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Pre paid energy meter

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A project report on prepaid energy meter. It contains the effective use of power and hints in decreasing the losses suffered by the govt for power theft and debts of the consumer.

A project report on prepaid energy meter. It contains the effective use of power and hints in decreasing the losses suffered by the govt for power theft and debts of the consumer.

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  • 1. CONTENT 1. ABSTRACT…………………………2 2. DESIGN PRINCIPLE…………….3 3.CIRCUIT DESCRIPTION a. Power Supply…………………………12 b. Motherboard………………………….15 c. LCD Display……………………………33 d. Relay & Buzzer Driver…………….42 e. Comparator Section………………..45 f. Neutral Tempering…………………..49 g. Opto Isolator………………………….51 4. FUTURE EXPANSION……………….53 5. CONCLUSION………………………….54 1
  • 2. 1. ABSTRACT In the scenario of power crises it is very important to monitor power distribution at consumer end. The maximum demand protection is very much required to limit the customer to connect maximum load to the electrical connection given by the supply company. As excess connection of load doctorates the distribution conditions and create unbalance loading also allied problems such as negative phase sequence currents etc. In this project the maximum demand is limited to a customer if the customer uses the load more then the allotted value for more then a pre defined time then automatically the system disconnect the supply from the consumer. The Pre- paid Energy Meter facilitate the customer to use the pre allotted energy quota and avoid misuse and theft of energy. 2. DESIGN PRINCIPLE: Energy meters, the only direct revenue interface between utilities and the consumers, have undergone several advancements in the last decade. The conventional electro-mechanical meters are being replaced with electronic meters to improve accuracy in meter reading. Asian countries are currently looking to introduce prepaid electricity meters across their distribution network, buoyed up by the success of this novel methodology in South Africa. The existing inherent problems with the post-paid system and privatization of state held power distribution companies are the major driving factors for this market in Asia. 2
  • 3. Over 40 countries have implemented prepaid meters in their markets. In United Kingdom the system, has been in use for well over 70 years with about 3.5 million consumers. The prepaid program in South Africa was started in 1992, since then they have installed over 6 million meters. Other African counties such as Sudan, Madagascar are following the South African success. The concept has found ground in Argentina and New Zealand with few thousands of installations. The prepaid meters in the market today are coming up with smart cards to hold information on units consumed or equivalent money value. When the card is inserted, the energy meter reads it, connects the supply to the consumer loads, and debits the value. The meters are equipped with light emitting diodes (LED) to inform consumers when 75 percent of the credit energy has been consumed. The consumer then recharges the prepaid card from a sales terminal or distribution point, and during this process any changes in the tariff can also be loaded in the smart card. The concept of pre paid is one of the immerging fields for the paid service providers. The concept becomes so popular because it has so many advantages. The services like electricity, gas, water telephone etc are now days get privatized. The service provider company some time incurs heavy losses due to non collection of bills. These service items cannot be recovered from the user after providing so the concept of pre paid reduce risk and increase profitability. Also the bill collection infrastructure is not necessary which intern increase improve the efficiency of the service providing companies. The concept of pre paid starts in the manual form by receiving advance deposits but now due to the revolution of IT and electronics industry the manual recharging process is replaced with automatic and 3
