60 Seconds Voice Recording and Playback Device

download 60 Seconds Voice Recording and Playback Device

of 35

Embed Size (px)

Transcript of 60 Seconds Voice Recording and Playback Device

  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    CHAPTER: 1


    The APR9600 device offers true single-chip voice recording, non-volatile storage, and

    playback capability for 40 to 60 seconds. The device supports both random and sequential access of

    multiple messages. Sample rates are user-selectable, allowing designers to customize their design for

    unique quality and storage time needs. Integrated output amplifier, microphone amplifier, and AGC

    circuits greatly simplify system design. The device is ideal for use in portable voice recorders, toys, and

    many other consumer and industrial applications. APLUS integrated achieves these high levels of storage

    capability by using its proprietary analog/multilevel storage technology implemented in an advanced Flash

    non-volatile memory process, where each memory cell can store 256 voltage levels. This technology

    enables the APR9600 device to reproduce voice signals in their natural form. It eliminates the need for

    encoding and compression, which often introduce distortion.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    CHAPTER: 2


    1. Diodes

    IN4007 4 No

    2. Resistors

    4.7k 2No

    1.2k 1No220k 1No

    100k 2No

    1k 1No

    68k 1No

    0.56k 2No

    3. Capacitors

    0.1F 5No

    0.04 F 1No

    4. Transistors

    7805 1No

    5. LEDS

    Red 1No

    White 1No

    6. Filters

    1000F 1No

    220F 1No

    22F 1No



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    2.2F 1No

    4.7F 1No

    10F 1No

    100F 1No

    47f 1No

    7. IC

    LM386 1No

    APR9600 1No

    8. Slide on-off switch 1No

    9. Preset Resistor 10k 1No

    10. Battery 9v

    11. Push button 6No

    12. Mike 1No

    13. Speaker 1No (4-16, 10w)


    1. DIODE

    In electronics, a diode is a type of two-terminalelectronic component with a nonlinearcurrent

    voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of

    semiconductor material connected to two electrical terminals. A vacuum tube diode (now rarely used

    except in some high-power technologies) is a vacuum tube with two electrodes: aplate and acathode.

    The most common function of a diode is to allow an

    electric current to pass in one direction (called the diode's

    forward direction), while blocking current in the opposite

    direction (the reverse direction). Thus, the diode can be

    thought of as an electronic version of a check valve. This

    unidirectional behavior is called rectification, and is used to convert alternating current to direct current

    and to extract modulation from radio signals in radio receivers.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    However, diodes can have more complicated behavior than this simple onoff action

    Semiconductor diodes do not begin conducting electricity until a certain threshold voltage is present in the

    forward direction (a state in which the diode is said to be forward biased). The voltage drop across a

    forward biased diode varies only a little with the current, and is a function of temperature; this effect can

    be used as a temperature sensor or voltage reference.

    Semiconductor diodes have nonlinear electrical characteristics, which can be tailored by

    varying the construction of theirPN junction. These are exploited in special purpose diodes that perform

    many different functions. For example, diodes are used to regulate voltage (Zener diodes), to protect

    circuits from high voltage surges (Avalanche diodes), to electronically tune radio and TV receivers

    (varactor diodes), to generate radio frequency (oscillationstunnel diodes, Gunn diodes, IMPATT diodes)

    and to produce light (light emitting diodes). Tunnel diodes exhibit negative resistance, which makes them

    useful in some types of circuits.

    Diodes were the first semiconductor electronic devices. The discovery of crystals' rectifying

    abilities was made by German physicist Ferdinand Braun in 1874. The first semiconductor diodes, called

    cat's whisker diodes, developed around 1906, were made of mineral crystals such as galena. Today most

    diodes are made ofsilicon, but othersemiconductorssuch as germanium are sometimes used.

    A modern semiconductor diode is made of a crystal of semiconductor like silicon that has

    impurities added to it to create a region on one side that contains negative charge carriers (electrons)

    calledn-type semiconductor, and a region on the other side that contains positive charge carriers (holes)

    called p-type semiconductor. The diode's terminals are attached to each of these regions. The boundary

    within the crystal between these two regions, called a PN junction, is where the action of the diode takes

    place. The crystal conducts a current of electrons in a direction from the N-type side (called the cathode)

    to the P-type side (called the anode), but not in the opposite direction. However, conventional current

    flows from anode to cathode in the direction of the arrow (opposite to the electron flow, since electrons

    have negative charge).

    Another type of semiconductor diode, the Schottky diode, is formed from the contact between

    a metal and a semiconductor rather than by a pn junction.

    Currentvoltage characteristic



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    A semiconductor diodes behavior in a circuit is given by its currentvoltage characteristic, or

    IV graph (see graph below). The shape of the curve is determined by the transport of charge carriers

    through the so-called depletion layerordepletion regionthat exists at thepn junction between differing

    semiconductors. When a pn junction is first created, conduction-band (mobile) electrons from the N-

    doped region diffuse into the P-doped region where there is a large population of holes (vacant places for

    electrons) with which the electrons "recombine". When a mobile electron recombines with a hole, both

    hole and electron vanish, leaving behind an immobile positively charged donor (dopant) on the N side and

    negatively charged acceptor (dopant) on the P side. The region around the pn junction becomes depleted

    ofcharge carriers and thus behaves as an insulator.

    However, the width of the depletion region (called the depletion width) cannot grow without

    limit. For each electronhole pairthat recombines, a positively charged dopant ion is left behind in the N-

    doped region, and a negatively charged dopant ion is left behind in the P-doped region. As recombination

    proceeds more ions are created, an increasing electric field develops through the depletion zone which acts

    to slow and then finally stop recombination. At this point, there is a "built-in" potential across the

    depletion zone.

