Wednesday, 13 October 2010

Electric Motor

There is no basic difference between the construction of DC motors and generators. Rotating machines of this type must have the following basic features.
1.       A magnetic field system
2.       A system of conductors
3.       Provision for relative movement between the field and the conductors
In most DC machines the magnetic field is set up by the stationary part of the machine, which is called the field system. The commutator and the conductors which form the armature winding, are mounted on the rotating part of the machine.
The body of the machine is a hollow cylinder of cast steel called the yoke. Which forms the basis for construction of the machine and is part of the magnetic circuit. Fixed pole pieces made of solid steel or iron are fixed inside the yoke.
Each pole has one or more field windings placed over it to produce a magnetic field. There is always an even number of poles.
Then there are the armature windings of the DC machine which are often very complex, there are two basic types.
1.       Wave windings – these tend to be high voltage, low current windings, and always have two conducting paths in parallel.
2.       Lap windings – these tend to be low voltage high current windings, and have as man conducting paths in parallel as there are poles. 
The ends of the winding are brought out of the slots at one end, where they are connected to the lugs on the commutator by welding or soldering. A typical commutator will be made up of many hard drawn copper segments each one insulated from the other with mica.
The completed armature is mounted on bearings, often supported by end plates mounted on the yoke. The carbon brushes are mounted so that the pressure exerted by them on the commutator can be adjusted, and so that the pressure will remain reasonably constant as the brushes wear.
Below is a picture of a DC motor with a spilt yoke, showing much of the above descriptions. 

Monday, 4 October 2010

Micro Set up

I created this blog post, just to show you all how i set up my micro project for college last year, it composes of two boards, the one directly below is a input and output board. 
the other one is where the actual micro that is programmed is contained.
The 3rd picture is them connected together and to a power supply, while the last picture shows them connected to a PC by a serial port.

The serial ports where the micro is connected to the PC 

Friday, 1 October 2010


Static RAM (SRAM)- Static RAM is a type of random access memory that is used to hold data without external refresh circuitary to keep the data together. The memory is held for as long as there is power supplied to the circuit.
Dynamic RAM (DRAM)- Dynamic RAM only holds data if a refresh circuit has continuous acess to the Dynamic RAM. The refresh circuit reads each memory cell even if the cell being scanned has no information stored in it, this refreshes the memory contents. this process is repeated hundreds of times per second. If this process is not repeated, the Dynamic RAM loses its memory even if power is still supplied. This process gives the name Dynamic. All PC’s use Dynamic RAM for their main system memory.
Static RAM and Dynamic RAM compared.
·         Static RAM doesn’t require external refresh circuitary to help to retain the data stored whereas dynamic RAM needs external refresh otherwise the data stored is lost.
·         Static RAM is faster than Dynamic RAM
·         Dynamic RAM is more complicated than Static RAM due to the external refresh circuits required
·         Dynamic RAM is cheaper than Static RAM
·         Static RAM is larger than Dynamic RAM because Static RAM is made up of four or more transistors per bit whereas Dynamic RAM uses one transistor and a capacitor.

Read Only Memory (ROM)- ROM is a type of memory that can only be read and is used in PC’s. the data stored in ROM is permanently present with or without power connected. ROM can be removed, stored for a long period of time and replaced without the data being lost which makes ROM non-volatile, whereas RAM is volatile memory.
Parallel ports- a parallel port is an interface found on computers and are used to connect peripherals to the computer.