  • 4. electronic recharging. The recharging methods can be with wire based like telephone line and also by using wireless technology like radio and blue tooth communication. The prepaid system is designed with a smart technology using microcontroller and the recharging process is by some method of communication. Benefits of Prepaid Meters Improved operational efficiencies: The prepaid meters are likely to cut the cost of meter reading as no meter readers are required. In addition, they eliminate administrative hassles associated with disconnection and reconnection. Besides, going by South Africa’s experience, prepaid meters could help control appropriation of electricity in a better way than conventional meters. Reduced financial risks: Since the payment is up-front, it reduces the financial risk by improving the cash flows and necessitates an improved revenue management system. Better customer service: The system eliminates billing delay, removes cost involved in disconnection/reconnection, enables controlled use of energy, and helps customers to save money through better energy management. In this project the Prepaid Energy meter can be charged from a remote by using a mobile. Once the user feel to recharge The prepaid energy meter he can transfer the amount to the service provider bank account and the service provider will make a call to the system and log in to that and charge it by entering digits from its key pad. The recharging can be done from any mobile set but the system access code must be put in to log into the energy meter. This type of systems are now days getting popular and many popular and well known companies make products and sale in the market. 4
  • 5. Market Drivers Power sector reforms: The upcoming competitive and customer focused deregulated power distribution market will force the market participants to make the existing metering and billing process more competent. This is likely to drive the prepaid market. Increasing non-technical losses: Metering errors, tampering with meters leading to low registration and calibration related frauds are some of the key components of non-technical losses. India reports greater than 10 percent of non-technical losses. It has been reported that prepaid meters control non- technical losses better than conventional ones. Opportunities in the emerging electrifying markets: Most of the Asian countries do not have 100 percent electrification; hence new markets are being created by the increasing generating capacity. Prepaid systems can be more easily introduced in such new markets rather than the existing ones. The Prepaid Energy meter is designed by using a 8 bit microcontroller. The Microcontroller receive the pulse by interfacing optical pickups from a traditional electromagnetic energy meter. The electrical Induction energy meter works with the principle as follows, CIRCUIT DESCRIPTION a) POWER SUPPLY :-( +ve) Circuit connection: - In this we are using Transformer (0-12) v, 1Amp, IC 7805 & 7812, diodes IN 4007, LED & resistors. Here 230V, 50 Hz ac signal is given as input to the primary of the transformer and the secondary of the transformer is given to the bridge rectification diode. The o/p of the diode is 5
  • 6. given as i/p to the IC regulator (7805 &7812) through capacitor (1000mf/35v). The o/p of the IC regulator is given to the LED through resistors. Circuit Explanations: - When ac signal is given to the primary of the transformer, due to the magnetic effect of the coil magnetic flux is induced in the coil(primary) and transfer to the secondary coil of the transformer due to the transformer action.” Transformer is an electromechanical static device which transformer electrical energy from one coil to another without changing its frequency”. Here the diodes are connected in a bridge fashion. The secondary coil of the transformer is given to the bridge circuit for rectification purposes. During the +ve cycle of the ac signal the diodes D2 & D4 conduct due to the forward bias of the diodes and diodes D1 & D3 does not conduct due to the reversed bias of the diodes. Similarly during the –ve cycle of the ac signal the diodes D1 & D3 conduct due to the forward bias of the diodes and the diodes D2 & D4 does not conduct due to reversed bias of the diodes. The output of the bridge rectifier is not a power dc along with rippled ac is also present. To overcome this effect, a capacitor is connected to the o/p of the diodes (D2 & D3). Which removes the unwanted ac signal and thus a pure dc is obtained. Here we need a fixed voltage, that’s for we are using IC regulators (7805 & 7812).”Voltage regulation is a circuit that supplies a constant voltage regardless of changes in load current.” This IC’s are designed as fixed voltage regulators and with adequate heat sinking can deliver output current in excess of 1A. The o/p of the bridge rectifier is given as input to the IC regulator through capacitor with respect to GND and thus a fixed o/p is obtained. The o/p of the IC regulator (7805 & 7812) is given to the LED for indication purpose through resistor. Due to the forward bias of the LED, the LED glows ON state, and the o/p are obtained from the pin no-3. 6
