Basic steps in PLC programming for beginners.

Development of an algorithm

The first step in developing a control program is the definition of the control task. The control task specifies what needs to be done and is defined by those who are involved in the operation of the machine or process. The second step in control program development is to determine a control strategy, the sequence of processing steps that must occur within a program to produce the desired output control.A set of guidelines should be followed during program organization and implementation in order to develop an organized system. Approach guidelines apply to two major types of projects: new applications and modernizations of existing equipment.

Flow charting can be used to plan a program after a written description has been developed. A flowchart is a pictorial representation of the process that records, analyzes, and communicates information, as well as defines the sequence of the process.

Certain parts of the system should be left hardwired for safety reasons. Elements such as emergency stops and master start push buttons should be left hardwired so that the system can be disabled without PLC intervention.

Special cases of input device programming include the program translation of normally closed input devices, fenced MCR circuits, circuits that allow bidirectional power flow, instantaneous timer contacts, and complicated logic rungs.

• The programming of contacts as normally open or normally closed depends on how they are required to operate in the logic program. In most cases, if a normally closed input device is required to act as a normally closed input, its reference address is programmed as normally open.
• Master control relays turn ON and OFF power to certain logic rungs. In a PLC program, an END MCR instruction must be placed after the last rung an MCR will control.
• PLCs do not allow bidirectional power flow, so all PLC rungs must be programmed to operate only in a forward path.
• PLCs do not provide instantaneous contacts; therefore, an internal output must be used to trap a timer that requires these contacts.
• Complicated logic rungs should be isolated from the other rungs during programming.

Example Of Simple Start/Stop Motor Circuit

Figure 1 shows the wiring diagram for a three-phase motor and its corresponding three-wire control circuit, where the auxiliary contacts of the starter seal the start push button. To convert this circuit into a PLC program, first determine which control devices will be part of the PLC I/O system; these are the circled items in Figure 2. In this circuit, the start and stop push buttons (inputs) and the starter coil (output) will be part of the PLC system.

The starter coil’s auxiliary contacts will not be part of the system because an internal will be used to seal the coil, resulting in less wiring and fewer connections.

I/O Address
Module Type	Rack	Group	Terminal	Description
Input	0	0	0	Stop PB (NC)
	0	0	1	Start PB
	0	0	2	–
	0	0	3	–
Output	0	3	0	Motor M1
	0	3	1	–
	0	3	2	–
	0	3	3	–

To program the PLC, the devices must be programmed in the same logic sequence as they are in the hardwired circuit (see Figure 3). Therefore, the stop push button will be programmed as an examine-ON instruction (a normally open PLC contact) in series with the start push button, which is also programmed as an examine-ON instruction.

This circuit will drive output 030, which controls the starter.

If the start push button is pressed, output 030 will turn ON, sealing the start push button and turning the motor ON through the starter. If the stop push button is pressed, the motor will turn OFF.

Note that the stop push button is wired as normally closed to the input module. Also, the starter coil’s overloads are wired in series with the coil.

source:http://electrical-engineering-portal.com/

PLASTIC ROADS FOR A CLEANER AND GREENER FUTURE

Jambulingam Street, Chennai, is a local legend. The tar road in the bustling Nungambakkam area has weathered a major flood, several monsoons, recurring heat waves and a steady stream of cars, trucks and auto rickshaws without showing the usual signs of wear and tear. Built in 2002, it has not developed the mosaic of cracks, potholes or craters that typically make their appearance after it rains. Holding the road together is an unremarkable material: a cheap, polymer glue made from shredded waste plastic.

Jambulingam Street was one of India’s first plastic roads . The environmentally conscious approach to road construction was developed in India around 15 years ago in response to the growing problem of plastic litter. As time wore on, polymer roads proved to be surprisingly durable, winning support among scientists and policymakers in India as well as neighboring countries like Bhutan. “The plastic tar roads have not developed any potholes, rutting, raveling or edge flaw, even though these roads are more than four years of age,” observed an early performance report by India’s Central Pollution Control Board. Today, there are more than 21,000 miles of plastic road in India, and roughly half are in the southern state of Tamil Nadu. Most are rural roads, but a small number have also been built in cities such as Chennai and Mumbai.

