Linear time-invariant (LTI)
Linearity means that if you have two inputs and two corresponding outputs, if you take a linear combination of those two inputs you will get a linear combination of the outputs. An example of a linear system is a first order low-pass or high-pass filter. Linear systems are made out of analog devices that demonstrate linear properties. These devices don't have to be entirely linear, but must have a region of operation that is linear. An operational amplifier is a non-linear device, but has a region of operation that is linear, so it can be modeled as linear within that region of operation. Time-invariance means it doesn't matter when you start a system, the same output will result. For example, if you have a system and put an input into it today, you would get the same output if you started the system tomorrow instead. There aren't any real systems that are LTI, but many systems can be modeled as LTI for simplicity in determining what their output will be. All systems have some dependence on things like temperature, signal level or other factors that cause them to be non-linear or non-time-invariant, but most are stable enough to model as LTI. Linearity and time-invariance are important because they are the only types of systems that can be easily solved using conventional analog signal processing methods. Once a system becomes non-linear or non-time-invariant, it becomes a non-linear differential equations problem, and there are very few of those that can actually be solved. (Haykin & Van Veen 2003)
Common systems
Some common systems used in everyday life are filters, AM/FM radio, electric guitars and musical instrument amplifiers. Filters are used in almost everything that has electronic circuitry. Radio and television are good examples of everyday uses of filters. When a channel is changed on an analog television set or radio, an analog filter is used to pick out the carrier frequency on the input signal. Once it's isolated, the television or radio information being broadcast is used to form the picture and/or sound. Another common analog system is an electric guitar and its amplifier. The guitar uses a magnet with a coil wrapped around it (inductor) to turn the vibration of the strings into a small electric current. The current is then filtered, amplified and sent to a speaker in the amplifier. Most amplifiers are analog because it's easier and cheaper than making a digital amplifier. There are also many analog guitar effects pedals, although a large number of pedals are now digital (they turn the input current into a digitized value, perform an operation on it, then convert it back into an analog signal).
Tuesday, March 31, 2009
Domains electronicsjalil
Time domain
This is the domain that most people are familiar with. A plot in the time domain shows the magnitude of a signal at a point in time.
Frequency domain
This is the domain that engineers are glad exists. It's unfamiliar to most people, but makes the math associated with analog signal processing much easier than if it's analyzed in the time domain. A plot in the frequency domain shows either the phase shift or magnitude of a signal at each frequency that it exists at. These can be found by taking the Fourier transform of a time signal and are plotted similarly to a bode plot.
Signals
While any signal can be used in analog signal processing, there are many types of signals that are used very frequently.
Sinusoids
Sinusoids are the building block of analog signal processing. Theorem states that all real world signals can be represented by a sum of sinusoids. A sinusoid can be represented by a complex exponential, e^{st}.
Impulse
An impulse (Dirac delta function) is defined as a signal that has an infinite magnitude and an infinitesimally narrow width with an area under it of one, centered at zero. An impulse can be represented as an infinite sum of sinusoids that includes all possible frequencies. This definition is really hard to use in real life, so most engineers conceptualize it to a signal that is one at zero and zero everywhere else. The symbol for an impulse is delta(t). If an impulse is used as an input to a system, the output is known as the impulse response. The impulse response defines the system because all possible frequencies are represented in the input.
Step
A step function is a signal that has a magnitude of zero before zero and a magnitude of one after zero. The symbol for a step is u(t). If a step is used as the input to a system, the output is called the step response. The step response shows how a system responds to a sudden input, similar to turning on a switch. The period before the output stabilizes is called the transient part of a signal. The step response can be multiplied with other signals to show how the system responds when an input is suddenly turned on.
This is the domain that most people are familiar with. A plot in the time domain shows the magnitude of a signal at a point in time.
Frequency domain
This is the domain that engineers are glad exists. It's unfamiliar to most people, but makes the math associated with analog signal processing much easier than if it's analyzed in the time domain. A plot in the frequency domain shows either the phase shift or magnitude of a signal at each frequency that it exists at. These can be found by taking the Fourier transform of a time signal and are plotted similarly to a bode plot.
Signals
While any signal can be used in analog signal processing, there are many types of signals that are used very frequently.
Sinusoids
Sinusoids are the building block of analog signal processing. Theorem states that all real world signals can be represented by a sum of sinusoids. A sinusoid can be represented by a complex exponential, e^{st}.
Impulse
An impulse (Dirac delta function) is defined as a signal that has an infinite magnitude and an infinitesimally narrow width with an area under it of one, centered at zero. An impulse can be represented as an infinite sum of sinusoids that includes all possible frequencies. This definition is really hard to use in real life, so most engineers conceptualize it to a signal that is one at zero and zero everywhere else. The symbol for an impulse is delta(t). If an impulse is used as an input to a system, the output is known as the impulse response. The impulse response defines the system because all possible frequencies are represented in the input.
Step
A step function is a signal that has a magnitude of zero before zero and a magnitude of one after zero. The symbol for a step is u(t). If a step is used as the input to a system, the output is called the step response. The step response shows how a system responds to a sudden input, similar to turning on a switch. The period before the output stabilizes is called the transient part of a signal. The step response can be multiplied with other signals to show how the system responds when an input is suddenly turned on.
What are the Tools used in analog signal processing ?
A system's behavior can be mathematically modeled and is represented in the time domain as h(t) and in the frequency domain as H(s), where s is a complex number in the form of s=a+ib, or s=a+jb in electrical engineering terms (electrical engineers use j because current is represented by the variable i). Input signals are usually called x(t) or X(s) and output signals are usually called y(t) or Y(s).
Convolution
Convolution is the basic concept in signal processing that states an input signal can be combined with the system's function to find the output signal. The symbol for convolution is *.
That is the convolution integral and is used to find the convolution of a signal and a system; typically a = -∞ and b = +∞.
Fourier transform
The Fourier transform is a function that transforms a signal or system in the time domain into the frequency domain, but it only works for certain ones. The constraint on which systems or signals can be transformed by the Fourier Transform is that:
This is the Fourier transform integral:
Most of the time the Fourier transform integral isn't used to determine the transform. Usually a table of transform pairs is used to find the Fourier transform of a signal or system. The inverse Fourier transform is used to go from frequency domain to time domain:
Each signal or system that can be transformed has a unique Fourier transform; there is only one time signal and one frequency signal that goes together.
Laplace transform
The Laplace transform is a generalized Fourier transform. It allows a transform of any system or signal because it is a transform into the complex plane instead of just the jω line like the Fourier transform. The major difference is that the Laplace transform has a region of convergence for which the transform is valid. This implies that a signal in frequency may have more than one signal in time; the correct time signal for the transform is determined by the region of convergence. If the region of convergence includes the jω axis, jω can be substituted into the Laplace transform for s and it's the same as the Fourier transform. The Laplace transform is:
and the inverse Laplace transform is:
Bode plots
Bode plots are plots of magnitude vs. frequency and phase vs. frequency for a system. The magnitude axis is in Decibel (dB). The phase axis is in either degrees or radians. The frequency axes are in a logarithmic scale. These are useful because for sinusoidal inputs, the output is the input multiplied by the value of the magnitude plot at the frequency and shifted by the value of the phase plot at the frequency.
Convolution
Convolution is the basic concept in signal processing that states an input signal can be combined with the system's function to find the output signal. The symbol for convolution is *.
That is the convolution integral and is used to find the convolution of a signal and a system; typically a = -∞ and b = +∞.
