Audio Video Engineering Prof. Bodhale U.N. S.B.Patil Polytechnic,Indapur
w.e.f Academic Year 2012-13 G Scheme MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION, MUMBAI TEACHING AND EXAMINATION SCHEME FOR POST S.S.C. DIPLOMA COURSES COURSE NAME : ELECTRONICS ENGINEERING GROUP COURSE CODE : EJ/ET/EX/EN/ED/EI/DE DURATION OF COURSE : 6 SEMESTERS for ET/EN/EX/EJ/DE and 8 SEMESTERS for ED/EI WITH EFFECT FROM 2012-13 SEMESTER : FIFTH DURATION : 16 WEEKS FULL TIME / PART TIME : FULL TIME SCHEME : G TEACHING EXAMINATION SCHEME SR. Abbrevi SUB SUBJECT TITLE SCHEME SW NO. ation CODE PAPER TH (1) PR (4) OR (8) TW (9) (17500) TH TU PR HRS. Max Min Max Min Max Min Max Min 1 Computer Hardware & Networking β CHN 17533 02 -- 02 02 50 20 -- -- -- -- 25@ 10 2 Microcontroller β MIC 17534 03 -- 02 03 100 40 50# 20 25@ 10 3 Digital Communication DCO 17535 03 -- 02 03 100 40 50# 20 -- -- 25@ 10 4 Control System & PLC CSP 17536 03 -- 02 03 100 40 50# 20 -- -- 25@ 10 5 Audio Video Engineering AVE 17537 03 -- 02 03 100 40 -- -- -- -- 25@ 10 50 6 Behavioural Science $ BSC 17075 01 -- 02 -- -- -- -- -- 25# 10 25@ 10 7 EDP & Project β EDP 17066 01 -- 02 -- -- -- -- -- -- -- 25@ 10 8 Professional Practices - III / Industrial Training (Optional)** PPT 17067 -- -- 03 -- -- -- -- -- -- -- 50@ 20 TOTAL 16 -- 17 -- 450 -- 150 -- 25 -- 225 -- 50 Student Contact Hours Per Week: 33 Hrs. THEORY AND PRACTICAL PERIODS OF 60 MINUTES EACH. Total Marks : 900 @- Internal Assessment, # - External Assessment, No Theory Examination, $ - Common to all branches, #* - Online Theory Examination, β - Common to IE / IS / IC / EV / IU / MU ** Students who have done Industrial Training of four week after fourth semester examination during summer vacation will be exempted from some of the activities of Professional Practices-III of fifth Semester and Assessment of Industrial Training will be done in fifth semester under Professional Practices-III Abbreviations: TH-Theory, TU- Tutorial, PR-Practical, OR-Oral, TW- Term Work, SW- Sessional Work. Conduct two class tests each of 25 marks for each theory subject. Sum of the total test marks of all subjects is to be converted out of 50 marks as sessional work (SW). Progressive evaluation is to be done by subject teacher as per the prevailing curriculum implementation and assessment norms. Code number for TH, PR, OR and TW are to be given as suffix 1, 4, 8, 9 respectively to the subject code. MSBTE Final Copy Dt. 30/10/2013 1
w.e.f Academic Year 2012-13 G Scheme Course Name : Electronics Engineering Group Course Code : EJ/EX/ET/EN/DE Semester : Fifth Subject Title : Audio Video Engineering Subject Code : 17537 Teaching and Examination Scheme: Teaching Scheme TH TU PR PAPER HRS Examination Scheme TH PR OR TW TOTAL 03 -- 02 03 100 -- -- 25@ 125 NOTE: Two tests each of 25 marks to be conducted as per the schedule given by MSBTE. Total of tests marks for all theory subjects are to be converted out of 50 and to be entered in mark sheet under the head Sessional Work (SW). Rationale: The field of television engineering and video system has witnessed rapid growth especially in digital TV broadcast and recording system. Thus with widespread use of advanced audio and video equipments, the subject audio and video engineering is introduced in electronic engineering group of diploma courses.this subject is also useful for enhancing the knowledge of analog system applications. The topic on Audio engineering contains Hi-Fi amplifiers with mono and stereo amplifiers, public address system, and Dolby-NR recording system similarly CD player and disc recording of audio and video signals and their playback. The topic on Video Engineering contains TV fundamentals with basic parameters of TV, tri-colour theory, composite-video signal, CCIR-B standards. The contents of colour TV includes audio video-signal transmission and reception, positive and negative modulation, camera tubes, picture tube, colour TV decoder and latest TV technology such as HDTV, LCD TV, LED TV. The topic on cable TV explains how the TV signals are collected from different sources, mainly satellite and on due processing distributed from cable station to subscribers over the cable network. General Objectives: Students will able to 1) Understand operation of audio amplifiers. 2) Analyze quality of reception of various sound systems and graphic equalizer 3) Understand CD player mechanism. 4) Understand the principle of operation of various advanced TV systems. MSBTE - Final Copy Dt. 30/10/2013 24 17537 EXT5