    If an external voltage is placed across the diode with the same polarity as the built-in potential,

    the depletion zone continues to act as an insulator, preventing any significant electric current flow (unless

    electron/hole pairs are actively being created in the junction by, for instance, light. seephotodiode). This

    is the reverse bias phenomenon. However, if the polarity of the external voltage opposes the built-in

    potential, recombination can once again proceed, resulting in substantial electric current through the pn

    junction (i.e. substantial numbers of electrons and holes recombine at the junction). For silicon diodes, the

    built-in potential is approximately 0.7 V (0.3 V for Germanium and 0.2 V for Schottky). Thus, if an

    external current is passed through the diode, about 0.7 V will be developed across the diode such that the

    P-doped region is positive with respect to the N-doped region and the diode is said to be "turned on" as it

    has a forward bias.

    A diodes 'IV characteristic' can be approximated by four regions of operation.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    At very large reverse bias, beyond the peak inverse voltage or PIV, a process called reverse

    breakdownoccurs which causes a large increase in current (i.e. a large number of electrons and holes are

    created at, and move away from the pn junction) that usually damages the device permanently. The

    avalanche diode is deliberately designed for use in the avalanche region. In the zener diode, the concept of

    PIV is not applicable. A zener diode contains a heavily doped pn junction allowing electrons to tunnel

    from the valence band of the p-type material to the conduction band of the n-type material, such that the

    reverse voltage is "clamped" to a known value (called the zenervoltage), and avalanche does not occur

    Both devices, however, do have a limit to the maximum current and power in the clamped reverse-voltage

    region. Also, following the end of forward conduction in any diode, there is reverse current for a short

    time. The device does not attain its full blocking capability until the reverse current ceases.

    The second region, at reverse biases more positive than the PIV, has only a very small reverse

    saturation current. In the reverse bias region for a normal PN rectifier diode, the current through the

    device is very low (in the A range). However, this is temperature dependent, and at sufficiently hightemperatures, a substantial amount of reverse current can be observed (mA or more).

    The third region is forward but small bias, where only a small forward current is conducted.

    As the potential difference is increased above an arbitrarily defined "cut-in voltage" or "on-

    voltage" or "diode forward voltage drop (Vd)", the diode current becomes appreciable (the level of current

    considered "appreciable" and the value of cut-in voltage depends on the application), and the diode

    presents a very low resistance. The currentvoltage curve is exponential. In a normal silicon diode at rated

    currents, the arbitrary cut-in voltage is defined as 0.6 to 0.7 volts. The value is different for other diode

    types Schottky diodescan be rated as low as 0.2 V, Germanium diodes 0.25 to 0.3 V, and red or blue

    light-emitting diodes(LEDs) can have values of 1.4 V and 4.0 V respectively.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    At higher currents the forward voltage drop of the diode increases. A drop of 1 V to 1.5 V is typical at full

    rated current for power diodes.


    Resistor is a two-terminal, linear, passive electronic component that implements electrica

    resistance as a circuit element. Resistance is the property of a component which restricts the flow of

    electric current. Energy is used up as the voltage across the component drives the current through it and

    this energy appears as heat in the component.

    Resistance is measured in ohms, the symbol for ohm is an


    The behavior of an ideal resistor is dictated by the relationship specified

    by Ohm's law:

    Ohm's law states that the voltage (V) across a resistor is proportional to

    the current (I), where the constant of proportionality is the resistance (R).

    Equivalently, Ohm's law can be stated:

    This formulation states that the current (I) is proportional to the voltage (V) and inversely proportional to

    the resistance (R).


    Resistors restrict the flow of electric current, for example a resistor is placed in series with light-

    emitting diode(LED0 to limit the flow current passing through the LED.

    1 is quite small so resistor values are often gives in K and M .

    Resistor values are normally shown using coloured bands.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    Each colour represents a number as shown in the table:


    Most resistors have 4 bands:

    The first band gives the first digit.

    The second band gives the second digit.

    The third band indicates the number of zeros.



    BLACK 0

    BROWN 1

    RED 2

    ORANGE 3

    YELLOW 4

    GREEN 5

    BLUE 6

    VIOLET 7

    GRAY 8


  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    The fourth band is used to shows the tolerance of the resistor.

    Resistors connected in series:

    In a series configuration, the current through all of the resistors is the same, but the voltage

    across each resistor will be in proportion to its resistance. The potential difference (voltage) seen across

    the network is the sum of those voltages, thus the total resistance can be found as the sum of those


    As a special case, the resistance of N resistors connected in series, each of the same resistance

    R, is given by NR.

    Resistors connected in parallel:

    Resistors in aparallel configuration are each subject to the same potential difference (voltage)

    however the currents through them add. The conductances of the resistors then add to determine the

    conductance of the network. Thus the equivalent resistance (Req) of the network can be computed:

    The parallel equivalent resistance can be represented in equations by two vertical lines "||" (as

    in geometry) as a simplified notation. For the case of two resistors in parallel, this can be calculated using:


    Combination of series and parallel resistors:

    As a special case, the resistance of N resistors connected in parallel, each of the same

    resistance R, is given by R/N.