  • 7. b) MOTHER BOARD The motherboard of this project is designed with a MSC –51 core compatible micro controller. The motherboard is designed on a printed circuit board, compatible for the micro controller. 7 LED LED 1k - + IN4007*4 GND 9-0-9Vac/1Amp 1000uF/35V 7812 POWER SUPPLY +5V +12V230VAC 50Hz 2.2k 7805 0-12 V
  • 8. This board is consisting of a socket for micro controller, input /output pull-up registers; oscillator section and auto reset circuit. Micro controller core processor: Introduction Despite it’s relatively old age, the 89C51 is one of the most popular Micro controller in use today. Many derivatives Micro controllers have since been developed that are based on--and compatible with--the 8051. Thus, the ability to program an 89C51 is an important skill for anyone who plans to develop products that will take advantage of Micro controller. Many web pages, books, and tools are available for the 89C51 developer. The 89C51 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: On-Chip Memory, External Code Memory, and External RAM. 8
  • 9. On-Chip Memory refers to any memory (Code, RAM, or other) that physically exists on the Microcontroller itself. On-chip memory can be of several types, but we'll get into that shortly. External Code Memory is code (or program) memory that resides off-chip. This is often in the form of an external EPROM. External RAM is RAM memory that resides off-chip. This is often in the form of standard static RAM or flash RAM. Code Memory 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 and sizes: Code memory may be found on-chip, either burned into 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 a 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 on-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 specific capabilities and one of the distinguishing factors from chip to chip is how much ROM/EPROM space the chip has. However, code memory is most commonly implemented as off-chip EPROM. This is especially true in low-cost development systems and in systems developed by students. 9
  • 10. Programming Tip: Since code memory is restricted to 64K, 89C51 programs are limited to 64K. Some assemblers and compilers offer ways to get around this limit when used with specially wired hardware. However, without such special compilers and hardware, programs are limited to 64K. External RAM As an obvious opposite of Internal RAM, the 89C51 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. Programming Tip: The 8051 may only address 64k of RAM. To expand RAM beyond this limit requires programming and hardware tricks. You may have to do this "by hand" since many compilers and assemblers, while providing support for programs in excess of 64k, do not support more than 64k of RAM. This is rather strange since it has been my experience that programs can usually fit in 64k but often RAM is what is lacking. Thus if you need more than 64k of RAM, check to see if your compiler supports it-- but if it doesn't, be prepared to do it by hand. 10
  • 11. On-Chip Memory As mentioned at the beginning of this chapter, the 89C51 includes a certain amount of on-chip memory. On-chip memory is really one of two types: Internal RAM and Special Function Register (SFR) memory. The layout of the 89C51's internal memory is presented in the following memory map: As is illustrated in this map, the 8051 has a bank of 128 bytes of Internal RAM. This Internal RAM is found on-chip on the 8051 so it is the fastest RAM available, and it is also the most flexible in terms of reading, writing, and modifying it’s contents. Internal RAM is volatile, so when the 8051 is reset this memory is cleared. The 128 bytes of internal ram is subdivided as shown on the memory map. 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 11
  • 12. addresses 08h through 1Fh. We'll discuss "register banks" more in a later chapter. For now it is sufficient to know that they "live" and are part of internal RAM. Bit Memory also lives and is part of internal RAM. We'll talk more about bit memory very shortly, but for now just keep in mind that bit memory actually resides in internal RAM, from addresses 20h through 2Fh. The 80 bytes remaining of Internal RAM, from addresses 30h through 7Fh, may be used by user variables that need to be accessed frequently or at 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 the stack and user variables. SFR Descriptions There are different special function registers (SFR) designed in side the 89C51 micro controller. In this micro controller all the input , output ports, timers interrupts are controlled by the SFRs. The SFR functionalities are as follows. This section will endeavor to quickly overview each of the standard SFRs found in the above SFR chart map. It is not the intention of this section to fully explain the functionality of each SFR--this information will be covered in separate chapters of the tutorial. This section is to just give you a general idea of what each SFR does. 12
