2012
[COMPILATION OF TASK AND
PROJECTS IN CONSUMER
This compilation was created as a tribute and response to the leanings that I have got in this electronic vocational
course. This will also serve as a practical guide for beginners in this field. The main objective of this reading material is to
help students in understanding and learning electronics in an easier way. Further, i intend to awaken the interest not
only of the students, but also of others who are definitely exposed and involved to advance technology.
This compilation is equipped with instructions and illustrations that would help students and readers in resolving
problems regarding troubleshooting.
Nonetheless, even though, this reference contains reliable information, still, the reader must undergo adequate and
proper training in order to correctly apply theoretical and scientific knowledge that were included in this book.
I would like to thank Mr. Leo Diche
for his help and support
ELECTRONICS
Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes
and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible and electronics is widely used in information processing, telecommunications and signal processing. The ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a working system.
Electronics is distinct from electrical and electro-mechanical science and technology, which deals with the generation, distribution, switching, storage and conversion of electrical energy to and from other energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors and other passive components. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters, receivers and vacuum tubes.
Today, most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.
SAFETY PRECAUTIONS
By maintaining a safe working practice you will protect not only your own safety but that of others who will come into contact with your work.
Always ensure grounding straps and leads are intact and securely connected.
Always use the correct fire extinguisher. Water can conduct electric currents, Carbon dioxide (CO2) and appropriate Halogenated extinguishers should be used and in some cases foam is appropriate.
Always ensure interlock switches are operating properly
Always ensure your tools and test equipment are kept clean, in good working order and always use the appropriate tool for the job.
Always discharge capacitors in a circuit. Some capacitors such as those in a power supply will hold a lethal charge long after the power has been removed.
Always familiarise yourself with the safety precautions associated with any solvents or chemicals you are about to use. Many give off strong fumes which can ignite or cause drowsiness.
Always use appropriate tools, equipment and protective clothes, Buy the best you can afford.
Always use the recommended replacement component, many devices have built in safety measures and narrow tolerance bands.
Always wear protective equipment, protective boots, hard-hats, goggles, overalls etc when they are needed.
Always remove all rings, bracelets, medallions or anything which could get caught in moving machinery or may conduct electricity.
Always read the manufacturers data and information sheets. They are an invaluable source of information and safety procedures for the equipment under test.
Always when working with electricity, keep your left hand in your pocket where possible to avoid providing an electrical path through your chest and heart.
Do not work when you are tired or taking medicine which makes you drowsy or affects your reactions and concentration.
Do not work under poor lighting conditions
Do not work in areas which are damp
Never use an extension or adapter to overcome grounding straps or earth leads.
Never work in wet clothing
Never assume a circuit is off. Always check for power with the appropriate instrument.
Never meddle with safety devices
Never override interlock safety switches.
BASIC PRINCIPLES OF ELECTRONICS
1. VOLTAGE- Electrical potential, or voltage, is the force or electrical energy required to move electrons from one place to another. Symbol for Voltage: Letter E
Unit of measurement: Volt
Symbol for unit of measurement: Letter V
The difference in electrical potentials between two points in an electric field (the space surrounding an electric charge) is known as the electrical potential difference. This difference is proportional to the electrostatic force that tends to push electrons or other charge carriers from one point to the other. Potential difference, electrical potential, and electromagnetic force are measured in volts, leading to the commonly used term voltage.
To have an electrical energy source, such as a battery, one terminal must be more positive or more negative than the other. This condition may be referred to as a difference of potential, an electromotive force, a potential, or a voltage. All of the terms are correct; however, voltage is the most commonly used.
Battery terminals (or any other points) having unequal electrical charges have the capacity to move electrical charges through a resistance because of this difference of potential energy. An automobile battery has an electromotive force, potential difference, or voltage of 12 volts. It is correct to say that the automobile battery voltage equals 12 volts, or E = 12 Volts.
2. CURRENT
- Electric current flow is the movement of free electrons through a conductor. The rate of movement is measured in
amperes. One ampere represents the movement of a specific number of electrons (6.28 x 1018 electrons = 1 coulomb = unit of electric charge) past a certain point in a conductor in one second.
-
Symbol for Current: Letter I Unit of measurement: Ampere
Symbol for unit of measurement: Letter A
When controlled by an external force, the electrons move generally in the same direction. The effect of this movement is felt almost instantly from one end of the conductor to the other. The electron movement is called electric current.
Electric current, defined historically as conventional current, is the term used for current flow from the most positive
part of a circuit to the most negative part. However, to simplify circuit analysis, most electronics illustrations depict “electron current” flow from the most negative part of a circuit to the most positive part since it is only the negatively charged electrons that actually flow.
It should be noted that depending on the conditions, an electric current can consist of a flow of charged particles in either direction or even in both directions at once.
A direct current (DC) is a unidirectional flow, while an alternating current (AC) reverses direction repeatedly.
3. RESISTANCE
Resistance is the opposition a device or material offers to the movement of electrons and is measured in ohms. Symbol for resistance: Letter R
Unit of measurement: Ohms
Symbol for unit of measurement: Greek Letter Omega (Ω)
When there is current in a material, the free electrons move through the material and occasionally collide with atoms. These collisions cause the electrons to lose some of their energy and restrict their movement. The more collisions mean the more opposition to the flow of electrons. The higher the resistor value, the greater the opposition to current flow.
4. IMPEDANCE
- Electrical impedance, or simply impedance, is a measure of the combined opposing forces to an alternating electric current.
Symbol for impedance: Letter Z Unit of measurement: Ohms
Unlike electrical resistance even though both are measured in ohms, the impedance of an electric circuit can be a complex number because it is determined by the vector sum of a circuit’s resistance, capacitive reactance, and inductive reactance.
5. POWER
- Electric power is the rate at which electrical energy is produced or consumed and is measured in watts. Symbol for Power: Letter P
Unit of Measurement: Watt
Symbol for unit of measurement: Letter W
Energy is typically defined as the ability to do work or, more specifically, the work resulting from a force acting on mass over a distance. Electrical energy is the energy that’s stored in an electric field or transported by an electric current. Some examples of electrical energy include:
The energy that is constantly stored in the earth’s atmosphere and is partly released during a thunderstorm in the form of lightning.
The energy that is stored in the coils of an electrical generator in a power station and is then transmitted by wires to the consumer; the consumer then pays for each unit of energy received.
The energy that is stored in a capacitor and can be released to drive a current through an electrical circuit. The operation of electrical circuits involves force (voltage) acting on mass (electrons) over a distance.