    A resistor network that is a combination of parallel and series connections can be broken up into smaller

    parts that are either one or the other. For instance,



  • 7/28/2019 60 Seconds Voice Recording and Playback Device



    Power dissipation:

    The power P dissipated by a resistor (or the equivalent resistance of a resistor network) is

    calculated as:



    Just like the resistor, the capacitor, sometimes referred to as a condenser, is a passive device

    and one which stores its energy in the form of an electrostatic field producing a potential difference (Static

    Voltage) across its plates. In its basic form a capacitor consists of two or more parallel conductive (metal)

    plates that do not touch or are connected but are electrically separated either by air or by some form of

    insulating material such as paper, mica or ceramic called the dielectric. The conductive plates of a

    capacitor can be square, circular or rectangular, or be of a cylindrical or spherical shape with the shapeand construction of a parallel plate capacitor depending on its application and voltage rating.

    When used in a direct-current or DC circuit, a capacitor blocks the flow of current through it, but when

    it is connected to an alternating-current or AC circuit, the current appears to pass straight through it with

    little or no resistance. If a DC voltage is applied to the capacitors

    conductive plates, a current flow charging up the plates with

    electrons giving one plate a positive charge and the other plate an

    equal and opposite negative charge. This flow of electrons to the

    plates is known as the Charging Current and continues to flow

    until the voltage across both plates (and hence the capacitor) is



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    equal to the applied voltage VC. At this point the capacitor is said to be fully charged with electrons with

    the strength of this charging current at its maximum when the plates are fully discharged and slowly

    reduces in value to zero as the plates charge up to a potential difference equal to the applied supply

    voltage and this is illustrated below.

    Capacitor Construction

    The parallel plate capacitor is the simplest form of capacitor and its capacitance value is fixed

    by the surface area of the conductive plates and the distance or separation between them. Altering any two

    of these values alters the value of its capacitance and this forms the basis of operation of the variable

    capacitors. Also, because capacitors store the energy of the electrons in the form of an electrical charge on

    the plates the larger the plates and/or smaller their separation the greater will be the charge that the

    capacitor holds for any given voltage across its plates. In other words, larger plates, smaller distance,

    more capacitance.

    By applying a voltage to a capacitor and measuring the charge on the plates, the ratio of the

    charge Q to the voltage V will give the capacitance value of the capacitor and is therefore given as: C =

    Q/V this equation can also be re-arranged to give the more familiar formula for the quantity of charge on

    the plates as: Q = C x V

    Although we have said that the charge is stored on the plates of a capacitor, it is more correct

    to say that the energy within the charge is stored in an "electrostatic field" between the two plates. When

    an electric current flows into the capacitor, charging it up, the electrostatic field becomes stronger as it

    stores more energy. Likewise, as the current flows out of the capacitor, discharging it, the potential



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    difference between the two plates decreases and the electrostatic field decreases as the energy moves out

    of the plates.

    The property of a capacitor to store charge on its plates in the form of an electrostatic field is

    called the capacitance of the capacitor. Not only that, but capacitance is also the property of a capacitor

    which resists the change of voltage across it.

    The Capacitance of a Capacitor

    The unit of capacitance is the farad (abbreviated to F) named after the British physicist Michael

    Faraday and is defined as a capacitor has the capacitance ofOne farad when a charge ofone coulomb is

    stored on the plates by a voltage ofOne volt. Capacitance, C is always positive and has no negative units.

    However, the Farad is a very large unit of measurement to use on its own so sub-multiples of the Farad are

    generally used such as micro-farads, nano-farads and pico-farads, for example.

    Units of Capacitance

    Micro farad (F) 1F = 1/1,000,000 = 0.000001 = 10-6 F

    Nano farad (nF) 1nF = 1/1,000,000,000 = 0.000000001 = 10-9 F

    Pico farad (pF) 1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F

    The capacitance of a parallel plate capacitor is proportional to the

    area, A of the plates and inversely proportional to their distance or separation, d (i.e. the dielectric

    thickness) giving us a value for capacitance ofC = k( A/d ) where in a vacuum the value of the constant k

    is 8.84 x 10-12 F/m or 1/4..9 x 109, which is the Permittivity of free space. Generally, the conductive

    plates of a capacitor are separated by air or some kind of insulating material or gel rather than the vacuum

    of free space.

    The Dielectric of a Capacitor



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    As well as the overall size of the conductive plates and their distance or spacing apart from

    each other, another factor which affects the overall capacitance of the device is the type of dielectric

    material being used. In other words the "Permittivity" ( ) of the dielectric. The conductive plates are

    generally made of a metal foil or a metal film but the dielectric material is an insulator. The various

    insulating materials used as the dielectric in a capacitor differ in their ability to block or pass an electrical

    charge. This dielectric material can be made from a number of insulating materials or combinations of

    these materials with the most common types used being: air, paper, polyester, polypropylene, Mylar,

    ceramic, glass, oil, or a variety of other materials.

    The factor by which the dielectric material, or insulator, increases the capacitance of the

    capacitor compared to air is known as the dielectric constant, k and a dielectric material with a high

    dielectric constant is a better insulator than a dielectric material with a lower dielectric constant. Dielectricconstant is a dimensionless quantity since it is relative to free space. The actual permittivity or "complex

    permittivity" of the dielectric material between the plates is then the product of the permittivity of free

    space (o) and the relative permittivity (r) of the material being used as the

    dielectric and is given as:

    Complex Permittivity

    As the permittivity of free space, o is equal to one, the value of the complex permittivity will

    always be equal to the relative permittivity. Typical units of dielectric permittivity, or dielectric constant

    for common materials are: Pure Vacuum = 1.0000, Air = 1.0005, Paper = 2.5 to 3.5, Glass = 3 to 10, Mica

    = 5 to 7, Wood = 3 to 8 and Metal Oxide Powders = 6 to 20 etc.