Fourier transform
The Fourier transform is a function that transforms a signal or system in the time domain into the frequency domain, but it only works for certain ones. The constraint on which systems or signals can be transformed by the Fourier Transform is that:
This is the Fourier transform integral:
Most of the time the Fourier transform integral isn't used to determine the transform. Usually a table of transform pairs is used to find the Fourier transform of a signal or system. The inverse Fourier transform is used to go from frequency domain to time domain:
Each signal or system that can be transformed has a unique Fourier transform; there is only one time signal and one frequency signal that goes together.
Laplace transform
The Laplace transform is a generalized Fourier transform. It allows a transform of any system or signal because it is a transform into the complex plane instead of just the jω line like the Fourier transform. The major difference is that the Laplace transform has a region of convergence for which the transform is valid. This implies that a signal in frequency may have more than one signal in time; the correct time signal for the transform is determined by the region of convergence. If the region of convergence includes the jω axis, jω can be substituted into the Laplace transform for s and it's the same as the Fourier transform. The Laplace transform is:
and the inverse Laplace transform is:
Bode plots
Bode plots are plots of magnitude vs. frequency and phase vs. frequency for a system. The magnitude axis is in Decibel (dB). The phase axis is in either degrees or radians. The frequency axes are in a logarithmic scale. These are useful because for sinusoidal inputs, the output is the input multiplied by the value of the magnitude plot at the frequency and shifted by the value of the phase plot at the frequency.
Analog signal processing statement electronicsjalil
Analog signal processing is any signal processing conducted on analog signals by analog means. "Analog" indicates something that is mathematically represented as a set of continuous values. This differs from "digital" which uses a series of discrete quantities to represent signal. Analog values are typically represented as a voltage, electric current, or electric charge around components in the electronic devices. An error or noise affecting such physical quantities will result in a corresponding error in the signals represented by such physical quantities.
Examples of analog signal processing include crossover filters in loudspeakers, "bass", "treble" and "volume" controls on stereos, and "tint" controls on TVs. Common analog processing elements include capacitors, resistors, inductors and transistors.
Examples of analog signal processing include crossover filters in loudspeakers, "bass", "treble" and "volume" controls on stereos, and "tint" controls on TVs. Common analog processing elements include capacitors, resistors, inductors and transistors.
Cable manufacturers electronicsjalil
Some global producers of electrical wire and cable include (in alphabetical order): Belden, Cables RCT, Cords Cable, [Draka], Fujikura, Furukawa Electric, Hitachi Cable, Igus, Leoni, LS Cable, Marmon Group, Nexans, Pirelli, Prysmian, Southwire, Sumitomo Electric Industries, Tyco
Electrical cable types electronicsjalil
Basic cable types are as follows:
Basic
• Coaxial cable
• Multicore cable (consist of more than one wire and is covered by cable jacket)
• Ribbon cable
• Shielded cable
Construction
Based on construction and cable properties it can be sorted into the following:
• Mineral-insulated copper-clad cable
• Twinax cable
• Flexible cables
Special
• Bowden cable
• Direct-buried cable
• Elevator cable
Application
• Wire rope (wire cable)
• Audiovisual cable
• Bicycle cable
• Communications cable
• Computer cable
• Mechanical cable
• Sensing cable
• Submersible cable
Basic
• Coaxial cable
• Multicore cable (consist of more than one wire and is covered by cable jacket)
• Ribbon cable
• Shielded cable
Construction
Based on construction and cable properties it can be sorted into the following:
• Mineral-insulated copper-clad cable
• Twinax cable
• Flexible cables
Special
• Bowden cable
• Direct-buried cable
• Elevator cable
Application
• Wire rope (wire cable)
• Audiovisual cable
• Bicycle cable
• Communications cable
• Computer cable
• Mechanical cable
• Sensing cable
• Submersible cable
Electrical cables electronicsjalil
Electrical cables may be made more flexible by stranding the wires. In this process, smaller individual wires are twisted or braided together to produce larger wires that are more flexible than solid wires of similar size. Bunching small wires before concentric stranding adds the most flexibility. Copper wires in a cable may be bare, or they may be coated with a thin layer of another material: most often tin but sometimes gold, silver or some other material. Tin, gold, and silver are much less prone to oxidisation than copper, which may lengthen wire life, and makes soldering easier. Tight lays during stranding makes the cable extensible (CBA - as in telephone handset cords).
Cables can be securely fastened and organized, such as by using cable trees with the aid of cable ties or cable lacing. Continuous-flex or flexible cables used in moving applications within cable carriers can be secured using strain relief devices or cable ties. Copper corrodes easily and so should be layered with Lacquer.
At high frequencies, current tends to run along the surface of the conductor and avoid the core. This is known as the skin effect. It may change the relative desirability of solid versus stranded wires.
Cables and electromagnetic fields
Any current-carrying conductor, including a cable, radiates an electromagnetic field. Likewise, any conductor or cable will pick up energy from any existing electromagnetic field around it. These effects are often undesirable, in the first case amounting to unwanted transmission of energy which may adversely affect nearby equipment or other parts of the same piece of equipment; and in the second case, unwanted pickup of noise which may mask the desired signal being carried by the cable, or, if the cable is carrying power-supply or control voltages, pollute them to such an extent as to cause equipment malfunction.
Coaxial cable.
Twisted pair.
The first solution to these problems is to keep cable lengths short, since pick up and transmission are essentially proportional to the length of the cable. The second solution is to route cables away from trouble. Beyond this, there are particular cable designs that minimise electromagnetic pickup and transmission. Three of the principal design techniques are shielding, coaxial geometry, and twisted-pair geometry.
Shielding makes use of the principle of the Faraday cage. The cable is encased for its entire length in foil or wire mesh. All wires running inside this shielding layer will be to a large extent decoupled from external electric fields, particularly if the shield is connected to a point of constant voltage, such as ground. Simple shielding of this type is not greatly effective against low-frequency magnetic fields, however – such as magnetic "hum" from a nearby power transformer.
Coaxial design helps to further reduce low-frequency magnetic transmission and pickup. In this design the foil or mesh shield is perfectly tubular – ie., with a circular cross section – and the inner conductor (there can only be one) is situated exactly at its centre. This causes the voltages induced by a magnetic field between the shield and the core conductor to consist of two nearly equal magnitudes which cancel each other.
The twisted pair is a simple expedient where two wires of a cable, rather than running parallel to each other, are twisted around each other, forming a pair of intertwined helices. This can be achieved by putting one end of the pair in a hand drill and turning while maintaining moderate tension on the line. Field cancellation between successive twists of the pair considerably reduces electromagnetic pickup and transmission.
Power-supply cables feeding sensitive electronic devices are sometimes fitted with a series-wired inductor called a choke which blocks high frequencies that may have been picked up by the cable, preventing them from passing into the device.
Fire protection
In building construction, electrical cable jacket material is a potential source of fuel for a fire. To limit the spread of fire along cable jacketing, one may use cable coating materials or one may use cables with jacketing that is inherently fire retardant. The plastic covering on some metal clad cables may be stripped off at installation to reduce the fuel source for accidental fires. In Europe in particular, it is often customary to place inorganic wraps and boxes around cables in order to safeguard the adjacent areas from the potential fire threat associated with unprotected cable jacketing.
To provide fire protection to a cable, there are two methods:
a) Insulation material is deliberately added up with fire retardant materials
b) The copper conductor itself is covered with mineral insulations( MICC cables)
Cables can be securely fastened and organized, such as by using cable trees with the aid of cable ties or cable lacing. Continuous-flex or flexible cables used in moving applications within cable carriers can be secured using strain relief devices or cable ties. Copper corrodes easily and so should be layered with Lacquer.
