REMOTE POWER MONITORING SYSTEM USING MICROCONTROLLER

Transcription

1 REMOTE POWER MONITORING SYSTEM USING MICROCONTROLLER A Project report Submitted in partial fulfillment of the requirement For the award of the degree of BACHELOR OF TECHNOLOGY IN ELECTRONICS AND COMMUNICATION ENGINEERING By B. MOHAN KRISHNA (05391A0468) B. VIDYA SAGAR (05391A0489) S.K. RABBANI (05391A0475) Under the guidance of (Mr. P.J.REGINALD) Assistant Professor Department of Electronics and Communication Engineering VIGNAN S ENGINEERING COLLEGE ISO Certified, NBA & NAAC Accredited with A Grade VADLAMUDI GUNTUR (Dt.) ( )

2 CERTIFICATE This is to certify that this project report entitled REMOTE POWER MONITORING USING SYSTEM MICROCONTROLLER is a bonafide record of work done by B. MOHAN KRISHNA (05391A0468) B. VIDYA SAGAR (05391A0489) S.K. RABBANI (05391A0475) Under my guidance and supervision and submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Technology in Electronics and Communication Engineering by the Jawaharlal Nehru Technological University, Kakinada. (Mr. P.J.REGINALD) Guide Certified by the Head of the Department (Dr. D. VENKATA RAO) Professor and Head Department of Electronics and Communication Engineering VIGNAN S ENGINEERING COLLEGE ISO Certified, NBA & NAAC Accredited with A Grade VADLAMUDI GUNTUR (Dt.) ( )

3 ACKNOWLEDGEMENT The completion of any project brings with it a sense of satisfaction, but it is never complete without thanking those people who made it possible and whose constant support has crowned our efforts with success. We would also like to thank our guide, Mr. P.J.REGINALD Assistant professor, Dept. of Electronics And Communication for his expert guidance, encouragement and valuable suggestions at every step. We would also like to express our gratitude to Dr. D. VENKATA RAO, Head of the Department, Electronics and Communication V.E.C, Vadlamudi, for encouraging and inspiring us to carry out the project in the department lab. We are grateful to our esteemed principal, VIGNAN S ENGINEERING COLLEGE, Vadlamudi, Dr. K.V.N.SRINIVASA RAO f o r supporting and funding this endeavor. We also would like to thank all the staff members of E&C dept., classmates for providing us with the required facilities and support towards the completion of the project. PROJECT ASSOCIATES B. MOHAN KRISHNA (05391A0468) B. VIDYA SAGAR (05391A0489) S.K. RABBANI (05391A0475)

4 ABSTRACT Electricity is the modern man's most convenient and useful form of energy without which the present social infrastructure would not be feasible. The increase in per capita production is the reflection of the increase in the living standard of people. When importance of electricity is on the increasing side, then how much should theft of this energy or illegal consumption of power from the transmission lines be averted? Power theft has become a great challenge to the electricity board. Our project identifies the Power theft and indicates it to the Electricity board through Power line. We had also dealt about the remote monitoring of an energy meter. The project is constructed with the popular microcontroller MC551 series 8051 microcontroller, power measurement IC, voltage, current transformers. The central office is having a PC connected to the different energy meters fixed at different organizations wireless link. The energy meter connected at the consumer point continuous reads power data and sends it to the PC. The program written in micro controller to read and transmit the power data to the PC on request. The PC can connected to number of users with there unique ID number. Initially PC transmits the ID code to the energy meters then the corresponding energy meters transmits the energy information to the PC with the help of this centrally we can monitor energy consumed by different consumers and useful for analyzing the unauthorized usage. The software is written in the PC for sending request to the energy meter and receiving the energy meter and receiving the energy data from consumer point.

5 CONTENTS 1. INTRODUCTION 1 2. BLOCK DIAGRAM 3 3. POWER MEASURMENT VOLTAGE TRANSFORMERS PRINCIPLE OF OPERATION TYPICAL TERMS USED FOR SPECIFYING A PT CURRENT TRANSFORMERS PRINCIPLE OF OPERATION 8 4. ADC PIN CONFIGURATION FEATURES KEY SPECIFICATIONS BLOCK DIAGRAM FUNCTIONAL DESCRIPTION MULTIPLEXER CONVERTER CHARACTERSTICS C52 MICROCONTROLLER INTRODUCTION DESCRIPTION FEATURES PIN DIGRAM PIN CONFIGURATIONS PIN DESCRIPTION MEMORY 23