As mentioned, energy is the capacity to do work, so in electrical circuits, energy is transformed into heat energy. When electrons flow through a conductor, the free electrons lose energy as they collide with atoms in the material. When there is current through a resistor, energy is converted to heat.
Power, therefore, can be viewed as the measure of how much energy is being converted to heat.
A common example of this is the light bulb. The current through the filament that produces light also produces heat because the filament has some opposition to current. All electrical devices dissipate or consume power. When an electrical component such as a light bulb or a stereo is connected to and draws current from a voltage source, the component is considered a load on that voltage source.
Every load device has a certain amount of resistance. This is load resistance. Load resistance is the resistance or opposition of the load device to current. Load current is the current drawn from the voltage source by the load device.
6. INDUCTANCE
- Inductance is an effect which results from the magnetic field that forms around a current-carrying conductor. Electrical current through the conductor creates a magnetic flux proportional to the current. A change in this current creates a change in magnetic flux that, in turn, generates an electromotive force (EMF) that acts to oppose this change in current. Inductance is a measure of the generated EMF for a unit change in current.
Symbol for Inductance: Letter L Unit of Measurement: Henry
Symbol for unit of measurement: Letter H
7. CAPACITANCE
- Capacitance is a measure of stored energy between two conductive electrodes, or plates, separated by an insulator (otherwise known as a capacitor). A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery.
Symbol for Capacitance: Letter C Unit of Measurement: Farad
Symbol for unit of measurement: Letter F
8. REACTANCE
- Reactance is the imaginary part of impedance and is caused by the presence of inductors or capacitors in the circuit. Reactance produces a phase shift between the electric current and voltage in the circuit.
Symbol for Reactance: Letter X Unit of Measurement: Ohms
Symbol for unit of measurement: Greek Letter Omega (Ω)
Inductive reactance (symbol XL) is caused by the fact that a current is accompanied by a magnetic field; therefore, a varying current is accompanied by a varying magnetic field––the latter gives an electromotive force that resists the changes in
current. The more the current changes, the more an inductor resists it: the reactance is proportional to the frequency (hence zero for DC). There is also a phase difference between the current and the applied voltage.
Capacitive reactance (symbol XC) reflects the fact that electrons cannot pass through a capacitor, yet effectively alternating current can: the higher the frequency the better. There is also a phase difference between the alternating current flowing through a capacitor and the potential difference across the capacitor’s electrodes.
ELECTRONIC PARTS AND EQUIPMENTS
CIRCUIT COMPONENTS- An electrical component is any component used in the generation, transmission, distribution, or consumption of electric power. The minimum requirements for a simple circuit are a power source, load device(s), and conductor(s). However, additional circuit components are usually added to provide control, protection, and monitoring capabilities.
I. POWER SOURCES
All electronic circuits require some source of energy in order to operate. Some of the more common sources for providing power are batteries, generators, and power supplies.
A. BATTERIES
- A battery is a device that converts chemical energy to electrical energy. A multicellular battery consists of two or more cells in a series (connected end-to-end). The negative terminal of one cell is connected to the positive terminal of another cell and so on to increase the battery’s voltage potential. Batteries can also be wired in parallel to increase their capacity.
B. GENERATORS
- An electrical generator is a device that converts mechanical energy to electrical energy, generally using the principle of electromagnetic induction. A force is required to provide the mechanical energy necessary to turn the rotor shaft of the generator and produce an electrical output. The driving force producing this mechanical energy input is called the prime mover. The prime mover can be any source of rotary motion such as that provided by waterfalls, windmills, steam engines, diesel engines, aircraft engines, or nuclear driving sources. Generator output is independent of the type of prime mover used, other than the requirement for a relatively constant rotational speed. A generator’s output voltage is controlled by a voltage regulator. A voltage regulator changes the output voltage by varying the resistance of the generator’s field circuit. Generators are rated in voltage amperes; in other words, how many volts they can produce at how many amps per phase.
C. POWER SUPPLIES
- A power supply, sometimes known as a power supply unit (PSU), is a device or system that supplies electrical or other types of energy to an output load or group of loads. The term is most commonly applied to electrical energy supplies such as rectifiers and inverters. Rectifiers are used to convert AC to DC while inverters are used to convert DC to AC.
II. LOAD DEVICES
A load is any device or circuit that absorbs power. Appliances plugged into a wall outlet are common examples of load devices. There are many electrical components that fit into this category, so we will only discuss a few of the main ones.
A. LAMP
- A lamp produces light from electricity and is often used to provide a visual indication of current flow. There are a wide variety of lamps used in electronics from standard filament-type lamps to light emitting diodes (LED).
B. RESISTOR
- A resistor is a passive device used to regulate current in a circuit. Electronic equipment uses a wide variety of
resistors made of resistive wire, metal film, or carbon composition. The two most common types of resistors are fixed and variable.
a) FIXED RESISTOR
- Many fixed resistors use a pattern of four, five, or six colored stripes (or bands) painted around the body of the resistor to indicate their resistance and tolerance values.
b) VARIABLE RESISTOR
- The variable resistor is a resistor whose resistance value can be adjusted, which in turn allows a circuit’s current value to be increased or decreased. Variable resistors, also called potentiometers or rheostats, are operated by turning a shaft or sliding a control. A common use of variable resistors is for dimming lights.
C. INDUCTOR
- Inductors are passive devices commonly used in signal processing circuits for their property of inductance, which, as you may recall, oppose changes in current. An inductor is usually constructed as a coil of conducting material, typically copper wire, wrapped around a core either of air or of ferromagnetic material. Core materials with a higher permeability than air confine the magnetic field closely to the inductor, thereby increasing the inductance. The opposition offered by a coil to the flow of alternating current is called inductive reactance.
D. CAPACITOR
- A capacitor is a passive electrical device that opposes changes in voltage and can be used to store energy in the electric field between a pair of closely spaced conductors called plates. When voltage is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each plate. They can also be used to differentiate between high-frequency and low-frequency signals, and this makes them useful in electronic filters.
III. SEMICONDUCTOR DEVICES
Semiconductor devices are electronic components that exploit the electronic properties of certain Semi-conductive materials– –typically silicon, germanium, and gallium arsenide. They use electronic conduction in the solid state by introduction of an electric field or from exposure to light, pressure, or heat; thus, semiconductors can make excellent sensors.
A. DIODE
- A diode is an active component that restricts the direction of movement of charge carriers. Essentially, it allows an electric current to flow in one direction but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a check valve.