    This then gives us a final equation for the capacitance of a capacitor as:



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    One method used to increase the overall capacitance of a capacitor is to "interleave" more plates

    together within a single capacitor body. Instead of just one set of parallel plates, a capacitor can have

    many individual plates connected together thereby increasing the area, A of the plate.


    7805 is a voltage regulator integrated circuit. It is a member of 78XX series of fixed linear

    voltage regulator ICs .The voltage source in a circuit may have fluctuations and would not give the fixed

    voltage output .the voltage regulator IC maintains the output voltage at a constant value. the XX in 78XX

    indicates the fixed output voltage it is designed to provide.7805 provides +5V regulator power supply.

    capacitors of suitable values can be connected at input and output pins depending upon the respective

    voltage levels.

    7805 voltage regulator


    A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator

    lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic

    component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across

    the visible, ultraviolet and infraredwavelengths, with very high brightness.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    When a light-emitting diode is forwardbiased(switched on), electronsare able to recombine

    with electron holeswithin the device, releasing energy in the form ofphotons. This effect is called

    electroluminescence and the colorof the light (corresponding to the energy of the photon) is

    Circuit symbol for LED

    determined by the energy gap of the semiconductor. LEDs are often small in area (less than 1 mm2), and

    integrated optical components may be used to shape its radiation pattern. LEDs present many advantages

    over incandescent light sources includinglower energy consumption, longerlifetime, improved

    robustness, smaller size, faster switching, and greater durability and reliability. LEDs powerful enough for

    room lighting are relatively expensive and require more precise current and heat management than

    compact fluorescent lamp sources of comparable output.

    The first practical visible-spectrum (red) LED was developed in 1962 byNick Holonyak Jr., while

    working at General Electric Company.

    Physics description:

    The LED consists of a chip of semiconducting material

    doped with impurities to create a p-n junction. As in other diodes,

    current flows easily from the p-side, or anode, to the n-side, or

    cathode, but not in the reverse direction. Charge-carrierselectrons

    and holesflow into the junction from electrodes with different

    voltages. When an electron meets a hole, it falls into a lowerenergy level, and releases energy in the form

    of aphoton.

    The wavelength of the light emitted, and thus its color depends on theband gap energy of the

    materials forming the p-n junction. In silicon orgermanium diodes, the electrons and holes recombine by

    a non-radiative transition which produces no optical emission, because these are indirect band gap



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    materials. The materials used for the LED have a direct band gap with energies corresponding to near

    infrared, visible or near-ultraviolet light.

    LED development began with infrared and red devices made with gallium arsenide. Advances in materials

    sciencehave enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors.

    LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on

    its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially

    GaN/InGaN, also use sapphire substrate.

    Most materials used for LED production have very high refractive indices. This means that

    much light will be reflected back into the material at the material/air surface interface. Thus, ligh

    extraction in LEDsis an important aspect of LED production, subject to much research and development.

    Light-emitting diodes are used in applications as diverse as replacements foraviation lighting, automotive

    lighting (particularly brake lamps, turn signals and indicators) as well as in traffic signals. The compact

    size, the possibility of narrow bandwidth, switching speed, and extreme reliability of LEDs has allowed

    new text and video displays and sensors to be developed, while their high switching rates are also useful in

    advanced communications technology. Infrared LEDs are also used in the remote control units of many

    commercial products including televisions, DVD players, and other domestic appliances.


    Electronic filters are electronic circuits which perform signal processing

    functions, specifically to remove unwanted frequency components from the signal, toenhance wanted ones, or both. Electronic filters can be:

    Passive oractive

    Analog ordigital

    High-pass, low-pass,bandpass,band-reject(band reject; notch), orall-pass.

    Discrete-time (sampled) orcontinuous-time


    Infinite impulse response (IIR type) orfinite impulse response(FIR type)



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    The most common types of electronic filters are linear filters, regardless of other aspects of their design

    See the article on linear filters for details on their design and analysis.

    Classification by technology

    Passive filters

    Passive implementations of linear filters are based on combinations of resistors (R), inductors

    (L) and capacitors (C). These types are collectively known as passive filters, because they do not depend

    upon an external power supply and/or they do not contain active components such as transistors.

    Inductors block high-frequency signals and conduct low-frequency signals, while capacitors do the

    reverse. A filter in which the signal passes through an inductor, or in which a capacitor provides a path to

    ground, presents less attenuation to low-frequency signals than high-frequency signals and is a low-pass

    filter. If the signal passes through a capacitor, or has a path to ground through an inductor, then the filter

    presents less attenuation to high-frequency signals than low-frequency signals and is a high-pass filter

    Resistors on their own have no frequency-selective properties, but are added to inductors and capacitors to

    determine the time-constants of the circuit, and therefore the frequencies to which it responds.

    The inductors and capacitors are the reactive elements of the filter. The number of elements

    determines the order of the filter. In this context, an LC tuned circuitbeing used in a band-pass or band-

    stop filter is considered a single element even though it consists of two components.

    At high frequencies (above about 100 megahertz), sometimes the inductors consist of single loops or strips

    of sheet metal, and the capacitors consist of adjacent strips of metal. These inductive or capacitive pieces

    of metal are called stubs.

    Single element types

    A low-pass electronic filter realized by an RC circuit



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    The simplest passive filters, RC andRL filters, include only one reactive element, except hybrid LC filter

    which is characterized by inductance and capacitance integrated in one element.