Thursday, 30 September 2010

Different types of electrical signals

         i.            A analogue signal is a electrical signal thats varies in frequency or amplitude and can used to measure curtain things such as heat, pressure or weight, with a high degree of accuracy, this is because analogue signals can be adjusted more finely, compared to digital in such respects, in the above application the as the temperature varies the analogue signal will also vary, and using preset values for the amount heat or lack of it, the temperature can be accurately read.

       ii.            Digital signals on the other hand are either fully on or fully off, and can be used in programming because you can represent these as 1’s or 0’s, this is useful in lighting or communications, in respects to the LED display stated above the signal you could program each number to be shown by using a combination of the LEDs on the display, or instance for a 8, all the LED’s could be turned on or a 7 it would be A, B and C on the diagram below. The PLC would assign each one of the LED’s a output and when a curtain number is needed it could use these outputs and a digital signal to turn a combination of them on.

      iii.            Wireless signals can be used to communicate with the need for hard wires and actual physical connections, the most famous and commonly used is radio, but in respects to PLC’s wireless signals differ to radio signals, PLC’s can communicate with each other using devices such as the Omron WD30 which use connects a master PLC to slave PLC’S, below are the specifications of the WD30 showing the wave lengths and frequencies ect.
This wireless system would work by using a PC to program a master PLC, and using that PLC to communicate to other slave PLC’s which could be used to operate machinery, basically using a master plc to tell other ones what to do and control output from one source, without wires, as shown below in the diagram, this is also of the omron FAQ section.

Tuesday, 28 September 2010

Energy Diversification - Just a little bit more

The future of energy generation is unclear but exciting, as a whole range of new technologies emerges from various companies, governments and scientists.  
Current world energy usage. 

As you can see fossil fuels accounts for over  86% of world energy production, so when we run out of them, we will have to find a lot of alternative energy resources, rather than one new alternative to this problem i imagine it will be a combination of renewables, nuclear and possible future technology like hydrogen.
This will require a large investment from governments and private companies, from all around the world, as well as unprecedented international cooperation and development, the economics implications for oil producing nations such as Russia, USA, Iraq, Saudi Arabia and many more could be far reaching and very destabilising in many parts of the world.

Energy Diversification

There are many reasons why a country will try and diversify its energy production, the main objective is the continuous and stable production of energy, because the economies and essential services of modern society rely so much on electricity dependant functions.
For example if a country’s entire energy output relies on one source, and that source is interrupted or depleted it will no longer be able to produce electricity, crippling services, industry as well as the economy. The mark of a modern developed country is the ability to provide safe and stable electricity to anyone that needs it, and this is a factor in why some companies chose to set up in the UK for example.
A investment in renewable is more a investment for the future, as non-renewable energy sources are cheaper in the short term, but eventually will run out, and as renewable wont it makes them eventually essential.
Green peace for instance wants the whole of the UK’s energy to come from fully renewable sources, and minimize pollution completely; they want this to be achieved over the next 20 amount of years, on their website they even say...
Between them, wind, wave and tidal power could deliver more than twice as much electricity than the new fleet of nuclear reactors being debated - and the renewables would be built more quickly. Even then, the full potential of these sources would not have been tapped - much more could be harnessed in the future. But we have to start now if we're going to end our dependence on fossil fuels and reduce emissions. Ambitious support for renewables will bring benefits - not just of clean, fuel-free energy, but the jobs and economic growth that come from pioneering new industries and technology.”
Source From Green Peace
Another good reason to diversify is the fluxuations in global prices of raw materials, for example since china increased its use of coal power the price has rocketed, making coal suddenly more expensive plus increased demand with clean coal technology increases price even more.
So if a country has a range of different energy sources it won’t be as affected by sudden increases in for instance oil or gas, these two tend to change the most, for many geo-political and economic reasons.
And as for political motives, it is political pressure from pressure groups than force the government to spend more on renewable and to subsidize new technologies, this is because the government wants to keep these groups happy and appear to be doing the right thing in terms of the environment.
The future of energy generation is unclear but exciting, as a whole range of new technologies emerges from various companies, governments and scientists.   