B. TRANSISTOR
- A transistor is a semiconductor device that uses a small amount of voltage or electrical current to control a larger change in voltage or current. A transistor can be thought of as an electronic version of a switch and is the fundamental building block of the circuitry that governs the operation of all modern electronics.
IV. ELECTROMAGNETIC DEVICES
Electromagnetic devices exploit the properties of the region of space where electric charges experience a physical influence. This region is commonly called the electromagnetic field. The term electromagnetism comes from the fact that electrical and magnetic forces are involved simultaneously. The phenomenon of electromagnetic induction, which provides for the operation of electrical generators, induction motors, and transformers, is based on the principle that a changing electric field generates a magnetic field. Similarly, a changing magnetic field produces an electric field.
A. TRANSFORMERS
- A transformer is a device that is used to transfer electrical energy from one circuit to another by means of an electromagnetic field. One circuit is connected to a power source and is referred to as the primary. The other circuit is connected to a load device and is referred to as the secondary. Transformers operate using the principles of mutual induction and electromagnetism as there are no direct connections between the primary and secondary windings. A transformer may perform several functions depending on its purpose in the circuit; it may increase (step up) voltage and decrease the current, decrease (step down) voltage and increase current, isolate circuits, match impedance of different circuits, or shift phases between circuits. Accordingly, transformers come in a range of sizes and can be
classified in many ways such as by its power level, frequency, voltage class, or by a ratio of the amount of voltage required to step up or down.
B. RELAYS AND SOLENOIDS
- Relays and solenoids are used for controlling or switching electrical circuits from a remote location. The primary circuit is the controlling or actuating circuit. The current flow that energizes the coil of the relay is the primary current. The secondary circuit is the controlled circuit. A relay’s contacts are made to close or open. Closed contacts provide continuity in the controlled or secondary circuit of a relay; open contacts remove continuity from the secondary circuit. The configuration of contacts available may offer one or many secondary circuit paths. One possible application of a relay is to use a single primary current path to control several secondary current paths.
C. MOTORS
- Electric motors convert electrical energy into mechanical energy. They come in many types and sizes that allow them to perform different tasks. They work on the principle that electrical energy develops a magnetic field that produces a mechanical force. The mechanical force of attraction and repulsion rotates a shaft 360 degrees. DC motors are commonly used in battery-operated devices such as drills, shavers, toys, or larger items, such as a golf cart. They are also found in some AC devices after being rectified for use in low-voltage applications such as video cassette recorders and compact disc players.
V. CONDUCTORS
Of course, simply having a power source and load device does not make a circuit. They must be connected for continuity. This is usually accomplished by wiring or soldering the components together resulting in a closed loop. On electronic drawings, or schematics, wires are illustrated as the line(s) that connect two or more components together.
A. WIRING
A wire is a single, usually cylindrical, elongated strand of drawn metal.
Types
There are several types of wiring used to carry electricity and telecommunications signals.
SOLID – solid wire or solid-core wire consists of one piece of metal wire.
STRANDED - Stranded wire is composed of a bundle of small-gauge wires wrapped in a particular pattern inside insulation to
make a larger conductor. Stranded wire is more flexible than a solid strand of the same overall gauge.
CABLES - Cables are two or more wires that are bound together, typically in a common protective jacket or sheath.
TWISTED PAIRS - Twisted-pair cabling is a form of wiring in which two conductors are wound together for the purposes of
cancelling out radio frequency interference and electromagnetic interference (RFI/EMI) from external sources and cross talk from neighboring wires.
COAXIAL - Coaxial cable is made up of two wires: a wire conductor in the center and a circumferential outer conductor with
an insulator separating the two conductors. The dimension and material of the conductors and insulation determine the cables’ characteristic impedance and attenuation at various frequencies.
FIBER-OPTIC – Fiber-optic cables are not made out of metal but rather glass or plastic fibers that are designed to guide light
along the fiber length by total internal reflection. A layer of cladding surrounds the fiber to redirect light and keep it within the core. Fiber-optic cables are often used as a medium for telecommunication and networking because they offer the advantages of improved bandwidth and noise immunity over traditional types of wiring.
B. SOLDERING
Soldering is a method of joining metal parts using a filler material (solder) that has a low melting point, typically below 450 degrees Celsius (450° C) (842° Fahrenheit [F]). In the soldering process, heat is applied to the parts to be joined causing the solder to melt and be drawn into the joint by capillary action. The most frequent application of soldering is assembling electronic components to printed circuit boards (PCB). PCBs are used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a nonconductive substrate.
VI. CONTROL DEVICES
Control devices allow the operator to control the aspects of the circuit’s operation. The most common control device is the switch. A switch is a device for changing the flow of current in a circuit; a switch, when closed, provides zero resistance to the circuit while an open switch introduces an infinite amount of resistance. Switches are commonly used to apply power or to control a certain function of a circuit. There are several types of switches, but you will primarily be concerned with single-pole single-throw (SPST), single-pole double-throw (SPDT), and double-pole double-throw (DPDT) switches.
A. SINGLE-POLE SINGLE-THROW SWITCH
- An SPST switch is a simple on-off switch, such as a light switch, that either opens or closes the circuit. The P refers to the term pole, which is the movable portion or arm of the switch. The T is the throw, which identifies the number of circuits that the pole opens or closes when the switch is operated.
B. SINGLE-POLE DOUBLE-THROW SWITCH
- An SPDT switch is a toggle switch that provides a continuity path to one of two possible circuits. Figure 1–10 shows the switch, or “bat” that toggles between one of the two circuit paths. An example of a SPDT switch is an AM/FM selector switch on a radio.
C. DOUBLE-POLE DOUBLE-THROW SWITCH
- A DPDT switch provides twice the options as a SPDT switch. It could be used to connect two circuits together by throwing one switch that is mechanically connected as illustrated by the dashed line.
VII. PROTECTIVE DEVICES
Protective devices provide current limiting with the purpose of protecting circuits from the harmful effects of excess current flow. Excess current, if permitted to flow, can cause circuitry to become hot and melt, resulting in an open circuit and possibly damaging components along the way. Current limiters can reduce the peak current flowing in a circuit by taking the excess current for a short period until the fault clears or until additional protective devices activate. The most common protective devices are fuses and circuit breakers.