    L filter

    An L filter consists of two reactive elements, one in series and one in parallel.

    T and filters

    Low-pass filter

    High-pass T filter

    Three-element filters can have a 'T' or '' topology and in either geometries, a low-pass, high-

    pass,band-pass, orband-stop characteristic is possible. The components can be chosen symmetric or not,

    depending on the required frequency characteristics. The high-pass T filter in the illustration, has a very

    low impedance at high frequencies, and a very high impedance at low frequencies. That means that it can

    be inserted in a transmission line, resulting in the high frequencies being passed and low frequencies being

    reflected. Likewise, for the illustrated low-pass filter, the circuit can be connected to a transmission line,

    transmitting low frequencies and reflecting high frequencies. Using m-derived filtersections with correct

    termination impedances, the input impedance can be reasonably constant in the pass band.

    Multiple element types

    Multiple element filters are usually constructed as a ladder network. These can be seen as a

    continuation of the L,T and designs of filters. More elements are needed when it is desired to improve

    some parameter of the filter such as stop-band rejection or slope of transition from pass-band to stop-band



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    Active filters

    Active filters are implemented using a combination of passive and active (amplifying)

    components, and require an outside power source. Operational amplifiers are frequently used in active

    filter designs. These can have high Q factor, and can achieve resonance without the use of inductors

    However, their upper frequency limit is limited by the bandwidth of the amplifiers used.

    Digital filters

    A general finite impulse response filter with n stages, each with an independent delay, di and

    amplification gain, ai.

    Digital signal processingallows the inexpensive construction of a wide variety of filters. The

    signal is sampled and an analog-to-digital converterturns the signal into a stream of numbers. A computer

    program running on a CPU or a specialized DSP (or less often running on a hardware implementation of

    the algorithm) calculates an output number stream. This output can be converted to a signal by passing it

    through a digital-to-analog converter. There are problems with noise introduced by the conversions, but

    these can be controlled and limited for many useful filters. Due to the sampling involved, the input signal

    must be of limited frequency content oraliasingwill occur.

    The transfer function

    The transfer function of a filter is the ratio of the output signal to that of the input

    signal as a function of the complex frequency :

    with .



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    The transfer function of all linear time-invariant filters, when constructed of discrete

    components, will be the ratio of two polynomials in , i.e. a rational function of . The order of the

    transfer function will be the highest power of encountered in either the numerator or the denominator.


    7. LM 386 IC:LM 386 is a low voltage audio power amplifier.

    The LM 386 is a power amplifier designed for use in low voltage consumer applications. The

    gain is internally set to 20 to keep external part count low, but the addition of an external resistor and

    capacitor between pin 1 and pin 8 will increase the gain to any value from 20 to 200.

    LM 386 IC pin diagram

    The input are ground referenced while the output automatically biases to one half the supply

    voltage. The quiescent power drain is only 24milliwatts.When operating from a 6V supply, making the

    LM 386 ideal for battery operation.

    LM386 Features:

    Battery operation.

    Maximum external parts.

    Wide supply voltage range 4V-12V or 5V-18V.

    Low quiescent current drain 4mA.

    Voltage gains from 20 to 200.

    Ground reference input.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device



    AM-FM radio amplifiers.


    TV sound systems.

    Line drivers.

    Ultrasonic drivers.

    Small servo drivers.

    ower converters.


    There are three important features to consider when selecting a switch:

    Contacts (e.g. single pole, double throw)

    Ratings (maximum voltage and current)

    Method of Operation (toggle, slide, key etc.)

    circuit symbol

    Several terms are used to describe switch contacts:

    Pole - number of switch contact sets.

    Throw - number of conducting positions, single or double.

    Way - number of conducting positions, three or more.

    Momentary - switch returns to its normal position when released.

    Open - off position, contacts not conducting.

    Closed - on position, contacts conducting, there may be several on positions.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    For example: the simplest on-off switch has one set of contacts (single pole) and one switching position

    which conducts (single throw). The switch mechanism has two positions: open (off) and closed (on), but it

    is called 'single throw' because only one position conducts.

    Switch Contact Ratings

    Switch contacts are rated with a maximum voltage and current, and there may be different

    ratings for AC and DC. The AC values are higher because the current falls to zero many times each

    second and an arc is less likely to form across the switch contacts.

    For low voltage electronics projects the voltage rating will not matter, but you may need to check the

    current rating. The maximum current is less for inductive loads (coils and motors) because they cause

    more sparking at the contacts when switched off.


    Single Pole, Double Throw = SPDT

    This switch can be on in both positions, switching on a separate device in each case. It is often called

    a changeover switch. For example, a SPDT switch can be used to switch on a red lamp in one position and

    a green lamp in the other position.

    ON-ON Switch symbol

    A SPDT toggle switch may be used as a simple on-off switch by connecting to COM and one of the A

    or B terminals shown in the diagram. A and B are interchangeable so switches are usually not labeled.




  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    A preset is a three legged electronic component which can be made to offer varying resistance in a

    circuit. The resistance is varied by adjusting the rotary control over it. The adjustment can be done by

    using a small screw driver or a similar tool.

    The resistance does not vary linearly but rather varies in exponential or logarithmic manner. Such variable

    resistors are commonly used for adjusting sensitivity along with a sensor.

    Preset symbol

    These are miniature versions of the standard variable resistor. They are designed to be mounted

    directly onto the circuit board and adjusted only whenthe circuit is built. For

    example to set the frequency of an alarm tone or the sensitivity of a light-sensitive

    circuit. A small screwdriver or similar tool is required to adjust presets.

