Home automation and industrial protocols

After comment in tickets earlier them forms of interact physical and wireless, are going to describe them protocols more important to communicate systems industrial or home automation. Us will focus only in those standards since there are thousands of protocols owners that only serve to interact among devices of the same manufacturer.

TCP/IP

The Protocol most known and widespread, each machine is assigned one IP that comes as his own phone number, when a computer wants to communicate with another element to that IP, usually called are used with ethernet or wifi protocols. It allows us to have all the computers an industry, robots and controllers in a network, which can lead to security problems if it is very large or we have wifi network. To know a little more how it works you can see a previous article here. I don't want to dwell too much on this model since it is the most known and there is lots of information on the internet.

ANALOG CONNECTIONS

It is not a proper communication protocol but many sensors use a standardized output 4-20mA or 0-10V, we can read and interpolate to get to know the real measure. The case of use rather than 0mA 4mA is simple if we have a null intensity the device is not connected. Mention that there is a protocol called HART introduced a digital signal into analogue to have some control over the device.

MODBUS

If we talk about industry and protocols have to comment the modbus is communication between a master and one or more slaves. Are going to assume that have an automaton that controls a process and receives measurements of various sensors modbus, but also allows activate solenoid valves, each one of these devices has an address modbus (255 devices when the program of the PLC indicates to a device that you of a measurement, you called by his name modbus.) The Protocol basically allows you to do two things, read a record of device (can be several steps, a sensor of temperature and humidity) or forcing a record (in an updater tells if opened or closed or the percentage of opening). With which the message that goes by Modbus basically is, to who will be directed, if is reading or writing and of that record. Connect the Modbus devices is using Protocol RS-285.

Plot Möbus
Plot Modbus

 

I want to put a second example, Let's imagine a local domotic and decides wired from a web server, which makes door between the internet and the building, a wiring modbus to control air conditioning. We are entering our web to control our business and we want to know the temperature, web server asks for modbus air conditioning that temperature reading has, and received 14 degrees, which seems little and we decided to upload it, then the web server tells the air conditioning to keep the temperature to 21. The air conditioning has records that we want to read and others that we are interested in acting, not only is a sensor or actuator is the two things and of course has more records that we can interest, as the power of the fan, or winter or summer mode. We can see all these records in any datasheet component.

Modbus is a free encryption protocol therefore in many applications is not safe. In the case of the air conditioning usually be enough, since, send a cable direct Modbus of the PLC to each split or fan oil, each one would have an address different and the application of security serious the network ethernet or wifi e internet. The same thing happens in the industry where a robot which manages a machine and its RS-485 wiring is independent of the rest of the network. But there are better industrial communications in computer security as we will see later.

As clarification will remember that only the master can order services from slaves, these never start a comunacion are "quiet" waiting to give them an order, just may be a master, for each slave, it is important because

MODBUS / IP

The classic modbus is a protocol for an automaton peripherals, but there was a problem. Imagine an industrial plant and automation that tell it different processes with sensors and remote actuators. Using ethernet or Wi-Fi network and with the IP protocol can reach each device, this system will assume that it controls two or more zones away, each has a modbus gateway IP and we control the process from a computer located in the office. The operator wishes to know the temperature in zone 1 which has an IP, as configured by us static on our LAN, then the PC sends a message to that address IP-1, in that part we have several temperature sensors each with an address modbus that we will read your logs and various valves will operate on them. On the other hand now are interested in knowing part of the process of the area 2, the PC you sends the message Modbus to the IP2 and this it converts directly to the standard modbus. Equally raster modbus not this encrypted but if there is option and recommended course always from hide as best as possible the message while it circulates over the LAN network of the plant, where anyone could enter and modify data or sabotage us.

Modbus/IP
Modbus/IP

 

A normal modbus important difference, is that modbus/IP allows to have several teachers, this is not entirely true, the real teacher is the gateway modbus/IP, which is that sends requests to slaves, as the walkway is open to certain IP within the LAN, anyone who can access may be a "virtual maestro".

DALI

It is an intelligent Protocol for systems home lighting system consists of five cables, three will be those of power and earth ground required by regulations and two additional for communications, regardless of the polarity. You control electronic ballasts and these stored in its memory the results, the response curve is logarithmic more according to the perception of the human eye. We can say that it is similar to the modbus when a driver makes master and slave luminaires.

Intelligent Light System DALI
Intelligent Light System DALI

PTZ

Are protocols associated with the movement of CCTV cameras, both analogue and digital, are used for movement, focus or zoom, both automatic (movement, heat, sound…) ) as a recorder (DVR) or platform through web. Open protocols are each brand usually contains its own. In analog cameras is carried by RS-485 while which IP cameras by connecting the own TCP/IP connection.

 

LONWORKS and KNX

Two home automation protocols are currently KNX and Lonworks (or simply Lon), the first more implanted in Europe while the second most in United States. Those have included in one only to compare both, and study which may be best for each application.

