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  • 2. TABLE OF CONTENTS CHAPTER ONE: INTRODUCTION 1.1 Introduction 1.2 Methodology 1.3 Scope of Work 1.4 Aims of the GSM ROBOT CONTROL 1.5 Objectives of the GSM ROBOT CONTROL CHAPTER TWO: THEORETICAL BACKGROUND AND LITERATURE REVIEW 2.0 Theoretical Background 2.1 GSM Architecture 2.2 Technical Details 2.3 Main Cellular Standards 2.4 GSM Frequencies 2.5 Network Structure 2.6 Subscriber Identity Module (SIM) 2.7 Literature Review 2.8 GSM Security 2.9 Circuit Diagram of the GSM ROBOT CONTROL and Power Supply CHAPTER THREE: DESIGN AND CONSTRUCTION 3.1 GSM Modem 3.1.1 Accessing GSM MODEM using Microsoft HyperTerminal 3
  • 3. 3.2 Testing of GSM Modem 3.3 List of Important AT Commands 3.4 Microcontroller – MODEM Interfacing 3.4.1. DTE and DCE 3.4.2. RS-232 3.4.3. RTS/CTS Handshaking 3.4.4. Specifying Baud Rate, Parity & Stop bits 3.4.5 DCE Baud Rates CHAPTER FOUR: TESTS, RESULTS, AND DISCUSSION 4.1 Testing a DB-9 RS-232 serial port in HyperTerminal 4.2 Testing and Observations 4.3 Operational Flowchart 4.4 Initializations 4.4.1 Serial transfer using TI and RI flags 4.4.2 Validity Check 4.4.3 Display 4.5 Programmer 4.6 Simulator 4.6 Burner 4
  • 5. CHAPTER ONE INTRODUCTION GSM and GPRS based Designs have developed another innovative and Public utility product for mass communication [1]. This is a Robot Control Device which control the Robot through messages received as SMS or GPRS Packets and also send acknowledgement of task. Such Devices can be used at different areas of the human being life. Such offices, houses, factories etc. Sent command from Mobiles or PCs to these devices for move the motor left, right, stop. These devices are designed to remotely control the Robot from anywhere and anytime. Wireless communication has announced its arrival on big stage and the world is going mobile [2]. We want to control everything and without moving an inch. This remote control Robot Control device is possible through Embedded Systems. The use of “Embedded System in Communication” has given rise to many interesting applications that ensures comfort and safety to human life [3]. The main aim of the project will be to design a SMS electronic Robot Control toolkit which can replace the traditional Robot Control Devices. 6 The toolkit
  • 6. receives the SMS, validates the sending Mobile Identification Number (MIN) and perform the desired operation after necessary code conversion. The system is made efficient by SIMs so that the SMS can be received by number of devices boards in a locality using techniques of time division multiple access. The main components of the toolkit include microcontroller, GSM modem. These components are integrated with the device board and thus incorporate the wireless features. The GSM modem receives the SMS. The AT commands are serially transferred to the modem. In return the modem transmits the stored message through the wireless link. The microcontroller validates the SMS and then perform specific task on the device. The microcontroller used in this case is ATMEL AT89S52 .Motorola W220 is used as the GSM modem. In this prototype model, LCD display is used for simulation purpose. The results presented in the thesis support the proper functionalities and working of the system. The timing diagram suggests the response of the modem to various AT (attention) commands. 7
  • 7. 1.2 METHODOLOGY The method used to carry out this project is the principle of serial communication in collaboration with embedded systems. This is a very good project for Industries. This project has a Robot Control, which will be used as the electronic device, and also a GSM modem, which is the latest technology used for communication between the mobile and the embedded devices. System will work like when the user wants to on/off the device; he has to send the message in his mobile defining the messages and then the password of the system to the number of the subscriber identity module (SIM) which is inserted in the display system MODEM. Then, the MODEM connected to the display system will receive the SMS, the microcontroller inside the system is programmed in such a way that when the modem receives any message the microcontroller will read the message from serial headphone and verify for the password, if the password is correct then it will start performing desire task. 1.3 Scope of Work I will use liquid crystal display for displaying the message; I will also use GSM modem (Motorola W220) as an interface between 8
  • 8. mobile and microcontroller. I will send message from any phone irrespective of the GSM network to the modem connected to the programmable device using a password. The message will get by the GSM Modem of the device and do specific task. 1.4 AIMS OF THE GSM ELECTRONIC ROBOT CONTROL Uses: This is a very useful and innovative project you can use this project in industries to control the robot for different tasks. 1.5 OBJECTIVES OF THE GSM ELECTRONIC ROBOT CONTROL Programming of the mobile phone with AT (Attention) command sequence Interfacing the programming chip with the personal computer Interfacing the programmable chip with the Robot. Interfacing of the mobile phone with the programmable chip Sending messages from the remote phone to control device. 9
  • 11. COMPONENT LIST WIRELESS ROBOT – CONTROL Name Capacity Quantity Code Regulator 7805 1 U1 Regulator 7812 1 U3 Capacitor 1000µf 1 C1 Capacitor 10µf 1 C2 Ceramic Capacitor 22pf 2 C3,C4 Diode 4 D1,D2,D3,D4 Push Button 1 Mobile Phone 1 DC MOTOR 100rpm 2 LCD 16*2 1 40 Pin Base 1 U2 16 Pin Base 1 U4 8051(AT89S52) 1 L293D 1 Oscillator 11.0592mhz 1 1 LED X1 D5 Resistance 220 1 R1 Resistance 1k 1 R3 Resistance 10k 1 R2 12
  • 12. CHAPTER TWO THEORETICAL BACKGROUND AND LITERATURE REVIEW 2.0 Theoretical Background GSM (Global System for Mobile communications: originally from GROUPE Special Mobile) is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 80% of the global mobile market uses the standard. GSM is used by over 3 billion people across more than 212 countries and territories [4]. Its ubiquity makes international roaming very common between mobile phone operators enabling subscribers to use their phones in many parts of the world. GSM differs from its predecessors in that both signaling and speech channels are digital, and thus is considered a second generation (2G) mobile phone system [5]. This has also meant that data communication was easy to build into the system. 2.1 GSM Architecture GSM is a complex system and difficult to understand. The Mobile Station (MS) refers to the mobile equipment [6]. The 13