6 5.7.1 ON-CHIP MEMORY EXTERNAL CODE MEMORY EXTERNAL RAM SPECIAL FUNCTION REGISTER (SFR) MEMORY ADDRESSING MODES IMMEDIATE ADDRESSING DIRECT ADDRESSING EXTERNAL INDIRECT PROGRAMMING THE FLASH MEMORY PROGRAMMING ALGORITHM SERIAL COMMUNICATION SPEED OF TRANSMISSION RS RS-232 CABLING MAX 232C LOGIC DIAGRAM OPERATING CIRCUIT FEATURES APPLICATIONS RS-232 DRIVERS RS-232 RECEIVERS 41 7.CIRCUIT DIAGRAM HARDWARE PHOTOGRAPHY 45 9.RESULT CONCLUSION AND SCOPE OF FUTURE WORK 47

7 11. MICROCONTROLLER PROGRAM BIBLIOGRAPHY 71

8 1. INTRODUCTION With the electric industry undergoing change, increased attention is being focused on power supply reliability and power quality. Power providers and users alike are concerned about reliable power, whether the focus is on interruptions and disturbances or extended outages. One of the most critical elements in ensuring reliability is monitoring power system performance. Monitoring can provide information about power flow and demand and help identify the cause of power system disturbances. It can even help identify problem conditions on a power system before they cause interruptions or disturbances. The implementation of this project is to monitor the power consumed by a model organization such a household consumers from a centrally located point. Monitoring the power means calculating the power consumed exactly by the user at a given time. The power consumed by the user is measured and communicated to the controlling substation when ever needed by the person at the sub station. The communication can be of two types 1. Wired communication like using the existing transmission lines and sending the data by modulating with high frequency carrier signal or using the existing telephone lines. 2. Wireless communication based on the available technologies like IR communication, Bluetooth technology or GSM technology. Among these two communications, the one used in our project is wired communication which suits best for long distance communication. A microcontroller is equipped at the 1

9 consumers terminal to measure the power consumed by the user at a given instant. The process is not continuous it does this when ever there is a request from the substation control person. The power can be on and off to the user from the substation by operating a relay connected in series to the user. Whenever there is no supply at the user the information can be obtained at the substation. The practical application of the project can be implemented along with a data backup for billing and dispatching the bills with out manual labor and avoid any disturbances in supply at the user side. The project consists of the topics 1. Power measurement unit 2. 89C52 microcontroller 3. ADC Serial communication with the PC Power measurement unit consists of the power measurement by using the instrument transformers and their features. Serial communication with the PC includes the hardware and software description of how the communication is done using the serial port of a PC 2

10 2. BLOCK DIAGRAM The block diagram consists of Load, current transformer, voltage transformer, 89C52 microcontroller, ADC 0809, and a differential relay. The household load to be supplied is connected in series to the AC supply mains through a switch which is operated by the action of a relay. Current transformer is used to measure the current required for the user and the voltage transformer is used to measure the voltage of operation for the user. The measured values are given to the ADC to convert the analog values to the digital values. These values are stored in microcontroller registers and the information is transmitted to the pc when ever there is a request for the data from the remote controlling station. Oscillator is provided for the ADC and microcontroller for the clock signal and the reference voltage is given for the each of the IC used. 3

11 This supplier side is the basic for the operation of the project; the entire consumer side is controlled in accordance with the program written on this supplier side. The supplier side (substation) is located remotely at some distance away from the user and the signal is sent to the consumer side for data or to control the supply of power to the user. The request for information and the power data is received from the user side via RS232. Microcontroller is interfaced to the personal computer serial port through MAX23C to drive between RS232 and TTL levels. 3. POWER MEASUREMENT 4

12 The main aim of the Remote power monitoring is to measure the exact amount of power that is consumed by the user at a given instant of time so the power measurement unit is essential and is connected on the consumer side. The power is measured by using the instrument transformers. Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Their role in electrical systems is of primary importance as they are a means of "stepping down" the current or voltage of a system to measurable values, such as 5A or 1A in the case of a current transformers or 110V or 100V in the case of a voltage transformer. This offers the advantage that measurement and protective equipment can be standardized on a few values of current and voltage. The types of instrument transformers available are Voltage transformers Current transformers 3.1VOLTAGE TRANSFORMERS 3.1.1PRINCIPLE OF OPERATION: The voltage transformer is one in which "the secondary voltage is substantially proportional to the primary voltage and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." In an "ideal" transformer, the secondary voltage vector is exactly opposite and equal to the primary voltage vector, when multiplied by the turns ratio. In a "practical" transformer, errors are 5