w.e.f Academic Year 2012-13 G Scheme Learning Structure: Applications Trouble shooting and maintenance in T.V. and radio broadcasting stations, A.V. studios. Procedure Operation of various sections of audio systems. Operation of various sections of video systems. Principle Principles of mono, Stereo, Hi-Fi and PA system. Principles of CD system. VCD/ DVD MP3. Principles of PAL TV. Principles of cable TV, M.A TV, CCTV System. HDTV and LCD display. Concept Graphic equalizer, Dolby NR system, crossover network, detection mechanism in CD player. Aspect ratio, interlace scanning, VSB transmission and tricolor theory. Fact Modulation and demodulation process, working of transmission lines,antennas and wave propagation MSBTE - Final Copy Dt. 30/10/2013 25 17537 EXT5
w.e.f Academic Year 2012-13 G Scheme Contents: Theory Topic and Contents Topic 1] Hi Fi Audio Amplifier Specific Objectives: Students will be able to Distinguish between different types of Audio amplifiers Explain the principle and operation of Graphic equalizer Draw labeled sketch of Hi-Fi amplifier Define pre-emphasis and de-emphasis Contents: Introduction to Amplifiers: Mono, Stereo, Public Address. Difference between stereo amplifier and Mono amplifier. Block diagram of Hi Fi amplifier and its working. Controls available on it and their function, Graphic equalizer concept- circuit diagram and operation. (5-Point Circuit diagram) Dolby NR recording system Types of speaker woofer, Mid-range, Tweeter Cross over network circuit and its function Topic 2] CD player Specific Objectives: Describe the principle of detection mechanism of CD player List the components used in CD mechanism Contents: CD Material used, Size and Capacity. Block diagram and operation of CD player. Component used for CD mechanism: CD pick-up assembly, gear system, drive motors, CD lens. Function of front panel controls. Function of remote control transmitter and receiver unit used in CD player. Advantageous of Vacuum florescent. Topic 3] TV Fundamentals Specific Objectives: Define various terms used in TV system Draw and label composite video signal wave-forms State CCIR-B standards for TV system 3.1 [04 Marks] Concept: Aspect ratio, image continuity, interlace scanning, scanning periods horizontal and vertical, vertical resolution, horizontal resolution. Vestigial sideband transmission, bandwidth for Colour signal, brightness, contrast, viewing distance, luminance, Hue, saturation, compatibility. 3.2 [08 Marks] Colour theory, primary colours and secondary colours Grassman s law, additive Colour mixing subtractive Colour mixing. 3.3 [08 Marks] Composite Video Signal - Pedestal height, Blanking pulse, Colour burst, Horizontal sync pulse details, Vertical sync pulse details, Equalizing pulses, CCIR B standards for Colour signal transmission & reception. TV channel allocation for band I & band III. Hours Marks 07 12 05 12 09 20 MSBTE - Final Copy Dt. 30/10/2013 26 17537 EXT5
w.e.f Academic Year 2012-13 G Scheme TOPIC 4] TV Transmitter and Receiver Specific Objectives: Identify modulation technique used for audio and video signal transmission Distinguish between positive and negative modulation Describe TV camera tube and colour picture tube Explain the function of Color TV transmitter and receiver. Contents: 4.1 [04 Marks] Audio and Video signal transmission using AM and FM modulation. Positive and Negative modulation, Merits and Demerits of Negative modulation. 4.2 [08 Marks] Introduction to TV camera tube, principle and working of Vidicon Plumbicon Solid State camera based on CCD. Color Picture tube, principle and working of PIL Delta gun picture tube. Trinitron 4.3 [08 Marks] Block diagram of Colour TV transmitter. Block Diagram and operation of color TV receiver (PAL D type) Topic 5] Colour TV Specific Objectives: Draw and explain PAL D Decoder Explain the operation of different sections of TV receiver Differentiate between NTSC,PAL and SECAM system Explain HDTV, LCDTV and LEDTV Contents: 5.1 [12 Marks] Block diagram and operation of of PAL-D decoder. Construction, operation and applications of Yagi Uda Antenna. Circuit diagram of chroma signal amplifier, Burst pulse blanking, Colour killer control, Basic Circuit for Separation of U and V signals. ACC Amplifier. Colour signal matrixing, RGB drive amplifier. EHT generation: circuit explanation for line output stage using transistor or IC in Colour TV. 5.2 [04 Marks] HDTV: Development of HDTV, NHK MUSE System and NHK Broadcast. 5.3 [04 Marks] LCD/LED Technology: Principle and working of LCD and LED TV systems. 09 20 12 20 MSBTE - Final Copy Dt. 30/10/2013 27 17537 EXT5
