| − | <br>Programmable Logic Controllers (PLCs) have become an integral part of the industrial environment. As a technician involved with the processes controlled by PLCs, it is important to understand their basic functionalities and capabilities. What is a Programmable Logic Controller? A programmable logic controller (PLC) is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures.[https://Www.Youtube.com/watch?v=qtHWK3G998c youtube.com] PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.<br><br><br>Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. Figure 1 shows a graphical depiction of typical PLCs. PLC invention was in response to the needs of the American automotive manufacturing industry where software revision replaced the re-wiring of hard-wired relay based control panels when production models [http://tcsdcc.com/ changed]. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles relied on hundreds or, in some instances, thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually and manually rewire each and every relay.<br><br><br>In 1968 GM Hydramatic issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associateseighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: MODICON, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, the "father" of the PLC. In other industries, PLCs replaced relay systems used in manufacturing applications. This eliminated the high cost of maintaining these inflexible systems.<br><br><br>In 1970, with the innovation of the microprocessor, the machine that was originally used as a relay replacement device only, evolved into the advanced PLC of today. Flexibility: One single PLC can easily run many machines. Ease of Troubleshooting: Back before PLCs, wired relay-type panels required time for [https://Www.Youtube.com/watch?v=CjuCujYhaHo rewiring] of panels and devices. With PLC control any change in circuit design or sequence is as simple as retyping the logic. Correcting errors in PLC is both fast and cost effective. Space Efficient: Fewer components are required in a PLC system than in a conventional hardware system. The PLC performs the functions of timers, counters, sequencers, and control relays, so these hardware devices are not required.<br><br><br>The only field devices that are required are those that directly interface with the system such as switches and motor starters. Low Cost: Prices of PLCs vary from few hundreds to few thousands. This is minimal compared to the prices of the contact, coils, and timers that companies pay to match the same things. Using PLCs also saves on installation cost and shipping. Testing: A PLC program can be tested, evaluated, and validated in a lab prior to implementation in the field. Visual observation: When running a PLC program a visual operation displays on a screen or module mounted status lamps assist in making troubleshooting a circuit quick, easy, and relatively simple. All PLCs have the same basic components. These components work together to bring information into the PLC from the field, evaluate that information, and send information back out to various field.<br><br><br>Without any of these major components, the PLC will fail to function properly. The basic components include a power supply, central processing unit (CPU or processor), co-processor modules, input and output modules (I/O), and a peripheral device. Output modules convert control signals from the CPU into digital or analog values that can be used to control various output devices. The programming device is used to enter or change the PLCs program or to monitor or change stored values. Once entered, the program and associated variables are stored in the CPU. In addition to these basic elements, a PLC system may also incorporate an operator interface device to [https://www.youtube.com/watch?v=2__g1Fntx4o simplify monitoring] of the machine or process. The function of the power supply is to provide the DC power to operate the PLC.<br><br><br>It is supplied by single-phase 120 or 240 VAC line power that powers the PLC system. The Power Supply is a module located in the PLC system module rack. The DC power (voltage and current) it provides power the other modules in the rack, such as the CPU, Co-processor Modules, and I/O Modules. The line power provided to the PLC system also powers the I/O Field Devices. The PLC system is protected against PLC module or field device malfunctions. The Fuse in Figure 4 provides this protection. The function of the CPU is to store and run the PLC software programs. It also interfaces with the Co-Processor Modules, the I/O Modules, the peripheral device, and runs diagnostics. It is essentially the "brains" of the PLC.<br><br><br>The CPU, shown in Figure X, contains a microprocessor, memory, and interface adapters. The microprocessor codes, decodes, and computes data. The memory (ROM, PROM/EEPROM/UVPROM, and RAM) stores both the control program and the data from the field devices. The I/O Interface adapter connects the Co-Processor Modules, the I/O Modules and the Peripheral Device to the CPU. Co-Processor Modules are programmable general-purpose microcomputers that expand the capability and functionality of a PLC system. A Co-Processor Module is controlled by the CPU, and interfaces with the CPU as shown above. The function of Software is to provide instructions to the CPU and Co-Processor Modules.