13 introduced because some current is drawn for the magnetization of the core and because of drops in the primary and secondary windings due to leakage reactance and winding resistance. One can thus talk of a voltage error, which is the amount by which the voltage is less than the applied primary voltage, and the phase error, which is the phase angle by which the reversed secondary voltage vector is displaced from the primary voltage vector TYPICAL TERMS USED FOR SPECIFYING A PT a. RATED PRIMARY VOLTAGE: This is the rated voltage of the system whose voltage is required to be stepped down for measurement and protective purposes. b. RATED SECONDARY VOLTAGE: This is the voltage at which the meters and protective devices connected to the secondary circuit of the voltage transformer operate. c. RATED BURDEN: This is the load in terms of volt-amperes (VA) posed by the devices in the secondary circuit on the VT. This includes the burden imposed by the connecting leads. The VT is required to be accurate at both the rated burden and 25% of the rated burden. d. RATED VOLTAGE FACTOR: Depending on the system in which the VT is to be used, the rated voltage factors to be specified are different. The table below is adopted from Indian and International standards. 6

14 Rated voltage factor Rated time Method of connecting primary winding in system 1.2 Continuous Between phases in any network Between transformer star-point and earth in any network Continuous Between phase and earth in an effectively earthed for 30 second neutral system Continuous Between phase and earth in a non-effectively earthed for 30 second neutral system with automatic fault tripping Continuous for 8 hours Between phase and earth in an isolated neutral system without automatic fault tripping or in a resonant earthed system without automatic fault tripping e. TEMPERATURE CLASS OF INSULATION: The permissible temperature rise over the specified ambient temperature. Typically, classes E, B and F. f. RESIDUAL VOLTAGE TRANSFORMER (RVT): RVTs are used for residual earth fault protection and for discharging capacitor banks. The secondary residual voltage winding is connected in open delta. Under normal conditions of operation, there is no voltage output across the residual voltage winding. When there is an earth fault, a voltage is developed across the open delta winding which activates the relay. When using a three phase RVT, the primary neutral should be earthed, as 7

15 otherwise third harmonic voltages will appear across the residual winding. 3 phase RVTs typically have 5 limb construction. 3.2 CURRENT TRANSFORMERS PRINCIPLE OF OPERATION: A current transformer is defined as "as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." This highlights the accuracy requirement of the current transformer but also important is the isolating function, which means no matter what the system voltage the secondary circuit need be insulated only for a low voltage. The current transformer works on the principle of variable flux. In the "ideal" current transformer, secondary current would be exactly equal (when multiplied by the turns ratio) and opposite to the primary current. But, as in the voltage transformer, some of the primary current or the primary ampere-turns is utilized for magnetizing the core, thus leaving less than the actual primary ampere turns to be "transformed" into the secondary ampere-turns. This naturally introduces an error in the transformation. The error is classified into two-the current or ratio error and the phase error. 8

16 4. ADC 0809 The ADC0809, data acquisition component is a monolithic CMOS device with an 8- bit analog-to-digital converter, 8-channel multiplexer and microprocessor compatible control logic. The 8-bit A/D converter uses successive approximation as the conversion technique. The converter features a high impedance chopper stabilized comparator, a 256R voltage divider with analog switch tree and a successive approximation register. The 8-channel multiplexer can directly access any of 8-single-ended analog signals. The device eliminates the need for external zero and full-scale adjustments. Easy interfacing to microprocessors is provided by the latched and decoded multiplexer address inputs and latched TTL TRI- STATE outputs. The design of the ADC0809 has been optimized by incorporating the most desirable aspects of several A/D conversion techniques. The ADC0809 offers high speed, high accuracy, minimal temperature dependence, excellent long-term accuracy and repeatability, and consumes minimal power. These features make this device ideally suited to applications from process and machine control to consumer and automotive applications 9

17 4.1 PIN CONFIGURATION 4.2 FEATURES Easy interface to all microprocessors Operates ratio metrically or with 5 VDC or analog span adjusted voltage reference No zero or full-scale adjust required 8-channel multiplexer with address logic 0V to 5V input range with single 5V power supply Outputs meet TTL voltage level specifications Standard hermetic or molded 28-pin DIP package 28-pin molded chip carrier package 10

18 4.3 KEY SPECIFICATIONS Resolution 8 Bits Total Unadjusted Error ±1 2 LSB and ±1 LSB Single Supply 5V DC Low Power 15 mw Conversion Time 100 μs 4.4 BLOCK DIAGRAM 11

19 4.5 FUNCTIONAL DESCRIPTION MULTIPLEXER The device contains an 8-channel single-ended analog signal multiplexer. A particular input channel is selected by using the address decoder. Table shows the input states for the address lines to select any channel. The address is latched into the decoder on the low-to-high transition of the address latch enable signal CONVERTER CHARACTERISTICS THE CONVERTER The heart of this single chip data acquisition system is its 8-bit analog-to-digital converter. The converter is designed to give fast, accurate, and repeatable conversions over a wide range of temperatures. The converter is partitioned into 3 major sections: the 256R ladder network, the successive approximation register, and the comparator. The converter s 12

