[[wysiwyg_imageupload:2141:]]This project report is contributed by Mr. Pratap Reddy.
CHAPTER 1 INTRODUCTION
The utilization of electrical power progressively increases in now-a-days. The demand for the electrical power is also increases over the entire world, particularly in India the demand for electrical power increases more and more because of the increase in population. The people utilize the power higher than their requirements because of their sophisticated needs in the day to day life. The major part of electrical power is consumed by the urban areas than the rural areas .The people lived in the urban areas wants to make their life luxurious with the use of more power for their home appliances.
The power conservation is more important to reach the demand of the electrical power; there are several methods available for the conservation of electrical power.
Every system is automated in order to face new challenges in the present day situation. Automated systems have less manual operations, so that the flexibility, reliabilities are high and accurate. Hence every field prefers automated control systems. Especially in the field of electronics automated systems are doing better performance increasingly
The use of modern technologies is to achieve the power conservation not only through the proper design of respective devices and other parameters in the power system. A major part of power conservation can be achieved by consumer‘s proper usage of the power for home appliances, for this purpose “CELL PHONE BASED DEVICE CONTROL WITH VOICE ACKNOWLEDGEMENT” is one of the optimal way .Which uses Mobile technology that keeps monitoring of the various appliances, and will control the operation of these appliances with respect to the signal sent by the mobile. For utilization of appliances the new concept has been thought to manage them remotely by using mobile, which enables the user to remotely control switching of domestic appliances. Just by dialing keypad of remote telephone, from where you are calling you can perform ON / OFF operation of the appliances.
The mobile communications has become one of the driving forces of the digital revolution. Every day, millions of people are making phone calls by pressing a few buttons. Little is known about how one person’s voice reaches the other person’s phone that is thousands of miles away. Even less is known about the security measures and protection behind the system. The complexity of the cell phone is increasing as people begin sending text messages and digital pictures to their friends and family. The cell phone is slowly turning into handheld computer. All the features and advancements in cell phone technology require a backbone to support it. The system has to provide security and the capability for growth to accommodate future enhancements.
The main aim of our project is to operate our home appliances like lights and water pump from office or any other remote places. So if we forgot to switch off the lights or other appliances while going out, it helps us to turn off the appliances with our cell phone. Cell phone works as the remote control for our home appliances. We can control the desire appliance by pressing the corresponding key. The system also gives us voice acknowledgement of the appliance status.
In this project we use several numbers of integrated circuits, network elements such as diodes, rectifiers, filters, resisters, capacitors, etc. In this project we use the microprocessor program based integrated circuit namely IC AT89C51 micro controller, APR9600 audio recording and playback device, MT8870 DTMF receiver, ULN2003 relay driver and other electrical and electronic components for the desired performance of this project. These are explained in the corresponding chapters.
The process of the whole project depends upon the functions of the switches and mobile keys. The functions of switches and mobile keys also explained in the corresponding chapters.
Parts of the System
Detailed tutorials are given on the site. See the below tutorials:
We are going through a period of micro-electric revolution. For a common person, the role of electronics is limited to audio-visual gadgets like radio and television, but the truth is, today the growth of any industry like communication, control, instrumentation or computer, is depend upon electronics to a great extent .And integrated circuits are electronics. The term IC reflects the capabilities of semiconductor industry to fabricate complex electronic circuit consisting of a large number of components on a single substrate. The IC is a miniature, low cost electronic circuit consisting of active and passive components that irreparably joined together on a single chip of silicon. Most of the components used in ICs are not similar to conventional components in appearance although they perform similar electrical functions. These circuits naturally offer a number of advantages over those made by interconnecting discrete components
These are broadly classified as Digital ICs and Linear ICs .Based upon the above requirements , two distinctly different IC technology namely MONOLITHIC and HYBRID technologies have been developed. In monolithic ICs, all circuits’ components, both active and passive elements and their interconnections are manufactured into or on top of a single chip of silicon. The monolithic circuit is ideal for applications where identical circuits are required in very large quantities and hence provides lowest per unit cost and higher order of reliability .Based upon the active devices used, ICs can be classified as bipolar and unipolar (BJT & FET).
1. Miniaturization and hence increased equipment density.
2. Cost reduction due to batch processin.
3 .Improved functional performance
4. Matched devices, Increased operating speed.
3.2 VOICE RECORDING AND PLAYBACK:
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 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 filter automatically adjusts its response according to the sampling frequency selected so Shannon’s Sampling Theorem is satisfied. After anti-aliasing filtering is accomplished the signal is ready to be clocked into the memory array .This storage 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.
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 by connecting 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.
3.3MESSAGE MANAGEMENT GENERAL DESCRIPTION:
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.
Random access mode with 2, 4, or 8 fixed-duration messages Tape mode, with multiple variable-duration messages, provides two options:(a)- Auto rewind (b) – Normal
Modes 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 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.
3.4RANDOM ACCESS MODE:
Random 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 Table3.1). Random access mode provides easy indexing to message segments.
3.4.1 A 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
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 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.