At high frequencies, current tends to run along the surface of the conductor and avoid the core. This is known as the skin effect. It may change the relative desirability of solid versus stranded wires.
Cables and electromagnetic fields
Any current-carrying conductor, including a cable, radiates an electromagnetic field. Likewise, any conductor or cable will pick up energy from any existing electromagnetic field around it. These effects are often undesirable, in the first case amounting to unwanted transmission of energy which may adversely affect nearby equipment or other parts of the same piece of equipment; and in the second case, unwanted pickup of noise which may mask the desired signal being carried by the cable, or, if the cable is carrying power-supply or control voltages, pollute them to such an extent as to cause equipment malfunction.
Coaxial cable.
Twisted pair.
The first solution to these problems is to keep cable lengths short, since pick up and transmission are essentially proportional to the length of the cable. The second solution is to route cables away from trouble. Beyond this, there are particular cable designs that minimise electromagnetic pickup and transmission. Three of the principal design techniques are shielding, coaxial geometry, and twisted-pair geometry.
Shielding makes use of the principle of the Faraday cage. The cable is encased for its entire length in foil or wire mesh. All wires running inside this shielding layer will be to a large extent decoupled from external electric fields, particularly if the shield is connected to a point of constant voltage, such as ground. Simple shielding of this type is not greatly effective against low-frequency magnetic fields, however – such as magnetic "hum" from a nearby power transformer.
Coaxial design helps to further reduce low-frequency magnetic transmission and pickup. In this design the foil or mesh shield is perfectly tubular – ie., with a circular cross section – and the inner conductor (there can only be one) is situated exactly at its centre. This causes the voltages induced by a magnetic field between the shield and the core conductor to consist of two nearly equal magnitudes which cancel each other.
The twisted pair is a simple expedient where two wires of a cable, rather than running parallel to each other, are twisted around each other, forming a pair of intertwined helices. This can be achieved by putting one end of the pair in a hand drill and turning while maintaining moderate tension on the line. Field cancellation between successive twists of the pair considerably reduces electromagnetic pickup and transmission.
Power-supply cables feeding sensitive electronic devices are sometimes fitted with a series-wired inductor called a choke which blocks high frequencies that may have been picked up by the cable, preventing them from passing into the device.
Fire protection
In building construction, electrical cable jacket material is a potential source of fuel for a fire. To limit the spread of fire along cable jacketing, one may use cable coating materials or one may use cables with jacketing that is inherently fire retardant. The plastic covering on some metal clad cables may be stripped off at installation to reduce the fuel source for accidental fires. In Europe in particular, it is often customary to place inorganic wraps and boxes around cables in order to safeguard the adjacent areas from the potential fire threat associated with unprotected cable jacketing.
To provide fire protection to a cable, there are two methods:
a) Insulation material is deliberately added up with fire retardant materials
b) The copper conductor itself is covered with mineral insulations( MICC cables)
Cable electronicsjalil
6" or 15cm outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. These cables are connected to powerful pumps that pump the oil through them while in operation. Safety switches turn off the oil flow in the event of a leak, in order to limit the effects of a hydrocarbon fire.
Fire test in Sweden, showing rapid fire spread through burning of cable jackets from one cable tray to another.
500MCM 1C Power Cable Marking
A cable is two or more wires or ropes running side by side and bonded, twisted or braided together to form a single assembly. In mechanics, cables are used for lifting and hauling; in electricity they are used to carry electrical currents. An optical cable contains one or more optical fibers in a protective jacket that supports the fibers. Mechanical cable is more specifically called wire rope.
History
Ropes made of multiple strands of natural fibers such as hemp, sisal, manila, and cotton have been used for millennia for hoisting and hauling. By the 19th century, deepening of mines and construction of large ships increased demand for stronger cables. Invention of improved steelmaking techniques made high quality steel available at lower cost, and so wire ropes became common in mining and other industrial applications. By the middle of the 19th century, manfacture of large submarine telegraph cables was done using machiners similar to that used for manufacture of mechanical cables.
In the 19th century and early 20th century, electrical cable was often insulated using cloth, rubber and paper. Plastic materials are generally used today, except for high reliability power cables.
Fire test in Sweden, showing rapid fire spread through burning of cable jackets from one cable tray to another.
500MCM 1C Power Cable Marking
A cable is two or more wires or ropes running side by side and bonded, twisted or braided together to form a single assembly. In mechanics, cables are used for lifting and hauling; in electricity they are used to carry electrical currents. An optical cable contains one or more optical fibers in a protective jacket that supports the fibers. Mechanical cable is more specifically called wire rope.
History
Ropes made of multiple strands of natural fibers such as hemp, sisal, manila, and cotton have been used for millennia for hoisting and hauling. By the 19th century, deepening of mines and construction of large ships increased demand for stronger cables. Invention of improved steelmaking techniques made high quality steel available at lower cost, and so wire ropes became common in mining and other industrial applications. By the middle of the 19th century, manfacture of large submarine telegraph cables was done using machiners similar to that used for manufacture of mechanical cables.
In the 19th century and early 20th century, electrical cable was often insulated using cloth, rubber and paper. Plastic materials are generally used today, except for high reliability power cables.
Art Work
A Rat's Nest
Once the schematic has been made, it is converted into a layout that can be fabricated onto a Printed Circuit Board (PCB). The layout is usually prepared by the process of schematic capture. The result is what is known as a Rat's Nest. The Rat's Nest is a jumble of wires (lines) criss crossing each other to their destination nodes. These wires are routed either manually or by the use of Electronics Design Automation (EDA) tools. The EDA tools arrange and rearrange the placement of components and finds paths for tracks to connect various nodes. This results into an Art Work.
A generalized design flow would be as:
Schematic → Schematic Capture → Rat's Nest → Routing → Art Work → PCB Development & etching → Component Mounting → Testing
Once the schematic has been made, it is converted into a layout that can be fabricated onto a Printed Circuit Board (PCB). The layout is usually prepared by the process of schematic capture. The result is what is known as a Rat's Nest. The Rat's Nest is a jumble of wires (lines) criss crossing each other to their destination nodes. These wires are routed either manually or by the use of Electronics Design Automation (EDA) tools. The EDA tools arrange and rearrange the placement of components and finds paths for tracks to connect various nodes. This results into an Art Work.
A generalized design flow would be as:
Schematic → Schematic Capture → Rat's Nest → Routing → Art Work → PCB Development & etching → Component Mounting → Testing
Organization of drawings electronicsjalil
It is a usual although not universal convention that schematic drawings are organized on the page from left to right and top to bottom in the same sequence as the flow of the main signal or power path. For example, a schematic for a radio receiver might start with the antenna input at the left of the page and end with the loudspeaker at the right. Positive power supply connections for each stage would be shown towards the top of the page, with grounds, negative supplies, or other return paths towards the bottom. Schematic drawings intended for maintenance may have the principle signal paths highlighted to assist in understanding the signal flow through the circuit. More complex devices have multi-page schematics and must rely on cross-reference symbols to show the flow of signals between the different sheets of the drawing.
Detailed rules for the preparation of circuit diagrams (and other document kinds used in electrotechnology) are provided in the International standard IEC61082-1.
Relay logic line diagrams (also called ladder logic diagrams) use another common standardized convention for organizing schematic drawings, with a vertical power supply "rail" on the left and another on the right, and components strung between them like the rungs of a ladder.
Art Work
A Rat's Nest
Once the schematic has been made, it is converted into a layout that can be fabricated onto a Printed Circuit Board (PCB). The layout is usually prepared by the process of schematic capture. The result is what is known as a Rat's Nest. The Rat's Nest is a jumble of wires (lines) criss crossing each other to their destination nodes. These wires are routed either manually or by the use of Electronics Design Automation (EDA) tools. The EDA tools arrange and rearrange the placement of components and finds paths for tracks to connect various nodes. This results into an Art Work.