  • 13. P0 (Port 0, Address 80h, Bit-Addressable): This is +input/output port 0. Each bit of this SFR corresponds to one of the pins on the Microcontroller. For example, bit 0 of port 0 is pin P0.0, bit 7 is pin P0.7. Writing a value of 1 to a bit of this SFR will send a high level on the corresponding I/O pin whereas a value of 0 will bring it to a low level. Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your hardware uses external RAM or external code memory (i.e., your program is stored in an external ROM or EPROM chip or if you are using external RAM chips) you may not use P0 or P2. This is because the 8051 uses ports P0 and P2 to address the external memory. Thus if you are using external RAM or code memory you may only use ports P1 and P3 for your own use. SP (Stack Pointer, Address 81h): This is the stack pointer of the Microcontroller. This SFR indicates where the next value to be taken from the stack will be read from in Internal RAM. If you push a value onto the stack, the value will be written to the address of SP + 1. That is to say, if SP holds the value 07h, a PUSH instruction will push the value onto the stack at address 08h. This SFR is modified by all instructions which modify the stack, such as PUSH, POP, LCALL, RET, RETI, and whenever interrupts are provoked by the Microcontroller. Programming Tip: The SP SFR, on startup, is initialized to 07h. This means the stack will start at 08h and start expanding upward in internal RAM. Since alternate register banks 1, 2, and 3 as well as the user bit variables occupy internal RAM from addresses 08h through 2Fh, it is necessary to initialize SP in your program to some other value if you will be using the alternate register banks and/or bit memory. It's not a bad idea to initialize SP to 2Fh as the first instruction of every one of your programs unless you are 100% sure you will not be using the register banks and bit variables. 13
  • 14. DPL/DPH (Data Pointer Low/High, Addresses 82h/83h): The SFRs DPL and DPH work together to represent a 16-bit value called the Data Pointer. The data pointer is used in operations regarding external RAM and some instructions involving code memory. Since it is an unsigned two-byte integer value, it can represent values from 0000h to FFFFh (0 through 65,535 decimal). Programming Tip: DPTR is really DPH and DPL taken together as a 16-bit value. In reality, you almost always have to deal with DPTR one byte at a time. For example, to push DPTR onto the stack you must first push DPL and then DPH. You can't simply plush DPTR onto the stack. Additionally, there is an instruction to "increment DPTR." When you execute this instruction, the two bytes are operated upon as a 16-bit value. However, there is no instruction that decrements DPTR. If you wish to decrement the value of DPTR, you must write your own code to do so. PCON (Power Control, Addresses 87h): The Power Control SFR is used to control the 8051's power control modes. Certain operation modes of the 8051 allow the 8051 to go into a type of "sleep" mode, which requires much, less power. These modes of operation are controlled through PCON. Additionally, one of the bits in PCON is used to double the effective baud rate of the 8051's serial port. TCON (Timer Control, Addresses 88h, Bit-Addressable): The Timer Control SFR is used to configure and modify the way in which the 8051's two timers operate. This SFR controls whether each of the two timers is running or stopped and contains a flag to indicate that each timer has overflowed. Additionally, some non-timer related bits are located in the TCON SFR. 14
  • 15. These bits are used to configure the way in which the external interrupts are activated and also contain the external interrupt flags which are set when an external interrupt has occurred. TMOD (Timer Mode, Addresses 89h): The Timer Mode SFR is used to configure the mode of operation of each of the two timers. Using this SFR your program may configure each timer to be a 16-bit timer, an 8-bit auto reload timer, a 13-bit timer, or two separate timers. Additionally, you may configure the timers to only count when an external pin is activated or to count "events" that are indicated on an external pin. TL0/TH0 (Timer 0 Low/High, Addresses 8Ah/8Ch): These two SFRs, taken together, represent timer 0. Their exact behavior depends on how the timer is configured in the TMOD