    Presets are much cheaper than standard variable resistors so they are sometimes used

    in projects where a standard variable resistor would normally be used.

    10. BATTERY

    A nine-volt battery, the most common of which (and the one referred to here unless otherwise

    stated) is designated a PP3 battery, is shaped as a rounded rectangular prism. 9-volt batteries are

    commonly used in pocket transistor radios, smoke detectors, carbon monoxide alarms, guitar effect units

    andradio-controlled vehiclecontrollers. They are also used as backup power to keep the time in digita

    clocks and alarm clocks.

    Nine-volt alkaline batteries are constructed of six individual 1.5V LR61

    cells enclosed in a wrapper. These cells are slightly smaller than standard LR8D425

    AAAA cellsand can be used in their place for some devices, even though they are 3.5

    mm shorter.

    As of 2007, 9-volt batteries accounted for 4% of alkaline primary battery sales in the US. In

    Switzerland as of 2008, 9-volt batteries totalled 2% of primary battery sales and 2% of secondary battery




  • 7/28/2019 60 Seconds Voice Recording and Playback Device



    The connector (snap) consists of two connectors: one smaller circular (male) and one larger,

    typically either hexagonal or octagonal (female). The connectors on the battery are the same as on the

    connector itself; the smaller one connects to the larger one and vice versa.The same connector is used on

    most other battery types in the Power Pack(PP) series. The battery has both terminals on one end. Battery

    polarization is obvious since mechanical connection is only possible in one configuration.

    A problem with this style of connector is that it is very easy to connect two batteries together in

    a short circuit, which quickly discharges both batteries, generating heat and possibly a fire. The clips on

    the nine-volt battery can be used to connect several nine-volt batteries in series to create higher voltage.


    A push-button or simply button is a simple switch mechanism for controlling some aspect of a

    machine or a process. Buttons are typically made out of hard material, usually plastic or metal. The

    surface is usually flat or shaped to accommodate the human finger or hand, so as to be easily depressed or

    pushed. Buttons are most often biased switches, though even many un-biased buttons (due to their

    physical nature) require a springto return to their un-pushed state. Different people use different terms for

    the "pushing" of the button, such as press, depress, mash, and punch.

    The "push-button" has been utilized in calculators, push-button telephones, kitchen appliances, and

    various other mechanical and electronic devices, home and commercial.

    In industrial and commercial applications, push buttons can be linked together by a

    mechanical linkage so that the act of pushing one button causes the other button to be released. In this

    way, a stop button can "force" a start button to be released. This method of linkage is used in simple

    manual operations in which the machine or process have no electrical circuitsfor control.

    12. Microphone

    A microphone (colloquially called a mic or mike) is an acoustic-to-electric transducerorsensor

    that converts sound into an electrical signal. In 1876, Emile Berlinerinvented the first microphone used as

    a telephone voice transmitter. Microphones are used in many applications such as telephones, tape

    recorders, karaokesystems, hearing aids,motion pictureproduction, live and recorded audio engineering



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice,

    speech recognition,VoIP, and for non-acoustic purposes such as ultrasonic checking orknock sensors.

    Most microphones today use electromagnetic induction (dynamic microphone), capacitance

    change (condenser microphone), piezoelectric generation, or light modulation to produce an electrical

    voltage signal from mechanical vibration.

    A fiber optic microphone converts acoustic waves into electrical signals by sensing changes in

    light intensity, instead of sensing changes in capacitance or magnetic fields as with conventional


    During operation, light from a laser source travels through an optical fiber to illuminate the surface of a

    reflective diaphragm. Sound vibrations of the diaphragm modulate the intensity of light reflecting off the

    diaphragm in a specific direction. The modulated light is then transmitted over a second optical fiber to a

    photo detector, which transforms the intensity-modulated light into analog or digital audio for

    transmission or recording. Fiber optic microphones possess high dynamic and frequency range, similar to

    the best high fidelity conventional microphones

    Fiber optic microphones do not react to or influence any electrical, magnetic, electrostatic or

    radioactive fields (this is called EMI/RFI immunity). The fiber optic microphone design is therefore ideal

    for use in areas where conventional microphones are ineffective or dangerous, such as inside industria

    turbines or in magnetic resonance imaging(MRI) equipment environments.

    Fiber optic microphones are robust, resistant to environmental changes in heat and moisture

    and can be produced for any directionality or impedance matching. The distance between the

    microphone's light source and its photo detector may be up to several kilometers without need for any

    preamplifier and/or other electrical device, making fiber optic microphones suitable for industrial and

    surveillance acoustic monitoring.

    Fiber optic microphones are used in very specific application areas such as for infrasound

    monitoring and noise-canceling. They have proven especially useful in medical applications, such as

    allowing radiologists, staff and patients within the powerful and noisy magnetic field to converse



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    normally, inside the MRI suites as well as in remote control rooms.) Other uses include industrial

    equipment monitoring and sensing, audio calibration and measurement, high-fidelity recording and law



    A loudspeaker (or "speaker") is an electro acoustictransducerthat produces sound in response

    to an electricalaudio signal input. Non-electrical loudspeakers were developed as accessories to

    telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful.

    The most common form of loudspeaker uses a paper cone supporting a

    voice coil electromagnet acting on a permanent magnet, but many other

    types exist. Where accurate reproduction of sound is required, multiple

    loudspeakers may be used, each reproducing a part of the audible

    frequency range. Miniature loudspeakers are found in devices such as

    radio and TV receivers, and many forms of music players. Larger

    loudspeaker systems are used for music, sound in theatres and concerts,

    and in public address.