20 digital outputs are positive true. The 256R ladder network approach was chosen over the conventional R/2R ladder because of its inherent monotonicity, which guarantees no missing digital codes. Monotonicity is particularly important in closed loop feedback control systems. A non-monotonic relationship can cause oscillations that will be catastrophic for the system. Additionally, the 256R network does not cause load variations on the reference voltage. The bottom resistor and the top resistor of the ladder network in are not the same value as the remainder of the network. The difference in these resistors causes the output characteristic to be symmetrical with the zero and full-scale points of the transfer curve. The first output transition occurs when the analog signal has reached +1 2 LSB and succeeding output transitions occur every 1 LSB later up to full-scale. The successive approximation register (SAR) performs 8 iterations to approximate the input voltage. For any SAR type converter, n-iterations are required for an n-bit converter. In the ADC0809, the approximation technique is extended to 8 bits using the 256R network. The A/D converter s successive approximation register (SAR) is reset on the positive edge of the start conversion start pulse. The conversion is begun on the falling edge of the start conversion pulse. A conversion in process will be interrupted by receipt of a new start conversion pulse. Continuous conversion may be accomplished by tying the end of conversion (EOC) output to the SC input. If used in this mode, an external start conversion pulse should be applied after power up. End-of-conversion will go low between 0 and 8 clock pulses after the rising edge of start conversion. 13

21 5. 89C52 MICROCONTROLLER 5.1 INTRODUCTION Micro controller is a true computer on a chip. Microprocessors are intended to be general-purpose digital computers whereas micro controllers are intended to be special purpose digital controllers. Generally microprocessors contain a CPU, memory- addressing units and interrupt handling circuits. Micro controllers have these features as well as timers, parallel and serial I/O and internal RAM and ROM. Like the microprocessor, a micro controller is a general-purpose device, but one that is meant to read data, and control its environmental based on those calculations. The contrast between a micro controller and a microprocessor is best exemplified by the fact that microprocessors have many operational codes for moving data from external memory to CPU; microcontrollers may have one or two. Microprocessors may have one or two types of bit-handling instructions; micro controllers will have many. The microprocessor is concerned with the rapid movement of code and data from external addresses to the chip; the microcontroller is concerned with rapid movements of bits with in the chip. The micro controller can function as a computer with the addition of no external digital parts; the microprocessor must have many additional parts to be operational. Generally 4-bit microcontrollers are intended for use in large volumes as true 1-chip computers. Typical applications consist of appliances and toys. Eight bit micro controllers represent a transition zone between the dedicated, high volume, 4-bit micro controllers and 14

22 the high performance, 16 and 32-bit units. Eight bit micro controllers are very useful word size for small computing tasks. 16-bit controllers have also been designed to take the advantage of high level programming languages in the expectation that very little assembly language programming will be done when employing these controllers in sophisticated applications. 32 bit controllers are also used in high speed control and signal processing applications. 5.2 DESCRIPTION The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C52 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. 5.3 FEATURES 1. Compatible with MCS-51 Products 2. 8K Bytes of In-System Reprogrammable Flash Memory (Endurance: 1,000 Write/Erase Cycles) 3. Fully Static Operation: 0 Hz to 24 MHz 15

23 4. Three-level Program Memory Lock x 8-bit Internal RAM Programmable I/O Lines 7. Two 16-bit Timer/Counters 8. Six Interrupt Sources 9. Programmable Serial Channel 10. Low-power Idle and Power-down Modes 5.4 PIN DIAGRAM: (T2) P1.0 (T2 EX) P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RST (RXD) P3.0 (TXD) P3.1 (INT0) P3.2 (INT1) P3.3 (T0) P ATMEL 8 9 C VCC P0.0(AD0) P0.1(AD1) P0.2(AD2) P0.3(AD3) P0.4(AD4) P0.5(AD5) P0.6(AD6) P0.7(AD7) EA/VPP ALE/PROG PSEN P2.7(A15) P2.6(A14) (T1) P3.5 (W R) P3.6 (RD) P P2.5(A13) P2.4(A12) P2.3(A11) XTAL P2.2(A10) XTAL1 GND P2.1(A9) P2.0(A8) 16

24 5.5 PIN CONFIGURATIONS The AT89C52 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture, a full duplex serial port, and on chip oscillator and clock circuitry. IN addition, the AT89C52 is designed with static logic for operation down to zero frequency and supports two software selectable power selecting 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 contents but freezes the oscillator all other chip functions until the next hardware reset. 5.6 PIN DESCRIPTION VCC Supply voltage. GND Ground. Port 0 Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 may also be configured to be the multiplexed low order 17