Adding flexible materials to strengthen tar roads is not a new idea. Commercially made polymer-modified asphalts first became popular in the 1970s in Europe. Now, North America claims 35% of the global market. Modified asphalts are made from virgin polymers and sometimes crumb rubber (ground tires). They are highly versatile: Illinois uses them to build high-traffic truck roads, Washington State uses them for noise reduction and in rural Ontario they are used to prevent roads from cracking after a harsh winter. Polymerized asphalts also tend not to buckle in extreme heat the way conventional roads do – plastic roads will not melt unless the temperature goes beyond 66C (150F), compared to 50.2C (122.5F) for ordinary roads – and are frequently used on roads in the Middle East.

But even in the US, cost is a significant barrier. The most widely used polymer, styrene-butadiene-styrene, can increase the price of a road by 30-50%. In India, high-stress roads like runways and expressways are increasingly using polymer modified asphalts made by manufacturers like DuPont. 

While polymer roads in the US are made with asphalt that comes pre-mixed with a polymer, plastic tar roads are a frugal invention, made with a discarded, low-grade polymer. Every kilometer of this kind of road uses the equivalent of 1m plastic bags, saving around one tonne of asphalt and costing roughly 8% less than a conventional road. Dr R Vasudevan, a chemistry professor and dean at the Thiagarajar College of Engineering in Madurai, came up with the idea through trial and error, sprinkling shredded plastic waste over hot gravel and coating the stones in a thin film of plastic. He then added the plastic-coated stones to molten tar, or asphalt. Plastic and tar bond well together because both are petroleum products. The process was patented in 2006.

A modified version of the road which adds road scrap to plastic-coated gravel was tested out in March this year on a highway connecting Chennai with Villupuram. It was the first time plastic road technology was used for a national highway. It is expected to reduce construction costs by 50%.

Dr Vasudevan’s lab contains all the raw materials he needs to make a plastic road: shredders, a gas cylinder, a wok – and a pile of garbage. “This is my raw material,” Vasudevan says, pointing to a small pile of bags, plastic cups and foam packaging. These materials are the dregs of the plastic world, worthless even to rag pickers who cannot recycle them. Vasudevan melts shredded plastic over low heat to avoid emissions. Polystyrene is toxic when burned but, when softened, it makes an excellent pothole filler.

In India, plastic roads serve as a ready-made landfill for a certain kind of ubiquitous urban trash. Flimsy, single-use items like shopping bags and foam packaging are the ideal raw material. Impossible to recycle, they are a menace, hogging space in garbage dumps, clogging city drains and even poisoning the air. Delhi’s air, in particular, has been called a “toxic pollutant punchbowl” partly due to contaminants from plastic-fueled street bonfires.

However, urban plastic roads are still a rarity in India. Chennai was an early adopter of the technology, building its plastic roads from waste materials donated by the public. One satellite town even offered a gram of gold as an incentive for citizens to collect discarded plastic bags in 2012. But a year later, the plan was abandoned, because the city could not produce enough shredded plastic waste. It was also rumored that influential road builders, threatened by the prospect of pothole-free roads, had scuttled the project. Late last year, the mayor of Chennai announced the plastic road project was being revived, triggered in part by the devastation to Chennai’s roads after the floods of 2015.

Last November, the Indian government announced that plastic roads would be the default method of construction for most city streets, part of a multibillion-dollar overhaul of the country’s roads and highways. Urban areas with more than 500,000 people are now required to construct roads using waste plastic. The project even has the blessing of India’s prime minister, Narendra Modi, who has made “Swachh Bharat” (which translates to “Clean India”) a kind of personal crusade.

India’s road upgrade is long overdue. A recent road safety report by the World Health Organization (WHO) found that 17% of the world’s traffic fatalities occur in India, with crumbling roads partly responsible for the high death toll. In 2014, potholes alone caused more than 3000 deaths. According to the latest budget released by the Indian government, more roads projects were greenlit in 2015 than in previous years.