w.e.f Academic Year 2012-13 G Scheme Topic 6] Cable Television Specific Objectives: List specifications of various components used in cable TV Interpret the architecture of cable TV Differentiate between MATV,CATV and CCTV Describe working of db meter and DTH system 6.1 [06 Marks] Constructional details, working and radiation pattern of Dish antenna Working principle of following components LNBC, Multiplexer, Attenuators Connectors (two ways and three ways), Amplifier and cable. 6.2 [08 Marks] MATV, CATV and CCTV. Interpret the architecture of cable TV network. Block diagram of db meter with working principle. Direct to Home System (DTH) Introduction and Block Diagram Practicals: To develop following skills: 06 16 Total 48 100 Intellectual Skills: 1. Analyze the parameters and identify faults in audio amplifier and colour TV receiver. 2. Trouble shooting of faults in audio amplifier and colour TV receiver. 3. Discriminate different sections of TV system. 4. Estimate cost of various TV system. Motor Skills: 1. Draw and illustrate different sections of audio and video systems. 2. Test different sections of audio and video systems. 3. Measure various parameters of audio and video systems. 4. Install DTH system. List of Practicals: 1. Trace out put stage of Hi Fi amplifier & Draw the component layout of it. 2. Locate Fault by voltage analysis method in a Hi Fi Audio amplifier (Any three different faults) 3. Plot frequency response of Graphic equalizer 4. Identify various control of front panel of CD player & Draw the drive mechanism layout of CD player 5. Trace: a) Chroma Section, b) Picture Tube of colour TV receiver. 6. Trace: a) Horizontal section b) Vertical section of colour TV receiver. 7. Voltage analysis of colour TV receiver a) Chroma section, b) Picture Tube 8. Voltage analysis of colour TV receiver a) Vertical Section b) horizontal section 9. Locate the Faults and rectify in given Colour TV a) No raster b) Red colour only MSBTE - Final Copy Dt. 30/10/2013 28 17537 EXT5
w.e.f Academic Year 2012-13 G Scheme c) Blue colour only d) Green colour only e) Magenta colour only f) Cyan colour only g)yellow colour only h) No sound 10. Locate the Faults and rectify in given Colour TV: a) Fault in HSYNC section. b) Fault in VSYNC section. c) Fault in SYNC separator. d) Fault in video amplifier. 11. Trace the circuit layout of LED television receiver. 12. Trace the circuit layout of LCD television receiver. Assignments: 1. To collect information about Set Top box used for Cable TV at home and Installation of DTH System. 2. To estimate the cost and layout of Cable TV. 3. To collect information about LED and LCD display used in TV. 4. Visit to TV transmitter station and write report. Learning Resources: 1) Books: Sr. Title Author Publisher No. 01 Television & Radio Engineering A.M Dhake Tata McGraw-Hill 02 Modern TV Pratice (4 th edition ) R.R Gulati New age International 03 Television Engineering and Video System R.G Gupta Tata McGraw-Hill 04 Audio Video Systems R.G Gupta Tata McGraw-Hill 05 06 Basic Television and Video System Modern CD Player Servicing Manual Bernard Grob Manohar Lotia 2) Websites: http://en.wikipedia.org/wiki/compact_disc_player. http://en.wikipedia.org/wiki/high-definition_television. http://www.howstuffworks.com. http://en.wikipedia.org/wiki/backlight. Tata McGraw-Hill BPB Publication MSBTE - Final Copy Dt. 30/10/2013 29 17537 EXT5
As there is rapid growth in the television engineering, we have to enhance the knowledge regarding analog system. As the subject title given Audio Video Engineering contain information regarding audio & video devices such as Hi-Fi amplifier, CD Player, Television etc. As audio Engineering consider it contain Hi-Fi Amplifier with Mono and stereo amplifier, PA system and Dolby system etc, In CD player how the CD player working and components used in CD player. The topic video Engineering contain the information about Television like working of monochrome,colour TV, composition of Video Signal, picture tube and latest TV technology such as HDTV, LCD TV, LED TV. In cable television, containing information related to cable communication.
