to work towards the integration of different systems.
In the fast growing electronics industry almost everyday new accessories are coming out, which integrate better, faster, and more functions. From these the manufacturer produce more advanced control, and communication equipment in almost the same short period of time. Parallel with the above mentioned processes, new term, concepts, and expressions coming out, which even confuses the experts.
I want to contribute with the numbers appearing in the next articles to pull this sometimes seemingly mystical world a little closer in Hungary. Therefore, a series of article designed to introduce the previously mentioned system structures, elements, described as simple examples, which are tangible for professionals who do not directly deal with electronics and computers. We hope that those articles can provide knowledge to make decisions easier, and to make computerized monitoring systems more popular in our country.
Author: Tibor Erdélyi

DDC devices

The building automation's most important elements are the DDC (Direct Digital Control) devices. The basic structure of these equipments is very similar, depending on the manufacturer. The functional units of the digital apparatus is shown in the following diagram: Despite the fact that readers are aware of this, I consider it appropriate to drop a few worlds about each unit, and their duty. Processor or controller unit The DDC device's character, capacity, intelligence level is primarily determined by the unit.
The processor or controller units used to be a simple microprocessor (earlier 8, later 16 bits), the associated storage elements (EPROM - basic program memory, RAM - data memory) and the system operating circuits. This configuration is known from the world of microcomputers ZX Spectrum and Commodore 64) before PC era.
Previously that type of machinery was use for controlling and regulating building monitoring systems. In the field of personal computers the demand for program execution performance and storage capacity has grown, and nowadays it is keep growing. This provoked PC hardware development, in the way that it's based on faster, and larger storage managing processors. This demand is higher then the level that supports easier control and management function. On the other hand, it is essential to have the smallest possible footprint, with the best disturbance security, and to implement this with minimal number of hardware components. It was a goal to integrate the environment of the processors into the housing. So they began to manufacture low power microcontrollers, which are programmable, and contain as much housing program, data memory, analog-digital converter, direct digital in and outputs, and serial line, to able to solve basic level tasks easily and quickly. Of course, there are higher performance microcontrollers, where it is possible to expand the internal memory by matching it with external memory module. This may be necessary in complicated cases, such as freely programmable devices that can handle larger amounts of data, and can perform energy optimization.
In summary, the controller unit is responsible for operating, by a program, which is built into to memory, a variety of in and outputs and to ensure the connection of the serial communication line through line to the outside world, which can be a monitoring network or service computer.
Power supply
It supplies power, and protects the high voltage signals from the network, surges and short circuits. Communication interface unit
This unit provides the communication interface according to communication protocol to the higher-level components, display, and other actuator devices. It can include several serial communication lines, thus making to have access from multiple points (local and remote monitoring). The circuits are located here, which defines the physical characteristics of the communication (line type, line speed...). In case of systems requiring complex communication, the device connection communication is intelligent, so it contains the communication processor. I am not covering protocols because I would like to find out more detail on this topic in a future article.
In- and output units
These units are designed for receiving a variety of signals, signs from technology, and prepare it for the controller units for processing, secondly to transfer the control and regulator signal from the output to the peripheral devices. The aforementioned units are the in, while the latter mentions are called output units. Both the input and output can be two types: analog and digital signals. The analog signal needs to be converted into digital values for the processor (A/D), and the signal calculated by the processors needs to be converted back into analog signal (D/A). For understanding the digital control, we need to know how to create digital values from analog signals, so here I mention a bit more details. The principle of A/D and D/A conversion can be seen in the following figure. We can see that the analog signal has value in every moment, which is the signal's characteristic. In contrast, the digital signal only picks up value in certain moments. It is like the analog signal is connected to a switch, and we turn it on for a period of time, then real the current values. In other word, sometime we take a sample of the signal. Therefore this is called sampling time. The size is depending on the speed of change.
Without the need for accuracy, we can say that in the case when the analog signal is changing slowly (e.g. room temperature), then the sampling time may be greater, because the rarely read actual values is also showing the proper analog signal. This means that the controller card needs to process a temperature sensor's signal sometimes, but otherwise it can perform other tasks. These may be another sensor signal processing or communication tasks as well. The control digital value calculated by algorithm needs to be converted into analog signal for the proper operation of peripheral devices. Because the digital values are not changing on the given channel, therefore a holding circuit is used, which hold the analog value on the output. Here you can see if the change is slow, then the sampling time may be longer, because it can only be reconstructed with a small error. Briefly we reviewed the skills that are essential for understanding the digital control process. In the sequel, I will go into details.
Author: Tibor Erdélyi