  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    Figure: 1circuit diagram

    3.2 Functional Description:

    APR9600 block diagram is included in order to describe the device's internal architecture. At

    the left hand side of the diagram are the analog inputs. A differential microphone amplifier, including

    integrated AGC, is included on-chip for applications requiring use. The amplified microphone signals fed

    into the device by connecting the ANA_OUT pin to the ANA_IN pin through an external DC blocking

    capacitor. Recording can be fed directly into the ANA_IN pin through a DC blocking capacitor, however,

    the connection between ANA_IN and ANA_OUT is still required for playback. The next block

    encountered by the input signal is the internal anti-aliasing filter. The filters automatically adjust itsresponse according to the sampling frequency selected so Shannons Sampling Theorem is satisfied. After

    anti-aliasing filtering is accomplished the signal is ready to be clocked into the memory array. This storage



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    is accomplished through a combination of the Sample and Hold circuit and the Analog Write/Read circuit.

    These circuits are clocked by either the Internal Oscillator or an external clock source

    Figure2: The APR9600 DIP & SOP is not [PIN TO PIN]

    When playback is desired the previously stored recording is retrieved from memory, low pass

    filtered, and amplified as shown on the right hand side of the diagram. The signal can be heard byconnecting a speaker to the SP+ and SP- pins. Chip-wide management is accomplished through the device

    control block shown in the upper right hand corner. Message management is provided through the

    message control block represented in the lower center of the block diagram. More detail on actual device

    application can be found in the Sample Application section. More detail on sampling control can be found

    in the Sample Rate and Voice Quality section. More detail on Message management and device control

    can be found in the Message Management section.



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    Figure 3 APR9600 Block Diagram

    3.3Message Management:

    Playback and record operations are managed by on-chip circuitry. There are several available

    messaging modes depending upon desired operation. These message modes determine message

    management style, message length, and external parts count. Therefore, the designer must select the

    appropriate operating mode before beginning the design. Operating modes do not affect voice quality; for

    information on factors affecting quality refer to the Sampling Rate & Voice Quality section. The device

    supports five message management modes (defined by the MSEL1, MSEL2 and /M8_OPTION pins

    shown in Figures 1 and 2):

    Random access mode with 2, 4, or 8 fixed-duration messages Tape mode, with multiple variable-

    duration messages, provides two options:

    -Auto rewind

    -Normal Mode cannot be mixed. Switching of modes after the device has recorded an initial message

    is not recommended. If modes are switched after an initial recording has been made some unpredictable

    message fragments from the previous mode may remain present, and be audible on playback, in the new

    mode. These fragments will disappear after a Record operation in the newly selected mode. Table 1



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    defines the decoding necessary to choose the desired mode. An important feature of the APR9600

    Message management capabilities is the ability to audibly prompt the user to change in the device's status

    through the use of "beeps" superimposed on the device's output. This feature is enabled by asserting a

    logic high level on the BE pin.

    Tabel: 2

    The APR9600 device incorporates several features design help simplify microprocessor

    Controlled message management When controlling messages the microprocessor essentially toggles pins

    as described in the message management sections described previously. The /BUSY, /STROBE, and

    /M7_END pins are included to simplify handshaking between the microprocessor and the APR9600

    The /BUSY pin, when low, indicates to the host processor that the device is busy and that No commands

    can be accepted. When this pin is high the device is ready to accept and execute commands from the host.

    The /STROBE pin pulses low each time a memory segment is used. Counting pulses on this pin enablesthe host processor to accurately determine how much recording time has been used, and how much

    recording time remains. The APR9600 has a total of eighty memory segments. The /M7_END pin is used

    as an indicator that the device has stopped its current record or playback operation.

    During recording a low going pulse indicates that all memory has been used. During playback

    a low pulse indicates that the last message has played. Microprocessor control can also be used to link

    several APR9600 devices together in order to increase total available recording time. In this application

    both the speaker and microphone signals can be connected in parallel. The microprocessor will then

    control which device currently drives the speaker by enabling or disabling each device using its respective

    /CE pins.

    A continuous message cannot be recorded in multiple devices however because the transition



    Random Access 2 fixed duration messages 0 1 Pull this pin to VCC through l00K resistor

    Random Access 4 fixed duration messages 1 0 Pull this pin to VCC through l00K resistor

    Random Access 8 fixed duration messages 1 1 The /M8 message trigger becomes input pin

    Tape mode, Auto rewind operation 0 0 0

    Tape mode, Normal operation 0 0 1


  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    from one device to the next will incur a delay that is noticeable upon playback. For this reason it is

    recommended that message boundaries and device boundaries always coincide.

    3.4 Random Access ModeRandom access mode supports 2, 4, or 8 Message segments of fixed duration. As suggested

    recording or playback can be made randomly in any of the selected messages. The length of each message

    segment is the total recording length available (as defined by the selected sampling rate) divided by the

    total number of segments enabled (as decoded in Table1). Random access mode provides easy indexing to

    message segments.