Chapter 01:- Hi-Fi Amplifier 1.1 Introduction of Audio Amplifier The word audio means sound comes from the recording. The range of audio frequency varies form 20 Hz to 20Khz. An audio amplifier is an electronic device that increases the strength (amplitude) of audio signals that pass through it. An audio amplifier amplifies low-power audio signals to a level which is suitable for driving loudspeakers. The input signal of an audio amplifier may only measure a few hundred microwatts, but its output may be tens or even thousands of watts. Design parameters for audio amplifiers include gain, frequency response, distortion and noise. Hi-Fi amplifier means High fidelity amplifier. Fidelity means faithfulness in sound ( the sound which you believe) The characteristics required for faithfulness in sound are:- 1. Completely exclusive from noise. The signal to noise ratio should be infinite. 2. Flat frequency response that is zero degree for complete audio frequency from 20 Hz to 20 KHz. It means that there is no frequency distortion. 3. Ability to sense the direction of sound 4. Environmental condition should be simulated where the sound is being reproduced. But it is highly impossible to get ideal fidelity. The best fidelity system are less perfect but when the sound is reproduce with the degree of similarity original sound. The system can be set to high fidelity. The listening test are carried out all over the world and reproduced sound is known as hi-fi sound. Specification:- 1. Signal to noise ratio should be better than 50db. 2. Frequency response should be that within +- 1db over the frequency range of 40 Hz to 4 KHz. 3. Nonlinear distortion occurs is 1 should not be more than 1. For Hi-Fi system telephonic effects should be provided. 1.2 Types of Amplifier a) Mono Amplifier The meaning of monophonic means one sound or one directional sound. In monophonic sound only one amplifier is used. Such as single amplifier monophonic system is known as mono amplifier. In monophonic system audio signal are mixed together and send via only one channel. The out can connect several channels. It used in Public Address system
MIC Pre-A plifier Power A plifier b) Stereo Phonic amplifier Stereo means solid and phonic means sound in greek means three dimensional sound. The sound arises from two different amplifier so that sound appears to be surrounded It has two different channel ( left and right) correspond to two amplifiers and loud speaker. It used in Hi- Fi system. c) Public Address system A system of microphones, amplifiers, and loudspeakers used to amplify speech or music in a large building or at an outdoor gathering. It used in sports meet, public meet, auditorium, concerts, functions etc. 2.1 Block Diagram of Hi-Fi amplifier Figure Blo k diagra of Hi-Fi A plifier a. Sources : source. The source of Hi- Fi amplifier is stereo Tape or Disc. in live system microphone work as a b. Processing circuit: It consist of preamplifier, Equalizer, Matching circuit etc. i) Pre amplifier :
A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for further amplification or processing. It is a low noise, high gain amplifier giving flat frequency response. ii) Equalizer : Equalization is the process of adjusting the balance between frequency components within an electronic signal. An equalizer is the circuit or equipment used to achieve equalization. iii) Amplifier: Amplifier follows the equalizer have flat frequency response. Negative feedback is incorporated (combined) in these amplifier to reduce the distortion to considerable extent. iv) Matching Circuit : Impedance matching between amplifier output and loudspeaker can be achieve by using these circuit. v) Balancing Circuit: The function of balancing circuit is to balance out any imbalance in the characteristics of identical circuit in both channels. vi) Loudspeaker: The function of loudspeaker is to convert the electrical signal into voice or auditable signal. The Hi-Fi system consist of number of dynamic speaker. The moment of diaphragm creates a sound. These sound can be divided into on the basis of frequency range covered by sound like Woofer covers low frequency sound Tweeter cover high frequency sound Squawker (Mid-Range) covers the mid frequency 2.2 Controls available in Hi-Fi Amplifier i) Balance control: ii) iii) Two amplifiers of a stereo system, although independent of each other are built as matched pair to give equal output for the same input. In spite of the two amplifiers being identical, there may be variations in the characteristics of transistors and ICs and positioning of loudspeakers and furnishings with respect to the listener. The circuit used to compensate for such variations are called Balance control. Loudness control: Sometime music is at low level of volume (as in case of the background music). At low levels there is considerable loss in bass in reproduction. It is therefore, necessary that there should be substantial boosting of the bass at low levels. Boosting at treble may be only nominal because loss at high notes is quite small. The control which provides desired big boosting at bass and a little boosting at treble is called loudness control. Bass and Treble control: It is provided to tailor bass treble as per personal taste of the listener.
