Automation And Control Gear

The word automation is defined as: the use of machines to do work that was previously done by people. That explanation implies that people are out of the equation altogether; that of course is not the case, as a factory that is fully automated still needs engineers to ensure that everything runs smoothly. They also have to cope with the inevitable breakdowns when they occur and to initiate and stop production runs. The control gear dictates the way in which the machines operate when the start button is pressed.

Control gear consists of the computer systems, switching, hydraulics, pneumatics and all the other elements that work together to tell the machines what to do and when to do it. In our high-tech world, automation and control gear is now a part of modern factories and is also found in, and is a vital part of, ships, aircraft and the most technically advanced of all machines, those used in defence and space exploration. In this article we will cover more everyday forms of control gear that nevertheless play a vital role in running modern production facilities.

 

RFID

We are all now familiar with the bar codes that the operators scan through the reader at the supermarket check out. When the item is scanned the computer identifies the product and displays its price on the display. It will also note for stock control purposes that that particular product has been sold. That successful system, which has been in use for some considerable time now, is about to be replaced by the use of radio frequency identification (RFID) tags.

This new generation of the bar code is far more intelligent than its predecessor. It has the ability to communicate with a computer network and will tell it exactly what you are placing into your shopping trolley and what to charge for it. If you take this initiative to its logical conclusion the day will almost certainly come when a registered customer will enter a store, select the goods required and walk out. The cost of the items will simply be charged to a registered credit card or bank account.

RFID tags had rather a humble beginning, as they were originally developed in the agriculture industry to track cattle. The full potential of the system was soon recognised and its use has now expanded to enter the retail arena as mentioned above, also to vehicles, pets and passengers at airports, and even to tracking individuals that are suffering from Alzheimer’s disease.

 

Cable tidies

Although essential to enable us all to live in our technologically advanced world, electrical cables can be a real nuisance if not managed properly. Of particular interest to many is the muddle of wires that lurk behind our TV cabinets; however, there are numerous ways in which electrical cables of all descriptions can be kept in an ordered and tidy state, from home uses to major electrical and computer installations.

Cable ties are ingenious and extremely useful strips of ridged plastic that have a locking device that will keep the tie tight around a number of cables. This keeps wires tidily together to avoid a spaghetti situation developing. They are commonly used in the engine compartments and throughout the wiring loom cable runs on motor vehicles.

Also commonly seen in use in offices to keep computer cables in some sort of reasonable order are flexible plastic protective sheaths. These tubes are made in such a way that they can be wrapped around a bunch of wires, rather than the wires having to be passed through them. This allows them to be installed and quickly removed for reuse, thus saving money. There is a small tool available that makes inserting the wires into the quite rigid sheath much easier. Other minor variations of this design are available.

Cable tidy units are also in common use. These small plastic boxes allow extension blocks to be safely concealed and will also reduce cable clutter. They have a click-on lid that keeps everything contained within the box.

 

Energy saving light bulbs

The old tungsten incandescent light bulbs have been phased out to make way for the far more environmentally friendly energy saving light bulbs. These were not universally popular when first introduced as some users were irritated by the flickering prevalent in some of the earlier versions of this product. The latest types of compact fluorescent bulbs (CFLs) have reduced this effect and the bulbs are now in common use. 

The main benefit of energy saving light bulbs is that very fact; they consume far less energy to produce the same amount of light than their incandescent predecessors. Life expectancy is also increased with many of these bulbs reliably providing illumination for thousands of hours. Although more expensive to purchase than tungsten bulbs this is far outweighed by the longevity of the modern version.

 

Thermistor

A thermistor acts as a resistor, the resistance levels of which vary with temperature. These components are mostly used in self-regulating heating elements; overcurrent protectors with the ability to reset, temperature sensors, and as inrush limiters of current. The material used in the manufacture of thermistors is usually a polymer or a ceramic, while other resistors use metal. Thermistors operate accurately within a limited temperature range of -900C to 1300C.

There are two distinct types of thermistor - the positive temperature coefficient (PTC) thermistor and the negative temperature coefficient (NTC) thermistor. The names are self-explanatory, as in one the resistance increases and in the other it decreases as the temperature rises.