  • 13. Base Station Subsystem controls the radio link with the Mobile Station. The Network Subsystem performs main functions such as switching of calls between mobile users, mobility management operations, and proper operation and setup of a network [7]. These functions are controlled by the Mobile Services Switching Center (MSC). 2.2 TECHNICAL DETAILS GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. 2.3 MAIN CELLULAR STANDARDS YEAR STANDARD MOBILE TECHNO PRIMARY TELEPHONE LOGY MARKETS SYSTEM 1981 NMT540 NORDIC MOBILE ANALOG TELEPHONY 1985 TACS TOTAL UE ACCESS ANALOG COMMUNUNICATION UE EUROPE,MIDDL E EAST EUROPE CHINA SYSTEM 1986 NMT900 NORDIC MOBILE ANALOG 14 EUROPE, AND
  • 15. 2.4 GSM FREQUENCIES GSM networks operate in a number of different frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G). Most 2G GSM networks operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz frequency bands were already allocated. Most 3G GSM networks in Europe operate in the 2100 MHz frequency band [9] 2.5 NETWORK STRUCTURE The network behind the GSM seen by the customer is large and complicated in order to provide all of the services which are required. The Base Station Subsystem (the base stations and their controllers). 16
  • 16. The Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network. The GPRS Core Network (the optional part which allows packet based Internet connections). All of the elements in the system combine to produce many GSM services such as voice calls and SMS. 2.6 SUBSCRIBER IDENTITY MODULE (SIM) One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information and phone book. This allows the user to retain his or her information after switching handsets [10]. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM locking, and is illegal in some countries [11]. 17
  • 17. 2.7 LITERATURE REVIEW This project is an implementation to the idea of the wireless communication between a mobile phone and a microcontroller. Currently the main work that has been done on this proposed system is through serial port to the computer but not wireless. If they want to control the GENERATOR, they have to go to the remote area and change the rotation and one /off the GENERATOR. But in this new design, the systems need not be reprogrammed to control GENERATOR changing the programming of microcontroller. The user will send SMS from his phone and he will be able to control the GENERATOR. 2.8 GSM SECURITY GSM was designed with a moderate level of security. The system was designed to authenticate the subscriber using a preshared key and challenge-response. Communications between the subscriber and the base station can be encrypted. 18
  • 18. Fig. 2.2 Block Diagram As we see in the above figure, there are at least three interfacing circuits, MAX-232 with Microcontroller, LCD display with microcontroller, and MAX-232 with GSM MODEM. 19
  • 19. HARDWARE DISCRIPTION POWER SUPPLY: Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others. Here in our application we need a 5v DC power supply for all electronics involved in the project. This requires step down transformer, rectifier, voltage regulator, and filter circuit for generation of 5v DC power. Here a brief description of all the components is given as follows: TRANSFORMER: A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils or "windings". Except for air-core 20
  • 20. transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magneticallycoupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction. If a load is connected to the secondary circuit, electric charge will flow in the secondary winding of the transformer and transfer energy from the primary circuit to the load connected in the secondary circuit. The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP by a factor equal to the ratio of the number of turns of wire in their respective windings: 21
  • 21. By appropriate selection of the numbers of turns, a transformer thus allows an alternating voltage to be stepped up — by making NS more than NP — or stepped down, by making it BASIC PARTS OF A TRANSFORMER In its most basic form a transformer consists of: A primary coil or winding. A secondary coil or winding. A core that supports the coils or windings. Refer to the transformer circuit in figure as you read the following explanation: The primary winding is connected to a 60-hertz ac voltage source. The magnetic field (flux) builds up (expands) and collapses (contracts) about the primary winding. The expanding and contracting magnetic field around the primary winding cuts the secondary winding and induces an alternating voltage into the winding. This voltage causes alternating current to flow through the load. The voltage may be 22
  • 22. stepped up or down depending on the design of the primary and secondary windings. THE COMPONENTS OF A TRANSFORMER Two coils of wire (called windings) are wound on some type of core material. In some cases the coils of wire are wound on a cylindrical or rectangular cardboard form. In effect, the core material is air and the transformer is called an AIR-CORE TRANSFORMER. Transformers used at low frequencies, such as 60 hertz and 400 hertz, require a core of low-reluctance magnetic material, usually iron. This type of transformer is called an IRON-CORE TRANSFORMER. 23 Most power
  • 23. transformers are of the iron-core type. The principle parts of a transformer and their functions are: The CORE, which provides a path for the magnetic lines of flux. The PRIMARY WINDING, which receives energy from the ac source. The SECONDARY WINDING, which receives energy from the primary winding and delivers it to the load. The ENCLOSURE, which protects the above components from dirt, moisture, and mechanical damage. 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. 24
  • 24. BASIC OPERATION According to the conventional model of current flow originally established by Benjamin Franklin and still followed by most engineers today, current is assumed to flow through electrical conductors from the positive to the negative pole. In actuality, free electrons in a conductor nearly always flow from the negative to the positive pole. In the vast majority of applications, however, the actual direction of current flow is irrelevant. Therefore, in the discussion below the conventional model is retained. In the diagrams below, when the input connected to the left corner of the diamond is positive, and the input connected to the right corner is negative, current flows from the upper supply terminal to the right along the red (positive) path to the output, and returns to the lower supply terminal via the blue (negative) path. 25
  • 25. When the input connected to the left corner is negative, and the input connected to the right corner is positive, current flows from the lower supply terminal to the right along the red path to the output, and returns to the upper supply terminal via the blue path. In each case, the upper right output remains positive and lower right output negative. Since this is true whether the input is AC 26