iv) Master Gain control: A master gain control is used for adjusting overall volume without disturbing the balance. This is achieved by using dual concentric shafts, the inner shaft adjust the balance control and the outer shaft, the overall gain or volume of the amplifier. v) Blend control: The stereo effect is diluted by this control when it is too much left- right effect. 2.3 Graphic Equalizer A graphic equalizer is a high-fidelity audio control that allows the user to see graphically and control individually a number of different frequency bands in a stereophonic system. A typical graphic equalizer consists of several audio filter/amplifiers, each centered at a specific frequency in the audio range. Most graphic equalizers have two identical sets of filter/amplifiers, one for each channel in a stereophonic system In sound recording system the low power frequency notes should be emphasized before recording, so that these notes are carried to much higher power level, compared to noise signal. This will improve signal to noise ratio of the recording system. At the receiving end or the playback end, these should be a facility to bring the boosted signal back to their original levels. This is similar to pre-emphasis and de-emphasis process. The recovery of the original sound signal from the playback circuit by conversion process of deemphasis at the receiver is called equalization. In this type of tone control the audio spectrum is divided in to narrow band. Each band has an individual slider which can boost or cut the signals in that band from +15 to -15dB. The center frequency of each band is generally based on an octave. So to get boost or cut in frequency to get the proper effect like classical, jazz, rock or pop as well as treble and bass effect we need the graphic equalizer.
The Main of function of graphic Equalizer is to improve the signal to noise ratio of recording system. The recovery of original sound from playback circuit by Converse process of de-emphasis at receiver is called equalization. Dolby NR system The name Derby is synonyms with noise reduction system Dr Ray Dolby introduce a novel system so the name is given. In practice, system used for pre Emphasis of high notes and de-emphasis for low notes by equalization Dolby system provides 10 to 15 disable improvement in signal to noise ratio. In this system, weak signal below 40 db, above noise is boosted before recording all the signal which are 40 db or higher, pass through Dolby system direct without change. The figure indicates that signal to noise ratio is finally improved. Signal in absence of boosting is showing in figure (a) after posting recording noise remains unchanged but signal are boosted as shown in figure(b) during playback signal and noise both are reduced as shown in figure (c) Dolby system mainly having two types Dolby A system and Derby B system. Dolby A system Boosting is done in four bands
1. Below 80 Hz 2. 80Hz to 2999Hz 3. 3KHz and above 4. 9 KHz and above Bank III and IV overlap above 9 Khz so that the high frequency noise in the form of hissing sound is considerably reduced. Each frequency band is processor separately by using low pass, Band pass and high pass filter and limits. Thus, we have following technique 1. low pass filter take care of 16 Hz to 80Hz sound signal and improve the signal to noise ratio with respect to hum ( sound with closer lips) and Rumble (Low heavy sound) 2. Band pass filter take care of 80Hz and 2999-hertz frequency band. improvement the signal to noise ratio of musical sound is achieved in the frequency band 3. High Pass filter take care of sound signal exceeding 3Khz and 9 KHz, thereby improving the signal to noise ratio with respect to hiss and modulation noise. The output of four separate unit is added All this is done in a side branch and this branch is known as differential network The output of differential network goes to the adder of main branch as shown in figure the output of adder is the Dolby processed signal called Dolby Signal. In playback, the differential network separate output the boosted signal in the side branch and subtract them from the input signal. Dolby A system used and improvement of 10 db in the signal to noise ratio upto 5KHz increasing it as the frequency increases until it becomes 15 db at 15 khz. It then remain at 15 db for frequency higher than 15 Hz. Dolby B system