 

KNX No,
POWER SUPPLY  One per line You do not need
CONFIGURATION DEVICES Manual and individual, type modbus, must previously tell each component your address Each device has a sticker with your ID and that it is possible to read a barcode.
TOPOLOGY OF THE WIRING It is free but can not make loops, if by mistake we connect loop would have an error. It is free and allows loops providing connection even if a section of wiring is cut.
CABLING There is a cable approved shielded without bring to Earth. There are different types of cable but if used shielded it must bring to Earth.
AUTHENTICATION/ENCRYPTION Not available. It is possible to perform authentication even though it consumes bandwidth.
SOFTWARE OF CONFIGURATION Use the ETS LonMaker and lonscaner…
SPEED 9600 bps 72000bps
MEDIUM ACCESS TECHNOLOGY CSMA-CD CSMA-CD
DISTRIBUTIONS AND EXPANSION KNX is the European market practically. Manufacturers and American brands.
PRESENT AND FUTURE Domotics/inmotics building automation / smartcities.

BACNET

BACnet is a prototocolo which gradually spreads in home automation systems. As Lonworks and KNX protocols are decentralized, i.e., they do not require a controller to manage the network, BACnet is centralized is used for large installations of intelligent buildings.

PROTOCOLS BASED ON RS-485

The modbus is the most expanded with RS-485 connection protocols but with the passage of time have come more and more communications that are based on this medium, each one with its advantages and disadvantages, enumerate them in tabular form to perform the comparison. Modbus had seen that a master controls multiple slaves, as there are multimaestro protocols, varos PLCs require looking at the same pressure of a sensor.

 

PROFIBUS_rgb
logo_devicenet
Length 1000 m 500 m
Speed 9.6 kbit/s to 12Mbit/s 500 kbit / s
Stations 32 64
Market European North America
Multimaster If Not
Authentication If Not

 

The table shows the values more favorable, those protocols with different configurations can modify their parameters, for example the length is lower if we increase the speed.

 

PROTOCOLS BASED ON ETHERNET

Another option to install distributed periphery is to use ethernet cables from the factory, usually those nearby sensors normally use RS-485 and periphery remote controller if we will use these protocols. Many of them have been to implement already existing RS-485 to IP technology communications.

 

 PROTOCOL EXPANSION  DESCRIPTION
PROFINET Europe basically The IP version of the Profibus, come to be similar, p0r else is the same protocol. Exactly the same as Modbus / Modbus/TCP. For this reason we do not alargaremos much.
ETHERNET/IP  United States Ethernet / IP (Industrial Protocool) combines the own Protocol Ethernet with CIP (Commom Industrial Protocool), to which belongs DeviceNet, by which this Protocol equal that the former is a combination of both.
SERCOS Movement system: CNC, robotics, printers,… They are currently the third version SERCOS III, it is a protocol used for systems in motion, so more raw material is its low jitter and high speed.

GATEWAY OR GATEWAYS

Mention that there are many gateways that make a Protocol, including physical media. Imagine a set of old control based on Modbus to which we must change the PLC by a problem of wear and work with u Profibus, will need a conversoe that understands both magnitudes. Of equal it forms already spoken above doors TCP/IP, Modbus, Profibus and Devicenet. On the other hand if we have two parts of the factory and we must communicate their two networks with fiber optic, we use an Ethernet to fiber gateway. Own Routers perform this function by communicating internet with PPP (Point to Point Protocool), Ethernet and Wifi.

Also for intelligent buildings where we want to attack an air conditioner and you can select between different cards to gain access to the (Modbus, Lon, KNX and Ethernet…), although other manufacturers bring it's series and we must incorporate any gateway also, many devices bring several protocols that can be used. Perhaps in the future there is a standardization as it already exists in LANs (Ethernet or Wifi), but the industry these themes are more complicated each company fights for your system and they are usually three fronts, North America, Europe and Asia (here not be have told Japanese protocols). Perhaps the most extended and the grandfather of them all is Modbus, it is the most standardized, should keep this in mind because it may be the "common" between two lesser-known protocols.

KNX Modbus gateway
KNX Modbus gateway

 

DPN3

DPN

In systems with RTU SCADA is often use protocols such as DPN3 (North America) or IEC-60870 101 and IEC-60870 104 (Europe), with this intelligent communication system and its importance, and differs from the previous ones is that it is oriented to events, i.e. There is communication there is no an event that activates it. On the other hand, measures are accompanied by the time taken to send various data together. Features of mechanisms of authentication making it more secure. It is widely used in the industry of North American electricity transmission (United States and Canada).

OPC

OPC (OLE for Process Control) is a control system based on Microsoft technologies, it is a platform open against the proprietary drivers position. Initially was only linked to operating systems Windows (OPC DA) at present there is an OPC Foundation (Open Platform communications, note which is different) that standardizes the OPC UA, creating an open system and safer having all the ballots to be a standard in the future.

OPC

 

OPC DA OPC UA
Based on DCOM Based on SOA
Not protected Publicizing security
Architecture Local friendly Firewall
Windows Cross-platform
Very defined use Expanding use
Independent brands

 

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