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
3.4.3 Sampling Rate & Voice Quality:
According to Shannon’s sampling theorem, the highest possible frequency component 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 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 as 4 kHz. You can control the quality/duration trade off by controlling the sampling frequency. Mode An internal oscillator provides the APR9600 sampling clock. Oscillator frequency can be changed by changing the resistance from the OscR pin to GND. The pin configuration and the IC APR9600 internal circuit diagrams are shown in fig 3.1 and 3.2.
3.5 DTMF RECEIVER:
The M-8870 is a full DTMF Receiver that integrates both band split filter and decoder functions into a single18-pin DIP or SOIC package. Manufactured using CMOS process technology, the M-8870 offers low power consumption (35 mW max) and precise data handling. Its filter section uses switched capacitor.
Technology for both the high and low group filters and for dial tone rejection. Its decoder uses digital counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. External component count is minimized by provision of an on-chip differential input bus. Minimal external components required include a low-cost 3.579545 MHz color burst crystal, a timing resistor, and a timing capacitor .The M-8870-02 provides a “power-down” option which, when enabled, drops consumption to less than 0.5 mW. The M-8870-02 can also inhibit the decoding of fourth column digits (see Tone Decoding table).
3.5.2 Functional Description:
M-8870 operating functions (see block diagram fig 3.3) include a band split filter that separates the high and low tones of the received pair, and a digital decoder that verifies both the frequency and duration of the received tones before passing the resulting 4-bitcode to the output bus.
The low and high group tones are separated by applying the dual-tone signal to the inputs of two 6th order switched capacitor band pass filters with bandwidths that correspond to the bands enclosing the low and high group tones. The filter also incorporates notches at 350 and 440 Hz, providing excellent dial tone rejection. Each filter output is followed by a single-order switched capacitor section that smooth the signal prior to limiting. Signal limiting is performed by high gain comparators provided with hysteresis to prevent detection of unwanted low-level signals and noise. The comparator outputs provide full-rail logic swing sat the frequencies of the incoming tones.
The M-8870 decoder uses a digital counting technique to determine the frequencies of the limited tones and to verify that they correspond to standard DTMF frequencies. A complex averaging algorithm is used to protect against tone simulation by extraneous signals(such as voice) while tolerating small frequency variations The algorithm ensures an optimum combination of immunity to talk off and tolerance to interfering signals(third tones) and noise. When the detector recognizes the simultaneous presence of two valid tones (known as signal condition), it raises the Early Steering flag (EST). Any subsequent loss of signal condition will cause EST to fall.
(Tone Decoding table)
3.5.5 Steering Circuit:
Before a decoded tone pair is registered, the receiver checks for valid signal duration (referred to as character-recognition-condition). This check is performed by an external RC time constant driven by EST. Logic high on EST causes VC to rise as the capacitor discharges. Provided that signal condition is maintained (EST remains high) for the validation period (tGTF), VC reaches the threshold (VTSt) of the steering logic to register the tone pair, thus latching its corresponding 4-bit code into the output latch. At this point, the GT output is activated and drives VC to VDD.GT continue to drive high as long as ESF remains high. Finally, after a short delay to allow the output latch to settle, the delayed steering output flag (SOF) goes high, signaling that a received tone pair has been registered. The contents of the output latch are made available on the 4-bit output bus by raising the three state control input (OE) to logic high. The steering circuit works in reverse to validate the inter digit pause between signals. Thus, as well as rejecting signals too short to be considered valid, the receiver will tolerate signal interruptions (dropouts) too short to be considered a valid pause. This capability, together with the ability to select the steering time constants externally, allows the designer to tailor performance to meet a wide variety of system requirements
3.5.6 Guard Time Adjustment:
Where independent selection of signal duration and inter digit pause are not required, the simple steering circuit of Basic Steering Circuit is applicable. Component values are chosen according to the formula: tREC = tDP + tGTPtGTP @ 0.67 RC The value of tDP is a parameter of the device and tREC is the minimum signal duration to be recognized by the receiver. A value for C of 0.1 ?F is recommended for most applications, leaving R to be selected by the designer. For example, a suitable value of R for a tREC of 40 ms would be 300 ?k. The timing requirements for most telecommunication applications are satisfied with this circuit. Different steering arrangements may be used to select independently the guard times for tone-present (tGTP) and tone-absent (tGTA).This may be necessary to meet system specification that place both accept and reject limits on both tone duration and inter digit pause. Guard time adjustment also allows the designer to tailor system parameters such as talk off and noise immunity .Increasing tREC improves talk off performance ,since it reduces the probability that tones simulated by speech will maintain signal condition long enough to be registered. On the other hand, a relatively short tRE with a long tDO would be appropriate for extremely noisy environments where fast acquisition time and immunity to dropouts would be required. Design information
3.5.7 Input Configuration:
The input arrangement of the M-8870 provides a differentia input operational amplifier as well as a bias source (VREF) to bias the inputs at mid-rail. Provision is made for connection of a feedback resistor to the op-amp output (GS) for gain adjustment below. In a single-ended configuration, the input pins are connected as shown in the Single – Ended Input Configuration on page 3 with the op-amp connectedfor unity gain and VREF biasing the input at 1/2VDD.The Differential Input Configuration bellow permitsgain adjustmen
3.5.8 DTMF Clock Circuit:
The internal clock circuit is completed with the addition of a standard 3.579545 MHz television color burst crystal. It can be connected to a single M-8870 as shown in the Single – Ended Input Configuration on fig3.5, or to a series of M-8870s. As illustrated in the Common Crystal Connection, a single crystal can be used to connect a series of M-8870s by coupling the oscillator output of each M-8870 through a 30pF capacitor to the oscillator input of the next M-8870.t with the feedback resistor R5.