A more simplified system than Dolby A system has been developed for home use and is known as Dolby B system In Dolby B system the encoded signal covers signal frequency, band from 500 Hz upwards. Signal below a specified threshold value in label are passed through a variable filter, which increases the level, by about 1 decibel at 500 Hz. The process of a signal from the variable filter and the direct input signal are added. The added gives the Dolby output. For playback the signal is inverted and Fed to the variable filter. The output of the filter gives to the adder to give decoded output. Basic blocks of encoder/ Decoder are as shown in fig. Loudspeaker A Loudspeaker is a device, which converts electrical energy into sound energy. A single speaker cannot have flat frequency response for the full audio frequency range for that purpose loudspeaker is divided into various Woofer:- The loudspeaker which is design to cover a low audio frequency that is 16 Hz to 1KHz is called Woofer. Squawker:- The loudspeaker which is used to cover the mid frequency range that is 500 Hz to 5 KHz Tweeter:- The loudspeaker which covers all high frequency is called Twitter that is 5KHz to 16 KHz Cross over network When a multiple of speaker system used to get a flat frequency response for the entire range of audio frequency it is essential to have a cross for network to divide the incoming signal into separate frequency range for each speaker
Figure Basi Crosso er Net ork Audio & Video Engineering In absence of cross over network, the speaker will suffer over hearting and the output will be distorted when full power at frequency outside their range is fed to them. The overall efficiency will be much reduced in the absence of crossover network. Crossover Network make use of the fact that capacitive reactance decreases with increase in frequency and inductive reactance increases with increase in frequency. The circuit consists of low pass LC filter across the woofer and High pass filter across the tweeter. The low pass filter permits only low audio frequencies (16Hz to 1000Hz) to go to the woofer. The series reactance of L and shunt capacitance of C for high audio frequencies prevent these frequencies from going to the woofer. The high pass filter consisting of C in series and L in shunt allow the High audio frequency to pass to the Tweeter and block the low frequencies. Figure Respo se Cur e of asi ross o er et ork A commercial 3 Way divided network is as shown in figure in this circuit the capacitor of 1 microfarad in series with the Tweeter prevents low and mid frequency from reaching the Tweeter. Similarly in inductance LW of 5mH is in series with the woofer prevents high frequency from reaching the woofer. Inductance L s-1 and L s-2 of 0.5 mh and 5mH, respectively in the squawker circuit allow only mid frequency and previous too low and too high frequencies from reaching the squawker. A typical divider curve for a three way network of fig. is as shown in fig.. A single element in filtering gives attenuation of 6 db per octave and double elements give 12 db per octave.
Chapter 02:- CD player A CD player is an electronic device that plays audio compact discs, which are a digital optical disc data storage format. A compact disc is a thin, circular disc of metal and plastic about 12cm (just over 4.5 inches) in diameter. It's actually made of three layers. Most of a CD is made from a tough, brittle plastic called polycarbonate. Sandwiched in the middle there is a thin layer of aluminum. Finally, on top of the aluminum, is a protective layer of plastic and lacquer. The first thing you notice about a CD is that it is shiny on one side and dull on the other. The dull side usually has a label on it telling you what's on the CD; the shiny side is the important part. It's shiny so that a laser beam can bounce off the disc and read the information stored on it.