A generalized design flow would be as:
Schematic → Schematic Capture → Rat's Nest → Routing → Art Work → PCB Development & etching → Component Mounting → Testing
Detailed rules for the preparation of circuit diagrams (and other document kinds used in electrotechnology) are provided in the International standard IEC61082-1.
Relay logic line diagrams (also called ladder logic diagrams) use another common standardized convention for organizing schematic drawings, with a vertical power supply "rail" on the left and another on the right, and components strung between them like the rungs of a ladder.
Art Work
A Rat's Nest
Once the schematic has been made, it is converted into a layout that can be fabricated onto a Printed Circuit Board (PCB). The layout is usually prepared by the process of schematic capture. The result is what is known as a Rat's Nest. The Rat's Nest is a jumble of wires (lines) criss crossing each other to their destination nodes. These wires are routed either manually or by the use of Electronics Design Automation (EDA) tools. The EDA tools arrange and rearrange the placement of components and finds paths for tracks to connect various nodes. This results into an Art Work.
A generalized design flow would be as:
Schematic → Schematic Capture → Rat's Nest → Routing → Art Work → PCB Development & etching → Component Mounting → Testing
What are the European and Australian codes ?
The following codes which vary slightly from the American codes are in common use in European and Australian standard electrical circuit diagrams. These codes are used for the "reference designators" printed on PCBs (which match the corresponding ones written on the corresponding schematic).
• A: Assemblies
• B: Transducers (photo cells, inductive proximity, thermocouple, flame detection)
• C: Capacitors
• D: Storage devices
• E: Miscellaneous
• F: Fuses
• G: Generator, battery pack
• H: Indicators, lamps (not for illumination), signalling devices
• K: Relays, contactors
• L: Inductors and filters
• M: Motors
• N: Analogue devices
• P: Measuring/test equipment
• Q: Circuit breakers, isolators, re-closers
• R: Resistors, brake resistors
• S: Switches, push buttons, emergency stops and limit switches
• T: Transformers
• U: Power converters, variable speed drives, soft starters, DC power supplies
• V: Semiconductors
• W: Wires, conductors, power, neutral and earthing busses
• X: Terminal strips, terminations, joins
• Y: Solenoids, electrical actuators
• Z: Filters
Detailed rules for reference designations are provided in the International standard IEC 61346 .
• A: Assemblies
• B: Transducers (photo cells, inductive proximity, thermocouple, flame detection)
• C: Capacitors
• D: Storage devices
• E: Miscellaneous
• F: Fuses
• G: Generator, battery pack
• H: Indicators, lamps (not for illumination), signalling devices
• K: Relays, contactors
• L: Inductors and filters
• M: Motors
• N: Analogue devices
• P: Measuring/test equipment
• Q: Circuit breakers, isolators, re-closers
• R: Resistors, brake resistors
• S: Switches, push buttons, emergency stops and limit switches
• T: Transformers
• U: Power converters, variable speed drives, soft starters, DC power supplies
• V: Semiconductors
• W: Wires, conductors, power, neutral and earthing busses
• X: Terminal strips, terminations, joins
• Y: Solenoids, electrical actuators
• Z: Filters
Detailed rules for reference designations are provided in the International standard IEC 61346 .
Typical Circuit diagram electronicsjalil
The circuit diagram for a 4 bit TTL counter, a type of state machine
A circuit diagram (also known as an electrical diagram, wiring diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.
Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire connections being used. The diagram does not show the physical arrangement of components. A drawing meant to depict what the physical arrangement of the wires and the components they connect is called "artwork" or "layout" or the "physical design."
Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.
Legends
Common circuit diagram symbols (with US Resistor Symbol)
On a circuit diagram, the symbols for components are labelled with a descriptor (or reference designator) matching that on the list of parts. For example, C1 is the first capacitor, L1 is the first inductor, Q1 is the first transistor, and R1 is the first resistor(note that this is not written as a subscript, as in R1, L1,…). The letters that precede the numbers were chosen in the early days of the electrical industry, even before the vacuum tube (thermionic valve), so "Q" was the only one available for semiconductor devices in the mid-twentieth century[Often the value or type designation of the component is given on the diagram beside the part, but detailed specifications would go on the parts list.
Symbols
See also: Electronic symbols
Circuit diagram symbols have differed from country to country and have changed over time, but are now to a large extent internationally standardized. Simple components often had symbols intended to represent some feature of the physical construction of the device. For example, the symbol for a resistor shown here dates back to the days when that component was made from a long piece of wire wrapped in such a manner as to not produce inductance, which would have made it a coil. These wirewound resistors are now used only in high-power applications, smaller resistors being cast from carbon composition (a mixture of carbon and filler) or fabricated as an insulating tube or chip coated with a metal film. The internationally standardized symbol for a resistor is therefore now simplified to an oblong, sometimes with the value in ohms written inside, instead of the zig-zag symbol. A less common symbol is simply a series of peaks on one side of the line representing the conductor, rather than back-and-forth as shown here.
Standards
There are several national and international standards for graphical symbols in circuit diagrams, in particular:
• IEC 60617 (also known as British Standard BS 3939)
• ANSI standard Y32 (also known as IEEE Std 315)
IEC 60617 originally consisted of 13 parts, from resistors and capacitors to logic symbols and even a generalised drawing standard of connections and bus line widths. It is now published as a subscription online database IEC 60617-DB.
Different symbols may be used depending on the discipline using the drawing; for example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.
Linkages
Schematic wire junctions:
1. Old style: (a) connection, (b) no connection.
2. One CAD style: (a) connection, (b) no connection.
3. Alternative CAD Style: (a) connection, (b) no connection.
The linkages between leads were once simple crossings of lines; one wire insulated from and "jumping over" another was indicated by it making a little semicircle over the other line. With the arrival of computerized drafting, a connection of two intersecting wires was shown by a crossing with a dot or "blob", and a crossover of insulated wires by a simple crossing without a dot. However, there was a danger of confusing these two representations if the dot was drawn too small or omitted. Modern practice is to avoid using the "crossover with dot" symbol, and to draw the wires meeting at two points instead of one. It is also common to use a hybrid style, showing connections as a cross with a dot while insulated crossings use the semicircle.
A circuit diagram (also known as an electrical diagram, wiring diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified standard symbols, and the power and signal connections between the devices. Arrangement of the components interconnections on the diagram does not correspond to their physical locations in the finished device.
Unlike a block diagram or layout diagram, a circuit diagram shows the actual wire connections being used. The diagram does not show the physical arrangement of components. A drawing meant to depict what the physical arrangement of the wires and the components they connect is called "artwork" or "layout" or the "physical design."
Circuit diagrams are used for the design (circuit design), construction (such as PCB layout), and maintenance of electrical and electronic equipment.
Legends
Common circuit diagram symbols (with US Resistor Symbol)
On a circuit diagram, the symbols for components are labelled with a descriptor (or reference designator) matching that on the list of parts. For example, C1 is the first capacitor, L1 is the first inductor, Q1 is the first transistor, and R1 is the first resistor(note that this is not written as a subscript, as in R1, L1,…). The letters that precede the numbers were chosen in the early days of the electrical industry, even before the vacuum tube (thermionic valve), so "Q" was the only one available for semiconductor devices in the mid-twentieth century[Often the value or type designation of the component is given on the diagram beside the part, but detailed specifications would go on the parts list.