1. Linear ICs are used in a number of electronic applications such as in fields like audio and radio communications, medical electronics, instrumentation control.
2. A number of linear and non-linear applications of ICs such as subtractor, adder, integrator, differentiator, instrumentation amplifier.
3. Log/antilog amplifiers, analog computation techniques.
4. Clipper / clamper wave generators, variable voltage regulator and switched mode power supply.
5. Comparators, active filters, 555-timer, phase locked loops, DAC and ADC.
6. Ac amplifier, Voltage to current and current to voltage converter.
7. Sample and hold circuit is very useful in digital interfacing and analog to digital and pulse code modulation systems, operational Trans-conductance amplifier (OTA).
8. Power Amplifiers, Multivibrator, and voltage regulators.
10. Half wave and Full wave rectifier circuits.
11. Peak detector, find application in test and measurement instrumentation as well as in amplitude modulation communication.
12. Static relays in power systems
13.Multiplier used in frequency doubling ,measurement of real power ,detecting phase angle difference between two signals of equal frequency ,multiplying two signals ,taking square root of a signal.
14. Linear switched reluctance motor and stepper motor control circuits.
15. Siren, Alarm using LM380 power amplifier.
Diode is an electronic device that allows the passage of current in only one direction. The first such devices were vacuum-tube diodes, consisting of an evacuated glass or steel envelope containing two electrodes a cathode and an anode. Because electrons can flow in only one direction, from cathode to anode, the vacuum-tube diode could be used in rectification. The diodes most commonly used in electronic circuits today are semiconductor diodes. The simplest of these, the germanium point-contact diode, dates from the early days of radio, when the received radio signal was detected by means of a germanium crystal and a fine, pointed wire that rested on it. In modern germanium (or silicon) point-contact diodes, the wire and a tiny crystal plate are mounted inside a small glass tube and connected to two wires that are fused into the ends of the tube.
Junction-type diodes consist of a junction of two different kinds of semiconductor material. The zener diode is a special junction-type diode, using silicon, in which the voltage across the junction is independent of the current through the junction. Because of this characteristic, zener diodes are used as voltage regulators. Another special junction-type diode is used in solar cells; a voltage appears spontaneously when the junction is illuminated. In light-emitting diodes (LEDs), on the other hand, a voltage applied to the semiconductor junction results in the emission of light energy. LEDs are used in numerical displays such as those on electronic digital watches and pocket calculators. See Photoelectric Effect.
Capacitor, device for storing an electrical charge, sometimes called a condenser. In its simplest form a capacitor consists of two metal plates separated by a non-conducting layer called the dielectric. The dielectric may be air, plastic, waxed paper, or another substance such as the mineral mica. When one plate of a capacitor is charged using a battery or other source of direct current, the other plate becomes charged with the opposite sign; that is, positive if the original charge is negative, and negative if the original charge is positive
The electrical size of a capacitor is its capacitance, that is the amount of electric charge it can hold per unit potential difference across its plates—C =
Q/V. The SI unit of capacitance is the farad (F). Because this is such a large unit, capacitors commonly have their size expressed in µF (1 microfarad = 10-6 F) or pF (1 picofarad = 10-9 F). The capacitance of a parallel plate capacitor can be calculated from the relationship: Where A is the area of the plates, d is the distance between them, e0 is the permittivity of free space, and er is the relative permittivity of the dielectric between the two plates
Capacitors can hold a limited amount of electric charge. As more and more charge is added to the plates of a capacitor, the potential difference between the plates increases. Eventually this potential difference becomes so great that the atomic structure of the dielectric breaks down, and charge “leaks” through it. Capacitors can conduct direct current for only an instant but are able to act as conductors in alternating-current circuits, as they constantly charge and discharge as the direction of the current constantly changes. This property makes them useful when direct current must be prevented from entering some part of an electric circuit. Fixed-capacity and variable-capacity capacitors are used with coils in resonant circuits in radios and other electronic equipment. Because the dielectric of a capacitor may break down, there is a limit to the potential difference that may be applied across a capacitor. Capacitors are therefore labeled not only with their capacitance but also with their working potential difference in order to prevent breakdown of the dielectric in use
Light-Emitting Diode (LED), semiconductor device that gives out light when a small current (typically 10 milliamps) flows through it. LEDs are used extensively as electronic indicators. They are available in a range of sizes and shapes, and give out light of a variety of colours. The most common types are cylindrical and glow red, green, or yellow. They are used in displays on devices such as bedside radios and car instruments.