With so many projects underway, the Indian government is looking to a range of alternative materials to lower costs. The Delhi-Meerut Expressway, for example, which is currently under construction, may use unsegregated trash from one of the capital’s overflowing landfills to build its base and embankments. In an interview with the Times of India, India’s roads minister Nitin Gadkari said: “Delhi will get rid of these mounds and we will get the material for laying base with little expense.”

The reintroduction of plastics into the environment is not entirely without consequence. Old roads or poorly built ones are likely to shed plastic fragments into the soil and eventually waterways when they deteriorate as a result of photodegradation, which causes plastics to break down when exposed to environmental factors such as light and heat.

These minute plastic particles called microplastics act like magnets for pollutants like polychlorinated biphenyls (PCBs) and can have an impact on their surroundings. “Once in the soil, these particles may persist, accumulate, and eventually reach levels that can affect the functioning and biodiversity of the soil,” writes Matthias C Rillig, a professor of plant and soil ecology at Freie Universität Berlin.

In the short run, the bigger challenge for plastic roads is execution. They require a hefty dose of government intervention to succeed. Tamil Nadu was the first state in India to actively develop a cottage industry around shredded plastic. Most plastic shredders are women who buy subsidized shredding machines and sell their finished product for a small profit. Job creation for waste pickers and small entrepreneurs is an added benefit of the roads – a point not lost on India’s prime minister.

Source- www.theguardian.com

An introduction to SCADA SYSTEM

Control and Supervision

It is impossible to keep control and supervision on all industrial activities manually. Some automated tool is required which can control, supervise, collect data, analyses data and generate reports. A unique solution is introduced to meet all this demand is SCADA system.

SCADA stands for supervisory control and data acquisition. It is an industrial control system where a computer system monitoring and controlling a process.

Another term is there, Distributed Control System (DCS). Usually there is a confusion between the concept of these two.

Components of SCADA

1. Human Machine Interface (HMI)

It is an interface which presents process data to a human operator, and through this, the human operator monitors and controls the process.

2. Supervisory (computer) system

It gathers data on the process and sending commands (or control) to the process.

3. Remote Terminal Units (RTUs)

It connect to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system.

4. Programmable Logic Controller (PLCs)

It is used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.

5. Communication infrastructure

It provides connectivity to the supervisory system to the Remote Terminal Units.

SCADA System Concept

The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything between an industrial plant and a country)Most control actions are performed automatically by Remote Terminal Units (RTUs) or by programmable logic controllers (PLCs).

Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but  the  SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded.

source:http://electrical-engineering-portal.com/

Turning your living room into a wireless charging station

This is a simple representation of the in-home wireless power transfer scheme being proposed. A device similar to a flat-screen TV could continuously charge multiple devices throughout a room.

Credit: David Smith, Duke University

The flat-screen TV on your living room wall could soon be remotely charging any device within its line of sight. Well, not your actual TV, but a device that is similar in size and shape.

In a paper posted October 23, 2016 on the arXiv pre-print repository, engineers at Duke University, the University of Washington and Intellectual Ventures' Invention Science Fund (ISF) show that the technology already exists to build such a system -- it's only a matter of taking the time to design it.

"Whether its headphones, cell phones, watches, or even your mouse and keyboard, a major irritation for consumers is the hassle of being tethered to cords to recharge batteries," said David Smith, professor and chair of the Department of Electrical and Computer Engineering at Duke. "And of course they always run dry at the worst possible moment. Our proposed system would be able to automatically and continuously charge any device anywhere within a room, making dead batteries a thing of the past."

Some wireless charging systems already exist to help power speakers, cell phones and tablets. These technologies rely on platforms that require their own wires, however, and the devices must be placed in the immediate vicinity of the charging station.