Symbols
See also: Electronic symbols
Circuit diagram symbols have differed from country to country and have changed over time, but are now to a large extent internationally standardized. Simple components often had symbols intended to represent some feature of the physical construction of the device. For example, the symbol for a resistor shown here dates back to the days when that component was made from a long piece of wire wrapped in such a manner as to not produce inductance, which would have made it a coil. These wirewound resistors are now used only in high-power applications, smaller resistors being cast from carbon composition (a mixture of carbon and filler) or fabricated as an insulating tube or chip coated with a metal film. The internationally standardized symbol for a resistor is therefore now simplified to an oblong, sometimes with the value in ohms written inside, instead of the zig-zag symbol. A less common symbol is simply a series of peaks on one side of the line representing the conductor, rather than back-and-forth as shown here.
Standards
There are several national and international standards for graphical symbols in circuit diagrams, in particular:
• IEC 60617 (also known as British Standard BS 3939)
• ANSI standard Y32 (also known as IEEE Std 315)
IEC 60617 originally consisted of 13 parts, from resistors and capacitors to logic symbols and even a generalised drawing standard of connections and bus line widths. It is now published as a subscription online database IEC 60617-DB.
Different symbols may be used depending on the discipline using the drawing; for example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics.
Linkages
Schematic wire junctions:
1. Old style: (a) connection, (b) no connection.
2. One CAD style: (a) connection, (b) no connection.
3. Alternative CAD Style: (a) connection, (b) no connection.
The linkages between leads were once simple crossings of lines; one wire insulated from and "jumping over" another was indicated by it making a little semicircle over the other line. With the arrival of computerized drafting, a connection of two intersecting wires was shown by a crossing with a dot or "blob", and a crossover of insulated wires by a simple crossing without a dot. However, there was a danger of confusing these two representations if the dot was drawn too small or omitted. Modern practice is to avoid using the "crossover with dot" symbol, and to draw the wires meeting at two points instead of one. It is also common to use a hybrid style, showing connections as a cross with a dot while insulated crossings use the semicircle.
Computer engineering electronicsjalil
Computer Engineering (also called Electronic and Computer Engineering or Computer Systems Engineering) is a discipline that combines elements of both Electrical Engineering and Computer Science Computer engineers usually have training in electrical engineering, software design and hardware-software integration instead of only software engineering or electrical engineering. Computer engineers are involved in many aspects of computing, from the design of individual microprocessors, personal computers, and supercomputers, to circuit design. This engineering monitors the many subsystems in motor vehicles
Usual tasks involving computer engineers include writing software and firmware for embedded microcontrollers, designing VLSI chips, designing analog sensors, designing mixed signal circuit boards, and designing operating systems.[ Computer engineers are also suited for robotics research, which relies heavily on using digital systems to control and monitor electrical systems like motors, communications, and sensors.
Computer engineering as an academic discipline
The first accredited computer engineering degree program in the United States was established at Case Western Reserve University in 1971; as of October 2004 there were 170 ABET-accredited computer engineering programs in the US.
Due to increasing job requirements for engineers, who can design and manage all forms of computer systems used in industry, some tertiary institutions around the world offer a bachelor's degree generally called computer engineering. Both computer engineering and electronic engineering programs include analog and digital circuit design in their curricula. As with most engineering disciplines, having a sound knowledge of mathematics and sciences is necessary for computer engineers.
In many institutions, computer engineering students are allowed to choose areas of in-depth study in their junior and senior year, as the full breadth of knowledge used in the design and application of computers is well beyond the scope of an undergraduate degree. The joint IEEE/ACM Curriculum Guidelines for Undergraduate Degree Programs in Computer Engineering defines the core knowledge areas of computer engineering as
• Algorithms
• Computer architecture and organization
• Computer systems engineering
• Circuits and signals
• Database systems
• Digital logic
• Digital signal processing
• Electronics
• Embedded systems
• Human-computer interaction
• Interactive Systems Engineering
• Operating systems
• Programming fundamentals
• Social and Professional issues
• Software engineering
• VLSI design and fabrication
The breadth of disciplines studied in computer engineering is not limited to the above
Usual tasks involving computer engineers include writing software and firmware for embedded microcontrollers, designing VLSI chips, designing analog sensors, designing mixed signal circuit boards, and designing operating systems.[ Computer engineers are also suited for robotics research, which relies heavily on using digital systems to control and monitor electrical systems like motors, communications, and sensors.
Computer engineering as an academic discipline
The first accredited computer engineering degree program in the United States was established at Case Western Reserve University in 1971; as of October 2004 there were 170 ABET-accredited computer engineering programs in the US.
Due to increasing job requirements for engineers, who can design and manage all forms of computer systems used in industry, some tertiary institutions around the world offer a bachelor's degree generally called computer engineering. Both computer engineering and electronic engineering programs include analog and digital circuit design in their curricula. As with most engineering disciplines, having a sound knowledge of mathematics and sciences is necessary for computer engineers.
In many institutions, computer engineering students are allowed to choose areas of in-depth study in their junior and senior year, as the full breadth of knowledge used in the design and application of computers is well beyond the scope of an undergraduate degree. The joint IEEE/ACM Curriculum Guidelines for Undergraduate Degree Programs in Computer Engineering defines the core knowledge areas of computer engineering as
• Algorithms
• Computer architecture and organization
• Computer systems engineering
• Circuits and signals
• Database systems
• Digital logic
• Digital signal processing
• Electronics
• Embedded systems
• Human-computer interaction
• Interactive Systems Engineering
• Operating systems
• Programming fundamentals
• Social and Professional issues
• Software engineering
• VLSI design and fabrication
The breadth of disciplines studied in computer engineering is not limited to the above
Datasheet Definition
A datasheet is a document summarizing the performance and other characteristics of a component (e.g. an electronic component), a sub-system (e.g. a power supply) or software in sufficient detail to be used by a design engineer to design the component into a system. Typically a datasheet is created by system manufacturer and begins with an introductory page describing the rest of the document, followed by listings of specific components, with further information on the connectivity of the devices. In cases where there is relevant source code to include, it is usually attached near the end of the document or separated into another file.
Typical datasheet information
A typical datasheet for an electronic component contains most of the following information:
• manufacturer's name
• product number and name
• a list of available package formats (with images) and ordering codes
• notable device properties
• a short functional description
• pin connection diagram
• absolute minimum, maximum ratings (supply voltage, power consumption, input currents, temperatures for storage, operating, soldering, etc)
• recommended operating conditions (as absolute minimum, maximum ratings)
• a table of DC specifications (various temperatures, supply voltages, input currents etc)
• a table of AC specifications (various temperatures, supply voltages, frequencies etc)
• an input/output wave shape diagram
• physical device diagram showing minimum/typical/maximum physical dimensions, including contact locations and sizes
• test circuit
• ordering codes for differing packages and performance criteria
• liability disclaimer regarding device use in high risk environments such as nuclear power stations and life-critical systems
• application recommendations, such as required filter capacitors, circuit board layout, etc.
• Date and Revision Code at the end of the pages
• Errata Datasheet (Some manufactures use errata-datasheet before write a revision)
The datasheet sometimes contains circuit diagrams of typical use, however this information is often placed in a separate application note, with a high level of detail.
Historically, datasheets were typically available in a databook containing many data sheets, usually grouped by manufacturer or general type. Today, they are also available from the Internet in table form or downloadable PDF format.
Application notes
An application note is a document that gives more specific details on using a component in a specific application, or relating to a particular process, e.g. the physical assembly of a product containing the component. Application notes are especially useful for giving guidance on more unusual uses of a particular component, which would be irrelevant to many readers of the more widely read datasheet.