Specialized displays often use a number of LEDs in their construction. For example, a seven-segment display indicates a numeral from 0 to 9, and consists of seven LEDs arranged in a figure of eight. Different segments are illuminated to form the different digits. LED indicators tend to have a limited viewing angle, so it is difficult to see whether they are illuminated except by looking directly from the front.
In common with many other types of diode, the LED is a junction diode, consisting of two kinds of semiconductor (p-type and n-type) joined together (see Semiconductor: Doping). It is usually made from gallium arsenide phosphide, which emits light when a suitable current flows through it. The light output is caused by a release of energy that occurs as electrons pass from one side of the semiconductor junction to the other. The current flowing through an LED must be strictly limited to avoid damaging the device.
· High reliability
· High radiant intensity
· Peak wave length of 940nm
· Low forward voltage
· Free air transmission system
· Infrared remote control units with high power requirements
· Smoke detector
· Infrared applied system
The oscillator are the amplifiers having the gain infinity with which they are capable of generating the pulse itself without any input source , the function of the oscillator is to generate the timing pulses of the specified frequency.
The oscillators of crystal type are of vast usage in the field of linear and digital electronics. Operation of the particular IC in the PCB will be done with the generation of the pulse of the required frequency.
The oscillators are also used in the microcontrollers, embedded system.
Sine wave oscillators based on the use of feedback amplifiers is also used. It consists of amplifier with a gain of A and the transfer ratio B. The quantity AB represents the loop gain of the system. The output signal can be continuously obtained without any input signal if we satisfy the condition AB=1
The above is called Barkhausen criterion for oscillators. The above condition can be satisfied only at one specified frequency for the given component values. But the above condition is difficult to maintain due to temperature variations, aging of components, and change of supply voltage.
5.1 POWER SUPPLY:
The power supplies are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronic circuits and other devices. A power supply can by broken down into a series of blocks, each of which performs a particular function. A D.C power supply which maintains the output voltage constant irrespective of A.C mains fluctuations or load variations is known as “Regulated D.C Power Supply” For example a 5V regulated power supply system as shown below
A transformer is an electrical device which is used to convert electrical power from one electrical circuit to another without change in frequency.
Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC. Step-up transformers increase in output voltage, step-down transformers decrease in output voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage to a safer low voltage. The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils; instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core. Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is stepped up. The ratio of the number of turns on each coil, called the turn’s ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.
Turns ratio = Vp/ VS = Np/NS
Power Out= Power In
VS X IS=VP X IP
Vp = primary (input) voltage
Np = number of turns on primary coil
Ip = primary (input) current
A circuit which is used to convert A.C to D.C is known as RECTIFIER. The process of conversion A.C to D.C is called “RECTIFICATION”
5.3.1 Types of Rectifier:
18.104.22.168 Half wave Rectifier
22.214.171.124 Full wave rectiier
1. Centre tap full wave rectifier
2. Bridge type full bridge rectifier
5.5Comparison of rectifier circuits:
Type of Rectifier
Half wave Full wave Bridge
Number of diodes
PIV of diodes
D.C output voltage
RMS voltage Vrms
5.4.1 Full-wave Rectifier:
From the above comparison we came to know that full wave bridge rectifier as more advantages than the other two rectifiers. So, in our project we are using full wave bridge rectifier circuit.
Bridge Rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification. This is a widely used configuration, both with individual diodes wired as shown and with single component bridges where the diode bridge is wired internally.
A bridge rectifier makes use of four diodes in a bridge arrangement as shown in fig 5.2 to achieve full-wave rectification. This is a widely used configuration, both with individual diodes wired as shown and with single component bridges where the diode bridge is wired internally.
During positive half cycle of secondary, the diodes D2 and D3 are in forward biased while D1 and D4 are in reverse biased as shown in the fig(5.4). The current flow direction is shown in the fig 5.3 with dotted arrows.
During negative half cycle of secondary voltage, the diodes D1 and D4 are in forward biased while D2 and D3 are in reverse biased as shown in the fig 5.4. The current flow direction is shown in the fig 5.4 with dotted arrows.
Filter & Regulator
A Filter is a device which removes the A.C component of rectifier output but allows the D.C component to reach the load
5.4.1 Capacitor Filter:
We have seen that the ripple content in the rectified output of half wave rectifier is 121% or that of full-wave or bridge rectifier or bridge rectifier is 48% such high percentages of ripples is not acceptable for most of the applications. Ripples can be removed by one of the following methods of filtering.
(a) A capacitor, in parallel to the load, provides an easier by –pass for the ripples voltage though it due to low impedance. At ripple frequency and leave the D.C.to appears the load.
(b) An inductor, in series with the load, prevents the passage of the ripple current (due to high impedance at ripple frequency) while allowing the D.C (due to low resistance to D.C)
(c) Various combinations of capacitor and inductor, such as L-section filter section filter, multiple section filter etc. which make use of both the properties mentioned in (a) and (b) above. Two cases of capacitor filter, one applied on half wave and another with full wave rectifier.