This is because existing chargers use the resonant magnetic near-field to transfer energy. The magnetic field produced by current flowing in a coil of wire can be quite large close to the coil and can induce a similar current in a neighboring coil. Magnetic fields also have the added bonus of being considered safe for human exposure, making them a convenient choice for wireless power transfer.

The magnetic near-field approach, however, is not an option for power transfer over larger distances. This is because the coupling between source and receiver -- and thus the power transfer efficiency -- drops rapidly with distance. The wireless power transfer system proposed in the new paper operates at much higher microwave frequencies, where the power transfer distance can extend well beyond the confines of a room.

To maintain reasonable levels of power transfer efficiency, the key to the system is to operate in the Fresnel zone -- a region of an electromagnetic field that can be focused, allowing power density to reach levels sufficient to charge many devices with high efficiency.

"As long as you're within a certain distance, you can build antennas that gather electromagnetic energy and focus it, much like a lens can focus a beam of light," explained Smith.

The problem to date has been that the antennas in a wireless power transfer system would need to be able to focus on any device within a room. This could be done with a movable antenna dish, for example, but that would take up too much space, and nobody wants a big, moving satellite dish on their mantel.

Another solution is a phased array -- an antenna with a lot of tiny antennas grouped together, each of which can be independently adjusted and tuned. That technology also exists, but would be too costly and consume too much energy for household use.

The solution proposed by Smith and his colleagues in the new paper instead relies on metamaterials -- a synthetic material composed of many individual, engineered cells that together produce properties not found in nature.

"Imagine you have an electromagnetic wave front moving through a flat surface made of thousands of tiny electrical cells," said Smith. "If you can tune each cell to manipulate the wave in a specific way, you can dictate exactly what the field looks like when it comes out on the other side."

If this technology sounds far-fetched, it's not. Smith and his laboratory used this principle to create the world's first cloaking device that bends electromagnetic waves around an object held within.

Several years ago, Nathan Kundtz, a former graduate student and postdoc from Smith's group, led an ISF team that developed the metamaterials technology for satellite communications. The team founded Kymeta, which builds powerful, flat antennas that could soon replace the gigantic revolving satellite dishes often seen atop large boats. Three other companies, Evolv, Echodyne and Pivotal have also been founded using different versions of the metamaterials for imaging, radar and wireless communications, respectively.

"One of the coolest things about our approach to this problem is that it allows us to manufacture our antennas at the same plants that produce LCD televisions," said Kundtz. LCD refers to liquid crystal displays; it is the liquid crystal integrated with the metamaterial elements that enables Kymeta's reconfigurable satellite antennas. Kymeta has been producing antennas using this production capacity for about one year.

In the paper, Smith and his colleagues work through calculations to illustrate what a metamaterials-based wireless power system would be capable of. According to the results, a flat metamaterial device no bigger than a typical flat-screen television could focus beams of microwave energy down to a spot about the size of a cell phone within a distance of up to 10 meters. It should also be capable of powering more than one device at the same time.

"The ability to safely direct focused beams of microwave energy to charge specific devices, while avoiding unwanted exposure to people, pets and other objects, is a game-changer for wireless power," said co-author Matt Reynolds, associate professor of electrical engineering and computer science and engineering at the University of Washington. "Our proposed Fresnel-zone approach takes advantage of widely used LCD technology to enable seamless wireless power delivery to all kinds of smart devices. And we're looking into alternatives to liquid crystals that could allow energy transfer at much higher power levels over greater distances."

There are, of course, challenges to engineering such a wireless power transfer system. A powerful, low cost, highly efficient electromagnetic energy source would need to be developed. The system would have to automatically shut off if a person or a pet were to walk into the focused electromagnetic beam. And the software and controls for the metamaterial lens would have to be optimized to focus powerful beams while suppressing any unwanted secondary "ghost" beams.

But the technology is there.

"All of these issues are possible to overcome -- they aren't roadblocks," said Smith. "We actually came up with some nice analytical formulas for coverage areas and efficiencies that would be possible. I think building a system like this, which could be embedded in the ceiling and wirelessly charge everything in a room, is a very feasible scheme. Moreover, there are versions of the concept that can deliver larger power over much larger distances"

എന്തുകൊണ്ട് കുതിരാൻ ?????