CD- Material used, Size and Capacity The CD is circular plastic coated disc of 4.75 inch that is 120 mm diameter On one side of disk the audio signal are recorded and on other side the label indicating the content of the disk are printed. CD thickness is 1.2 mm that contain the 70 minutes of audio information. On the CD player, reading of audio information is done by using laser beam This laser beam is generated inside the CD player by small power laser diode made of Aluminium gallium arsenide (AlGaAs). Material used:- Plastic base reflective surface coated with aluminium layer. This reflective coating covered with transparent plastic polycarbonate lacquire coating. CDs are made from an original "master" disc. The master is "burned" with a laser beam that etches bumps (called pits) into its surface. A bump represents the number zero, so every time the laser burns a bump into the disc, a zero is stored there. The lack of a bump (which is a flat, unburned area on the disc, called a Flat/ land) represents the number one. Thus, the laser can store all the information sampled from the original track of music by burning some areas (to represent zeros) and leaving other areas unburned (to represent ones). Although you can't see it, the disc holds this information in a tight, continuous spiral of about 3 5 billion pits. If you could unwrap the spiral and lay it in a straight line, it would stretch for about 6 km (roughly 3.5 miles)! Each pit occupies an area about two millionths of a millionth of a square meter. Block diagram and operation of CD player
The CD player is also known as CLV or constant linear velocity system. In a CLV device such as a CD player the rotation speed of the disc player is adjusted with the movement of the reading mechanism on the disc surface. Function of Block diagram in CD Player Focus and Tracking coil: Focus and tracking coil to focus the laser beam to the CD surface and to move the Assembly to the proper track across the disc surface. Optical Pickup Assembly: The audio signal stored on the CD surface as pits and flats area are first picked up by the optical pickup assembly made of lens assembly prism, photo detectors and Laser diodes assembly in the Optical pickup unit. Photodiode array convert light rays in electrical signal. High frequency Amplifier: The signal is very weak so high frequency RF amplifier circuit to bring signal to the proper level. This amplified and filtered high frequency signal contain audio signal as well as synchronization signals in 14 bit EFM ( Eight to fourteen modulated) format, this signal is sent to an EGM demodulator circuit. EFM Demodulator:
The EFM demodulator separates the modulated data and the timing signal from the signal received at its input. It also removes the additional coupling nits and convert the 14 bit EGM symbol to actual 8 bit data. The amplified and filtered EGM signal from the high frequency amplifier is also given to the clock generation circuit to the synchronization detecting and timing circuit. These circuits are used to recover the bit clock and the sync pattern from the data. The timing signal separates by this circuit is used to provide timing signal to the system. ERCO circuit Demodulated data from the EGM demodulator is send to an error correction (ERCO) circuit. This demodulated data signal is also send to control and display decoding circuit, which recover the control and display signals multiplexed into the signal received from the CD. Interpolation and Muting ERCO circuit is used for error detection and correction purpose any error found in incoming data signal is send to interpolation and muting section by ERCO circuit. The interpolation and muting section uses the following methods to correct and error on in the data stream or read from the disc. 1. Muting 2. Last word held 3. Linear interpolation Muting In muting, when an error is detected in the data steam, the player will mute the sound is not send to the speaker. CLV using clock signal: The ERCO also responsible for maintaining constant linear velocity of CD motar, for this the ERCO circuit compares the clock signal derived from the incoming data with reference clock frequency. Digital filter and De- multiplexer In this section, the signals are filtered and separate into left and right channel data. D/A converter The output of digital filter and de-multiplexer circuit is sent to a d / a converter. The right and left channel signal are processed by separate D/A converters. These converter convert the 16 bit digital signal into the original analog audio signal. Because of the oversampling, done in the digital filter and De- multiplexer circuit a simple low pass filter is used. Loudspeaker : convert into sound signal.
Components used for CD Mechanism Different components used for CD Mechanism 1. CD pick-up assembly 2. CD Lens: Collimation Lens Concave Lens Objective Lens Cylindrical Lens 3. Drive motors Tray, loading motor Slide, sled, feed motor Splindle, disc, turntable motor. 4. Gear system Optical pickup assembly The optical pickup assembly consist of A low power laser diode to eliminate the CD tracks. Lens and prism arrangement to direct a laser beam and the CD surface and to direct the reflected laser beam towards photodiode array. Photodiode array to obtain data, focus and tracking signal from the reflected laser beam. Some optically units do not contain the tracking coil for example signal Beam Redial tracking assembly, Working: In the optical pickup unit the laser diode emits laser beam from a small point into an elliptical or conical distribution. This beam is pa ssed through various prism and lens to form a very small diameter light beam on the disc surface at the centre on the track. The objective lens is controlled by the tracking and focusing coil to keep the beam focused on the CD and to keep the condensed beam at the centre of the track. This LASER beam is reflected back by the flat area and the pits on the disc surface. This reflected beam is applied to a group of photo-diodes through objectives lens, collimation lens, and some prism arrangement.