Filtering is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output. Filtering significantly increases the average DC voltage to almost the peak value (1.4 × RMS value).
To calculate the value of capacitor(C),
C = ¼*?3*f*r*Rl
f = supply frequency,
r = ripple factor,
Rl = load resistance
5.5 REGULATOR AND ITS FEATURES:
Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable output voltages. The maximum current they can pass also rates them. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current (‘overload protection’) and overheating (‘thermal protection’). Many of the fixed voltage regulator ICs has 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. The LM7805 is simple to use. You simply connect the positive lead of your unregulated DC power supply (anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin and then when you turn on the power, you get a 5 volt supply from the output pin.
The Bay Linear LM78XX is integrated linear positive regulator with three terminals. The LM78XX offer several fixed output voltages making them useful in wide range of applications. When used as a zener diode/resistor combination replacement, the LM78XX usually results in an effective output impedance improvement of two orders of magnitude, lower quiescent current. The LM78XX is available in the TO-252, TO-220 & TO-263packages,
• Output Current of 1.5A
• Output Voltage Tolerance of 5%
• Internal thermal overload protection
• Internal Short-Circuit Limited
• No External Component
• Output Voltage 5.0V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 24V
• Offer in plastic TO-252, TO-220 & TO-263
• Direct Replacement for LM78XX
The schematic arrangement of an attracted armature type relay consists of a laminated electromagnet M carrying a coil C and a pivoted laminated armature. The armature is balanced by a counterweight and carries a pair of spring at its free end.Under normal operatin-g conditions
the current through the relay coil C is such that counter weight holds the armature in the position shown. However, when a short circuit occurs, the current through relay coil increases sufficiently and the relay armature is attracted upwards. The contacts on the relay armature bridge a pair of stationary contacts attached to the relay frame. This completes the trip which results in the opening of the circuit breaker and disconnection of the faulty circuit. The minimum current at which the relay armature is attracted to close the trip circuit is called pick up current. It is a usual practice to provide a number of tapping’s, on the relay coil so that the number of turns in use and the setting value can be varied
6.2.3 Induction type relay:
The induction relays operate based on the electromagnetic principle. therefore , these relays can be used only on A.C circuits and not on D.C circuits. Depending upon the type of rotor being used ,these relays are categorized as (a) induction disc type and(b) induction cup type of relays. In disc type of relays disc is moving element on which moving contact of relay is fixed where as in case of induction cup the contact is fixed with the cup. there are two structures available under the induction disc type of relay(1) shaded pole (2) watt hour meter structures respectively. In shaded pole type structure the disc is placed between the shaded and un shaded poles of the relay. The relay consists of an operating coil which is fed by the current proportional to the system current. The air gap flux produced by this flux is split into two out of phase components by a shading ring made of copper that encircles the part of the pole phase of each pole at the air gap. The disc is normally made of aluminium so as to have low inertia and, therefore, requires less deflecting torque for its motion. Unless the contacts of the other relay are closed, the shading coil remains open and hence no torque can be developed.
6.3 MERITS AND DEMERITS:
Merits of relays:
· Relays can switch AC and DC, transistors can only switch DC.
· Relays can switch high voltages, transistors cannot.
· Relays are a better choice for switching large currents (> 5A).
· Relays can switch many contacts at once.
· Relays are used in long power transmission lines
Demerits of relays:
· Relays are bulkier than transistors for switching small currents.
· Relays cannot switch rapidly (except reed relays), transistors can switch many times per second.
· Relays use more power due to the current flowing through their coil.
Relays require more current than many chips can provide, so a low power transistor may be needed to switch the current for the relays.
Voice Control System
CELL PHONE BASED DEVICE CONTROL
The rapid development of the modern technologies in electric field results in the innovation of the earlier instruments and devices as well as the control methods and the inventions too. The cell phone based device control is one of the control method implemented for the control of a device from the remote place the main advantage of this is prevent the utilization of power under the absence of the consumer in the home, office. Especially for the farmer who will be a larger consumer of power in a day as well as night for the water pumps, lightening and for the protection of field. After the use of the pumps at night times with the CBDC he can switch on/off the pump from his home itself. The user can easily operate the turn ON and turn OFF a particular device, because of the voice recording/play back device in the CBDC gives the voice acknowledgement to the user regarding the status of that particular device . the main merit and demerit of CBCD . when it is installed in home , the installation need two handsets among them one will be connected to the circuit permanently and the other one is the user’s, the circuit provides the facility to control the user and their family member and friends , and the demerit is that by knowing the service number of the handset installed at the circuit others can control the devices. The CBCD will be a one of the optimal way to save power.