Application notes can either be appended to a datasheet, or presented as a separate document.
Typical details in PC datasheet
Following are details commonly listed on personal computer datasheets:
• Expansion bays
o 5.25 inch bays
o 3.5 inch bays
• Mainboard
o CPU socket
Front side bus (FSB)
Back side bus (BSB)
o Chipset
North bridge
South bridge
o Fans and temperature monitoring
o BIOS
o Form factor
• Graphics card
o AGP type
o Memory
• Audio card
Typical datasheet information
A typical datasheet for an electronic component contains most of the following information:
• manufacturer's name
• product number and name
• a list of available package formats (with images) and ordering codes
• notable device properties
• a short functional description
• pin connection diagram
• absolute minimum, maximum ratings (supply voltage, power consumption, input currents, temperatures for storage, operating, soldering, etc)
• recommended operating conditions (as absolute minimum, maximum ratings)
• a table of DC specifications (various temperatures, supply voltages, input currents etc)
• a table of AC specifications (various temperatures, supply voltages, frequencies etc)
• an input/output wave shape diagram
• physical device diagram showing minimum/typical/maximum physical dimensions, including contact locations and sizes
• test circuit
• ordering codes for differing packages and performance criteria
• liability disclaimer regarding device use in high risk environments such as nuclear power stations and life-critical systems
• application recommendations, such as required filter capacitors, circuit board layout, etc.
• Date and Revision Code at the end of the pages
• Errata Datasheet (Some manufactures use errata-datasheet before write a revision)
The datasheet sometimes contains circuit diagrams of typical use, however this information is often placed in a separate application note, with a high level of detail.
Historically, datasheets were typically available in a databook containing many data sheets, usually grouped by manufacturer or general type. Today, they are also available from the Internet in table form or downloadable PDF format.
Application notes
An application note is a document that gives more specific details on using a component in a specific application, or relating to a particular process, e.g. the physical assembly of a product containing the component. Application notes are especially useful for giving guidance on more unusual uses of a particular component, which would be irrelevant to many readers of the more widely read datasheet.
Application notes can either be appended to a datasheet, or presented as a separate document.
Typical details in PC datasheet
Following are details commonly listed on personal computer datasheets:
• Expansion bays
o 5.25 inch bays
o 3.5 inch bays
• Mainboard
o CPU socket
Front side bus (FSB)
Back side bus (BSB)
o Chipset
North bridge
South bridge
o Fans and temperature monitoring
o BIOS
o Form factor
• Graphics card
o AGP type
o Memory
• Audio card
What are the Frequency domain ?
Main article: Frequency domain
Signals are converted from time or space domain to the frequency domain usually through the Fourier transform. The Fourier transform converts the signal information to a magnitude and phase component of each frequency. Often the Fourier transform is converted to the power spectrum, which is the magnitude of each frequency component squared.
The most common purpose for analysis of signals in the frequency domain is analysis of signal properties. The engineer can study the spectrum to determine which frequencies are present in the input signal and which are missing.
Filtering, particularly in non realtime work can also be achieved by converting to the frequency domain, applying the filter and then converting back to the time domain. This is a fast, O(n log n) operation, and can give essentially any filter shape including excellent approximations to brickwall filters.
There are some commonly used frequency domain transformations. For example, the cepstrum converts a signal to the frequency domain through Fourier transform, takes the logarithm, then applies another Fourier transform. This emphasizes the frequency components with smaller magnitude while retaining the order of magnitudes of frequency components.
Frequency domain analysis is also called spectrum- or spectral analysis.
Applications
The main applications of DSP are audio signal processing, audio compression, digital image processing, video compression, speech processing, speech recognition, digital communications, RADAR, SONAR, seismology, and biomedicine. Specific examples are speech compression and transmission in digital mobile phones, room matching equalization of sound in Hifi and sound reinforcement applications, weather forecasting, economic forecasting, seismic data processing, analysis and control of industrial processes, computer-generated animations in movies, medical imaging such as CAT scans and MRI, MP3 compression, image manipulation, high fidelity loudspeaker crossovers and equalization, and audio effects for use with electric guitar amplifiers.
Implementation
Digital signal processing is often implemented using specialised microprocessors such as the DSP56000, the TMS320, or the SHARC. These often process data using fixed-point arithmetic, although some versions are available which use floating point arithmetic and are more powerful. For faster applications FPGAsmight be used. Beginning in 2007, multicore implementations of DSPs have started to emerge from companies including Freescale and startup Stream Processors, Inc. For faster applications with vast usage, ASICs might be designed specifically. For slow applications, a traditional slower processor such as a microcontroller may be adequate.
Techniques
• Bilinear transform
• Discrete Fourier transform
• Discrete-time Fourier transform
• Filter design
• LTI system theory
• Minimum phase
• Transfer function
• Z-transform
• Goertzel algorithm
Related fields
• Analog signal processing
• Automatic control
• Data compression
• Electrical engineering
• Information theory
• Telecommunication
Signals are converted from time or space domain to the frequency domain usually through the Fourier transform. The Fourier transform converts the signal information to a magnitude and phase component of each frequency. Often the Fourier transform is converted to the power spectrum, which is the magnitude of each frequency component squared.
The most common purpose for analysis of signals in the frequency domain is analysis of signal properties. The engineer can study the spectrum to determine which frequencies are present in the input signal and which are missing.
Filtering, particularly in non realtime work can also be achieved by converting to the frequency domain, applying the filter and then converting back to the time domain. This is a fast, O(n log n) operation, and can give essentially any filter shape including excellent approximations to brickwall filters.
There are some commonly used frequency domain transformations. For example, the cepstrum converts a signal to the frequency domain through Fourier transform, takes the logarithm, then applies another Fourier transform. This emphasizes the frequency components with smaller magnitude while retaining the order of magnitudes of frequency components.
Frequency domain analysis is also called spectrum- or spectral analysis.
Applications
The main applications of DSP are audio signal processing, audio compression, digital image processing, video compression, speech processing, speech recognition, digital communications, RADAR, SONAR, seismology, and biomedicine. Specific examples are speech compression and transmission in digital mobile phones, room matching equalization of sound in Hifi and sound reinforcement applications, weather forecasting, economic forecasting, seismic data processing, analysis and control of industrial processes, computer-generated animations in movies, medical imaging such as CAT scans and MRI, MP3 compression, image manipulation, high fidelity loudspeaker crossovers and equalization, and audio effects for use with electric guitar amplifiers.
Implementation
Digital signal processing is often implemented using specialised microprocessors such as the DSP56000, the TMS320, or the SHARC. These often process data using fixed-point arithmetic, although some versions are available which use floating point arithmetic and are more powerful. For faster applications FPGAsmight be used. Beginning in 2007, multicore implementations of DSPs have started to emerge from companies including Freescale and startup Stream Processors, Inc. For faster applications with vast usage, ASICs might be designed specifically. For slow applications, a traditional slower processor such as a microcontroller may be adequate.
Techniques
• Bilinear transform
• Discrete Fourier transform
• Discrete-time Fourier transform
• Filter design
• LTI system theory
• Minimum phase
• Transfer function
• Z-transform
• Goertzel algorithm
Related fields
• Analog signal processing
• Automatic control
• Data compression
• Electrical engineering
• Information theory
• Telecommunication
What are the Time and space domains?
Main article: Time domain
The most common processing approach in the time or space domain is enhancement of the input signal through a method called filtering. Filtering generally consists of some transformation of a number of surrounding samples around the current sample of the input or output signal. There are various ways to characterize filters; for example:
• A "linear" filter is a of input samples; other filters are "non-linear." Linear filters satisfy the superposition condition, i.e. if an input is a weighted linear combination of different signals, the output is an equally weighted linear combination of the corresponding output signals.
