LEARN PLC ELECTRO & REPAIR

PLC (Programmable Logic Controller) is a tool used to replace some of the relay circuit is found in the conventional process control systems. PLC works by reading the input (via the associated sensors), then do the process and act as we want, which is a turn on or turn off or turn on the output (logic 0 or 1). Users create a program in accordance with what was planned (which is generally called a ladder diagram or ladder diagram) which is then stored and executed by the PLC in question. In other words, the PLC to determine what action needs to be done on the instrument output related to the status of a size or magnitude were observed.


PLCs are widely used in industrial applications, eg in the packaging, material handling, automated assembly and so forth. In other words, almost all applications requiring electrical or electronic control requires PLC.In other words, the more complex process that must be addressed, the more important the use of PLC to facilitate these processes (and also replace some conventional tools). Besides the conventional process control system has several disadvantages compared with the PLC, among others:• Need to work hard as do the wiring.• Difficulties when do the replacement and / or changes.• Difficulty tracking error when done.• When there is a problem, take a long time.While the use of PLC controller has several advantages compared with conventional control systems, among others:• Compared with the conventional process control system, the amount of cable required can be reduced by 80%.• PLC consumes less power than the conventional process control system (based on the relay / contactor).• diagnostic functions in a PLC controller allows the detection of errors easily and quickly.• Changes on the order of operations or processes or applications can be done easily, simply by making changes or replacement program, either through a console terminal or PC computer.• Does not require a lot of spare part.• Less expensive than conventional systems, especially in the case of the use of the instrument I / O is quite a lot and operational functions of the process is quite complex.• Security PLC is much better than the auto-mechanical relays.PLC vs DCS
  In various articles saying that the PLC and DCS has the same function. Current DCS and PLC distinction has blurred as each has another take on the role. PLC took some of the role of DCS and vice versa.This is very different from that understood all along that:• DCS (Distributed Control System) as the name suggests is a CONTROL SYSTEM that works using multiple controllers and coordinate the work of all these controllers. Each controller is handling a separate plant. Controller in question is PLC.• The PLC (Programmable Logic Controller) as the name suggests is a CONTROLLER to be programmed again. If the PLC is not only a stand-alone and combined with other PLC, DDC SYSTEM pengontrolannya called.So, PLC is a sub system of a large system called DCS. Equal in this respect is the DDC to DCS and FF, as well as the SLC PLC, Microcontroller, and so forth.Is this true?Early development of the PLC, functioned more to the logic Control (Discrete Input / Output). But now, the PLC has to accommodate not only the discrete Input / Output, in it is able to receive signals from Thermocouple, RTD, Load Cell, and so directly to the I / O PLC.Maybe this is a "fuzzy", where the functions previously held by the DCS, now with PLC alone can.Basically just PLC programmable logic controller. Although the development of the PLC is equipped with an analog signal, the ability aritmatiknya very limited compared with the DCS.While the DCS, Distributed Control System The emphasis is on its 3D, which is three things DISTRIBUTION: The distribution of risk of failure, the location and distribution of Man Power Distribution and Control.Traditionally, it is true that the response is slower than the DCS PLC. Due to regulatory control does not need to respond too quickly because if it fails there is still a safety shutdown system. One (1) second overall was sufficient for almost all applications. Unlike the application which is often a safety PLC field.Now, apparently because the hardware is different from that traditionally DCS vendors are increasingly "like a PLC".Some say, "Install and Forget PLC's it", if DCS opposite, because it is more complex and need monitoring.When viewed from the complexity of the system, depending on how the configuration of the installed system. Plant Shutdown System using a PLC-based can also be very complex, far more complex than the DCS. If not, why the experts in such a matter until the issue of IEC-61 508, IEC-61 511, IEC-62 601 and so on.The current PLC is able to process large amounts of information in real time because it has a RAM between 2-6 MB, you have connectivity to Ethernet and can be programmed in ladder logic or structured text, and is equipped with a Human Machine Interface, HMI (eg Rockwell RSView), which allows the adoption of Visual Basic applications, Hysys and other applications.PLC and DCS difference now is not there anymore, because the development of advanced technology .. where PLC is a lot that serves as DCS, PLC even more than it can act like SAP ...!PLC is often used for safety system (from a trip system equipment). Although there are facilities in the DCS LOGIC or sequences, mostly for the trip system, the signal is fed to the PLC tripnya remain, such as Low Level alarms from steam drum level signal is fed to the PLC for TRIP to the Boiler.So ama DCS PLC difference lies in the speed of response.