SFR; however, these timers always count up. What is configurable is how and when they increment in value. TL1/TH1 (Timer 1 Low/High, Addresses 8Bh/8Dh): These two SFRs, taken together, represent timer 1. Their exact behavior depends on how the timer is configured in the TMOD SFR; however, these timers always count up. What is configurable is how and when they increment in value. P1 (Port 1, Address 90h, Bit-Addressable): This is input/output port 1. Each bit of this SFR corresponds to one of the pins on the Microcontroller. For example, bit 0 of port 1 is pin P1.0, bit 7 is pin P1.7. Writing a value of 1 to a bit of this SFR will send a high level on the corresponding I/O pin whereas a value of 0 will bring it to a low level. SCON (Serial Control, Addresses 98h, Bit-Addressable): The Serial Control SFR is used to configure the behavior of the 8051's on-board serial port. This SFR controls the baud rate of 15
  • 16. the serial port, whether the serial port is activated to receive data, and also contains flags that are set when a byte is successfully sent or received. Programming Tip: To use the 8051's on-board serial port, it is generally necessary to initialize the following SFRs: SCON, TCON, and TMOD. This is because SCON controls the serial port. However, in most cases the program will wish to use one of the timers to establish the serial port's baud rate. In this case, it is necessary to configure timer 1 by initializing TCON and TMOD. SBUF (Serial Control, Addresses 99h): The Serial Buffer SFR is used to send and receive data via the on-board serial port. Any value written to SBUF will be sent out the serial port's TXD pin. Likewise, any value which the 8051 receives via the serial port's RXD pin will be delivered to the user program via SBUF. In other words, SBUF serves as the output port when written to and as an input port when read from. P2 (Port 2, Address A0h, Bit-Addressable): This is input/output port 2. Each bit of this SFR corresponds to one of the pins on the Microcontroller. For example, bit 0 of port 2 is pin P2.0, bit 7 is pin P2.7. Writing a value of 1 to a bit of this SFR will send a high level on the corresponding I/O pin whereas a value of 0 will bring it to a low level. Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your hardware uses external RAM or external code memory (i.e., your program is stored in an external ROM or EPROM chip or if you are using external RAM chips) you may not use P0 or P2. This is because the 8051 uses ports P0 and P2 to address the external memory. Thus if you are using external RAM or code memory you may only use ports P1 and P3 for your own use. 16
  • 17. IE (Interrupt Enable, Addresses A8h): The Interrupt Enable SFR is used to enable and disable specific interrupts. The low 7 bits of the SFR are used to enable/disable the specific interrupts, where as the highest bit is used to enable or disable ALL interrupts. Thus, if the high bit of IE is 0 all interrupts are disabled regardless of whether an individual interrupt is enabled by setting a lower bit. P3 (Port 3, Address B0h, Bit-Addressable): This is input/output port 3. Each bit of this SFR corresponds to one of the pins on the Micro controller. For example, bit 0 of port 3 is pin P3.0, bit 7 is pin P3.7. Writing a value of 1 to a bit of this SFR will send a high level on the corresponding I/O pin whereas a value of 0 will bring it to a low level. 17
  • 18. 18
  • 19. Auto reset Circuit: RST 10uF 22pF 22pF 8.2k 4-12Mhz VCC=+5vdc AT89C51 9 18 19 29 30 31 1 2 3 4 5 6 7 8 21 22 23 24 25 26 27 28 10 11 12 13 14 15 16 17 39 38 37 36 35 34 33 32 RST XTAL2 XTAL1 PSEN ALE/PROG EA/VPP P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P2.5/A13 P2.6/A14 P2.7/A15 P3.0/RXD P3.1/TXD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 MICROCONTROLLER The auto reset circuit is a RC network as shown in the mother board circuit diagram. A capacitor of 1-10mfd is connected in series with a 8k2 resister the R-C junction is connected to the micro controller pin –9 which is reset pin. The reset pin is one when ever kept high( logic 1) the programme counter (PC) content resets to 0000h so the processor starts executing the programme. from that location. When ever the system is switched ON the mother board gets power and the capacitor acts as short circuit and the entire voltage appears across the resistor, so the reset pin get a logic 1 and the system get reset, whenever it is being switched ON. 19