PLC's - Programmable Logic Computers

There are three types of PLC’s which can be used for many applications
·         these are Unitary
·         Modular
·         and Rack Mounted PLC’s.
The reason there are three types of PLC’s is because that some are better suited to use in various applications.
When selecting a PLC for an application there are a number of factors to consider. Such as memory size, speed of operation, cost, compatibility.
 An good application for a Modular PLC would be theme park rides. This PLC is more suited to this application as a Modular PLC can be built up and changed over time as the park or application changes. This type of PLC is quite expensive, but this is because the number of input/outputs can be changed to suit the application. Also adding more inputs/outputs on this type of PLC is easier as more modules can be added to the PLC. Maintenace in modular PLC’s is easier because if one module goes faulty, this is the only component that needs to be replaced unlike with Unitary PLC which would all need to be replaced. This PLC can also be networked so that they can all be monitored from one location, although unitary PLC’s can also be networked with a added on section.
Unitary PLC’s could be suited for many things, just one of these is a lighting system such as in a factory or warehouse. This is because a lighting system requires less inputs and outputs. The size of the program is relatively small, therefore the cost of a Unitary PLC is greatly cheaper than a Modular PLC which is an important factor as each system would have its own PLC. Also a Unitary PLC takes up much less room than a modular PLC so installation is easier, although both pof these are rack mounted its not really a major issue in most applications although modular are seen as the more durable of the two.
An ideal application for a Rack Mounted PLC would be in car manufacturing. This PLC would be best used in this environment as it uses both Modular and Unitary PLC’s, so you have advantages of both PLC’s and you have the ability to communicate more with other netoworks. This is useful as this type of application requires various programs to operate multiple tasks, which in a car factory are quite considerable as there are many factors of production in producing one car. Rack Mounted are probably the most expensive PLC but they do have the advantages of both types of PLC’s at hand. This means that this one Rack Mounted PLC can run an entire operation line in the factory, from maintenance to operation, so if effiency is more important than the over all initial investment then rack mounted are a suitible choice.

Monday, 27 September 2010

The Ideal Op-amp
1.       Voltage gain - infinite                                                      need to use negative feedback
2.       Input resistance – infinite                                                 no input to current to op amp
3.       Output resistance – zero                                                 no voltage signal los at output
4.       Bandwidth – infinite                                                        works on DC and AC up to any frequency

1.       Voltage Gain (Av) - 200,000                                         need to use negative feedback                
2.       Input resistance  - 1 MΩ                                                input current to Op-Amp will be pA
3.       Output resistance - 75Ω                                                 very little output signal loss
4.       Bandwidth up to - 1MHz                                               works on DC and AC up to 1 MHz

Range of frequencies over which the circuit functions

·         A connection between output and input in a circuit or system
·         Most commonly negative feedback to tend to reduce the effect of the input and maintain a stable state

Output voltage can never exceed power supply voltage
Basically a small voltage from a circuit controlling a large voltage 

Amusing infomation sheets

Different Types Of Capacitors

Charge And Capacitors
types of capacitors:
There are many different types of capacitors that have different properties.
Electrolytic.Electrolytic capacitors are polarised. This means that they have a positive and a negative electrode, usually made out of Aluminium. If the current to the capacitor is reversed, the capacitor will not work or could blow. The Electrolytic capacitor can have axial electrodes. This means that instead of the electrodes exiting the capacitor at the bottom, they have one at the top and one at the bottom. Usually have a value in micro-farads normally ranging from one micro-farad to thousands of micro-farads. The aluminium electrolytic capacitor is usually used as a filter to bypass low frequency signals but cannot be used for high frequency signals.

Tantalum capacitors

Tantalum capacitors are electrolytic capacitors that use a material called tantalum for the electrodes instead of aluminium. Large values of capacitance can be obtained like the aluminium capacitor but are superior to aluminium electrolytic capacitors in both temperature and frequency characteristics and can be used for analogue signal circuits.

Ceramic capacitors.
Ceramic capacitors have no polarity and are commonly used for high frequency circuits because they are not constructed as a coil internally, but the ceramic capacitor cannot be used for analogue signals as the capacitor distorts the signal.

Polystyrene Capacitors.

In these capacitors, a polystyrene film is used as the dielectric material. These capacitors cannot be used in high frequency circuits due to their coil like structure but are used in filter circuits or timing circuits. These capacitors do not have a certain polarity

Polyester film capacitors.
These capacitors use a film of polyester as the dielectric material and have no polarity. These capacitors have a low tolerance but are cheap.