A. FUSES
- A fuse is a type of overcurrent protection device. Its critical component is a thin metal wire that will melt when heated by a prescribed electric current, opening the circuit of which it is a part, and so protecting the circuit from an overcurrent condition. Fuses are rated with current and voltage ratings that indicate the maximum circuit current and voltage in which the fuse can be used. Fuses should be replaced with only suitable substitutes even though many fuses are physically the same size. You can replace a blown (open) fuse with another having the same size, voltage, and current characteristics, or it is permissible to use one with a larger voltage rating and/or a smaller current rating. For example, fuses carrying a 250V rating can be safely used in a 125V circuit, but a 125V fuse cannot be used in a 250V circuit as the fuse may not be capable of safely interrupting the arc in a circuit of a higher voltage. Conversely, fuses carrying a 2 amp rating can be safely used in a 5 amp circuit, but a 5 amp fuse cannot be used in a 2 amp circuit.
B. CIRCUIT BREAKERS
- A circuit breaker serves the same purpose as a fuse, but it works a little differently. When excessive current passes through a circuit breaker, it energizes and creates a break in the circuit. When this happens, the circuit breaker is said to have “tripped” or “popped.” An advantage of the circuit breaker over the fuse is the ability to reset and reuse the circuit breaker after the overload has been removed, while the fuse must be replaced.
C. GROUND
- Ground is a point in a circuit used as a common reference point from which voltages are measured. Voltages may be either positive or negative with respect to ground, which has a potential of zero volts. You are probably familiar with the electrical ground on an automobile where the chassis is the common reference point. Ground may be either an earth ground, which means that point has been connected to a metal stake driven into the earth; or as in the case of most electronic equipment, the ground symbol denotes the metal chassis. When completing each electrical circuit, common points are connected directly to the metal chassis; current flows through the metal chassis (conductor) to each other points of the circuit.
ELECTRONIC SIGN AND SYMBOLS
CELLPHONE REPAIR TOOLS AND EQUIPMENTS
Basically these are the primary tools when you are going to repair cell phones.
1. Multi-Tester ( Analog/Digital)- Used to measure Voltages, Currents and Resistance in electronic components. 2. Screwdrivers - Used to loosen the phones screws.
3. Tweezers - used to hold and pick small cell phone component parts. 4. Soldering iron - used to solder / re-solder electronic parts.
6. Soldering Flux and Paste - Used to tightened soldering quality.
7. BGA Rework station - Applied Heat to remove and replaced parts and IC chips.
8. Re balling Kits - Tools for re balling IC bumps, this composed of Stencil plates, Ball Leads and Spatula
9. DC Regulated Power Supply- Used to substitute battery voltage when working on hardware troubleshooting. 10. Flashing and Unlocking Device- it is a Software Tool that is used to unlock and flash mobile phones
programmable circuits.
11. Cables and Wires - Used as an Interface from PC to cell phones when working on like flashing, unlocking and jail breaking.
PARTS OF ANALOG
MULTITESTER
1. Indicator Zero Connector 2. Indicator Pointer
3. Indicator Scale
4. Continuity Indicating 5. Range Selector Switch knob
0-ohms adjusting knob /0- centering meter
(NULL meter) adjusting knob 6. Measuring Terminal + 7. Measuring Terminal - COM 8. Series Terminal Capacitor OUTPUT 9. Panel
10. LED (CONTINUITY) 11. Rear Case
1.) Resistance (OHMS) scale
2.) DCV, A scale and ACV scale (10V or more)
3.) 0-centerig (NULL) +/- DCV scale 4.) ACV 2.5 (AC 2.5V) exclusive scale 5.) Transistor DC amplification factor (hFE) scale
6.) 1.5 battery test (BATT 1.5V) 7.) OHMS range terminal to terminal current
(Li) scale)
8.) OHMS range terminal to terminal voltage
(LV) scale
9.) Decibel (dB) scale
10.) Continuity Indicating LED 11.0 Mirror: To obtain most accurate readings, the mirror is devised to make operator eyes, the indicator pointer, and the indicator pointer reflexed to the mirror put together in line.
TOOLS TO MAKE A PROPER SOLDER
MATERIALS FOR SOLDERING
1. Master Appliance Soldering Iron 2. Modeler’s Vise or Frame
3. Solder 4. Damp Sponge 5. Flux to remove oxides
RUNNING LIGHTS USING LED
If we wasp one size miniature serial loudspeaker (8 ohm speaker) suits, Flashing LED number FRL – 4403 will lighten and can blink. But it must not use other equipment help unless, power supply is given with it only. You will already hear the sound goes out the loudspeaker in the rhythm that it works with.
VOLTAGE
DOUBLER/MULTIPLIER
PARTS: U1 NE555 timer IC R1 2.2k ohm resistor R2 15k ohm resistor C1 0.01 uF ceramic capacitor C2, C3 220 uF electrolytic capacitor C4 470 uF electrolytic capacitor D1, D2 1N4002 diodeAll resistors are 5 or 10 percent tolerance, 1/4-watt all capacitors are 10 percent tolerance This circuit roughly doubles the voltage of the input, however the current output is low. Doubled output is at 'V
source.'
SWITCH-MODE POWER SUPPLY(SMPS)
A switched-mode power supply (switching-mode power supply, SMPS, or simply switcher) is an electronic power supply that incorporates a switching regulator in order to be highly efficient in the conversion of electrical power. Like other types of power supplies, an SMPS transfers power from a source like the electrical power grid to a load (such as a personal computer) while converting voltage and current characteristics. An SMPS is usually employed to efficiently provide a regulated output voltage, typically at a level different from the input voltage.
Unlike a linear power supply, the pass transistor of a switching mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions (which minimizes wasted energy). Ideally, a switched-mode power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight.
BASIC POWER SUPPLY USING REGULATOR
A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.
Measures of regulator quality
The output voltage can only be held roughly constant; the regulation is specified by two measurements:
load regulation is the change in output voltage for a given change in load current (for example: "typically 15 mV,
line regulation or input regulation is the degree to which output voltage changes with input (supply) voltage
changes - as a ratio of output to input change (for example "typically 13 mV/V"), or the output voltage change over the entire specified input voltage range (for example "plus or minus 2% for input voltages between 90 V and 260 V, 50-60 Hz").
AUDIO AMPLIFIER(LM383)
An audio power amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio power amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio power amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts.
Mission Cyrus 1 Hi Fi integrated audio amplifier (1984)
AMPLIFIERS
The task of an audio amplifier is to take a small signal and make it bigger without making any other changes in it. This is a demanding task, because
a musical sound usually contains several frequencies, all of which must be amplified by the same factor to avoid changing the waveform and hence the quality of the sound. An amplifier which multiplies the amplitudes of all frequencies by the same factor is said to be linear. Departures from linearity lead to various types of distortions.