  • 20. Pull-UP Resisters: AT89C51 9 18 19 29 30 31 1 2 3 4 5 6 7 8 21 22 23 24 25 26 27 28 10 11 12 13 14 15 16 17 39 38 37 36 35 34 33 32 RST XTAL2 XTAL1 PSEN ALE/PROG EA/VPP P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P2.5/A13 P2.6/A14 P2.7/A15 P3.0/RXD P3.1/TXD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 10k PORT-0 VCC=+5V The PORT0 and PORT2 of the MCS-51 architecture is of open collector type so on writing logic 0 the pins are providing a perfect ground potential. Where as on writing logic 1 the port pins behaves as high impedance condition so putting a pull-up resister enables the port to provide a +5volt( logic 1). Port1 and Port3 are provided with internal pull-ups. A pull-up resister is normally a 10K resistance connected from the port pin to the Vcc (+5) volt. Crystal Oscillator 20
  • 21. The 8051 family microcontroller contains an inbuilt crystal oscillator, but the crystal has to be connected externally. This family of microcontroller can support 0 to 24MHz crystal and two numbers of decoupling capacitors are connected as shown in the figure. These capacitors are decouples the charges developed on the crystal surface due to piezoelectric effect. These decoupling capacitors are normally between 20pf to 30pf. The clock generator section is designed as follows, The Microcontroller design consist of two parts 1) Hardware. 2) Software. HARDWARE: The controller operates on +5 V dc, so the regulated + 5v is supplied to pin no. 40 and ground at pin no. 20. The controller is used here need not required to handle high frequency signals, so as 4 MHz crystal is used for operating the processor. The pin no. 9 is supplied with a +5V dc through a push switch. To reset the processor .As prepare codes are store in the internal flash memory the pin no. 31 is connected to + Vcc 21
  • 22. Port assignment:- Port P0.0 to P0.7 is used as LCD data bus. Port P2.0 is connected to RS Port P2.1 is connected to R/W Port P2.2 is connected to EN Port P3.0 is used as input port from the phase tampering section. Port P3.1 is used as input port from the neutral tampering section. Port P3.2 (INT0) is connected to input from maximum demand section. Port P3.4 is connected to input from opto slot. Port P3.5 is connected to the input from maximum demand section. Port P3.6 is connected to Relay driver section. Port P3.7 is connected to Buzzer Driver. SOFTWARE: Algorithm 1. The controller continuously scans the ports receiving inputs from maximum demand section and optical pickup section. 2. If the optical pickup receives a pulse then the counter increments and display the unit consumed in the LCD display. The count is compared to display the warning for recharging. 3. After finishing up the units the tripping relay is activated to disconnect the power. 22
  • 23. 4. If the maximum demand section gives a pulse then it activates the tripling mechanism. 5. The controller rechecks continuously the maximum demand section and regain the power when load is reduced. 23
  • 24. 10uFRST AT89C51 9 18 19 29 30 31 1 2 3 4 5 6 7 8 21 22 23 24 25 26 27 28 10 11 12 13 14 15 16 17 39 38 37 36 35 34 33 32 RST XTAL2 XTAL1 PSEN ALE/PROG EA/VPP P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P2.5/A13 P2.6/A14 P2.7/A15 P3.0/RXD P3.1/TXD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 22pF 22pF VCC=+5V 4MHz BITS LCD CONTROL BITS NU COMP.. LCD DATA 8.2k MD COMP.. OPTO-SLOT MD COMP.. PH COMP RELAY DRIVER BUZZER DRIVER MOTHER BOARD 24
  • 25. c) LCD DISPLAY THE PRINCIPLES OF LCD TECHNOLOGY In this section, we will explain everything ranging from the properties of liquid crystal molecules to the basic principle of display technology by using TN type liquid crystals as an example. The parallel arrangement of liquid crystal molecules along grooves When coming into contact with grooved surface in a fixed direction, liquid crystal molecules line up parallelly along the grooves. Natural state When liquid crystals are sandwiched between upper and lower plates, they line-up with grooves pointing in directions 'a' and 'b,' respectively The molecules along the upper plate point in direction 'a' and those along the lower plate in direction 'b,' thus forcing the liquid crystals into a twisted structural arrangement./ (figure shows a 90-degree twist) (TN type liquid crystal) Light travels through the spacing of the molecular arrangement The light also "twists" as it passes through the twisted liquid crystals 25
  • 26. Light passes through liquid crystals, following the direction in which the molecules are arranged. When the molecule arrangement is twisted 90 degrees as shown in the figure, the light also twists 90 degrees as it passes through the liquid crystals. Light bends 90 degrees as it follows the twist of the molecules Molecules rearrange themselves when voltage is applied When voltage is applied to the liquid crystal structure, the twisted light passes straight through. The molecules in liquid crystals are easily rearranged by applying voltage or another external force. When voltage is applied, molecules rearrange themselves vertically (along with the electric field) and light passes straight through along the arrangement of molecules. Blocking light with two polarizing filters When voltage is applied to a combination of two polarizing filters and twisted liquid crystal, it becomes a LCD display. 26