25 address/data bus during accesses to external program and data memory. In this mode P0 has internal pull ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull ups are required during program verification. Port 1 Port 1 is an 8-bit bi-directional I/O port with internal pull ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 1 also receives the low-order address bytes during Flash programming and verification. Port 2 Port 2 is an 8-bit bi-directional I/O port with internal pull ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the highorder address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses RI); Port 2 emits the contents of the P2 Special Function 18

26 Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port 3 Port 3 is an 8-bit bi-directional I/O port with internal pull ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull ups. Port 3 also serves the functions of various special features of the AT89C51 as listed below: Port 3 also receives some control signals for Flash programming and verification. RST Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. 19

27 ALE/PROG Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. PSEN Program Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. EA/VPP External Access Enable: EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to 20

28 VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP. XTAL1 circuit. Input to the inverting oscillator amplifier and input to the internal clock operating XTAL2 Output from the inverting oscillator amplifier. OSCILLATOR CHARACTERISTICS XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed. 21

29 IDLE MODE In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hardware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory. 22

30 POWER DOWN MODE: In the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize. PROGRAM MEMORY LOCK BITS: On the chip are three lock bits which can be left un programmed (U) or can be programmed (P) to obtain the additional features listed in the table below. When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly. 5.7 MEMORY The 8051 has three very general types of memory. To effectively program the 8051 it is necessary to have a basic understanding of these memory types. The memory types are illustrated in the following graphic. They are: 23

31 1. on-chip memory 2. External Code Memory 3. External RAM 4. Special function register memory ON-CHIP MEMORY This refers to any memories (Code, RAM or other) that physically exist on the microcontroller itself. On- Chip memory can be of several types. The 8051 has a bank of 128 bytes if Internal RAM. This internal RAM available and it is also the most flexible in terms of reading, writing, and modifying its contents. Internal RAM is volatile, so when the 8051 is rest this memory is cleared. The first 8 bytes (00h-07h) are register bank 0. By manipulating certain SFRs, a program may choose to use register banks 1, 2 or 3. These alternative register banks are located in internal RAM in addresses 08h through 1Fh. Bit memory also lives and is part of internal RAM. The 80bytes remaining of Internal RAM, from addresses 30h through 7Fh, may be used by user variables that need to be accessed frequently or at a high speed. This area is also utilized by the microcontroller as a storage area for the operating stack. This fact severely limits the 8051 s stack since, as illustrated in the memory map, the area reserved for the stack is only 80 bytes and usually it is less since this 80 bytes has to be shared between stack and user. 24

32 5.7.2 EXTERNAL CODE MEMORY This is code (or program) memory that resides off-chip. This is often in the form of an external (EPROM). Code Memory is the memory that holds the actual 8051 program that is to be run. This memory is limited to 64K and comes in many shapes ands sizes. Code Memory may be found on-chip, either burned in to the microcontroller as ROM or EPROM. Code may also be stored completely off-chip in an external ROM or, more commonly, an external EPROM. Flash RAM is also another popular method of storing program. Various combinations of these memory types may also be used-that is to say, it is possible to have 4K of code memory on-chip and 64K of code memory off-chip in an EPROM. When the program is stored in-chip the 64K maximum is often reduced to 4K, 8K or 16K. This varies depending on the version of the chip that is being used. Each version offers how much ROM/EPROM spacer the chip has. However, code memory is most commonly implemented as off-chip EPROM. This is especially true in low-cost development systems EXTERNAL RAM or flash RAM. This RAM memory resides off-chip. This is often in the form of standard static RAM 25

33 As an obvious of Internal RAM, the 8051 also supports what is called External RAM. As the name suggests, External RAM is any random access memory which is found off-chip. Since the memory is off-chip it is not as flexible in terms of accessing, and is also slower. For example, to increment an Internal RAM location by 1 requires only 1 instruction and 1 instruction cycle. To increment a 1-byte value stored in External RAM requires 4 instructions and 7 instruction cycles. In this case, external memory is 7 times slower. What external RAM loses in speed and flexibility it gains in quantity. While internal RAM is limited to 128 bytes (256 bytes with an 8052), the 8051 supports External RAM up to 64K SPECIAL FUNCTION REGISTER (SFR) MEMORY Special Function Register (SFRs) are areas of memory that control specific functionality of the 8051 processor. For example, four SFRs permit access to the 8051 s 32 input/output lines. Another SFR allows a program to read or write to the 8051 s serial port. Other SFRs allow the user to set the serial baud rate, control and access timers, and configure the 8051 s interrupt system. 26