These Photodiode induce voltage according to the reflected beam falling on it. Focus error and tracking error voltage generated by this photo-diode array is applied to the tracking and focusing coil to control the objective lens and data signal generated by this photo-diode array is sent to an amplifier to amplify the data signals picked up from the disc. Finally, the output from the amplifier is processed to produce the audio signal stored on the disc surface. CD Lens Collimation lens: The function of collimation lens is to produce parallel beam of laser. Concave Lens: A function of concave lens is to concentrate the laser beam reflected from the disc surface onto the photodiode array. This lens is mainly used for improve the sensitivity of photodiode array. Objective Lens: The main function of objective lens is to focus the laser beam on to the disc surface and to receive the reflected LASER beam. Objective lens move up and down to achieve the focus of laser beam on to the disc surface. Cylindrical Lens: The main function of cylindrical lens is to enable the reflected beam from the CD to assist in creating the necessary signal to make sure that focus of laser beam on the playing surface of the disc is maintained. Drive motors Tray, Loading (carriage) motor: This motor moves the tray in and out for loading and unloading the disc. In most players, this process is activated with a push button on font panel. Slide, Sled, Feed Motor The slide sled or feed motor moves the optical pickup assembly across the disc from the inside to the outside rim of the CD keeping objective lens constantly in with the centre of optical axis or track. The slide or feed motor move the laser pickup assembly from the centre to the outside rim of the CD and its control with either or transistor or IC driven circuit Spindle,disc, Turntable motor Main function of spindle motor is to rotate the disc after it is loaded a small platform that is mounted on the turntable motor shaft spin the CD at a variable Speed. the disc starts at
approximately 500 RPM and slow down to approximately 200 RPM as laser pickup assembly moves towards the outer edge of CD. Gear system Mainly the gear system are used to control the speed of motor and keep the speed constant to cover the constant distance. For example Tray loading motor used to load the CD on trey, when we press open button on CD player that s comes out of CD the motor rotates with constant speed and covers constant distance. To vary the speed of motor in steps then more than one gear are used. The number of grooves on gear diameter of gear also depend on speed type of motor used. Function of Front Panel control on CD player Symbol Unicode / Name / function Play / Pause / Play/Pause toggle / Reverse / Stop / Rewind (Fast Backwards) / Fast forward / Skip to the start or previous file/track/chapter / Skip to the end or next file/track/chapter
/ Record / Eject Shuffle Repeat (indefinitely) Repeat once i Info Reload, Refresh Remote control of CD player Most of the move forward or on CD. A typical remote control diagram is as shown in figure. Let us see the key and its function 1. Play: The Play key on remote can breast to start the CD player to play the operation 2. Reset: This key can be used to reset the play to the beginning of the first track on the disk is also put the CD player in standby mode 3. Manual search key remote contain a set of manual search keys to backward on the disc look for the particular track 4. Automatic Search Key This button on the remote control allow the music to be played directly from the beginning of the previous track or from the beginning of next track 5. Repeat program button This key when pressed make the player to repeat all the tracks on the CD. Some of the remote contain a set of repeat keys to select the track to be repeated. In this type of remote pressing of 1 will repeat the current track, pressing ALL on repeat keys will repeat all the track on CD, pressing A-B can be used to set a starting and end track to be repeatedly played. 6. Clear This button is pressed to clear any program and the repeat instructions given the CD player. 7. Direct Music Select (DMS) keys
The remote control also contain a set of Direct Music selection keys. Normally, 0to 9 total 10 different keys are provided on the remote, one can press a key or a combination of keys to select a track from the CD. Once the required track is select pressing of the play key will start playing selected track. 8. Intro The intro key can be pressed to play all the track on the CD for around 10 second each. This give an introduction of the CD placed into the player. 9. Random When this keys is pressed the CD player starts playing the tracks on the CD random order. Advantages of Vacuum Fluorescent Display 1. Emits a very bright light with clear contrast. 2. Easily support display elements of various colours. 3. The light produced by most VFDs contain many colours and can often be filtered to produce a more pure colour such as deep green or deep blue 4. Being rugged inexpensive 5. Easily configured to display a wide variety of customized messages. 6. Most VFD s continue to function normally in sub zero temperatures making them ideal for outdoor devices in cold climates.