  • 27. Light passes when two polarizing filters are arranged with polarizing axes as shown above, left. Light is blocked when two polarizing filters are arranged with polarizing axes as shown above, right. TN type LCDs A combination of polarizing filters and twisted liquid crystal creates a liquid crystal display. 27
  • 28. When two polarizing filters are arranged along perpendicular polarizing axes, light entering from above is re-directed 90 degrees along the helix arrangement of the liquid crystal molecules so that it passes through the lower When voltage is applied, the liquid crystal molecules straighten out of their helix pattern and stop redirecting the angle of the light, thereby preventing light from passing through the lower filter. This figure depicts the principle behind typical twisted nematic (TN) liquid crystal displays. In a TN type LCD, liquid crystals in which the molecules form a 90-degree twisted helix, are sandwiched between two polarizing filters. When no voltage is applied, light passes; when voltage is applied, light is blocked and the screen appears black. In other words, the voltage acts as a trigger causing the liquid crystals to function like the shutter of a camera. 28
  • 29. LCD panel consists of two patterned glass panels in which crystal is filled under vacuum. The thickness of glass varies according to end use. Most of the LCD modules have glass thickness in the range of 0.70 to 1.1mm Normally these liquid crystal molecules are placed between glass plates to form a spiral staircase to twist the twist the light. Light entering the top plate twist 900 before entering the bottom plate. Hence the LCDs are also called as optical switches. These LCD cannot display any information directly. These act as an interface between electronics and electronics circuit to give a visual output. Technology: - The liquid crystal display (LCD), as the name suggests is a technology based on the use of liquid crystal. It is a transparent material but after applying voltage it becomes opaque. This property is the fundamental operating principle of LCDs. An LCD consists of two-glass panel with a cavity in between. The panels are sealed together. The inner surface of glass is coated with transparent material to form characters or symbols for display. The most common type of liquid crystal used is ‘nematis’. In this type of crystal the long rod type molecules are arranged in parallel. It changes the optical characteristics with change in direction by applying voltage to it. There are two common type of LCDs which use this material. They are : 1. TN (Twisted nematic):-The twisted nematic field effect mode arranges the liquid crystal molecules by controlling their movement Witt electric voltage soaks twist them by 900 in the direction for their thickness. It controls the light passing through the polarized placed on the two plates of the LCD by controlling the movements of 29
  • 30. the liquid crystal molecules. Almost all the medium and small type segment LCD are these types. Hence this type is most common type used. 2. STN (Super twisted nematic) While the TN mode arranges the liquid crystal molecule by twisting them by 900 the STN effect mode arranges them by giving a still larger twist and provides a display by refringence effect of the liquid crystal. The LCD structure in STN mode is same as that in TN mode. But as it has a different arrangement of liquid crystal, and by bi-refringence effect of liquid crystal. The LCD structure in STN mode is same as that in TN mode but as it has a different arrangement of liquid crystal and bi-refringence effect there is a colour in display and also a background colour. In STN mode, a wide viewing angle is obtained. The STN mode also offers a high contrast display compare to the TN mode. This mode is widely used in large size full dot-matrix LCD modules. For colours it has multiple modes depending on the combination of the polarized and retardation film. Energy consumption: - LCD normally requires very little energy to operate typically 5µA to 25µA at five volts (per square inch) for a display. In addition, auxiliary lighting will require supplementary energy. ALL LCD require a pure AC drive voltage. Inadvertent DC voltage, such as DC component in an AC signal, can significantly reduce the life of LCDs and must be limited to 50mv DC. Direct drive: - Direct drive, static or simplex drive, means that each segment of the LCD has an independent connection to the driver. Direct drive LCD has the highest contrast over the widest temperature ranges. They are widely used in outdoor application. Direct drives typically requires drive frequency between 30HZ and 60HZ frequency. Frequency below 30HZ will 30