Kuthiran Tunnel

Kuthiran is infamous for the bad condition of the road for last few years. Even the NHAI responsible for the road doesn't bother to repair it. This holds true even after lot of protests by the bus associations and locals. Accidents are very common across this stretch. Recent news clips show that people traveling between Trichur and Palakkad are choosing alternate roads to save their lives, like the Trichur-Shoranur-Ottapalam-Palakkad, to save their and their vehicles' health.

Kuthiran Tunnel is an under construction tunnel in the Indian state of Kerala State in Thrissur District. When finished, it will be Kerala's first-ever tunnel for road transport.

Present traffic

Kuthiran gradient is situated in the Kuthiran Hills, which falls in the notified Wild Life Sanctuary. Presently, Kuthiran gradient is a major traffic bottleneck and accident spot on the crowded Thrissur-Palakkad stretch of the National Highway 544 (India) Once the works are completed, both the tunnels would reduce the distance between Thrissur to Palakkad up to 3 kilometers. The tunnel through the Kuthiran will also avoid vehicular congestions while traversing the hills.

Cost

Pragathi Engineering and Rail Project Private Limited has bagged the sub-contract for the Kuthiran tunnel construction at a cost of Rs 200 crore.

Dimension

The twin tube tunnels will have length of 1 kilometer (915 metre), while the width and height would be 14 metre and 10 metre respectively. The tunnels would be located in a gap of 20 metres. Two emergency crossover inside the tunnel is there inside the tunnel.

Ultralight 'Super-Material' Is 10 Times Stronger Than Steel

A new material is incredibly light yet stronger than steel. The new material gets its amazing strength from its unique geometric configuration.

A spongy new super-material could be lighter than the flimsiest plastic yet 10 times stronger than steel.

The new super-material is made up of flecks of graphene squished and fused together into a vast, cobwebby network. The fluffy structure, which looks a bit like a psychedelic sea creature, is almost completely hollow; its density is just 5 percent that of ordinary graphene, the researchers said.

What's more, though the researchers used graphene, the seemingly magical properties of the material do not totally depend on the atoms used: The secret ingredient is the way those atoms are aligned, the scientists said.

"You can replace the material itself with anything," Markus J. Buehler, a materials scientist at the Massachusetts Institute of Technology (MIT) said in a statement. "The geometry is the dominant factor. It's something that has the potential to transfer to many things."

Graphene, a material made up of flaky sheets of carbon atoms, is the strongest material on Earth — at least in 2D sheets. On paper, ultrathin sheets of graphene, which are just an atom thick, have unique electrical properties and indomitable strength. Unfortunately, these properties don't easily translate to 3D shapes that are used to build things. [7 Technologies That Transformed Warfare]

Past simulations suggested that orienting the graphene atoms a specific way could enhance strength in three dimensions. However, when researchers tried to create these materials in the lab, the results were often hundreds or thousands of times weaker than predicted, the researchers said in the statement. 

Stronger than steel

To address this challenge, the team got down to basics: analyzing the structure at the atomic level. From there, the researchers created a mathematical model that can accurately predict how to create remarkably strong super-materials. The researchers then used precise amounts of heat and pressure to produce the resulting curvy, labyrinthine structures, known as gyroids, which were first mathematically described by a NASA scientist in 1970.

"Actually making them using conventional manufacturing methods is probably impossible," Buehler said.

The material's strength comes from its enormous surface-area-to-volume ratio, the researchers reported in a study published Jan. 6 in the journal Science Advances. In nature, sea creatures like coral and diatoms also leverage a large surface-area-to-volume ratio to achieve incredible strength at tiny scales.

"Once we created these 3D structures, we wanted to see what's the limit — what's the strongest possible material we can produce," study co-author Zhao Qin, a civil and environmental engineering researcher at MIT, said in the statement.

The scientists created a series of models, built them, and then subjected them to tension and compression. The strongest material the researchers created was about as dense as the lightest plastic bag, yet stronger than steel.