  • 26. or DC, this circuit not only produces a DC output from an AC input, it can also provide what is sometimes called "reverse polarity protection". That is, it permits normal functioning of DC-powered equipment when batteries have been installed backwards, or when the leads (wires) from a DC power source have been reversed, and protects the equipment from potential damage caused by reverse polarity. Prior to availability of integrated electronics, such a bridge rectifier was always constructed from discrete components. Since about 1950, a single four-terminal component containing the four diodes connected in the bridge configuration became a standard commercial component and is now available with various voltage and current ratings. OUTPUT SMOOTHING For many applications, especially with single phase AC where the full-wave bridge serves to convert an AC input into a DC output, the addition of a capacitor may be desired because the bridge alone supplies an output of fixed polarity but 27
  • 27. continuously varying or "pulsating" magnitude (see diagram above). The function of this capacitor, known as a reservoir capacitor (or smoothing capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage waveform from the bridge. One explanation of 'smoothing' is that the capacitor provides a low impedance path to the AC component of the output, reducing the AC voltage across, and AC current through, the resistive load. In less technical terms, any drop in the output voltage and current of the bridge tends to be canceled by loss of charge in the capacitor. This charge flows out as additional current through the load. Thus the change of load current and voltage is reduced relative to what would occur without the capacitor. Increases of 28
  • 28. voltage correspondingly store excess charge in the capacitor, thus moderating the change in output voltage / current. The simplified circuit shown has a well-deserved reputation for being dangerous, because, in some applications, the capacitor can retain a lethal charge after the AC power source is removed. If supplying a dangerous voltage, a practical circuit should include a reliable way to safely discharge the capacitor. If the normal load cannot be guaranteed to perform this function, perhaps because it can be disconnected, the circuit should include a bleeder resistor connected as close as practical across the capacitor. This resistor should consume a current large enough to discharge the capacitor in a reasonable time, but small enough to minimize unnecessary power waste. Because a bleeder sets a minimum current drain, the regulation of the circuit, defined as percentage voltage change from minimum to maximum load, is improved. However in many cases the improvement is of insignificant magnitude. The capacitor and the load resistance have a typical time constant RC where C and R are the capacitance and load resistance respectively. As long as the load resistor is large 29
  • 29. enough so that this time constant is much longer than the time of one ripple cycle, the above configuration will produce a smoothed DC voltage across the load. In some designs, a series resistor at the load side of the capacitor is added. The smoothing can then be improved by adding additional stages of capacitor–resistor pairs, often done only for sub-supplies to critical high-gain circuits that tend to be sensitive to supply voltage noise. The idealized waveforms shown above are seen for both voltage and current when the load on the bridge is resistive. When the load includes a smoothing capacitor, both the voltage and the current waveforms will be greatly changed. While the voltage is smoothed, as described above, current will flow through the bridge only during the time when the input voltage is greater than the capacitor voltage. For example, if the load draws an average current of n Amps, and the diodes conduct for 10% of the time, the average diode current during conduction must be 10n Amps. This non-sinusoidal current leads to harmonic distortion and a poor power factor in the AC supply. 30
  • 30. In a practical circuit, when a capacitor is directly connected to the output of a bridge, the bridge diodes must be sized to withstand the current surge that occurs when the power is turned on at the peak of the AC voltage and the capacitor is fully discharged. Sometimes a small series resistor is included before the capacitor to limit this current, though in most applications the power supply transformer's resistance is already sufficient. Output can also be smoothed using a choke and second capacitor. The choke tends to keep the current (rather than the voltage) more constant. Due to the relatively high cost of an effective choke compared to a resistor and capacitor this is not employed in modern equipment. Some early console radios created the speaker's constant field with the current from the high voltage ("B +") power supply, which was then routed to the consuming circuits, (permanent magnets were then too weak for good performance) to create the speaker's constant magnetic field. The speaker field coil thus performed 2 jobs in one: it acted as a choke, filtering the power supply, and it produced the magnetic field to operate the speaker. 31
  • 31. REGULATOR IC (78XX) It is a three pin IC used as a voltage regulator. It converts unregulated DC current into regulated DC current. Normally we get fixed output by connecting the voltage regulator at the output of the filtered DC (see in above diagram). It can also be used in circuits to get a low DC voltage from a high DC voltage (for example we use 7805 to get 5V from 12V). There are two types of voltage regulators 1. fixed voltage regulators (78xx, 79xx) 2. variable voltage regulators (LM317) In fixed voltage regulators there is another classification 1. +ve voltage regulators 2. -ve voltage regulators POSITIVE VOLTAGE REGULATORS This include 78xx voltage 32
  • 32. regulators. The most commonly used ones are 7805 and 7812. 7805 gives fixed 5V DC voltage if input voltage is in (7.5V, 20V). THE CAPACITOR FILTER The simple capacitor filter is the most basic type of power supply filter. The application of the simple capacitor filter is very limited. It is sometimes used on extremely high-voltage, low-current power supplies for cathode ray and similar electron tubes, which require very little load current from the supply. The capacitor filter is also used where the power-supply ripple frequency is not critical; this frequency can be relatively high. The capacitor (C1) shown in figure 4-15 is a simple filter connected across the output of the rectifier in parallel with the load. Full-wave rectifier with a capacitor filter. 33