The operational details of amplifiers are buried in the field of electronics, but for audio purposes it is usually safe to say that current commercial audio amplifiers are so good that a normally operating amplifier is seldom the limitation on the fidelity of a sound reproduction system. One must be sure that the amplifier can provide enough power to drive the existing loudspeakers, but otherwise amplifiers are typically one of the most trouble-free elements of a sound system.
AMPLIFIER DISTORTION
The amplitudes of all frequencies within an amplifier's operating range must be amplified by the same factor to avoid distortion. An amplifier which satisfies this requirement is said to be perfectly linear. If the peaks of the waveform are clipped, this gives rise to what is called harmonic distortion. Another type of distortion is intermodulation distortion, which occurs when different frequencies in the signal mix to produce sum and difference frequencies which didn't exist in the signal. Transient distortion occurs when amplifier components cannot handle the rate of change of the signal, for example in rapid percussive attacks. There is also transient intermodulation distortion (TIM) to which modern integrated circuits are susceptible. Such circuits depend upon feedback for their linearity, but time delays in the feedback can cause intermodulation distortion on fast transients in the signal.
100 WATTS AMPLIFIER DIAGRAM
DescriptionThis is the circuit diagram of a fully transistorized sub woofer amplifier that can produce an output of 100W.There are seven transistors including four in the output stage. The transistors Q1 and Q2 form the preamplifier stage. Transistors Q4 to Q7 form the output stage. Since no ICs are used the circuit is very robust and can be easily assembled on a general purpose PCB.
Circuit diagram with Parts list.
Notes.
The circuit can be powered from a +35V/-35V, 5A dual power supply.
Use a 100W, 12 inch sub woofer at the output.
All electrolytic capacitors must be rated 100V.
INFARED SENSOR
IR detectors are little microchips
with a photocell that are tuned to
listen to infrared light. They are
almost always used for remote
control detection - every TV and
DVD player has one of these in the
front to listen for the IR signal
from the clicker. Inside the remote
control is a matching IR LED, which
emits IR pulses to tell the TV to
turn on, off or change channels. IR
light is not visible to the human
eye, which means it takes a little
more work to test a setup.
SCHEMATIC DIAGRAM OF RADIO
HISTORY OF TELEVISION
COLOR TELEVISION is part of the history of television, the technology of television and practices associated with television's
transmission of moving images in color video.
In its most basic form, a color broadcast can be created by broadcasting three monochrome images, one each in the three colors of red, green and blue (RGB). When displayed together or in rapid succession, these images will blend together to produce a full color image as seen by the viewer.
One of the great technical challenges of introducing color broadcast television was the desire to conserve bandwidth, potentially three times that of the existing black-and-white (B&W) standards, and not use an excessive amount of radio spectrum. In the United States, after considerable research, the National Television Systems Committeeapproved an all-electronic system developed by RCA which encoded the color information separately from the brightness information and greatly reduced the resolution of the color information in order to conserve bandwidth. The brightness image remained compatible with existing B&W television sets at slightly reduced resolution, while color televisions could decode the extra information in the signal and produce a limited-resolution color display. The higher resolution B&W and lower resolution color images combine in the eye to produce a seemingly high-resolution color image. The NTSC standard represented a major technical achievement.
TV VERTICAL SECTION PROBLEMS AND SOLUTIONS
.
Vertical lock lost:
This indicates a picture that is correct but rolling vertically. If the picture is rolling down the screen the frequency of the verticaloscillator is incorrect - too high - and this may be the problem. Generally,the free run frequency of the vertical oscillator should be a little belowthe video rate (of around 50 or 60 Hz depending on where you live). If it is rolling continuously without jumping, then there is a loss ofsync from the sync separator or faulty components in the vertical oscillatorcausing it to totally ignore the sync pulses. If it is rolling up rapidly and not quite able to remain locked, the freerun frequency may be too low or there could be a fault in the sync circuits resulting in an inadequate vertical pull-in range. On older sets, there was actually a vertical hold (and possibly even aSeparate vertical frequency) control. On anything made in the last decade, this is unlikely. There may be Vertical Frequency and Vertical Pull-in Range adjustments (and others) accessible via the service menu. However, if any of these ever change, it indicates a possible problem with the EEPROMlosing its memory as component drift is unlikely. As with everything else, bad connections are possible as well. You will need a schematic and possibly setup info to go beyond this.
Vertical squashed:
This is a vertical deflection problem - possibly a bad capacitor, badconnection, flyback/pump up diode, or other component. None of these should be very expensive (in a relative sort of way). If the symptoms change - particularly if they become less severe - as the set warms up, a dried up electrolytic capacitor is most likely. If they get worse, it could be a bad semiconductor. Freeze spray or a heat gun may be useful in identifying the defective component. It is often easiest to substitute a good
capacitor for each electrolytic in the vertical output circuit. Look for bad connections (particularly to the deflection yoke), then consider replacing the vertical output IC or transistor(s). A defective deflection yoke is also possible or in rare cases, a bad yoke damping resistor (e.g., 500 ohms, may be mounted on the yoke assembly itself). The following are NOT possible: CRT, flyback, tuner (except for the famous RCA/GE/Proscan or Sony models where the controller is at fault - see the sections on these specific brands). I am just trying to think of really expensive parts that cannot possibly be at fault :-). Note that some movies or laser karaoke discs are recorded in 'letterbox'format which at first glance looks like a squashed vertical problem. However, the picture aspect ratio will be correct and turning up the brightness will reveal a perfectly normal raster above and below the picture.
Part of picture cut off:
The following applies if the part of the picture is missing but nototherwise squashed or distorted. For example, 85% is missing but theportion still visible is normal size. Wow! That's an interesting one, more so than the typical run-of-the-mill"my TV just up and died on me". Or, "my pet orangutan just put a holein the CRT, what should I do"? Since the size of the picture fragment is correct but 85% is missing,my first thought would be to check waveforms going into the verticalOutput stage. The supply voltage is probably correct since that oftenDetermines the size. It almost sounds like the waveform rather thanbeing mostly on (active video) and off for the short blanking periodis somehow only on during the last part of the active video thus givingyou just the bottom of the picture. If there is a vertical output IC,it may be defective or the blanking input to it may be corrupted. Theproblem may be as far back as the sync separator. Then again who knows,maybe wait for the schematics.