34 5.8 ADDRESSING MODES An addressing mode refers to how you are addressing given memory location. In summary, the addressing modes are as follows, with an example of each: Immediate Addressing Direct Addressing In Direct Addressing External Direct Code Indirect MOV A,#20H MOVA,30H MOV MOVX Each of these addressing modes provides important flexibility IMMEDIATE ADDRESSING Immediate Addressing is so-named because the value to be stored in memory immediately follows the operation code in memory. That is to say, the instruction itself dictates what value will be stored in memory. For example, the instruction: MOV A, #20H This instruction uses Immediate Addressing because the Accumulator will be loaded with the value that immediately follows; in this case 20 (hexadecimal). Immediate addressing is very fast since the value to be loaded is included in the instruction. However, since the value to be loaded is fixed at compile-time it is not very flexible. 27

35 5.8.2 DIRECT ADDRESSING Indirect Addressing is a very powerful addressing which in many cases provides an exceptional level of flexibility. Indirect Addressing is also only way to access the extra 128 bytes of Internal RAM found on an Indirect Addressing appears as follows: MOV A,@R EXTERNAL INDIRECT External memory can also be accessed using a form of indirect addressing which I call External Indirect Addressing. This form of addressing is usually only used in relatively small projects that have a very small amount of external RAM. An example of this addressing mode is Eg: A. 5.9 PROGRAMMING THE FLASH MEMORY The AT89C52 is normally shipped with the on chip flash memory array in the erased state (that is, contents FFH) and ready to be programmed. The programming interface accepts either a high voltage (12-volt) or a low voltage (V CC ) program enable signal. The low voltage programming mode provides enable signal. The low voltage programming mode provides convenient way to program the AT89C52 inside the user s system, while the highvoltage programming mode is compatible with Flash or EPROM programmers. The 28

36 AT89C52 is shipped with either the high voltage or low voltage programming mode enabled. The AT89C52 code memory array is programmed byte by byte in either programming mode. The program any non blank byte in the chip Flash Memory, the entire memory must be erased using the Chip Erase Mode PROGRAMMING ALGORITHM: Before programming the AT89C52, the address, the data and control signals should be set up according to the flash programming mode table. To program the AT89C52, take the following steps: 1. Input the desired memory location on the address line 2. Input the appropriate data b byte on the data lines. 3. Activate the correct combination of control signals. 4. Raise EA/V PP to 12V for the high voltage programming mode. 5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte write cycle is self timed and typically takes no more than 1.5ms. repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. DATA POLLING: The AT89C52 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the 29

37 written datum on P0.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data polling may begin any time after a write cycle had been initiated. Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY.P3.4. is pulled high again when programming is done to indicate READY. Program Verify: If the lock bits LB1 and LB2 have not been programmed, the programmed code data can be read via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled. Chip Erase: The entire Flash array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10ms. The code array is written with all 1 s. The chip erase operation must be executed before the code memory can be reprogrammed. 30

38 READING THE SIGNATURE BYTES: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H and 032H except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as follows. (030H)=1EH indicates manufactured by Atmel (031H)=51H indicates 89C51 (032H)=FFH indicates 12V programming (032H)=05H indicated 5V programming PROGRAMMING INTERFACE: Every code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is self timed and once initiated, will automatically time itself to completion 31

39 6. SERIAL COMMUNICATION Serial communication is a popular means of transmitting data between a computer and a peripheral device such as a programmable instrument or even another computer. Serial communication uses a transmitter to send data, one bit at a time, over a single communication line to a receiver. You can use this method when data transfer rates are low or you must transfer data over long distances. Serial communication is popular because most computers have one or more serial ports, so no extra hardware is needed other than a cable to connect the instrument to the computer or two computers together Serial communication requires that you specify the following four parameters: The baud rate of the transmission The number of data bits encoding a character The sense of the optional parity bit The number of stop bits Each transmitted character is packaged in a character frame that consists of a single start bit followed by the data bits, the optional parity bit, and the stop bit or bits. Figure shows a typical character frame. 32

40 Baud rate is a measure of how fast data are moving between instruments that use serial communication. RS-232 uses only two voltage states, called MARK and SPACE. In such a two-state coding scheme, the baud rate is identical to the maximum number of bits of information, including control bits, that are transmitted per second. MARK is a negative voltage, and SPACE is positive. Figure 2 shows how the idealized signal looks on an oscilloscope. The truth table for RS-232: Signal>3V=0 Signal>-3V=1. The output signal level usually swings between +12 V and -12 V. The dead area between +3 V and -3 V is designed to absorb line noise. A start bit signals the beginning of each character frame. It is a transition from negative (MARK) to positive (SPACE) voltage. Its duration in seconds is the reciprocal of the baud rate. If the instrument is transmitting at 9,600 baud, the duration of the start bit and each subsequent bit is about ms. Data bits are transmitted upside down and backwards. That is, inverted logic is used, and the order of transmission is from least significant bit (LSB) to most significant bit 33