Polypropylene capacitors.
Polypropylene capacitors are normally used when a higher tolerance is needed that is too high for the polyester capacitor.  These capacitors have no polarity.

Mica capacitors.
Mica capacitors have a good stability because their temperature coefficient is small. Because their frequency characteristics are good, they are normally used in resonance circuits and high frequency filters. The mica capacitors can also be used for high voltage applications due to their good insulation but they are fairly expensive.

Darlington pair
This is two transistors connected together so that the current amplified by the first is amplified further by the second transistor. The overall current gain is equal to the two individual gains multiplied together:
Darlington pair current gain, hFE = hFE1 × hFE2 
 and hFE2 are the gains of the individual transistors)
This gives the Darlington pair a very high current gain, such as 10000, so that only a tiny base current is required to make the pair switch on.
A Darlington pair behaves like a single transistor with a very high current gain. It has three leads (BC and E) which are equivalent to the leads of a standard individual transistor. To turn on there must be 0.7V across both the base-emitter junctions which are connected in series inside the Darlington pair, therefore it requires 1.4V to turn on.
Darlington pairs are available as complete packages but you can make up your own from two transistors; TR1 can be a low power type, but normally TR2 will need to be high power. The maximum collector current Ic(max) for the pair is the same as Ic(max) for TR2.
A Darlington pair is sufficiently sensitive to respond to the small current passed by your skin and it can be used to make a touch-switch as shown in the diagram. For this circuit which just lights an LED the two transistors can be any general purpose low power transistors. The 100kohm resistor protects the transistors if the contacts are linked with a piece of wire. 

Mag Lev Trains

A new breed of trains that basically use magnets to propel themselves across set tracks.  The train uses electromagnets to levitate a train above the tracks; this means that when travelling friction is as low as possible meaning that a greater efficiency and speed can be achieved with trains reaching over 310MPH.

Pictured above is a basic composition of the maglev train and how it is attached to the tracks, as you can see electrical energy contained in the tracks that is used to propel the train. Electrical energy is used to energise the magnets and levitate the train just a quarter inch of the ground.
Once the train is levitated, power is supplied to the coils within the guide ways to create a system of magnetic fields that pull and push the train along the guide way.
 The electric current supplied to the coils in the guide way walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust.
an illustration that shows how the Yamanashi maglev guideway works


Ways in which the maglev can be improved
Con- Strong magnetic fields onboard the train would make the train inaccessible to passengers with pacemakers or magnetic data storage media such as hard drives and credit cards, necessitating the use of magnetic shielding; this will have a dramatic effect on the use of the train because many business people and ordinary passengers will need to be able to take on credit cards and electrical devices.

Possible remedy- A casing around the carriage of the train or passenger compartments could be a remedy of this problem, a protective layer of Mu-Metal, an iron nickel alloy, could provide enough protection due to its properties of dispersing low frequency magnetic fields.  It is the high permeability of mu-metal provides a low reluctance path for magnetic flux, creasing the desired effect. Further development in magnetic shielding could reducing the cost and the weight of said shielding, creasing a lighter more efficient train, that is cheaper to build. But a Mu-Metal casing might not be enough to shield from the stronger magnetic fields, and more advance materials must be developed with high permeability and lower resistance.
Con- The lack of infrastructure for maglev trains will be a major problem for the future wide spread development of the technology, the con is not so much the lack of infrastructure but the initial cost of setting it up, because the maglev has to be suspended above the ground, and they will have to run alongside existing train tracks, so space is more scarce. I think the future of maglev’s, will be high speed city links, a simple two track, going from a few pre-designated points, such as existing systems like in Shanghai.
Solution- I think the future of maglev’s, will be high speed city links, a simple two track, going from a few pre-designated points, such as existing systems like in Shanghai. This will maximise efficacy especially during rush hour, because passenger numbers will be high, and a maglev train will drastically cut commute times. The only way future developments in electrical technology will help infrastructure being built, is if new cheaper materials are developed, or cheaper ways are designed to erect and maintain the tracks.