  • 33. When this filter is used, the RC charge time of the filter capacitor (C1) must be short and the RC discharge time must be long to eliminate ripple action. In other words, the capacitor must charge up fast, preferably with no discharge at all. Better filtering also results when the input frequency is high; therefore, the full-wave rectifier output is easier to filter than that of the half-wave rectifier because of its higher frequency. For you to have a better understanding of the effect that filtering has on Eavg, a comparison of a rectifier circuit with a filter and one without a filter is illustrated in views A and B of figure 416. The output waveforms in figure 4-16 represent the unfiltered and filtered outputs of the half-wave rectifier circuit. Current pulses flow through the load resistance (RL) each time a diode conducts. The dashed line indicates the average value of output voltage. For the half-wave rectifier, Eavg is less than half (or approximately 0.318) of the peak output voltage. This value is still much less than that of the applied voltage. With no capacitor connected across the output of the rectifier circuit, the waveform in view A has a large pulsating component (ripple) compared with the average or dc component. When a capacitor 34
  • 34. is connected across the output (view B), the average value of output voltage (Eavg) is increased due to the filtering action of capacitor C1. UNFILTERED Half-wave rectifier with and without filtering. FILTERE 35
  • 35. The value of the capacitor is fairly large (several microfarads), thus it presents a relatively low reactance to the pulsating current and it stores a substantial charge. The rate of charge for the capacitor is limited only by the resistance of the conducting diode, which is relatively low. Therefore, the RC charge time of the circuit is relatively short. As a result, when the pulsating voltage is first applied to the circuit, the capacitor charges rapidly and almost reaches the peak value of the rectified voltage within the first few cycles. The capacitor attempts to charge to the peak value of the rectified voltage anytime a diode is conducting, and tends to retain its charge when the rectifier output falls to zero. (The capacitor cannot discharge immediately.) The capacitor slowly discharges through the load resistance (RL) during the time the rectifier is non-conducting. The rate of discharge of the capacitor is determined by the value of capacitance and the value of the load resistance. If the capacitance and load-resistance values are large, the RC discharge time for the circuit is relatively long. 36
  • 36. A comparison of the waveforms shown in figure 4-16 (view A and view B) illustrates that the addition of C1 to the circuit results in an increase in the average of the output voltage (Eavg) and a reduction in the amplitude of the ripple component (Er) which is normally present across the load resistance. Now, let's consider a complete cycle of operation using a halfwave rectifier, a capacitive filter (C1), and a load resistor (RL). As shown in view A of figure 4-17, the capacitive filter (C1) is assumed to be large enough to ensure a small reactance to the pulsating rectified current. The resistance of R L is assumed to be much greater than the reactance of C1 at the input frequency. When the circuit is energized, the diode conducts on the positive half cycle and current flows through the circuit, allowing C1 to charge. C1 will charge to approximately the peak value of the input voltage. (The charge is less than the peak value because of the voltage drop across the diode (D1)). In view A of the figure, the heavy solid line on the waveform indicates the charge on C1. As illustrated in view B, the diode cannot conduct on the negative half cycle because the anode of D1 is negative with respect to the cathode. During this interval, C1 discharges 37
  • 37. through the load resistor (RL). The discharge of C1 produces the downward slope as indicated by the solid line on the waveform in view B. In contrast to the abrupt fall of the applied ac voltage from peak value to zero, the voltage across C1 (and thus across RL) during the discharge period gradually decreases until the time of the next half cycle of rectifier operation. Keep in mind that for good filtering, the filter capacitor should charge up as fast as possible and discharge as little as possible. Figure 4-17A. - Capacitor filter circuit (positive and negative half cycles). POSITIVE HALF-CYCLE Figure 4-17B. - Capacitor filter circuit (positive and negative half cycles). NEGATIVE HALF-CYCLE 38
  • 38. Since practical values of C1 and RL ensure a more or less gradual decrease of the discharge voltage, a substantial charge remains on the capacitor at the time of the next half cycle of operation. As a result, no current can flow through the diode until the rising ac input voltage at the anode of the diode exceeds the voltage on the charge remaining on C1. The charge on C1 is the cathode potential of the diode. When the potential on the anode exceeds the potential on the cathode (the charge on C1), the diode again conducts, and C1 begins to charge to approximately the peak value of the applied voltage. After the capacitor has charged to its peak value, the diode will cut off and the capacitor will start to discharge. Since the fall of the ac input voltage on the anode is considerably more rapid than the decrease on the capacitor voltage, the cathode quickly 39
  • 39. become more positive than the anode, and the diode ceases to conduct. Operation of the simple capacitor filter using a full-wave rectifier is basically the same as that discussed for the half-wave rectifier. Referring to figure 4-18, you should notice that because one of the diodes is always conducting on. either alternation, the filter capacitor charges or discharges during each half cycle. (Note that each diode conducts only for that portion of time when the peak secondary voltage is greater than the charge across the capacitor.) Figure 4-18. - Full-wave rectifier (with capacitor filter). 40
  • 40. Another thing to keep in mind is that the ripple component (E r) of the output voltage is an ac voltage and the average output voltage (Eavg) is the dc component of the output. Since the filter capacitor offers relatively low impedance to ac, the majority of the ac component flows through the filter capacitor. The ac component is therefore bypassed (shunted) around the load resistance, and the entire dc component (or Eavg) flows through the load resistance. This statement can be clarified by using the formula for XC in a half-wave and full-wave rectifier. First, you must establish some values for the circuit. 41
  • 41. 42
  • 42. As you can see from the calculations, by doubling the frequency of the rectifier, you reduce the impedance of the capacitor by one-half. This allows the ac component to pass through the capacitor more easily. As a result, a full-wave rectifier output is much easier to filter than that of a half-wave rectifier. Remember, the smaller the XC of the filter capacitor with respect to the load resistance, the better the filtering action. Since the largest possible capacitor will provide the best filtering. Remember, also, that the load resistance is an important consideration. If load resistance is made small, the load current increases, and the average value of output voltage (Eavg) decreases. The RC discharge time constant is a direct function of the value of the load resistance; therefore, the rate of capacitor voltage discharge is a direct function of the current through the load. The greater the load current, the more rapid the discharge of the 43