<br><br><br>Physically, software is a large group of logic ones and [https://Www.Youtube.com/watch?v=XUFTH-kaE78 zeros stored] in the memory of the CPU. The function of the peripheral device is to input data and monitor the equipment operation. It may be a personal computer, handheld programmer, or an [http://www.controllinks.com/ operator touch] screen. The operation of a PLC is very simple. The processor makes decisions based on a "ladder logic" program written by the user. In order to use the program properly, the PLC must communicate with the various field devices it monitors and controls. It then compares the actual conditions of the field devices with what the program instructs them to do, and updates the output devices accordingly. Ladder logic is widely used to program PLCs, where [https://www.Youtube.com/watch?v=Wv2MgI2sFkM sequential control] of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems, or for reworking old hardwired relay circuits.<br><br><br>As PLCs became more sophisticated, it has also been used in very complex automation systems. Often the ladder logic program is used in conjunction with a HMI program operating on a computer workstation. Manufacturers of programmable logic controllers generally also provide associated ladder logic programming systems. Ladder logic is a rule-based language rather than a procedural language. A "rung" in the ladder represents a rule. When implemented with relays and other electromechanical devices, the various rules "execute" simultaneously and immediately. When implemented in PLC, the rules execute sequentially by software in a continuous loop (scan). By executing the loop fast enough, the effect of simultaneous and immediate execution is achieved to within the tolerance of the time required to execute every rung in the "loop" (the "scan time").<br><br><br>While hydronic does mean "liquid" and in portable systems often uses oil or silicone based materials, with in-floor radiant heating, only water is used. Water is the optimum heat transfer liquid in a whole house heating system. Water from your normal domestic supply is piped into a boiler where it is heated close to boiling and then pumped into heating zones. A zone can represent an entire room or a series of living spaces like a kitchen with dining room. Under the flooring of each zoom or room, are plastic tubing which transfers the heat from the hot water into the room above. Heat settings can be controlled either by a thermostats (one for each zone or a central one like normal) or by using a set of water control valves.<br><br><br>The main component to hydronic radiant heating is the natural circulation of heated air from floor to ceiling. The more heat is absorbed and remains in the flooring the longer the room above will stay warm. This is why a floor with good thermal mass (high capacity to store heat) is an excellent idea. Floors made with concrete or with ceramic or stone tiles are considered the best. These are called "wet" installations and while very good for heating purposes, can pose structural issues due to their relative weight. Newer, "dry" installations use hydronic radiant heating tubing "sandwiched" in between a normal subflooring and the standard carpet or wood. Why Hydronic Radiant Heating is is the Best for a New Home? Two main reasons are installation costs and long term heating costs. Studies have shown that when installed in a home at the time of construction that hydronic radiant heating systems are cheaper versus electric heating. The second reason is that hydronic heating has a more efficient energy use which translates into lower heating bills and greater savings to the homeowner over the life of house.<br><br><br>There are many different sites you can read about online today that compare water softeners. In fact, online marketing websites that sells other companies products also provide a comparison cost wise, function, durability, warranty and model. When searching for tanks, make sure you realize that the mineral and brine tanks are virtually identical to the ones you can purchase at home improvement softeners. Always make sure the tank has a warranty period of 10 years, and preferably longer. The control valves are an essential part of any water softener system. This important component keeps track of your water usage each week and is the determining factor for when to regenerate the resin bed. Make absolutely sure that you understand how this component works and that the water softeners you are considering possesses workable control valves.<br><br><br>Disc valves are simply a rotary disk style control valve; these are the least [https://instrumentationtools.com/control-valves-questions-answers/ expensive water] softeners you can buy. However, least expensive doesn't always mean low quality. As with any appliance you are considering purchasing, it varies from company to company. Piston valves will go through a number of spaces in order to determining when to regenerate the resin bed. These valves generally possess a very long life span, due to the short length of space it has to travel. Of course, with this generally comes a higher price tag.[http://Www.ieeecss.org/ ieeecss.org] Make your decision accordingly. There are several other kinds of water purifier systems available, but these are the most popular.