41 (MSB). To interpret the data bits in a character frame, you must read from right to left and read 1 for negative voltage and 0 for positive voltage. An optional parity bit follows the data bits in the character frame. The parity bit, if present, also follows inverted logic, 1 for negative voltage and 0 for positive voltage. This bit is included as a simple means of error handling. You specify ahead of time whether the parity of the transmission is to be even or odd. If the parity is chosen to be odd, the transmitter then sets the parity bit in such a way as to make an odd number of ones among the data bits and the parity bit. This transmission uses odd parity. There are five ones among the data bits, already an odd number, so the parity bit is set to SPEED OF TRANSMISSION: Knowing the structure of a character frame and the meaning of baud rate as it applies to serial communication, you can calculate the maximum transmission rate, in characters per second, for a given communication setting. This rate is just the baud rate divided by the bits per frame. This is the maximum character transmission rate. The hardware on one end or the other of the serial link might not be able to reach these rates, for various reasons. There are many different recommended standards of serial port communication, the most common types is as following 6.2 RS-232 The RS-232 is a standard developed by the Electronic Industries Association (EIA) and other interested parties, specifying the serial interface between Data Terminal Equipment 34

42 (DTE) and Data Communications Equipment (DCE). It is commonly used in computer serial ports. The RS-232 standard includes electrical signal characteristics (voltage levels), interface mechanical characteristics (connectors), functional description of interchange circuits (the function of each electrical signal), and some recipes for common kinds of terminal-to-modem connections. RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices. Parts of this standard have been adopted (with various degrees of fidelity) for use in serial communications between computers and printers, modems, and other equipment. The serial ports on standard IBMcompatible personal computers follow RS-232. Somewhere in your PC, typically on a Universal Asynchronous Receiver/Transmitter (UART) chip on your motherboard, the data from your computer is transmitted to a serial device from its Data Terminal Equipment (DTE) interface. Since data in your computer flows along parallel circuits and serial devices can handle only one bit at a time, the UART chip converts the groups of bits in parallel to a serial stream of bits. As your PC's DTE agent, it also communicates with the serial device, which, in accordance with the RS-232C standard, has a complementary interface called the Data Communications Equipment (DCE) interface. 6.3 RS-232 CABLING Devices that use serial cables for their communication are split into two categories. These are DCE and DTE. DCE are devices such as a modem, TA adapter, plotter, and so on, while DTE is a computer or terminal. RS-232 serial ports come in two sizes, the D-Type 25-35

43 pin connector and the D-Type 9-pin connector. Both of these connectors are male on the back of the PC. Thus, you require a female connector on the device. Table 1 shows the pin connections for the 9-pin Type connectors. Function Signal PIN DTE DCE Data TxD 3 Output Input RxD 2 Input Output RTS 7 Output Input CTS 8 Input Output Handshake DSR 6 Input Output DCD 1 Input Output STR 4 Output Input Common Com Other RI 9 Output Input 36

44 1. The TD (transmit data) wire is the one through which data from a DTE device is transmitted to a DCE device. This name can be deceiving, because this wire is used by a DCE device to receive its data. The TD line is kept in a mark condition by the DTE device when it is idle. The RD (receive data) wire is the one on which data is received by a DTE device, and the DCE device keeps this line in a mark condition when idle. 2. RTS stands for Request To Send. This line and the CTS line are used when "hardware flow control" is enabled in both the DTE and DCE devices. The DTE device puts this line in a mark condition to tell the remote device that it is ready and able to receive data. If the DTE device is not able to receive data (typically because its receive buffer is almost full), it will put this line in the space condition as a signal to the DCE to stop sending data. When the DTE device is ready to receive more data (i.e. after data has been removed from its receive buffer), it will place this line back in the mark condition. The complement of the RTS wire is CTS, which stands for Clear To Send. The DCE device puts this line in a mark condition to tell the DTE device that it is ready to receive the data. Likewise, if the DCE device is unable to receive data, it will place this line in the space condition. Together, these two lines make up what is called RTS/CTS or "hardware" flow control. DTR stands for Data Terminal Ready. Its intended function is very similar to the RTS line. DSR (Data Set Ready) is the companion to DTR in the same way that CTS is to RTS. Some serial devices use DTR and DSR as signals to simply confirm that a device is connected and is turned on. The Software Wedge sets DTR to the mark 37