 

Thermocouple

Thermocouples produce an electrical current as a response to a change in temperature. Because of that attribute they are used as control devices and measuring instruments. They operate efficiently and with great precision over a wide temperature range, up to really extreme levels, peaking at 1,6000C. These devices are strong and unsophisticated; as such they are ideal for use in extreme environments such as inside jet engines.

Many homes in the UK will have one or more of these devices installed, probably as a component in a central heating boiler or in a gas fire. In that application they act as a vital safety feature, turning off the flow of gas when a draught or a fault extinguishes a pilot light in the flame of which the thermocouple sensor is located. When the sensor is heated by the pilot light an electric current is generated that is sent to control an electromagnet. As long as that current flow is maintained the electromagnet will keep the gas valve open allowing gas to flow to the pilot light. When the light is extinguished the sensor cools and the flow of current will cease, the electromagnet then activates the valve causing the gas flow to be stopped. In this way the simple thermocouple has saved many lives.

 

Cable management

Efficient cable management is essential when constructing new buildings or when rewiring established structures. Cables have to be properly supported when they are passed through spaces and along the internal and external walls of buildings. This is not only to ensure safety for those using the building but also to make life far easier for engineers attending in the future to deal with faults or to add additional circuits.

Power cables are normally routed using plastic conduit, cable ladders, cable baskets and trays.

Cabling for IT purposes is dealt with somewhat differently, as the wiring may need to be altered or added to on a more frequent basis than would, for example, ring main cabling.

There are also special cable management requirements in some environments. Hospitals are a case in point where cabling has to be carefully controlled in treatment areas. To prevent interference with electronic equipment some hospital cabling needs to be particularly well shielded.

 

Contactors

Contactors are basically switches that are electrically controlled. They are used to switch power circuits in a similar way to a relay but work at higher levels of current. The contactor is actually controlled by a circuit that is operating at a far lower current level than the power circuit the contactor is controlling. They are universally used to control thermal evaporators, electric motors, heating, capacitor banks and lighting. That is not an exhaustive list as they are very versatile units that can be utilised in many different ways.

These devices come in many different forms and have a great variety of uses. They are unlike circuit breakers in that they are not designed to deal with a short circuit. Contactors deal with breaking currents ranging from thousands of amperes downwards. They can also be used to deal with anything from kilovolts down to 24 volt CD current.

Contactors are manufactured in varying physical dimensions. They can be as large as a one-metre cube to small devices of varying shapes. The devices have three main components, the contacts, an electromagnet and an enclosure. The contacts are the parts of the contactor that carry the electrical current; the electromagnet provides the force that is required to close the contacts and the insulated enclosure contains the aforementioned parts. The enclosure also protects the electromagnet and the contacts, and also adds an essential safety aspect as it prevents an individual touching the live contacts.

 

Light bulb

Electric light bulbs were simple objects, taken for granted in homes and workplaces. They were cheap, easy to fit and safe. They worked by the passage of current across wire filaments creating intense heat; as a result the filaments gave off a bright light. Their main failing was that they often didn’t last very long and would often fuse at inconvenient moments. Those old fashioned incandescent bulbs have now been superseded by far more efficient forms of lighting.

A change in thinking when it came to forms of electrically powered lighting was really forced upon the industry by the growing concerns over global warming. The necessity to reduce power consumption, however and wherever possible, was recognised by government and the industry was forced to research new ways of providing electric lighting in our homes and offices.

Early attempts by the big players in the industry to create light bulbs that would meet the criteria were not terribly successful. The bulbs were more bulky than the old tungsten bulbs and also much heavier. Problems were discovered when attempting to fit the new bulbs into old fittings; they often didn’t fit at all, effectively making the fittings redundant.

With the steady development and evolution in design of lighter and more compact fluorescent bulbs (CFLs) most of these problems were resolved. CFLs are now ubiquitous in UK homes.

Light emitting diode (LED) forms of lighting are now becoming far more common. They have two main benefits: little heat is created in operation and they consume very little power. Size is also very relevant with this form of lighting as LED bulbs can be produced in very small sizes – they are now very popular as Christmas tree lights.