• A "causal" filter uses only previous samples of the input or output signals; while a "non-causal" filter uses future input samples. A non-causal filter can usually be changed into a causal filter by adding a delay to it.
• A "time-invariant" filter has constant properties over time; other filters such as adaptive filters change in time.
• Some filters are "stable", others are "unstable". A stable filter produces an output that converges to a constant value with time, or remains bounded within a finite interval. An unstable filter can produce an output that grows without bounds, with bounded or even zero input.
• A "finite impulse response" (FIR) filter uses only the input signal, while an "infinite impulse response" filter uses both the input signal and previous samples of the output signal. FIR filters are always stable, while IIR filters may be unstable.
Most filters can be described in Z-domain (a superset of the frequency domain) by their transfer functions. A filter may also be described as a difference equation, a collection of zeroes and poles or, if it is an FIR filter, an impulse response or step response. The output of an FIR filter to any given input may be calculated by convolving the input signal with the impulse response. Filters can also be represented by block diagrams which can then be used to derive a sample processing algorithm to implement the filter using hardware instructions.
The most common processing approach in the time or space domain is enhancement of the input signal through a method called filtering. Filtering generally consists of some transformation of a number of surrounding samples around the current sample of the input or output signal. There are various ways to characterize filters; for example:
• A "linear" filter is a of input samples; other filters are "non-linear." Linear filters satisfy the superposition condition, i.e. if an input is a weighted linear combination of different signals, the output is an equally weighted linear combination of the corresponding output signals.
• A "causal" filter uses only previous samples of the input or output signals; while a "non-causal" filter uses future input samples. A non-causal filter can usually be changed into a causal filter by adding a delay to it.
• A "time-invariant" filter has constant properties over time; other filters such as adaptive filters change in time.
• Some filters are "stable", others are "unstable". A stable filter produces an output that converges to a constant value with time, or remains bounded within a finite interval. An unstable filter can produce an output that grows without bounds, with bounded or even zero input.
• A "finite impulse response" (FIR) filter uses only the input signal, while an "infinite impulse response" filter uses both the input signal and previous samples of the output signal. FIR filters are always stable, while IIR filters may be unstable.
Most filters can be described in Z-domain (a superset of the frequency domain) by their transfer functions. A filter may also be described as a difference equation, a collection of zeroes and poles or, if it is an FIR filter, an impulse response or step response. The output of an FIR filter to any given input may be calculated by convolving the input signal with the impulse response. Filters can also be represented by block diagrams which can then be used to derive a sample processing algorithm to implement the filter using hardware instructions.
Article about Signal sampling
Main article: Sampling (signal processing)
With the increasing use of computers the usage of and need for digital signal processing has increased. In order to use an analog signal on a computer it must be digitized with an analog to digital converter (ADC). Sampling is usually carried out in two stages, discretization and quantization. In the discretization stage, the space of signals is partitioned into equivalence classes and quantization is carried out by replacing the signal with representative signal of the corresponding equivalence class. In the quantization stage the representative signal values are approximated by values from a finite set.
The Nyquist–Shannon sampling theorem states that a signal can be exactly reconstructed from its samples if the sampling frequency is greater than twice the highest frequency of the signal. In practice, the sampling frequency is often significantly more than twice the required bandwidth.
A digital to analog converter (DAC) is used to convert the digital signal back to analog. The use of a digital computer is a key ingredient in digital control systems.
With the increasing use of computers the usage of and need for digital signal processing has increased. In order to use an analog signal on a computer it must be digitized with an analog to digital converter (ADC). Sampling is usually carried out in two stages, discretization and quantization. In the discretization stage, the space of signals is partitioned into equivalence classes and quantization is carried out by replacing the signal with representative signal of the corresponding equivalence class. In the quantization stage the representative signal values are approximated by values from a finite set.
The Nyquist–Shannon sampling theorem states that a signal can be exactly reconstructed from its samples if the sampling frequency is greater than twice the highest frequency of the signal. In practice, the sampling frequency is often significantly more than twice the required bandwidth.
A digital to analog converter (DAC) is used to convert the digital signal back to analog. The use of a digital computer is a key ingredient in digital control systems.
What are the DSP domains ?
In DSP, engineers usually study digital signals in one of the following domains: time domain (one-dimensional signals), spatial domain (multidimensional signals), frequency domain, autocorrelation domain, and wavelet domains. They choose the domain in which to process a signal by making an informed guess (or by trying different possibilities) as to which domain best represents the essential characteristics of the signal. A sequence of samples from a measuring device produces a time or spatial domain representation, whereas a discrete Fourier transform produces the frequency domain information, that is the frequency spectrum. Autocorrelation is defined as the cross-correlation of the signal with itself over varying intervals of time or space.qq
How is Digital signal processing
Digital signal processing (DSP) is concerned with the representation of the signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing. DSP includes subfields like: audio and speech signal processing, sonar and radar signal processing, sensor array processing, spectral estimation, statistical signal processing, digital image processing, signal processing for communications, biomedical signal processing, seismic data processing, etc.
Since the goal of DSP is usually to measure or filter continuous real-world analog signals, the first step is usually to convert the signal from an analog to a digital form, by using Often, the required output signal is another analog output signal, which requires a Even if this process is more complex than analog processing and has a discrete value range, the stability of digital signal processing thanks to and being less vulnerable to noise makes it advantageous over analog signal processing for many, though not all, applications.
DSP algorithms have long been run on standard computers, on specialized processors called digital signal processors (DSPs), or on purpose-built hardware such as application-specific integrated circuit(ASICs). Today there are additional technologies used for digital signal processing including more powerful general purpose microprocessors, field-programmable gate arrays (FPGAs), (mostly for industrial apps such as motor control), and stream processors, among others
Since the goal of DSP is usually to measure or filter continuous real-world analog signals, the first step is usually to convert the signal from an analog to a digital form, by using Often, the required output signal is another analog output signal, which requires a Even if this process is more complex than analog processing and has a discrete value range, the stability of digital signal processing thanks to and being less vulnerable to noise makes it advantageous over analog signal processing for many, though not all, applications.
DSP algorithms have long been run on standard computers, on specialized processors called digital signal processors (DSPs), or on purpose-built hardware such as application-specific integrated circuit(ASICs). Today there are additional technologies used for digital signal processing including more powerful general purpose microprocessors, field-programmable gate arrays (FPGAs), (mostly for industrial apps such as motor control), and stream processors, among others
Some information about Electronic waste
Defective and obsolete electronic equipment.
Electronic waste, e-waste, e-scrap, or Waste Electrical and Electronic Equipment (WEEE) is a loose category of surplus, obsolete, broken, or discarded electrical or electronic devices. The processing of electronic waste in developing countries causes serious health and pollution problems due to lack of containment, as do unprotected landfilling (due to leaching) and incineration. The Basel Convention and regulation by the European Union and individual United States aim to reduce these problems. Reuse and computer recycling are promoted as alternatives to disposal as trash.