  • 43. capacitor, and the lower the average value of output voltage. For this reason, the simple capacitive filter is seldom used with rectifier circuits that must supply a relatively large load current. Using the simple capacitive filter in conjunction with a fullwave or bridge rectifier provides improved filtering because the increased ripple frequency decreases the capacitive reactance of the filter capacitor. CIRCUIT DIAGRAM OF POWER SUPPLY 44
  • 44. DIODE The diode is a p-n junction device. Diode is the component used to control the flow of the current in any one direction. The diode widely works in forward bias. Diode When the current flows from the P to N direction. Then it is in forward bias. The Zener diode is used in reverse bias function i.e. N to P direction. Visually the identification of the diode`s terminal can be done by identifying he silver/black line. The silver/black line is the negative terminal (cathode) and the other terminal is the positive terminal (cathode). APPLICATION •Diodes: Rectification, free-wheeling, etc •Zener diode: Voltage control, regulator etc. 45
  • 45. •Tunnel diode: Control the current flow, snobbier circuit, etc RESISTORS The flow of charge through any material encounters an opposing force similar in many respects to mechanical friction .this opposing force is called resistance of the material .in some electric circuit resistance is deliberately introduced in form of resistor. Resistor used fall in three categories , only two of which are color coded which are metal film and carbon film resistor .the third category is the wire wound type ,where value are generally printed on the vitreous paint finish of the component. Resistors are in ohms and are represented in Greek letter omega, looks as an upturned horseshoe. Most electronic circuit require resistors to make them work properly and it is obliviously important to find out something about the different types of resistors available. Resistance is measured in ohms, the symbol for ohm is an omega ohm. 1 ohm is quite small for electronics so resistances are often given in kohm and Mohm. Resistors used in electronics can have resistances as low as 0.1 ohm or as high as 10 Mohm. 46
  • 46. FUNCTION Resistor restrict the flow of electric current, for example a resistor is placed in series with a light-emitting diode(LED) to limit the current passing through the LED. TYPES OF RESISTORS FIXED VALUE RESISTORS It includes two types of resistors as carbon film and metal film .These two types are explained under CARBON FILM RESISTORS During manufacture, at in film of carbon is deposited onto a small ceramic rod. The resistive coating is spiraled away in an automatic machine until the resistance between there two ends of the rods is as close as possible to the correct value. Metal leads and end caps are added, the resistors is covered with an 47
  • 47. insulating coating and finally painted with colored bands to indicate the resistor value Carbon Film Resistors Another example for a Carbon 22000 Ohms or 22 Kilo-Ohms also known as 22K at 5% tolerance: Band 1 = Red, 1st digit Band 2 = Red, 2nd digit Band 3 = Orange, 3rd digit, multiply with zeros, in this case 3 zero's Band 4 = Gold, Tolerance, 5% METAL FILM RESISTORS Metal film and metal oxides resistors are made in a similar way, but can be made more accurately to within ±2% or ±1% of their nominal vale there are some difference in performance between these resistor types, but none which affects their use in simple circuit. 48
  • 48. WIRE WOUND RESISTOR A wire wound resistor is made of metal resistance wire, and because of this, they can be manufactured to precise values. Also, high wattage resistors can be made by using a thick wire material. Wire wound resistors cannot be used for high frequency circuits. Coils are used in high frequency circuit. Wire wound resistors in a ceramic case, strengthened with special cement. They have very high power rating, from 1 or 2 watts to dozens of watts. These resistors can become extremely hot when used for high power application, and this must be taken into account when designing the circuit. TESTING Resistors are checked with an ohm meter/millimeter. For a defective resistor the ohm-meter shows infinite high reading. CAPACITORS In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work , 49
  • 49. then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons at the other terminal. BASIC Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect to two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or anything else that does not conduct electricity and keeps the plates from touching each other. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work. In an electronic circuit, a capacitor is shown like this: 50
  • 50. When you connect a capacitor to a battery, here’s what happens: •The plate on the capacitor that attaches to the negative terminal of the battery accepts electrons that the battery is producing. •The plate on the capacitor that attaches to the positive terminal of the battery loses electrons to the battery. TESTING To test the capacitors, either analog meters or specia l digital meters with the specified function are used. The nonelectrolyte capacitor can be tested by using the digital meter. Multi – meter mode : Continuity Positive probe : Negative probe : Second end Display occur) `OL` Result : Faulty OK 51 : One end `0`(beep sound
  • 51. LED LED falls within the family of P-N junction devices. The light emitting diode (LED) is a diode that will give off visible light when it is energized. In any forward biased P-N junction there is, with in the structure and primarily close to the junction, a recombination of hole and electrons. This recombination requires that the energy possessed by the unbound free electron be transferred to another state. The process of giving off light by applying an electrical source is called electroluminescence. LED is a component used for indication. All the functions being carried out are displayed by led .The LED is diode which glows when the current is being flown through it in forward bias 52
  • 52. condition. The LEDs are available in the round shell and also in the flat shells. The positive leg is longer than negative leg. DC MOTOR DC Motor has two leads. It has bidirectional motion If we apply +ve to one lead and ground to another motor will rotate in one direction, if we reverse the connection the motor will rotate in opposite direction. If we keep both leads open or both leads ground it will not rotate (but some inertia will be there). If we apply +ve voltage to both leads then braking will occurs. 53