One obstacle to creating these superstrong materials is the lack of industrial manufacturing capability for producing them, the researchers said. However, there are ways the material could be produced at larger scales, the scientists said

For instance, the actual particles could be used as templates that are coated with graphene through chemical vapor deposition; the underlying template could then be eaten or peeled away using chemicals or physical techniques, leaving the graphene gyroid behind, the researchers said.

In the future, massive bridges could be made of gyroid concrete, which would be ultrastrong, lightweight, and insulated against heat and cold because of all the myriad air pockets in the material, the researchers said.

Source- www.livescience.com

SMART WATCHES

                

Smart watches and similar portable devices are commonly used for measuring steps and physiological parameters, but have not generally been used to detect illness, until now.

Credit: © WavebreakMediaMicro / Fotolia

Can your smart watch detect when you are becoming sick? A new study from Stanford, publishing January 12th, 2017 in PLOS Biology, indicates that this is possible.

By following 60 people through their everyday lives, Stanford researchers found that smart watches and other personal biosensor devices can help flag when people have colds and even signal the onset of complex conditions like Lyme disease and diabetes. "We want to tell when people are healthy and also catch illnesses at their earliest stages," said Michael Snyder, PhD, Professor and Chair of Genetics at Stanford and senior author of the study. Postdoctoral scholars Xiao Li, PhD, and Jessilyn Dunn, PhD, and researcher Denis Salins share lead authorship.

Smart watches and similar portable devices are commonly used for measuring steps and physiological parameters, but have not generally been used to detect illness. Snyder's team took advantage of the portability and ease of using wearable devices to collect a myriad of measurements from participants for up to two years to detect deviations from their normal baseline for measurements such as heart rate and skin temperature. Because the devices continuously follow these measures, they potentially provide rapid means to detect the onset of diseases that change your physiology.

Many of these deviations coincided with times when people became ill. Heart rate and skin temperature tends to rise when people become ill, said Snyder. His team wrote a software program for data from a smart watch called 'Change of Heart' to detect these deviations and sense when people are becoming sick. The devices were able to detect common colds and in one case helped detect Lyme disease -- in Snyder, who participated in the study.

"I had elevated heart rate and decreased oxygen at the start of my vacation and knew something was not quite right," said Snyder. After running a low-grade fever for several days, Snyder visited a physician who confirmed the illness. Snyder took the antibiotic doxycycline and the symptoms disappeared. Subsequent tests confirmed the presence of Lyme. The smart watch and an oxygen sensor were useful in detecting the earliest signs of illness.

This research paves the way for the smart phone to serve as a health dashboard, monitoring health and sensing early signs of illness, likely even before the person wearing it does.

In addition to detecting illness, the study had several other interesting findings. Individuals with indications of insulin resistance and who are therefore are at high risk for Type 2 diabetes are often unaware that they have this risk factor. Personal biosensors could potentially be developed into a simple test for those at risk for Type 2 diabetes by detecting variations in heart rate patterns, which tend to differ from those not at risk.

Another interesting finding of the study is an effect that impacts many of us. The authors found that blood oxygenation decreases during airplane flights. Although this is a known effect, the authors were able to characterize it in greater detail than has been previously reported. Snyder's team found that reduced blood oxygenation typically occurs for a large fraction of a flight and further demonstrated that this is associated with fatigue. "Many of us have had the experience of feeling tired on airplane flights," Snyder said. "Sometimes people may attribute this to staying up late, a hectic work schedule, or the stress of travel. However, it is likely that cabin pressure and reduced oxygen also are contributors."

"The information collected could aid your physician, although we can expect some initial challenges in how to integrate the data into clinical practice," said Snyder. For example, patients may want to protect the privacy of their physiologic data or may want to share only some of it.

"Physicians and third-party payers will demand robust research to help guide how this comprehensive longitudinal personal data should be used in clinical care," Snyder said. "However, in the long-term I am very optimistic that personal biosensors will help us maintain healthier lives."

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