Of case studies, DCS can be replaced with MMI + PLC system. But usually, when the modern company there are two DCS and PLC systems. PLC for Fire / gas and Shutdown System, DCS for Continuous Control. Also many other applications, such as the specific controls for Compressor / turbine, Vibration Monitoring, Flow Computer System, Optimization, and others. And all apikasi it can be connected to the DCS. DCS can monitor all the existing systems (PLC + MMI, flow computers, turbine control, optimization software, etc.). Aja may actually be handled by only one DCS or PLC + MMI alone. But in the modern enterprise system is made much, one reason for the redundancy, if you use one system only once to die, die all plantnya. But, if in the food industry, MMI + PLC might be enough, because it's cheaper than buying an expensive DCS.Lainnnya opinion said that the PLC is not the same as DCS, PLC and DCS systems are not sub PLC DCS is not raised.When viewed from the initial formation of the two devices, the PLC is made to replace the Relay Logic that functions as a system shutdown. DCS is made to replace the Controller (single loop, multi-loop, closed loop, open loop, etc), the control of the process (Process Control). Process Controller is certainly not the same as Logic Controller, and not separated, because its meaning will be different.In aplikasinyapun so. Would if the safety system (ESD / PLC) our failure occurs, then all of a Process Control Uncontrol, because PLC is used as the System Control ..?? Or conversely, we have does not have a safety system (ESD / PLC), when the Control System of the process (DCS) there is a failure, because DCS is also used as an ESD ..?. Clearer if we look at the "reasonableness" designation both systems. PLC "fair / reasonable" is used for a safety system (ESD) compressors, pumps, turbines, heaters, boilers, and "Process Equipment" to another. While the DCS, the reasonableness of the allocation system "Control / Control". Control over changes in level, flow, press, and the "Process Variable" others.On development, PLC began using "Analog Input". Input from Transmitter or Thermocouple. But let's see the logic programming software. All analog inputs are converted into digital and back to digital parameters on Logic functions are used. Even if PLC and PID Controller function, were more likely intended for system and process control where ESD is a unity that can not be separated Sequence. For example, Turbo Machinery Control.But if the anti-surge applications, not the ESD, and more likely to function Control (not Logic). Can be seen from the following cases may be more visible where the PLC and DCS reasonably applied.On a compressor that uses Auto Start system for Lube Oil Pump (LO). The pump is operating normally Turbine Pump (PT) and Stand by the Pump Motor (PM). If the Press L.O. down for any reason such as PT Trip, after reaching the setting Press PM will Auto Start. The use of sensors Press L.O. a Smart Electronic Pressure Transmitter and Press.Trans. Analog input to the PLC.What happened is this: When the PT Trip, AM late start and compressor trip, because the press is very rapid decline in under one (1) second. After a delay of the response seen in Press.transmitter, although the damping is minimum. Apparently it all microprocessor-based equipment that would have Dead Time (also said to be in Manual Book). To overcome this re-use Pressure Switch for Auto Start system LO (According to the initial design). Is there a standard that said sensor from ESD Logic Systems must use a switch ..? It would be late again if the input from PLC DCS.From the story above, if we would menggukan DCS to PLC and PLC function for DCS ..?Talking about the difference between PLC and DCS will always be mixed if not set from the beginning of his speech frame at the level of definition or reality / hardware capabilities of its software architecture in a particular task.If by definition, then:PLC = Programmable Logic ControllerPLC by definition is a controller (processor) that can be programmed (programmable) whose function is to run (execute) logic functions. Logic is here, looking at the early history made, is a discrete / sequence function is usually handled by a relay. From the beginning of the vendor that carries the name of the PLC is engaged in the business of discrete / sequence control.DCS = Distributed Control SystemRegardless of the distributed control system (as opposed to the DDC = direct digital control) were categorized as DCS. DDC control at all done in the central processor so that when he was a failure, all control plants will also fail. DDC, used almost, if not entirely as the Regulatory Control. And of the first vendors that carry the name of the DCS is using the product as a regulatory control.Unfortunately, the vendors are there on each of these camps began to fight each market (especially the vendors who once claimed to vendor PLC). This is because the ability of the processor / CPU and memory are also growing rapidly and the price is also more expensive.They began to "betray" and begin to have cross application. Vendors who used to carry the name of the PLC has begun to enter the arena of regulatory control as they began to confident with their goods. Similarly, vendors who used to carry the name of the DCS became interested in entering the arena because in terms of discrete hardware is now allowing its processor has a fast execution time so that markets can be entered dicrete.That way, if it states the ability of architecture to see in what belongs to each one, then the sense of PLC and DCS have started to blur. So if the standards say it is "Programmable Electronic". Anything programmable and its electronic based devices.Especially with regard to the dichotomy of the switch and the transmitter, the transmitter response specifications timenya response (include dead time) is 100 ~ 500 miliseconds. Dead timenya own 40 ~ 100 miliseconds. Standard does not suggest which one is better used as both are equally well depending on the application (even due to the ability of the transmitter can be used to check the trend of analog data, the increasingly popular use of the transmitter.If there are problems with the transmitter do not immediately take the conclusion that the switch is better than the transmitter. It could be transmitters of ancient models, or incorrectly installed so that the backup pump settings way too late. How the speed of response to the pump itself that in fact the mechanical pump? Determination of the setting is more crucial than the question the switch or transmitter.In theory, the controller advised a separate safety control of the controller process control. However, this is not an absolute that must be followed. Sometimes a process control can not be separated by a safety control. Example: in a test station onshore, ESD is a process control itself, including the alarm system. Interlocking system that serves to identify and follow up on critical alarms such as HHLL the vessel also is part of the process control.The article referred to above is more accurate to say that "the DCS and PLC have much the same functionality." If it is said that "the DCS and the PLC has the same function", can mean that the entire functionality of DCS and PLC together, but there is still a lot of functionality that is not the same between DCS and PLC.Differences in functionality also means that the DCS and PLC can not be implemented in the same application. For example, for a large chemical plant, it is necessary both DCS and PLC systems, one each for the application in accordance with the design or usability of the system (DCS or PLC).• DCS is not a major PLC. We can have a DCS with 300 I / O Processor Module and 2, and PLC with 8000 I / O with one or two Processor Module: System Architecture DCS and PLC are different.• DCS nor PLC-PLC are integrated into one big system. The word "Controller" in the PLC is intended as a "Logic Controller", while the DCS is intended as a "Process Controller".• Both the DCS and PLC is a configurable and reconfigurable.• DDC and PLC incorporated or not are two different systems• We can not align the different systems, whereas the same for any system (DCS or another fellow PLC) is not easy to align with one another.But indeed they are. This topic is a classic topic that is often discussed in various technical forums, not only in Indonesia but also internationally, and still to no conclusion. What is important we use the system in accordance with the utility.