Single Vertical Line:
CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots. Since you have high voltage, the horizontal deflection circuits are almost certainly working (unless there is a separate high voltage power supply - almost unheard of in modern TVs and very uncommon in all but the most expensive monitors). Check for bad solder connections between the main board and the deflection yoke. Could also be a bad horizontal coil in the yoke, linearity coil, etc.There is not that much to go bad based on these symptoms assuming the high voltage and the horizontal deflection use the same fly back. It is almost certainly not an IC or transistor that is bad.
TWEAKING HORIZONTAL SECTON PROBLEMS OF TELEVISION
From: "Phil Nelson"
Subject: horizontal problem (or not?) in National TV-7W television
After much work, I have a good picture on my National TV-7W television.
If I turn up the brightness enough to show some retrace lines, however,
a faint vertical bar appears at the left of the screen.
It's almost as if the scan flies a little "too far left" before getting
back in sync. If I reduce the brightness to make the retrace lines
disappear, this problem disappears. Horizontal and vertical lock are
very stable.
Here is the schematic for the TV's horizontal section.
The vertical bar doesn't appear to contain any data. This looks more like a
retrace issue.
A little while ago, I adjusted the drive trimmer cap on pin 4 of the
horizontal output tube to correct a horizontal linearity problem
that caused the picture to be too squished and bright on the right side.
The 4.7 meg resistor on pin 4 has been replaced, but the two 47K
resistors have not been replaced. The trimmer is turned as far as it
can go at this point. Should I mess with other components on the output
tube until I can get a little more adjustment out of it? Or is that
barking up the wrong tree?
The actual picture looks considerably better than this blurry off-air
snapshot. If I turn down the brightness a bit, this problem is masked, but
it's distracting when changing channels. The ideal brightness/contrast/fine
tune adjustment for one channel won't necessarily give the best picture on
another station. Which brings up other questions involving AGC and
alignment, but . . . ---
From: "Brenda Ann"
That's the horizontal blanking interval... it's the same as the vertical
blanking interval, but at horizontal frequency (the bar you see when the
picture 'rolls'). Normally, I have seen this bar on the right side of the
screen, but depending upon the peculiarities of your horizontal sync
circuit it could sit on the left as well. It's not a big deal, but you can
try adjusting your horizontal hold to see if the bar disappears.
---
From: Robert Casey
Looks like a phase error. That is, the phase of the horizontal oscillator's
output is off in terms of time compared to the video signal. Looks like the
oscillator is a few microseconds too early in commanding a retrace. There
usually are RC circuits to separate the horizontal sync from the vertical
sync, and if one or more parts in those RC circuits are way off, could
cause phase errors.
Or a bad resistor in the oscillator could do it. I assume you replaced all
the wax caps. Don't use ceramic caps though, temperature drift can mess
up horizontal oscillators.
It's also possible that the designers expected you to over scan the image
more. C78, R33, R10 and R35 may be making a variable phase shifter as
well as horiz size. Adjusting R10 for more over scan might remove the phase
error. Of course the horizontal sync bar will disappear, but be sure the
TV image center is centered.
TELEVISION PROBLEM SYMPTOMS AND SOLUTIONS
WEAK CONTRASTThis symptom can be divided into two cases. One is accompanied with too much noise or snow, the other is not (simply weak in contrast).
Cause: Weak contrast and snowy picture are caused by a trouble in the antenna or in the RF amplifier circuit.
Plain weak contrast is caused by a trouble between the mixer and the video amplifier circuit inclusive. TROUBLE-SHOOTING PROCEDURE
Check whether the TV set has a weak contrast reception in all channels. If you observe weak contrast in only one station, check the faulty contact in the tuner. If there is weak contrast in all channels, adjust the AGC control (both RF and AGC) first. If the symptom cannot be eliminated, check if the symptom is accompanied with snow or not. If the picture is snowy, check for an open circuit in the antenna feeder cable or in the RF amplifier circuit. If the picture is not snowy, observe the output signal of the video detector with an oscilloscope. Normally, a signal of around 1.5 V p-p to 2 V p-p can be observed. If the strength of the signal is very low, check the mixer, VIF, video detector and the AGC circuits. If the output voltage of the video detector is normal, check the video amplifier circuit.
NO COLOR
This symptom is characterized by a monochrome picture even during color reception. There are three cases of this symptom. 1) color loss in all channels, 2) color loss in a particular channel and 3) intermittent color loss.
Cause
1 No color in all channels. A trouble in any of the following circuits may cause the symptom: bandpass amplifier, ACC, color killer, 3.58 MHz oscillator, 3.58 MHz output, burst gate and burst amplifier circuits.
2. No color in some or in a particular channel. This symptom is caused by a
misadjustment in the fine-tuning circuit (shift in the local oscillator frequency) or a loose contact in the channel selector switch.
3 Intermittent color loss. This is caused by a loose contact in the channel selector, mismatch between the antenna and the receiver or an intermittent operation of the 3.58 MHz oscillator.
TROUBLE-SHOOTING PROCEDURE
a Solid-state circuits
The trouble-shooting procedure for color loss in all channels will be discussed.
Nevertheless, it may serve as reference for trouble-shooting the receiver for the other cases of color loss.
Note that for this symptom, the defective component may be in any of the numerous possible defective circuits. Thus, for an efficient and prompt trouble-shooting, observe the symptom carefully. The exact method of trouble-shooting a receiver for this kind of symptom varies with the type of circuit used in the chroma or color circuits. The troubleshooting details that will be given are for circuits similar to the one given in Fig. 21-2. However, the trouble-shooting flow chart shown in Fig. 21-1 may be used as reference in trouble-shooting other types of circuits. First, adjust the fine-tuning control with the color intensity set at maximum and the
color killer set at minimum. If you cannot get the color, trouble-shoot the color circuits. Short the collector and the emitter of the ACC transistor (Q2) in Fig. 21-2. If the
color appears, the ACC circuit is defective. Otherwise, if you cannot regain the color, disconnect the short across the collector and the emitter of the ACC transistor and ground the emitter of the second bandpass transistor (Q3). After doing so, adjust the color killer control. If you cannot get the color, the trouble may be in the bandpass amplifier circuit. Otherwise, if you recover a normal color, the color killer circuit is defective. But if the brighter parts of the picture have a weak tint of blush green, the 3.58 MHz oscillator or the 3.58 MHz output circuit may be defective.
WEAK COLOR
This symptom is also usually referred to as faded or insufficient color. It is characterized by a weak maximum color
reproduction. This symptom can be divided into two cases: 1) weak color in all channels and 2) weak color in some stations.