Definition
"Electronic waste" may be defined as all secondary computers, entertainment device electronics, mobile phones, and other items such as TVs and refrigerators, whether sold, donated, or discarded by their original owners. This definition includes used electronics which are destined for reuse, resale, salvage, recycling, or disposal. Others define the reusables (working and repairable electronics) and secondary scrap (copper, steel, plastic, etc.) to be "commodities", and reserve the term "waste" for residue or material which was represented as working or repairable but which is dumped or disposed or discarded by the buyer rather than recycled, including residue from reuse and recycling operations. Because loads of surplus electronics are frequently commingled (good, recyclable, and nonrecyclable), several public policy advocates apply the term "e-waste" broadly to all surplus electronics. The United States Environmental Protection Agency (EPA) refers to obsolete computers under the term "hazardous household waste"
Debate continues over the distinction between "commodity" and "waste" electronics definitions. Some exporters may deliberately leave difficult-to-spot obsolete or non-working equipment mixed in loads of working equipment (through ignorance, or to avoid more costly treatment processes). Protectionists may broaden the definition of "waste" electronics. The high value of the computer recycling subset of electronic waste (working and reusable laptops, computers, and components like RAM) can help pay the cost of transportation for a large number of worthless "commodities".
Problems
Rapid technology change, low initial cost, and even planned obsolescence have resulted in a fast-growing surplus of electronic waste around the globe. Dave Kruch, CEO of Cash For Laptops, regards electronic waste as a "rapidly expanding" issue. Technical solutions are available, but in most cases a legal framework, a collection system, logistics, and other services need to be implemented before a technical solution can be applied.
In the United States, an estimated 70% of heavy metals in landfills comes from discarded electronics, while electronic waste represents only 2% of America's trash in landfills. The U.S. Environmental Protection Agency (EPA) states that unwanted electronics totaled 2 million tons in 2005. Discarded electronics represented 5 to 6 times as much weight as recycled electronics. The Consumer Electronics Association says that U.S. households spend an average of $1,400 annually on an average of 24 electronic items, leading to speculations of millions of tons of valuable metals sitting in desk drawers. The U.S. National Safety Council estimates that 75% of all personal computers ever sold are now gathering dust as surplus electronics. While some recycle, 7% of cellphone owners still throw away their old cellphones.
Surplus electronics have extremely high cost differentials. A single repairable laptop can be worth hundreds of dollars, while an imploded cathode ray tube(CRT) is extremely difficult and expensive to recycle. This has created a difficult free-market economy. Large quantities of used electronics are typically sold to countries with very high repair capability and high raw material demand, which can result in high accumulations of residue in poor areas without strong environmental laws. Trade in electronic waste is controlled by the Basel Convention. However, the Basel Convention specifically exempts repair and refurbishment of used electronics in Annex IX.
Electronic waste is of concern largely due to the toxicity and carcinogenicity of some of its substances, if processed improperly. Toxic substances in electronic waste may include lead, mercury, and cadmium. Carcinogenic substances in electronic waste may include polychlorinated biphenyls (PCBs). Capacitors, transformers, and wires insulated with or components coated with polyvinyl chloride (PVC), manufactured before 1977, often contain dangerous amounts of PCBs.
Up to 38 separate chemical elements are incorporated into electronic waste items. Many of the plastics used in electronic equipment contain flame retardants. These are generally halogens added to the plastic resin, making the plastics difficult to recycle. The unsustainability of discarding electronics and computer technology is another reason commending the need to recycle or to reuse electronic waste.
When materials cannot or will not be reused, conventional recycling or disposal via landfill often follow. Standards for both approaches vary widely by jurisdiction, whether in developed or developing countries. The complexity of the various items to be disposed of, the cost of environmentally approved recycling systems, and the need for concerned and concerted action to collect and systematically process equipment are challenges. One study indicates that two thirds of executives are unaware of fines related to environmental regulations
Electronic waste, e-waste, e-scrap, or Waste Electrical and Electronic Equipment (WEEE) is a loose category of surplus, obsolete, broken, or discarded electrical or electronic devices. The processing of electronic waste in developing countries causes serious health and pollution problems due to lack of containment, as do unprotected landfilling (due to leaching) and incineration. The Basel Convention and regulation by the European Union and individual United States aim to reduce these problems. Reuse and computer recycling are promoted as alternatives to disposal as trash.
Definition
"Electronic waste" may be defined as all secondary computers, entertainment device electronics, mobile phones, and other items such as TVs and refrigerators, whether sold, donated, or discarded by their original owners. This definition includes used electronics which are destined for reuse, resale, salvage, recycling, or disposal. Others define the reusables (working and repairable electronics) and secondary scrap (copper, steel, plastic, etc.) to be "commodities", and reserve the term "waste" for residue or material which was represented as working or repairable but which is dumped or disposed or discarded by the buyer rather than recycled, including residue from reuse and recycling operations. Because loads of surplus electronics are frequently commingled (good, recyclable, and nonrecyclable), several public policy advocates apply the term "e-waste" broadly to all surplus electronics. The United States Environmental Protection Agency (EPA) refers to obsolete computers under the term "hazardous household waste"
Debate continues over the distinction between "commodity" and "waste" electronics definitions. Some exporters may deliberately leave difficult-to-spot obsolete or non-working equipment mixed in loads of working equipment (through ignorance, or to avoid more costly treatment processes). Protectionists may broaden the definition of "waste" electronics. The high value of the computer recycling subset of electronic waste (working and reusable laptops, computers, and components like RAM) can help pay the cost of transportation for a large number of worthless "commodities".
Problems
Rapid technology change, low initial cost, and even planned obsolescence have resulted in a fast-growing surplus of electronic waste around the globe. Dave Kruch, CEO of Cash For Laptops, regards electronic waste as a "rapidly expanding" issue. Technical solutions are available, but in most cases a legal framework, a collection system, logistics, and other services need to be implemented before a technical solution can be applied.
In the United States, an estimated 70% of heavy metals in landfills comes from discarded electronics, while electronic waste represents only 2% of America's trash in landfills. The U.S. Environmental Protection Agency (EPA) states that unwanted electronics totaled 2 million tons in 2005. Discarded electronics represented 5 to 6 times as much weight as recycled electronics. The Consumer Electronics Association says that U.S. households spend an average of $1,400 annually on an average of 24 electronic items, leading to speculations of millions of tons of valuable metals sitting in desk drawers. The U.S. National Safety Council estimates that 75% of all personal computers ever sold are now gathering dust as surplus electronics. While some recycle, 7% of cellphone owners still throw away their old cellphones.
Surplus electronics have extremely high cost differentials. A single repairable laptop can be worth hundreds of dollars, while an imploded cathode ray tube(CRT) is extremely difficult and expensive to recycle. This has created a difficult free-market economy. Large quantities of used electronics are typically sold to countries with very high repair capability and high raw material demand, which can result in high accumulations of residue in poor areas without strong environmental laws. Trade in electronic waste is controlled by the Basel Convention. However, the Basel Convention specifically exempts repair and refurbishment of used electronics in Annex IX.
Electronic waste is of concern largely due to the toxicity and carcinogenicity of some of its substances, if processed improperly. Toxic substances in electronic waste may include lead, mercury, and cadmium. Carcinogenic substances in electronic waste may include polychlorinated biphenyls (PCBs). Capacitors, transformers, and wires insulated with or components coated with polyvinyl chloride (PVC), manufactured before 1977, often contain dangerous amounts of PCBs.
Up to 38 separate chemical elements are incorporated into electronic waste items. Many of the plastics used in electronic equipment contain flame retardants. These are generally halogens added to the plastic resin, making the plastics difficult to recycle. The unsustainability of discarding electronics and computer technology is another reason commending the need to recycle or to reuse electronic waste.
When materials cannot or will not be reused, conventional recycling or disposal via landfill often follow. Standards for both approaches vary widely by jurisdiction, whether in developed or developing countries. The complexity of the various items to be disposed of, the cost of environmentally approved recycling systems, and the need for concerned and concerted action to collect and systematically process equipment are challenges. One study indicates that two thirds of executives are unaware of fines related to environmental regulations
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