  • 53. H-BRIDGE This circuit is known as H-Bridge because it looks like ” H” Working principle of H-Bridge. If switch (A1 and A2 )are on and switch (B1 and B2) are off then motor rotates in clockwise direction 54
  • 54. If switch (B1 and B2 )are on and switch (A1 and A2) are off then motor rotates in Anti clockwise direction we can use Transistor, mosfets as a switch ( Study the transistor as a a switch) H-Bridge I.C (L293D) L293D is a H-Bridge I.C. Its contain two H-Bridge pair. 55
  • 55. Truth Table Input 1 Input 2 Result 0 0 No rotation 0 1 Clockwise rotation 1 0 Anti clockwise rotation 1 1 break Note:Connect motors pins on output 1 and output 2 and control signal at input 1 and input 2 will control the motion Connect another motor pins on output 3 and output 4 and control signal at input3and input 4 Truth table for i/p 3 and i/p 4 is same as above shown 0 means 0 V or Low 1 means High or +5V 56
  • 56. In Enable 1 and Enable 2 if you give high then you observe hard stop in condition 0 0 and 11. Unless slow stop of motor on low signal Required Motor voltage has given on pin 8 (Vs) i.e 12V DC – 24V DC SCHEMATIC OF L293D WITH DC MOTOR DUAL H-BRIDGE 2 7 10 15 +5V DC 1 9 8 16 IN1 IN2 IN3 IN4 OUT1 OUT2 OUT3 OUT4 DC MOTOR 3 6 11 14 EN1 EN2 VS VSS L293D DC MOTOR + 15 V DC + 5 V DC MOTOR VOLTAGE 57
  • 57. CHAPTER THREE 3.1 GSM Modem A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves. Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate [11]. 3.1.1 Accessing GSM MODEM using Microsoft HyperTerminal Microsoft HyperTerminal is a small program that comes with Microsoft Windows. We use it to send AT commands to the GSM modem. It can be found at Start -> Programs -> Accessories -> Communications -> HyperTerminal. Before programming our SMS application, it is required to check if the GSM modem and SIM card are working properly first [12]. The MS HyperTerminal is a handy tool when it comes to testing the GSM device. It is a good idea to test the GSM devices beforehand. When a problem occurs, sometimes it is difficult to 58
  • 58. tell what causes the problem. The cause can be the program, the GSM device or the SIM card. If GSM device and SIM card with MS HyperTerminal are operating properly, then it is very likely that the problem is caused by the program or other hardware [12]. For Linux users, Mincom can be used instead of HyperTerminal. 3.2 Testing of GSM Modem To use MS HyperTerminal to send AT commands to the GSM modem, the following procedure is followed 1. I put a valid SIM (MTN) card into the GSM modem. I obtain a SIM card by subscribing to the GSM service of a wireless network operator. 2. No need to install any driver for the GSM modem 3. Then I set up MS HyperTerminal by selecting Start -> Programs -> Accessories -> Communications -> HyperTerminal. 4. In the Connection Description dialog box (as shown in the screenshot given below), I enter any file name and choose an icon I like for the connection. Then I click the OK button. . In the Connect To dialog box, choose the COM port that your mobile phone or GSM modem is connecting to in the Connect 59
  • 59. using combo box. I choose COM1 because my mobile phone is connected to the COM1 port. Then click the OK button. Type "AT" in the main window. A response "OK" will be returned from the mobile phone or GSM modem. Type "AT+CPIN?" in the main window. The AT command "AT+CPIN?" is used to query whether the mobile phone or GSM modem is waiting for a PIN (personal identification number, i.e. password). If the response is "+CPIN: READY", it means the SIM card does not require a PIN and it is ready for use. If my SIM card requires a PIN, you need to set the PIN with the AT command "AT+CPIN=<PIN>". [ 3.3 List of Important AT Commands After successfully testing the MODEM for its correct operational state, I then set the MODEM parameters like Baud rate, Echo off etc to enable easier access via a microcontroller which I used in this project. The following are the ATCOMMAND used for programming the gsm modem Example: Changing and saving parameters AT+IPR=9600[Enter] Transfer rate to 9600bps 60
  • 60. AT&W [Enter] save parameters AT+CMGF means convert the message to machine instruction format AT+CPMS means selection of SMS memory AT+CMGR means read message from a given memory location AT+CMGD means delete message from a given memory location. 3.4 Microcontroller – Modem Interfacing 3.4.1. DTE and DCE The terms DTE and DCE are very common in the data communications market. DTE is short for Data Terminal Equipment and DCE stands for Data Communications Equipment. As the full DTE name indicates this is a piece of device that ends a communication line, whereas the DCE provides a path for communication. Let's say I have a computer on which wants to communicate with the Internet through a modem and a dial-up connection. To get to the Internet I tell my modem to dial the number of my provider. After my modem has dialed the number, the modem of the provider will answer my 61
  • 61. call and I will hear a lot of noise. Then it becomes quiet and I see my login prompt or my dialing program tells me the connection is established. Now I have a connection with the server from my provider and I can surf the Internet [13]. 3.5 Microcontroller – LCD Interfacing Above is the quite simple schematic. The LCD panel’s Enable and Register Select is connected to the Control Port. The Control Port is an open collector / open drain output. Therefore by incorporating the two 10K external pull up resistors, the circuit is more portable for a wider range of computers, some of which may have no internal pull up resistors. I make no effort to place the Data bus into reverse direction. Therefore I had wire the R/W line of the LCD panel, into write mode. This will cause no bus conflicts on the data lines. As a result I cannot read back the 62
  • 62. LCD’s internal Busy Flag which tells us if the LCD has accepted and finished processing the last instruction [20]. This problem is overcome by inserting known delays into my program. The 10k Potentiometer controls the contrast of the LCD panel. Nothing fancy here. I used a power supply of 5volt. The user may select whether the LCD is to operate with a 4-bit data bus or an 8- bit data bus. If a 4-bit data bus is used, the LCD will require a total of 7 data lines. If an 8-bit data bus is used, the LCD will require a total of 11 data lines [20]. LCD with 8-bit data bus is used for this design. The three control lines are EN, RS, and RW. EN line must be raised/lowered before/after each instruction sent to the LCD regardless of whether that instruction is read or write text or instruction. In short, I manipulate EN when communicating with the LCD. 63