Cause: Weak color in all channels is caused by a breakdown in the ACC circuit or by a bandpass amplifier with a decreased
gain. Weak color in some stations is caused by a poorly tuned fine-tuning circuit, a mismatch between the antenna and the feeder cable, a defective antenna, a defective feeder cable or an aging tuner.
TROUBLE-SHOOTING PROCEDURE
Set the color control at maximum and then adjust the fine-tuning circuit with the finetuning knob to get maximum color for every station. If only some stations have weak
color, check the condition and the matching of the antenna and the feeder cable. A mismatch between the antenna and the feeder cable affects the receiver’s reception and good color reproduction cannot be expected. Otherwise, if all channels have weak color and the color strength is not uniform, trouble-shoot the ACC and the bandpass amplifier.
A simple method of detecting a mismatch is to wrap the antenna cable just before the antenna terminals of the receiver with an aluminum foil about 10 cm long. Move the foil slowly away from the antenna terminals and observe its effect on the color on the screen.
If the color intensity changes as the foil is moved, then a mismatch between the cable and the antenna is confirmed. This mismatch causes weak color reproduction.
BASIC INFORMATION HOW CELLPHONE WORKS?
How Cellphone Works?As a basic Part of a Technician, It is fully advice that he/she must posses a basic knowledge of what technology he or she come up to.. Before we procced further, please take a simple brief to inhanced your knowlegde about the Field of What we are going to discuss hereafter.... Now first come first we all ever wonder how does the cellphone works?
Have you ever wondered how a cell phone works? What makes it different from a regular phone? What's inside of it and how do they created it? What do all those terms like PCS, GSM, CDMA and TDMA mean?
To start with, one of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). It was only natural that these two great technologies would eventually be combined.
If you prepare to take a deep knowledge, i recommended you to visit this site and have a brief of Fundamentals of Wireless Communication
A basic technician all need is just to have a simple understanding about cellphones, we do not need extreme and intimate deeper meaning about it, that's because what we are going to take around here is to fix what those various mobile phones company created and build....to make it as simple as that... We are going to fix somewhat if their product gets busted by the end user's who bought it...below is just a simple basic information I gathered to compensate somewhat of what we are going to learn.
Cell Phone Network Technologies: 2G Technology
There are three common technologies used by 2G cell-phone networks for transmitting information: * Frequency division multiple access (FDMA)
* Time division multiple access (TDMA) * Code division multiple access (CDMA)
Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one.
The first word tells you what the access method is. The second word, division, lets you know that it splits calls based on that access method.
* FDMA puts each call on a separate frequency.
* CDMA gives a unique code to each call and spreads it over the available frequencies.
The last part of each name is multiple access. This simply means that more than one user can utilize each cell. FDMA
FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band. FDMA is used mainly for analog transmission. While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission.
In FDMA, each phone uses a different frequency. TDMA
TDMA is the access method used by the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots.
Narrow band means "channels" in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has three times the capacity of an analog system using the same number of channels. TDMA systems operate in either the 800-MHz (IS-54) or 1900-MHz (IS-136) frequency bands.
TDMA splits a frequency into time slots. Unlocking Your GSM Phone
Any GSM phone can work with any SIM card, but some service providers "lock" the phone so that it will only work with their service. If your phone is locked, you can't use it with any other service provider, whether locally or overseas. You can unlock the phone using a special code -- but it's unlikely your service provider will give it to you. There are Web sites that will give you the unlock code, some for a small fee, some for free.
GSM
TDMA is also used as the access technology for Global System for Mobile communications (GSM). However, GSM implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III. GSM systems use encryption to make phone calls more secure. GSM operates in the 900-MHz and 1800-MHz bands in Europe and Asia and in the 850-MHz and 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. It is used in digital cellular and PCS-based systems. GSM is also the basis for Integrated Digital Enhanced Network (IDEN), a popular system introduced by Motorola and used by Nextel.
GSM is the international standard in Europe, Australia and much of Asia and Africa. In covered areas, cell-phone users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service providers in these different countries, GSM users simply switch subscriber identification module (SIM) cards. SIM cards are small removable disks that slip in and out of GSM cell phones. They store all the connection data and identification numbers you need to access a particular wireless service provider.
Unfortunately, the 850MHz/1900-MHz GSM phones used in the United States are not compatible with the international system. If you live in the United States and need to have cell-phone access when you're overseas, you can either buy a tri-band or quad-band GSM phone and use it both at home and when traveling or just buy a GSM 900MHz/1800MHz cell phone for traveling. You can get 900MHz/1800MHz GSM phones from Planet Omni, an online electronics firm based in California. They offer a wide selection of Nokia, Motorola and Ericsson GSM phones. They don't sell international SIM cards, however. You can pick up prepaid SIM cards for a wide range of countries at Telestial.com.
CDMA
CDMA takes an entirely different approach from TDMA. CDMA, after digitizing data, spreads it out over the entire available
bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range.
In CDMA, each phone's data has a unique code. All of the users transmit in the same wide-band chunk of spectrum. Each user's signal is spread over the entire bandwidth by a unique spreading code. At the receiver, that same unique code is used to recover the
signal. Because CDMA systems need to put an accurate time-stamp on each piece of a signal, it references the GPS system for this information. Between eight and 10 separate calls can be carried in the same channel space as one analog AMPS call. CDMA technology is the basis for Interim Standard 95 (IS-95) and operates in both the 800-MHz and 1900-MHz frequency bands. Ideally, TDMA and CDMA are transparent to each other. In practice, high-power CDMA signals raise the noise floor for TDMA receivers, and high-power TDMA signals can cause overloading and jamming of CDMA receivers.
2G is a cell phone network protocol. Click here to learn about network protocols for Smartphones. Now let's look at the distinction between multiple-band and multiple-mode technologies.
Multi-band vs. Multi-mode Cell Phones
Dual Band vs. Dual Mode
If you travel a lot, you will probably want to look for phones that offer multiple bands, multiple modes or both. Let's take a look at each of these options:
* Multiple band - A phone that has multiple-band capability can switch frequencies. For example, a dual-band TDMA phone could use TDMA services in either an 800-MHz or a 1900-MHz system. A quad-band GSM phone could use GSM service in the 850-MHz, 900-MHz, 1800-MHz or 1900-MHz band.
* Multiple mode - In cell phones, "mode" refers to the type of transmission technology used. So, a phone that supported AMPS and TDMA could switch back and forth as needed. It's important that one of the modes is AMPS -- this gives you analog service if you are in an area that doesn't have digital support.
* Multiple band/Multiple mode - The best of both worlds allows you to switch between frequency bands and transmission modes as needed.