The main intension of developing CBCD is to save energy by proper utilization
7.2 CIRCUIT DESCRIPTION:
Cell phone base device control with voice acknowledgement .It comprises microcontroller AT89C51, DTMF decoderMT8870, voice recording/play back device APR9600 and a few discrete components. Microcontroller AT89C51 is at the heart of the circuit. It is a low-power ,high-performance, 8-bit microcontroller with 4 kB of flash programmable and erasable read-only memory(PEROM) used as on-chip program memory, 128 bytes of RAM used as internal data memory, 32 individually programmable input/output (I/O)lines divided into four 8-bit ports, two16-bit programmable timers/counters ,a five-vector two-level interrupt architecture ,on-chip oscillator and clock circuitry .A 11.0592MHz crystal (XTAL1) is used to provide basic clock frequency for the microcontroller. Capacitor C3and resistor R3 forms the power-on reset circuit, while push-to-on switchS20 is used for manual reset. Port pins P1.0 through P1.7 of the microcontroller are configured to get the input from push-to-on switches S1through S8. Pins of Port P1 are pulled high via resistor network RNW1. Port pins P2.0 through P2.4 are configured to receive the decoded DTMF signal from DTMF receiver MT8870. The functions of the corresponding switches (S1 to S8) and cell phone keys are shown in Table 7.1.
The DTMF decoder is used for decoding the mobile signal. It gets DTMF tone from the mobile headset’s speaker pins and decodes it into 4-bit digital signal. The DTMF decoder is operated with a 3.579MHz crystal (XTAL2). In DTMF receiver MT8870 (IC3), capacitorC12 is used to filter the noise and resistors R6 and R7 help to amplify the input signal using the internal amplifier .Pin 16 of IC3 connected to resistorR5 provides the early steering output .It goes high immediately when the digital algorithm detects a valid tone pair (signal condition). Any momentary loss of signal condition causes Est. to return to low state. Pin 17 of IC3 connected to capacitorC11 are bidirectional, acting as steering input/guard time output (St/GT). A voltage greater than threshold of the steering logic VTSt detected at St Causes the device to register the detected tone pair. The guard time output resets the external steering time constant, and its state is a function of Est. and the voltage at St. Port P3 pins P3.6 and P3.7 of IC1are configured to select the control source for the devices. These are connected to DIP switches S17 and S18and pulled high via resistors R2 and R1, respectively. Here, we are using two control sources, switches and mobile’s key. DIP switches S17 and S18select the control sources as shown in Table 7.2.
Pin 2.5 of Port P2 is configured to show the rest status. That is, if none of the control sources is selected by DIP switches S17 and S18, LED1 glows. Resistor R14 limits the current throughLED1. Voice acknowledgement is provided by the APR9600 (IC2). It is a single-chip voice recording and play back device that can record and play multiple messages at random or in sequential mode for 60 seconds. The user can select sample rates with corresponding- quality recording lengths. Microphone amplifier, automatic gain control (AGC) circuits, internal anti -aliasing filter, internal output amplifier and message management are some of the features of the APR9600.Here the APR9600 is configured in random-access mode, which supports two, four and eight messages of fixed durations. The length of each message is the total recording length available divided by the total number of memory segments/tracks enabled. Audio processor APR9600 can store up to eight voice messages. Port P0pins and P2.7 are configured to communicate with IC2. Port P0 pins trigger selection of the message. Port pin P2.7 is the input signal to identify whether the voice message is playing or not. Pins P3.0 through P3.5 of Port P3 control the devices with the help of relays RL1 through RL6 via relay driver IC4.A speaker is connected to IC2 for audio output. The speaker output drives the mic input of the mobile for audio acknowledgement. An electrets microphone MIC1 is connected to IC2 to record the voice in IC2. LED2 flashes to show the busy status of IC2 during recording and playback. The audio messages to be recorded inAPR9600, by using trigger switchesS9 through S16, are shown in Table 7.3
SPST switch S19 is closed for recording and switch S19 is opened for play back. Fig.7.2 shows the power sup- ply circuit. The 230V AC mains is stepped down by transformer X1 to deliver the secondary output of 9V, 500 mA. The transformer output is rectified by a full-wave bridge rectifier comprising diodes D1 throughD4, filtered by capacitor C16 and then regulated by IC 7806 (IC5). CapacitorC15 bypasses the ripples present in the regulated 6V power supply.LED3 acts as a power-on indicator and resistor R16 limits the current through LED3.
Recording and Playback
7.3 VOICE RECORDING AND PLAYBACK:
To record the voice in IC2, follow Table III. Close SPST switch S19 to make pin27 of IC2 low. Thereafter, press and hold switches S9 through S16 to record corresponding voice messages. LED2flashes to indicate audio recording .For playback of any device status, open SPST switch S19 and press the corresponding switch (S9 through S16).The recorded audio can be heard from the speaker connected to pins 14 and15 of IC2. Fig. 2 shows the pin configuration of mobile headset.
Pin configuration of mobile headset:
Power Supply Circuit:
Circuit Diagram of CBDC:
After that, the main function checks through ‘Do’ loop which control source has been enabled by using DIP switch pins. If you select switch S17, it searches the input from the mobile only. If you select switch S18, it searches the input from the switches (S1 through S8) only. If you enable both switch S17and switch S18, it searches the inputs from switches and mobile. Else, the rest-status LED1 glows. Refer to Table 7.2 to select the control source. The mobile signal is decoded into the DTMF signal by IC3. The DTMF output for each mobile key (used in this project) pressed is shown in Table 7.4. After getting the input from the switches or mobile, the program goes to the device action subroutine and executes the corresponding action (refer Table 7.1).