<br><br><br>Obviously, the more money you spend on one, generally speaking, the higher quality water you will receive, and the less often you will have to replace it. The best method to finding the right water softeners is to locate friends or family members already using a water softener system and ask them which one works out for them. Often times, companies will attempt to pitch you on their particular product, and will obviously have a biased point of view. Your friends, however, often have tried more than one brand and know first hand how a particular companies' brand is working for them. Do your research, compare all the water softeners you can find, and choose the one that matches your interior design and your wallet.<br><br><br>If you are wondering about or considering a PLC career, follow along with a day on a project. The names have been changed and some details changed to safeguard security. I have to get more info on the actuator, so I leave the building and head to my laptop. It is times like these when I fully appreciate the ease of connecting to the internet and the availability of the documents on manufacturer’s websites. Back to the damper, I run through the setup procedure with the electrician but he is having some difficulty programming the actuator due to the flexing printed circuit board and him worrying about breaking it.<br><br><br>" So while they get to work on that, I look at some of the I/O while online with the PLC. The temperature and humidity still looked good so the new sensors appear to be working. I had scaled the analog inputs using the manufacturer data in the PLC modules rather than in the PLC's program. With the analog output I simply scaled 0-100% to the 4ma to 20ma output. That is the way the program was written and much easier to relate to while you are programming. For instance, say I need a valve half open, 50% or 12ma; which is easier? I cannot move forward until we free up that damper, so I get up to go take a look, walk out the office and turn back around. I forgot my hardhat.<br><br><br>Yes, when in the field or on the manufacturing floor safety gear is required and many employers take it very seriously for good reason. Consider safety as part of a PLC career. Back at the building, they have the coupling apart and can't move it. "So it is jammed![https://Www.Yokogawa.com/us/solutions/products-platforms/field-instruments/ yokogawa.com] " It is a new system and suspected the possibility last, I wish we proved its movement first. A large pipe wrench frees the damper. I verify that the position feedback for the exhaust damper is working (it is another 4-20ma input scaled to 0-100%) It is very important that this damper is proven open before we command the blower on. The 60 hp blower can over pressurize the system's design if the damper is closed.<br><br><br>I am worried that this might be another several hour ordeal. Luckily it was just in OFF mode in the MCC and at the local explosion proof disconnect switch. I dislike missing the dates for completion and thus having to travel back to the site again. A PLC career will very likely require travel, less so, if your work is in a manufacturing plant where you are based. We set up the Air damper actuator yesterday, cycled and positioned it (verified both visually and through a 4-20ma position feedback to our PLC) while online with the PLC. With all of the new I/O checked for operation, it is time to test the program written for this system.<br><br><br>I have to remove some actual conditions and change the values for set-points to get it to start. Very often the programming will be done before coming to the site to commission. There is less pressure and distraction at the office, hopefully, then at site. Progress picks up speed, a couple of tweaks to timing, some additional code, and start up and shutdown of the new system is now checked and complete. A PLC career is very rewarding, especially when you are directly involved from project beginning to end. If you like computers and programming, plus enjoy knowing how machines work it could be for you. Beware though, that you will not be just sitting in your comfortable office all the time, you will also be "getting your hands dirty" so to speak. That is the part that makes it so rewarding, seeing first-hand the new system come alive. Are you looking for PLC jobs? Find them at his site. Please Register or Login to post new comment. Why You Really Need BEST RECRUITING AGENCIES? Going for Online Recruiting? Are You a Perfectionist?<br><br><br>Security guarding is becoming more important with every passing day because the security concerns are increasing. Vandalism, robbery, theft and other petty antisocial activities are increasing at a rapid speed. Recession has made the situation worse because many people who were laid off often got involved in such anti social activities. This is the reason why our house, office or commercial space is not completely safe and secured anymore. Access control system (like CCTV, biometric access control system, etc.) is becoming more and more important for security guarding. One of the best known access control system is Biometric Access Control System. When biological data are measured through scientific way and then analysed in a strategic manner, the process is known as Biometrics. Every human body part has some characteristic feature and these are aspects that are considered as ‘biological data’.