  • 63. CHAPTER FOUR 4.2 Testing and Observations After inclusion of the validation module in the program code, I test the module with the device called universal programmer. In this prototype I used only one valid number. With more memory available three or four valid numbers can be included. When a message is sent to number carried by the SIM of the MODEM, the validation module of the program checks character by character the sender’s number with the number stored in the memory as the valid or authentic number. I then look for signals on the TX and RX lines. What you see below on the left are the signals on these lines with the ECHO being ON (ATE1). The corresponding picture on the right depicts the modem response after about 460 ms (variable as per message length: D) delay with the new message Test 12345 Please submit your Result Please submit your thesis thesis 12345 there will be a meeting There will be a meeting by 64
  • 64. by 2pm 2pm 12345 I want to see Mr. Musa I want to see Mr. Musa 12345 I will not come to I will not come to school today school today 12345 please enemy alert Please enemy alert 12345 I am in India I am in India 12345 please hurry up Please hurry up 1234 I will be in office in the I will be in office in the next 30 next 30 minute minute 12345 is the password of the GSM electronic notice board. Any message a user want to send has to be preceded by 12345 spaces the message. A user will then send the message to the GSM number that is inside the Motorola c168 4.3 Initializations The baud rate of the modem was set to be 9600 bps using the HyperTerminal, The ECHO from the modem was turned off using the command ATE0 at the HyperTerminal. For serial transmission and reception to be possible both the DTE and 65
  • 65. DCE should have same operational baud rates. Hence to set the microcontroller at a baud rate of 9600bps, I set terminal count of Timer 1 at 0FFh (clock frequency = 1.8432). The TCON and SCON registers were set accordingly. 4.4.1 Serial transfer using TI and RI flags After setting the baud rates of the two devices both the devices are now ready to transmit and receive data in form of characters. Transmission is done when TI flag is set and similarly data is known to be received when the Rx flag is set. The microcontroller then sends an AT command to the modem in form of string of characters serially just when the TI flag is set. After reception of a character in the SBUF register of the microcontroller (response of MODEM with the read message in its default format or ERROR message or OK message), the RI flag is set and the received character is moved into the physical memory of the microcontroller [22]. 4.4.2 Validity Check After serially receiving the characters the code then checks for start of the sender’s number and then compares the number character by character with the valid number pre stored in the 66
  • 66. memory. Since we are employing just one valid number, we are able to do the validation process dynamically i.e. without storing the new message in another location in the memory. For more than one valid numbers we would require more memory locations to first store the complete (valid/invalid) message in the memory and then perform the comparison procedure. 4.4.3 Display After validity check the control flow goes into the LCD program module to display the valid message stored in the memory. In case of multiple valid numbers all invalid stored messages are deleted by proper branching in the code to the “delete-message” module. 4.4 Programmer When we have to learn about a new computer we have to familiarize about the machine capability we are using, and we can do it by studying the internal hardware design (devices architecture), and also to know about the size, number and the size of the registers. 67
  • 67. A microcontroller is a single chip that contains the processor (the CPU), non-volatile memory for the program (ROM or flash), volatile memory for input and output (RAM), a clock and an I/O control unit. Also called a "computer on a chip," billions of microcontroller units (MCUs) are embedded each year in a myriad of products from toys to appliances to automobiles. For example, a single vehicle can use 70 or more microcontrollers. The following picture describes a general block diagram of microcontroller. 89S52: The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory pro-grammar. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller, which provides a highly flexible and cost-effective solution to many, embedded control 68
  • 68. applications. The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM con-tents but freezes the oscillator, disabling all other chip functions until the next interrupt 69
  • 69. The hardware is driven by a set of program instructions, or software. Once familiar with hardware and software, the user can then apply the microcontroller to the problems easily. The pin diagram of the 8051 shows all of the input/output pins unique to microcontrollers: 70
  • 70. The following are some of the capabilities of 8051 microcontroller. Internal ROM and RAM I/O ports with programmable pins Timers and counters Serial data communication The 8051 architecture consists of these specific features: 16 bit PC &data pointer (DPTR) 71
  • 71. 8 bit program status word (PSW) 8 bit stack pointer (SP) Internal ROM 4k Internal RAM of 128 bytes. 4 register banks, each containing 8 registers 80 bits of general purpose data memory 32 input/output pins arranged as four 8 bit ports: P0-P3 Two 16 bit timer/counters: T0-T1 Two external and three internal interrupt sources Oscillator and clock circuits. 4.5 Simulator KEIL Micro Vision is an integrated development environment used to create software to be run on embedded systems (like a microcontroller). It allows for such software to be written either in assembly or C programming languages and for that software to be simulated on a computer before being loaded onto the microcontroller. The software used is c programming 72
  • 72. that helps write, compile, and debug embedded programs. It encapsulates the following components: A project manager. A make facility. Tool configuration. Editor. 73
  • 73. A powerful debugger. To create a GSM ENOTICE board project in uVision3: 1. Select Project - New Project. 2. Select a directory and enter the name of the project file. 3. Select Project –Select Device and select a device from Device Database. 4. Create source files to add to the project 5. Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and add the Source files to the project. 6. Select Project - Options and set the tool options. Note that when the target device is selected from the Device Database all-special options are set automatically. Default memory model settings are optimal for most applications. 7. Select Project - Rebuild all target files or Build target. To create a new project, simply start micro vision and select “Project”=>”New Project” from the pull–down menus. In the file dialog that appears, a filename and directory was chosen for the project. It is recommended that a new directory 74