Cellular vs. PCS
Personal Communications Services (PCS) is a wireless phone service very similar to cellular phone service, but with an emphasis on personal service and extended mobility. The term "PCS" is often used in place of "digital cellular," but true PCS means that other services like paging, caller ID and e-mail are bundled into the service.
While cellular was originally created for use in cars, PCS was designed from the ground up for greater user mobility. PCS has smaller cells and therefore requires a larger number of antennas to cover a geographic area. PCS phones use frequencies between 1.85 and 1.99 GHz (1850 MHz to 1990 MHz).
Technically, cellular systems in the United States operate in the 824-MHz to 894-MHz frequency bands; PCS operates in the 1850-MHz to 1990-1850-MHz bands. And while it is based on TDMA, PCS has 200-kHz channel spacing and eight time slots instead of the typical 30-kHz channel spacing and three time slots found in digital cellular.
Changing bands or modes is done automatically by phones that support these options. Usually the phone will have a default option set, such as 1900-MHz TDMA, and will try to connect at that frequency with that technology first. If it supports dual bands, it will switch to 800 MHz if it cannot connect at 1900 MHz. And if the phone supports more than one mode, it will try the digital mode(s) first, then switch to analog.
You can find both dual-mode and tri-mode phones. The term "tri-mode" can be deceptive. It may mean that the phone supports two digital technologies, such as CDMA and TDMA, as well as analog. In that case, it is a true tri-mode phone. But it can also mean that it supports one digital technology in two bands and also offers analog support. A popular version of the tri-mode type of phone for people who do a lot of international traveling has GSM service in the 900-MHz band for Europe and Asia and the 1900-MHz band for the United States, in addition to the analog service. Technically, this is a dual-mode phone, and one of those modes (GSM) supports two bands.
3G and 3GS Technology
In the next section, we'll take a look at 3G mobile-phone technology.
3G technology is the latest in mobile communications. 3G stands for "third generation" -- this makes analog cellular technology
generation one and digital/PCS generation two. 3G technology is intended for the true multimedia cell phone -- typically called smartphones -- and features increased bandwidth and transfer rates to accommodate Web-based applications and phone-based
audio and video files.
3G comprises several cellular access technologies. The three most common ones as of 2005 are: * CDMA2000 - based on 2G Code Division Multiple Access (see Cellular Access Technologies)
* WCDMA (UMTS) - Wideband Code Division Multiple Access
* TD-SCDMA - Time-division Synchronous Code-division Multiple Access
3G networks have potential transfer speeds of up to 3 Mbps (about 15 seconds to download a 3-minute MP3 song). For comparison,
the fastest 2G phones can achieve up to 144Kbps (about 8 minutes to download a 3-minute song). 3G's high data rates are ideal for downloading information from the Internet and sending and receiving large, multimedia files. 3G phones are like mini-laptops and can accommodate broadband applications like video conferencing, receiving streaming video from the Web, sending and receiving faxes and instantly downloading e-mail messages with attachments.
3GS feels wonderfully familiar – it’s design is almost identical to the 3G, and it’s not until you switch the device on that you start to
appreciate the differences. The “S” stands for speed – Apple has used a faster processor in the 3GS, and the impact is immediate, with applications loading more briskly, programs running noticeably faster, and the already slick user-interface getting an extra layer of go-faster stripes. It’s also HSDPA compatible, a step up from 3G, meaning it can surf the web at faster speeds. Battery life is longer too; I was able to squeeze a full day out of my iPhone without needing to give it a lunchtime charging boost.
Learning with Block Diagram on How basically Cell-phone works? How basically Cell-phone works?
In this lesson we are going to take a brief familiarization of a typical block diagram of a cellphone. Block Diagram can help us
understand the flow of a certain part of a cellphone's circuit. A Cell-phone handset is basically composed of two sections, which is RF and Baseband Sections.
RF
RF refers to radio frequency, the mode of communication for wireless technologies of all kinds, including cordless phones, radar, ham radio, GPS, and radio and television broadcasts. RF technology is so much a part of our lives we scarcely notice it for its ubiquity. From baby monitors to cell phones, Bluetooth® to remote control toys, RF waves are all around us. RF waves are electromagnetic waves which propagate at the speed of light, or 186,000 miles per second (300,000 km/s). The frequencies of RF waves, however, are slower than those of visible light, making RF waves invisible to the human eye.
Baseband
In signal processing, baseband describes signals and systems whose range of frequencies is measured from zero to a maximum bandwidth or highest signal frequency. It is sometimes used as a noun for a band of frequencies starting at zero.
In telecommunications, it is the frequency range occupied by a message signal prior to modulation. It can be considered as a synonym to low-pass.
Baseband is also sometimes used as a general term for part of the physical components of a wireless communications product. Typically, it includes the control circuitry (microprocessor), the power supply, and amplifiers.
A baseband processor is an IC that is mainly used in a mobile phone to process communication functions.
Basically Baseband also composed of to sections which is the Analog and Digital Processing Sections. So, we are going to separate each other for better and easier to understand.
Cell-phone have three different sections which is the following.
I prepare this to be simple and easy instead of using or explaining it with deep technical terms .
In this manner, it is easy for us to understand the concepts and methods of how basically the cellphone works.
Cell-phone have three sections since baseband is differentiated by into two which is the Analog and Digital function while the RF section remains as a whole circuit section.. which is the following cosists.
1. Radio Frequency (RF Section) 2. The Analog Baseband Processor 3. And the Digital Baseband Processor.
Radio Frequency Processing Section
The RF section is the part of the cell-phone circuit is also known as RF Transceiver.
It is the section that transmit and receive certain frequency to a network and synchronize to other phone.
The RF - A radio section is based on two main Circuits. 1. Transmitter
2 . Reciever
A simple mobile phone uses these two circuits to correspond to an other mobile phone. A Transmitter is a circuit or device which is used to transmit radio signals in the air.and a reciever is simply like radios which are used to recieve transmissions(Radiation) which is spread in the air by any transmitter on a specific frequency.
The two way communication is made possible by setting two transmitters and two recievers sycronized in this form that a trasmitter in a cell phone is syncronised with the frequency of other cell phone's recieving frequency same like the transmitter of second cell phone is syncronised with the recieving frequency of first cell phone. So first cell phone transmits its radiation in the air while the other phone listens it and same process is present in the opposit side. so these hand held two cell phones correspond to one another.
the technology used in these days is a little bit different but it is based on the basic theory prescribed before. the today's technology will be discussed in later on.