<br><br><br>Fingerprints, facial pattern, iris and retina of eyes, hand measurement, DNA and others are some of the features that are unique for every person. This feature is used in the Biometric Access Control System. When such a system is installed at a particular place (say, a office, house or other commercial spaces), then the main motto is to give access to specified number of people only to the premises. Thus, characteristic features (fingerprints, facial pattern, iris and retina of eyes, hand measurement, DNA) of certain people are collected and then fed into the Biometric Access Control System. If any of the characteristic features doesn’t match with the already given features in the Biometric Access Control System, the system will not allow access to that particular person. This secured process has made Biometric Access Control System as the most secured access control system.<br><br><br>It has been considered by many that this system is used in the high security zones such as defence or nuclear power plant area. However, it is now used in the commercial complexes and also in some houses. Some of the most popular ones in the schools and offices are fingerprint and face recognition Biometric Access Control systems. This biometric system is widely used in United Kingdom and is very popular in the business community. In fact, this system is so popular that it is now being used in the personal spaces too. Biometric Access Control system has become more popular among the English people after the 9/11 terrorist attack in United States of America.<br><br><br>In fact, it has become so popular that UK has recorded the highest number of such system. Install Biometric Access Control systems and CCTV for security guarding and make your place secure and safe. Author's Bio: Derick Branson is a security guarding specialist as well as consultant. He has been associated with the industry for more than thirty years and is considered as a veteran in the security guarding industry. He has been advising commercial spaces and residential areas in installing - Biometric Access Control -System as well as CCTV. In this article he has given useful information on the same. Please Register or Login to post new comment. Where Do Penguins Live? Agile vs ADDIE: Which Is the Perfect Solution for Elearning Courses?<br><br><br>What is Heat Balance Diagram? This diagram also contains some information of steam properties like Pressure Temperature, enthalpy and mass of the steam at every junction of the line. What information the HBD has? As mentioned above, Heat Balance Diagram or HBD has the heat equation at points before and after every component. Considering the first point after the boiler, knowing the steam properties, pressure and temperatures, other properties like enthalpy of the steam can also be determined. Knowing the efficiencies and considerations like pressure drop across the control valves, these properties along the cycle can be determined, thus the heat rate of the system.<br><br><br>With help of heat rate, the mass of steam required can be determined. Why it is important? Heat Balance Diagram is generally one of the first produced diagrams and part of Process Control Diagrams(PCDs), by an engineering wing or consultancy while working on the specifications of the project (power plant). HBD helps to engineer the plant by way of providing the steam properties at different point across the steam cycle, thus providing vital information, helpful to design the whole system and supporting systems. In a way this diagram is critical to finalize the specifications of different components before initiating the bidding procedures by the consultants, especially working on EPC assignments. HBD, in fact also helps in estimating the cost of the plant as well as it provides the heat rate, operational cost can also be estimated. Knowing the both costs, it is easier to decide on refining the specifications of components (comparing initial investments as well as the operational costs), before bidding process, as mentioned above. Usually there has been no ways for the project owner to comment on the consultants decision about the specifications. Mostly it has to be dependent on individual discretion and experience and expertise.<br><br><br>Apr 23, 2019 (The Expresswire via COMTEX) -- Version Control Systems Market Report In-Depth Analysis of the Segmentation Which Comprises Product Type, Business Strategies, Development Factors and Forecast. Version Control Systems Market 2018 to 2023 Report primarily studies the size, recent trends and improvement status of the Version Control Systems market, as well as investment opportunities, government policy, market dynamics (drivers, restraints, opportunities), supply chain and competitive landscape. Technical invention and progression will further optimize the performance of the product, making it more widely used in downstream applications. Moreover, Porter's Five Forces Analysis (potential entrants, suppliers, substitutes, buyers, industry competitors) provides crucial information for knowing the Version Control Systems market.<br>
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