  • 74. be created for each project, as several files will be generated. Once the project has been named, the dialog shown in the figure below will appear, prompting the user to select a target device. The chip being used is the “AT89S52,” which is listed under the heading “Atmel”. Next, Micro Vision was instructed to generate a HEX file upon program compilation. A HEX file is a standard file format for storing executable code that is to be loaded onto the microcontroller. In the “Project Workspace” pane at the left, right–click on “Target 1” and select “Options for ‘Target 1’ ”.Under the “Output” tab of the resulting options dialog, ensure that both the “Create Executable” and “Create HEX File” options are checked. Then click “OK”. Next, a file must be added to the project that will contain the project code. To do this, expand the “Target 1” heading, right–click on the “Source Group 1” folder, and select “Add files…” Create a new blank file (the file name should end in “.c”), select it, and click “Add.” The new file should now appear in the “Project Workspace” pane under the “Source Group 1” 75
  • 75. folder. Double-click on the newly created file to open it in the editor. To compile the program, first save all source files by clicking on the “Save All” button, and then click on the “Rebuild All Target Files” to compile the program as shown in the figure below. If any errors or warnings occur during compilation, they will be displayed in the output window at the bottom of the screen. All errors and warnings will reference the line and column number in which they occur along with a description of the problem so that they can be easily located [23]. When the program has been successfully compiled, it can be simulated using the integrated debugger in Keil Micro Vision. To start the debugger, select “Debug”=>”Start/Stop Debug Session” from the pull–down menus. At the left side of the debugger window, a table is displayed containing several key parameters about the simulated microcontroller, most notably the elapsed time (circled in the figure below). Just above that, there are several buttons that control code execution. The “Run” button will cause the program to run continuously until a breakpoint is reached, 76
  • 76. whereas the “Step Into” button will execute the next line of code and then pause (the current position in the program is indicated by a yellow arrow to the left of the code). 4.6 PRO51 BURNER SOFTWARE PRO51 BURNER provides you with software burning tools for 8051 based Microcontrollers in their Flash memory. The 51 BURNER tools, you can burn AT89C/SXXXX series of ATMEL microcontrollers. 77
  • 77. CHAPTER FIVE 5.1 Conclusion The prototype of the GSM based Generator Control device was efficiently designed. This prototype has facilities to be integrated with a Generator thus making it truly mobile. The toolkit accepts the SMS, stores it, validates it and perform specific operations. The SMS is deleted from the phone each time it is read, thus making room for the next SMS. 5.2 Problem Encountered During soldering, many of the connection become short cktd. So we desolder the connection and did soldering again. A leg of the crystal oscillator was broken during mounting. So it has to be replaced. LED`s get damaged when we switched ON the supply so we replace it by the new one. TROUBLESHOOT Care should be taken while soldering. There should be no shorting of joints. Proper power supply should maintain. 78
  • 78. 5.2 Future Improvement In my project I am sending messages through GSM network and Control the home devices by utilizing AT (ATTENTION) commands. The same principle can be applied to display the message on electronics display board appliances at a distant location. Robots can be controlled in a similar fashion by sending the commands to the robots. These commands are read by using AT commands and appropriate action is taken. This can be used for spy robots at distant locations, utilized by the military to monitor movement of enemy troops. Currently farmers have to manually put on or off pumps, drippers etc by using electric switches. Using the principle of AT commands we can put on or off these appliances remotely. 5.3 Recommendation It is highly recommended that electronic board should be constructed for this new system (GSM electronic notice board) 79
  • 79. REFERENCES 1. The 8051Microcontroller by Kenneth J. Ayala 2. The 8051 Microcontroller and Embedded Systems by Muhammad Ali Mazidi. 3. Principles and Applications of GSM by Vijay Garg. 4. Artificial Intelligence – Elain Rich & Kevin Knight, Tata Mc Graw Hill, 2nd Edition. 5. Artificial Intelligence – A Modern approach – Slaurt Russel and Peter Norving, Pearson Education, 2nd Edition. 6. Introduction to Robotics – P.J.Mc Kerrow, Addisson Wesley, USA, 1991 Bernard Sklar, Digital Communications: Fundamentals and Applications, Prentice Hall, 2001. 7. A. Clark and R. Harun, Assessment of kalman-_lter channel estimators for an HF radio link," IEE Proceedings, vol. 133, pp. 513{521, Oct 1986. 8. ETS 300 502. European Digital Cellular Telecommunication System (Phase 2); Teleservices Supported by a GSM Public Land Mobile Network (PLMN). European Telecommunications Standards Institute. September 1994. 80
  • 80. 9. Matthew C. Valenti and Jian Sun, Chapter 12: Turbo Codes, Handbook of RF and Wireless 10. GSM Multiple Access Scheme, William Stallings Data and Computer Communications 7th Edition: Chapter 9 Spread Spectrum, 11. ETS 300 608. Digital Cellular Telecommunication System (Phase 2); Specification of the Subscriber Identity ModuleMobile Equipment (SIM-ME) Interface. European Telecommunications Standards Institute. May 1998. 12. ETR 100. European Digital Cellular Telecommunication System (Phase 2); Abbreviations and Acronyms. European Telecommunications Standards Institute. April 1995. 13. Jörg Eberspächer and Hans-Jörg Vögel. GSM switching, services and Protocols. John Wiley and Sons, 1999. 14. Klaus Vedder GSM: Security, Services, and SIM. State of the art in Applied Cryptography. Course on Computer Security and Industrial Cryptography. Leuven, Belgium, June 3-6, 1997. 81
  • 81. 15. J. Wu and A. H. Aghvami, A new adaptive equalizer with channel estimator for mobile radio communications," IEEE Transactions on Vehicular Technology, 16. L. J. Cimini, Analysis and simulation of a digital mobile channel using orthogonal frequency division multiplexing," IEEE Transactions on Communications, vol. 33, pp. 665{675, July 1985. 17. B. Saltzberg, Performance of an ancient parallel data transmission system," IEEE Trans. Commun. Techno., pp. 805{813, December 1967} 18. M. Zimmermann and A. Kirsch, The AN/GSC10/KATHRYN variable rate data modem for HF radio," IEEE Trans. Commun.Techn., vol. CCM{15,16} 19. Hardware and user manuals of the modem from MOTOROLA C168 20. 21. 22. 23. 82
  • 82. For futher details regarding to software and hardware and any further querie contact to the given address. HBeonLabs Off. No. 46, 1st Floor, Kadamba Complex Gamma-I, Greater Noida (India) - 201308 Contact us: +91-120-4298000 +91-9212314779 www. 83
  • 83. 84