45 state when the serial port is opened and leaves it in that state until the port is closed. The DTR and DSR lines were originally designed to provide an alternate method of hardware handshaking. It would be pointless to use both RTS/CTS and DTR/DSR for flow control signals at the same time. Because of this, DTR and DSR are rarely used for flow control. 3. CD stands for Carrier Detect. Carrier Detect is used by a modem to signal that it has a made a connection with another modem, or has detected a carrier tone. 4. The last remaining line is RI or Ring Indicator. A modem toggles the state of this line when an incoming call rings your phone. The Carrier Detect (CD) and the Ring Indicator (RI) lines are only available in connections to a modem. Because most modems transmit status information to a PC when either a carrier signal is detected (i.e. when a connection is made to another modem) or when the line is ringing, these two lines are rarely used. 6.4 MAX 232C MAX 232C is used to interface the transmitter and receiver circuit to the PC. It is used to match between the RS232C and TTL levels. The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply RS232C voltage levels from a single 5V supply. Each receiver converts RS232C inputs to 5V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30V inputs. Each driver converts TTL/CMOS input levels into RS232C levels. 38

46 6.4.1 LOGIC DIAGRAM: OPERATING CIRCUIT: 39

47 6.4.3 FEATURES: Meets or Exceeds RS232C Operates From a Single 5-V Power Supply with 1.0 microf Charge- Pump Capacitors Operates Up To 120 kbit/s Two Drivers and Two Receivers ±30-V Input Levels Low Supply Current of 8 ma Typical APPLICATIONS RS232C Battery-Powered Systems Terminals Modems Computers RS-232 DRIVERS The typical driver output voltage swing is ±8V when loaded with a nominal 5kΩ RS- 232 receiver and VCC = +5V. Output swing is guaranteed to meet the RS-232C specification, which calls for ±5V minimum driver output levels under worst-case 40

48 conditions. These include a minimum 3kΩ load, VCC = +4.5V, and maximum operating temperature. Unloaded driver output voltage ranges from (V+ -1.3V) to (V- +0.5V). Input thresholds are both TTL and CMOS compatible. The MAX232 has both a receiver threestate control line and a low-power shutdown control RS-232 RECEIVERS: RS-232C specifications define a voltage level greater than 3V as logic 0, so all receivers invert. Input thresholds are set at 0.8V and 2.4V, so receivers respond to TTL level inputs as well as RS-232C levels. The receiver inputs withstand an input overvoltage up to ±25V and provide input terminating resistors with nominal 5kΩ values. The receiver input hysteresis is typically 0.5V with a guaranteed minimum of 0.2V. 41

49 7. CIRCUIT DIAGRAM The above figure shows the circuit diagram for the consumer side. A relay operated switch is connected in series with the load. The switch is used to switch on and off the power. By the relay is initially in on state and whenever the voltage across its terminals changes the relay senses the voltage and trips which in turns closes the switch. The relay is connected to the port of the microcontroller through a transistor and zener diode to drive the relay. The current transformer primary is connected to the load in series to the mains and the 42

50 secondary is connected across the variable resistance to change the measured value to the close actual value. The potential transformer primary is connected in parallel to the load to measure the applied voltage and the secondary is connected to the variable resistance to adjust the measured value to the close accurate value. The outputs of this are given to the ADC analog input pins. A 555 timer is connected in astable multivibrator mode and is given as clock signal to the ADC. The digital outputs are given as inputs to the microcontroller port. The control pins of the ADC are given from the microcontroller port to select the input to be received. The voltage and current measured are received in accordance to the inputs given to the status pins A, B, C by the controller. The ADC starts the conversion at the end of the pulse Start and sends data at the end of the pulse EOC these are also connected to the port of the microcontroller. The microcontroller is provided with a quartz crystal to provide the clock signal, the clock frequency is changed by the capacitors connected to the crystal the operating frequency in this circuit is MHz. A series combination of the resistor and capacitor is taken and the capacitor voltage is given as the reset logic to the 9 th pin of the microcontroller. The 10 th pin of the microcontroller is the RXD pin is connected to the receiver data pin of RS232. The data from the RXD is stored internally for further processing. The 11 th pin of the microcontroller is the TXD pin is connected to the RS232 which transmits the data from the microcontroller. The microcontroller baud rate is set in accordance to the frequency of the 555 timer to ensure consistency of data. Thus data is transmitted from the microcontroller at a preset frequency and the request for data is received by the microcontroller connected to the port and the further processing is done as per the code written to calculate the power by taking the correction factors in to consideration. 43

51 The computer is programmed so as to send requests for data and receive data via the serial port. The work at TTL voltage levels and the computer works at RS232C voltage levels. So to bridge this voltage variation MAX 232C is used which is driver cum receiver. The driver is connected to the IR transmitter and the receiver is connected to the IR receiver. The data from data pin of IR receiver is given to the computer and displayed on the screen. IR transmitter is connected to the computer and the program is written to send the data via the serial port to the IR transmitter to send data at a given baud rate. The oscillator is connected to the transmitter to match the transmission with the baud rate. The oscillator used is 555 timer using astable multivibrator. 44

52 8. HARDWARE PHOTOGRAPHY 45