Smart home on the LOGO controller from SIEMENS

From a letter from a reader of the mailing list: “Using SIEMENS LOGO! Controller, I want to learn how to program controllers in practice, automate different processes and in the future create a comprehensive smart home system. Tell me if this is possible and what additional modules you need to buy for LOGO controller for organization smart home? " ...

In this article, we will try to answer the question of the newsletter reader - we will consider the possibility of using programmable logic controllers for the purposes of home automation and to create a smart home system.

Before considering the use of automation tools, let's understand what is generally understood by the concept "smart House? Is it possible to consider a dimmer installed in the circuit of one of the lamps as an intelligent home? If not, at what point does the “intellectuality” of the home begin? Indeed, even with the abundance of various devices installed in our apartments, not all of them can be tied to the concept of a “smart” home.

Apparently the term "smart home" implies a kind of complex system of devices that increase comfort, safety and rational use of resources. Then, several subsystems of control should be present in it in one volume or another. These are room security, fire safety, alarm systems for emergencies with water or electricity. Heating, air conditioning and ventilation control systems will not interfere. Traditionally, lighting control systems are needed. And for leisure - the management of multimedia devices.

Based on the above, far from complete list of tasks, we can proceed to the selection of devices on the basis of which the intelligent system will be built. From the abundance of offers on the market, try to try on this role logic programmable controllers from Siemens LOGO!.

When you first get acquainted with the LOGO line of logic controllers, doubts arise: it is very difficult, incomprehensible and not suitable for home use. Let's not rush. All products and standards without exception to create a “smart” or “smart” home There are pluses and minuses. In some, like X10, poor noise immunity, others are not suitable for the price or the need to often change power supplies.

If the complexity of the controllers lies in the programming procedure and the need for additional units (power, expansion), then the advantages are significant: I made the system, configured it and ... forgot about its existence. Moreover, this is true for Siemens controllers, which have the highest reliability and a variety of applications.

Briefly about the composition and purpose of the modules. The controllers include two types of modules: LOGO! Basic, which has a display and keyboard for manually entering programs and LOGO! Pure, into which programs are entered from the computer via an interface cable, or by installing a memory card with a recorded program. The memory of the controllers is designed for 200 software blocks (operations). In total, there are 8 modifications that differ in supply voltage, the number of input / output channels and the presence of real-time clocks.

In addition, the LOGO series contains 9 types of expansion modules to increase the number of inputs / outputs. The series also includes power supplies for sensors and expansion modules. The accessory kit includes a cable for programming controllers from a computer, Soft Comfort. It is designed to create control algorithms and emulate the operation of the circuit. Additionally, a display for displaying LOGO! TD.

Now back to the smart home.The first and most serious objection to LOGO controllers is that the task of automating a home is not simple by definition. If you solve the problem "head on", then the coexistence of several control subsystems will require an electric cabinet that is comparable in size to a wardrobe.

The second, no less important circumstance, is the need to lay power and signal wires. And for this, you must immediately have in your hands a comprehensive automation project for laying the required number of conductors. If you swipe at the implementation of all of the above subsystems, the number of wires will be dozens of dissimilar wires, and their total length under a kilometer.

The third drawback is associated with the very concept of building control systems on programmable controllers. It provides for the presence of a central single control panel, in which all information from the sensors flows and command signals are issued. Using such a system without remote controls is extremely inconvenient, and there are no mobile devices in the series of controllers.

Therefore, the prospect of obtaining a bulky system, with the procedure of wrapping wires around the apartment, and not allowing reconfiguration after elementary movements of furniture, makes this element base completely unattractive.

There is one more consideration, rather psychological. Automation of their homes is done by people of a peculiar character warehouse: restless and keen. The fact that today is for them the height of perfection and the subject of pride tomorrow becomes ordinary, and the day after tomorrow hateful. Hands begin to itch: I want to redo something, improve or reprogram.

This is where the LOGO controllers can show their “Nordic" character. There are not enough communication lines, the number of outputs or inputs is limited, the shield is clogged with modules to failure. The situation is even worse if there is a move. For residential premises this is a rare, if not exotic event. But for offices equipped with a system based on LOGO controllers, the problem of equipment transfer is almost not feasible. Removing modules, as the most expensive equipment, is still possible. But whether it is possible to quickly restore the electrical circuits in their original form is not a fact.

If the prospects for using LOGO controllers are so disappointing, why are messages about their successful use appearing in large numbers on the network? There may be several reasons: the authors of the work are associated with the use of controllers in production, and for them adapting devices to the home environment is not difficult. Another option is sadder: sellers of products aggressively advertise this series as the simplest product, which even a primary school student can apply.

In fact, one should not forget that logical controllers were originally intended to control simple, single equipment in production. In fact, this is a set of different programmable devices in one case. Therefore, you can simply use them to control a single pump, fan or several lamps. But an attempt to connect these functions into one system with various scenarios immediately dramatically complicates its composition and cost.

By the way, about the cost. A controller without expansion units costs from 123 Euros of the Pure type and up to 180 Euros of the Basic version. Putting such a device to control multiple lamps is a complete ruin. And to lay additional wires in the apartment after a recent renovation for the sake of several home appliances is even more ruin. Even more serious, the price will increase when you try to equip the system with a sensor (temperature, humidity or otherwise).

The controller accepts input analog signals of only the standard type, for example, 0-20mA. Therefore, the sensors must have normalized output signals. The cost of such sensors is comparable to the controller. Therefore, programmable controllers, and not only LOGO, today have received a limited distribution in home automation.

Let be programmable controllers currently work in production, and for the home there is a wide selection of devices that are designed specifically for such applications.

See also on this topic: The principle of operation and the basics of PLC programming