    3.4.1 Functional Description of Recording in Random Access Mode

    On power up, the device is ready to record or playback in any of the enabled message

    segments. To record,/CE must be set low to enable the device and /RE must be set low to enable

    recording. You initiate recording by applying a low level on the message trigger pin that represents the

    message segment you intend to use. The message trigger pins are labeled /M1_MESSAGE -

    /M8_OPTION on pins 1-9 (excluding pin 7) for message segments 1-8 respectively. Note: Message

    trigger pins of M1_MESSAGE,/M2_NEXT, /M7_END, and /M8_OPTION, have expanded names to

    represent the different functionality that these pins assume in the other modes. In random access mode

    these pins should be considered purely message trigger pins with the same functionality as /M3, /M4, /M5

    and /M6. For a more thorough explanation of the functionality of device pins in different modes please

    refer to the pin description table that appears later in this document. When actual recording begins the

    device responds with a single beep (if the BE pin is high to enable the beep tone) at the speaker outputs to

    indicate that it has started recording. Recording continues as long as the message pin stays low. The rising

    edge of the same message trigger pin during record stops the recording operation (indicated with a single

    beep).If the message trigger pin is held low beyond the end of the maximum allocated duration, recording

    stops automatically (indicated with two beeps), regardless of the state of the message trigger pin. The chip

    then enters low-power mode until the message trigger pin returns high. After the message trigger pin

    returns to high, the chip enters standby mode. Any subsequent high to low transition on the same message

    trigger pin will initiate recording from the beginning of the same message segment. The entire previous



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    message is then overwritten by the new message, regardless of the duration of the new message

    Transitions on any other message trigger pin or the /RE pin during the record operation are ignored until

    after the device enters standby mode.

    3.4.2Functional Description of Playback in Random Access Mode

    On power up, the device is ready to record or playback, in any of the enabled message

    segments. To playback,/CE must be set low to enable the device and /RE must be set high to disable

    recording & enable playback. You initiate playback by applying a high to low edge on the message trigger

    pin that represents the message segment you intend to playback. Playback will continue until the end of

    the message isreached. If a high to low edge occurs on the same message trigger pin during playback

    playback of the current message stops immediately. If a different message trigger pin pulses during

    playback, playback of the current message stops immediately (indicated by one beep) and playback of the

    new message segment begins. A delay equal to 8,400 cycles of he sample clock will be encountered

    before the device starts playing the new message. If a message trigger pin is held low, the selected

    message is played back repeatedly as long as the trigger pin stays low. A period of silence, of duration

    equal to 8,400 cycles of the sampling clock, will be inserted during looping as an indicator to the user of

    the transition between the end and the beginning of the message.

    3.5 Signal Storage:

    The APR9600 samples incoming voice signals and stores the instantaneous voltage samples in

    non-volatile FLASH memory cells. Each memory cell can support voltage ranges from 0 to 256 levels.

    These 256 discrete voltage levels are the equivalent of 8-bit (28=256) binary encoded values. During

    playback the stored signals are retrieved from memory, smoothed to form a continuous signal, and then

    amplified before being fed to an external speaker.

    3.6 Sampling Rate & Voice Quality:

    According to Shannon's sampling theorem, the highest possible frequency componen

    introduced to the input of a sampling system must be equal to or less than half the sampling frequency if

    aliasing errors are to be eliminated. The APR9600 automatically filters its input, based on the selected

    sampling frequency, to meet this requirement. Higher sampling rates increase the bandwidth and hence the



  • 7/28/2019 60 Seconds Voice Recording and Playback Device


    voice quality, but they also use more memory cells for the same length of recording time. Lower sampling

    rates use fewer memory cells and effectively increase the duration capabilities of the device, but they also

    reduce incoming signal bandwidth. The APR9600 accommodates sampling rates as high as 8 kHz and as

    low a 4 kHz. You can control the quality/duration trade off by controlling the sampling frequency.

    An internal oscillator provides the APR9600 sampling clock. Oscillator frequency can be Changed by

    changing the resistance from the OscR pin to GND. Table 2 summarizes resistance values and the

    corresponding sampling frequencies, as well as the resulting input bandwidth and duration.

    Table :3 Resistance Values & Sampling Frequencies

    3.7 Automatic Gain Control (AGC) :

    The APR9600 device has an integrated AGC. The AGC affects the microphone input but does

    not affect the ANA_IN input. The AGC circuit insures that the input signal is properly amplified. The

    AGC works by applying maximum gain to small input signals and minimum gain to large input signals

    This assures that inputs of varying amplitude are recorded at the optimum signal level. The AGC amplifier

    is designed to have a fast attack time and a slow decay time. This timing is controlled by the RC network

    connected to pin 19. A value of 220K and 4.7uF has been found to work well for the English language. Be

    aware that different languages, speakers from different countries, and music may all require modificationof the recommended values for the AGC RC network.


    ResistanceSampling FrequencyInput Bandwidth


    84 K 4.2 kHz 2.1 kHz 60 sec

    38 K 6.4 kHz 3.2 kHz 40 sec

    24 K 8.0 kHz 4.0 kHz 32 sec


  • 7/28/2019 60 Seconds Voice Recording and Playback Device



    Doorbell or entrance message. Greet your guests or customers with a welcome message.

    Watchdog" burglar alarm system. Record the barking of a dog and connect this circuit to a alarm

    system to deter burglars.

    Toys applications where you need speech or audio effects.

    Talking picture frames for personal or museum use. Add it to the back of a picture frame of a friend or

    relative to have his or her voice be played back at any time.

    With the looping mode of operation, you can connect the circuit to one of our FM Transmitters in order

    to build a FM Announcement System or talking sign which is ideal for real estate applications.


    Single-chip, high-quality voice recording &

    Playback solution

    - No external ICs required

    - Minimum external components

    Non-volatile Flash memory technology

    - No battery backup required

    User-selectable messaging options

    - Random access of multiple fixed-duration


    - Sequential access of multiple variable duration




  • 7/28/2019 60 Seconds Voice Recording and Playback Device