The device action subroutine changes the status of the device and calls the voice alert subroutine. The voice alert subroutine checks the device status and device name from the source input and controls the corresponding pins of IC2. First, it selects the voice signal for the device name .After playing that, it selects on/off status of corresponding device as mentioned in Table 7.3. If you press ‘*’ key followed by the device number on your mobile handset, it will not change the status of that device and inform the current device status. If you press device number
The program (Device_Control.BAS) for the microcontroller is written using BASCOM microcontroller programming software. In the program, first, initialize the ports (P0-P3) for corresponding controls. Thereafter, declare the variables for the program. After declaration, assign some initial value to variables. Here, microcontroller ports are initialized to make all the devices ‘off’ initially
Find the project code in attachments.
The project “Development of Cell-phone Based Device Control with Voice Acknowledgement” an effective switching system for controlling home and office appliances.” has been successfully designed and tested.
It has been developed by integrating features of all the hardware components used. Presence of every module has been reasoned out and placed carefully thus contributing to the best working of the unit.
Secondly, using highly advanced IC’s and with the help of growing technology the project has been successfully implemented.
Finally we conclude that “CELL-PHONE BASED WIRELESS HOME APPLIANCES MONITORING AND CONTROL” is an emerging field and there is a huge scope for research and development.
In this project we are monitoring and controlling the home appliances from remote places by using the mobile technology. This project can be further enhanced to the High voltage A.C Applications by changing the ratings of the Relay. By this we can control and monitoring the high speed induction motors as well as synchronous motors. This can be done in an economical way
IC Integrated Circuits
RAM Random access memory
ROM Read only memory
EPROM Erasable programmable read only memory
ADC Analog to digital converter
DAC Digital to analog converter
CPU Central processing unit
LSB Least significant bit
MSB Most significant bit
DIP Dual-in-line package
ALE Address latch enable
MOS Metal oxide semi-conductor
BJT Bipolar junction transistor
FET Field effect transisto
AGC Automatic gain control
DTMF Dual tone medium frequency
CMOS Complementary metal oxide semi-conductor
BE Byte enable
LED Light emitting diode
PCB Printed circuit board
PIV Peak inverse voltage
TUF Transformer utilization factor
NO Normally close
NC Normally open
SPDT Single pole Double through
DPDT Double pole Double through
Project Source Code
###$large$regfile = “89c51cc.DAT”$crystal = 11059200‘ DECLERATION OF FUNCTIONSDeclare Sub KeypadDeclare Sub Device_actionDeclare Sub Voice_alertDeclare Sub Dtmf_input‘ INPUT FROM DTMF DECODERDtmf_a Alias P2.4Dtmf_b Alias P2.3Dtmf_c Alias P2.2Dtmf_d Alias P2.1Dtmf_ack Alias P2.0‘ INPUT FROM KEYPADKey_1 Alias P1.0Key_2 Alias P1.1Key_3 Alias P1.2Key_4 Alias P1.3Key_5 Alias P1.4Key_6 Alias P1.5Key_a Alias P1.6Key_v Alias P1.7‘ OUTPUT TO AUDIO SELECTIONAud_1 Alias P0.0Aud_2 Alias P0.1Aud_3 Alias P0.2Aud_4 Alias P0.3Aud_5 Alias P0.4Aud_6 Alias P0.5Aud_on Alias P0.6Aud_off Alias P0.7‘Aud_rewind Alias P2.6‘INPUT FROM APR9600Aud_busy Alias P2.7‘OUTPUT TO DEVICEDevice_1 Alias P3.0Device_2 Alias P3.1Device_3 Alias P3.2Device_4 Alias P3.3Device_5 Alias P3.4Device_6 Alias P3.5‘CONTROLLING MODE SELECTIONDevice_a Alias P3.6Device_b Alias P3.7‘ DECLARING VARIABLESDim Keypad_value As ByteDim Device_1_status As BitDim Device_2_status As BitDim Device_3_status As BitDim Device_4_status As BitDim Device_5_status As BitDim Device_6_status As BitDim Common_status As BitDim Voice As BitDim Status_enable As Bit‘INTIALIZING VALUESKeypad_value = 15Aud_1 = 1Aud_2 = 1Aud_3 = 1Aud_4 = 1Aud_5 = 1Aud_6 = 1Aud_on = 1Aud_off = 1‘Aud_rewind = 0Device_1_status = 0Device_2_status = 0Device_3_status = 0Device_4_status = 0Device_5_status = 0Device_6_status = 0Device_1 = 0Device_2 = 0Device_3 = 0Device_4 = 0Device_5 = 0Device_6 = 0Voice = 1DoIf Device_a = 0 And Device_b = 0 ThenP2.5 = 0Elseif Device_a = 0 And Device_b = 1ThenP2.5 = 1Call Keypad‘If Keypad_value < 9 ThenCall Device_action‘End IfElseif Device_a = 1 And Device_b = 0ThenP2.5 = 1Call Dtmf_input‘If Keypad_value < 9 ThenCall Device_action‘End IfElseif Device_a = 1 And Device_b = 1ThenP2.5 = 1Call KeypadCall Dtmf_input‘If Keypad_value < 9 ThenCall Device_action‘ End IfEnd IfIf Status_enable = 1 ThenWhile Keypad_value > 7If Device_b = 1 ThenCall KeypadEnd IfIf Device_a = 1 ThenCall Dtmf_inputEnd IfWendCall Voice_alertStatus_enable = 0End IfLoopSub KeypadIf Key_1 = 0 ThenKeypad_value = 1Bitwait Key_1 , SetElseif Key_2 = 0 ThenKeypad_value = 2Bitwait Key_2 , SetElseif Key_3 = 0 ThenKeypad_value = 3Bitwait Key_3 , SetElseif Key_4 = 0 ThenKeypad_value = 4Bitwait Key_4 , SetElseif Key_5 = 0 ThenKeypad_value = 5Bitwait Key_5 , SetElseif Key_6 = 0 ThenKeypad_value = 6Bitwait Key_6 , SetElseif Key_a = 0 ThenKeypad_value = 7Bitwait Key_a , SetElseif Key_v = 0 ThenKeypad_value = 8Bitwait Key_v , SetElseKeypad_value = 15End IfEnd SubSub Device_actionIf Keypad_value = 1 ThenDevice_1_status = Not Device_1_statusDevice_1 = Device_1_statusCall Voice_alertElseif Keypad_value = 2 ThenDevice_2_status = Not Device_2_statusDevice_2 = Device_2_statusCall Voice_alertElseif Keypad_value = 3 ThenDevice_3_status = Not Device_3_statusDevice_3 = Device_3_statusCall Voice_alertElseif Keypad_value = 4 ThenDevice_4_status = Not Device_4_statusDevice_4 = Device_4_statusCall Voice_alertElseif Keypad_value = 5 ThenDevice_5_status = Not Device_5_statusDevice_5 = Device_5_statusCall Voice_alertElseif Keypad_value = 6 ThenDevice_6_status = Not Device_6_statusDevice_6 = Device_6_statusCall Voice_alertElseif Keypad_value = 7 ThenKeypad_value = 15Status_enable = 1Elseif Keypad_value = 8 ThenIf Voice = 1 ThenVoice = 0Elseif Voice = 0 ThenVoice = 1End IfEnd IfKeypad_value = 15End SubSub Dtmf_inputIf Dtmf_ack = 1 ThenBitwait Dtmf_ack , ResetIf Dtmf_d = 0 And Dtmf_c = 0 And Dtmf_b = 0 And Dtmf_a = 1 ThenKeypad_value = 1Elseif Dtmf_d = 0 And Dtmf_c = 0 AndDtmf_b = 1 And Dtmf_a = 0 ThenKeypad_value = 2Elseif Dtmf_d = 0 And Dtmf_c = 0 AndDtmf_b = 1 And Dtmf_a = 1 ThenKeypad_value = 3Elseif Dtmf_d = 0 And Dtmf_c = 1 AndDtmf_b = 0 And Dtmf_a = 0 ThenKeypad_value = 4Elseif Dtmf_d = 0 And Dtmf_c = 1 AndDtmf_b = 0 And Dtmf_a = 1 ThenKeypad_value = 5Elseif Dtmf_d = 0 And Dtmf_c = 1 AndDtmf_b = 1 And Dtmf_a = 0 ThenKeypad_value = 6Elseif Dtmf_d = 1 And Dtmf_c = 0 AndDtmf_b = 1 And Dtmf_a = 1 ThenKeypad_value = 7Elseif Dtmf_d = 1 And Dtmf_c = 1 AndDtmf_b = 0 And Dtmf_a = 0 ThenKeypad_value = 8ElseKeypad_value = 15End IfEnd IfEnd SubSub Voice_alertIf Voice = 1 And Keypad_value < 7 ThenIf Keypad_value = 1 ThenCommon_status = Device_1_statusAud_1 = 0Wait 1Aud_1 = 1Elseif Keypad_value = 2 ThenCommon_status = Device_2_statusAud_2 = 0Wait 1Aud_2 = 1Elseif Keypad_value = 3 ThenCommon_status = Device_3_statusAud_3 = 0Wait 1Aud_3 = 1Elseif Keypad_value = 4 ThenCommon_status = Device_4_statusAud_4 = 0Wait 1Aud_4 = 1Elseif Keypad_value = 5 ThenCommon_status = Device_5_statusAud_5 = 0Wait 1Aud_5 = 1Elseif Keypad_value = 6 ThenCommon_status = Device_6_statusAud_6 = 0Wait 1Aud_6 = 1End If‘Bitwait Aud_busy , SetWait 5If Common_status = 1 ThenAud_off = 0Wait 1Aud_off = 1Elseif Common_status = 0 ThenAud_on = 0Wait 1Aud_on = 1End IfBitwait Aud_busy , SetEnd IfEnd Sub.
Filed Under: Electronic Projects