  • 31. flicker the display. While frequency above 60HZ will excessive current draw in the circuit. This is very important for battery mode operation. If voltage frequency across the limit then LCD ’Off’ segments can be come in adherently energized. This partial activation of segment is known as cross talk or ghosting. LCD is available in a verity of model having one to four rows of 8 to 20 characters each. A display with two rows of 16 characters is used for this example project. Almost all aspects of the design can be used with other model of LCD, since the internal structure of the various LCD models are almost same, differencing only in the number of driver chips used. The display module is powered from a 5 V supply. Connecting an LCD to a micro controller is very simple, requiring either bit or an 8-bit bus. A 4-bit interface saves I/O pins but requires that the command and data be split into 4-bit pieces, which are sent one after the other. Thus the saving in I/O lines comes at the price of more complicated software. To simplify understanding of the software the example uses a 8-bit interface. Three control lines are required in addition to the data line. The voltage at the V0 pin adjusts the contrast of the display. Normally this voltage is provided by an adjustable voltage divider. The control line E (Enable) enables or disables the display. When the display is enabling it monitors the value of the other two control lines and interprets the data lines accordingly. When the display is disabled it ignores the status of the other two control lines and places its data line drivers in a high impedance state (tri-state). The data bus can then be used for other purpose. The control line R/W (Read /Write) determines weather data is read from or written to the LCD. Finally, the RS (Register select) line distinguishes between commands and display characters. 31
  • 32. LCD Controller device characteristics The HD44780 contains 80 bytes of internal RAM called Data display RAM (DDR) that is used for presentation of characters in the LCD. The size of the DDR is independent of the LCD configuration (number of rows and character). For an LCD having two rows of characters, the leftmost character in the first row is assigned to address 0 of the DDR. Each following character position in the first display row is assigned to the next following address in turn until the 40th character location reached, which is assigned to DDR address 27 hex. The character locations in the second row of the display are assigned to DDR address 40 hex through 67 hex. If for example a character is to be written to the third position from the left in the second row of the display, it must be written to DDR, so that for example with a display, it must be written to DDR location 42hex.If the LCD module displays fewer than 40 characters per row, then these are mapped into a ‘window’ within the DDR, so that for example with a display of 16 characters per line only 16 of the 40 available DDR locations per line can be displayed at one time. The HD44780 supports commands to move this window to the left or to the right to allow various regions of the DDR to be displayed. In additions to the DDR the HD44780 has a character genator ROM (CGROM) and a character-generator RAM (CGRAM). The CG ROM contains the dot-matrix patterns for the standard (fixed) character set, while the CGRAM allows the user to program additional character. Either eight4 X 7-point or four 5 X 10-point characters may be stored on the CGRAM. 32
  • 33. P0.2 C LED+R/W VCC=+5V P0.1 L LED- P0.0 DB7 10k P0.5 DB2 1k LIQUID CRYSTAL DISPLAY 10E EN P0.6 DB3 P0.7 BC557 P2.2 GND P2.1 Vcc MICROCONTROLLER D DB4 DB5 P2.0 DB1 DB0 CON. DB6 P0.4 VCC=+5V RS P0.3 33
  • 34. d) RELAY DRIVER & BUZZER DRIVER Relay section is designed to operate and drive the relays .The relays used here having following specifications. Operating voltage = 12V DC Coil resistance = 60Ω Capacity of contact point = 25A, 230V Type = single contact NO/NC The relay requires 12 volts and current= 12 volt/60Ω = 500mA. The driver now require for driving this relay must be designed for translating the TTL logic value into 12 volts and 500mA current. The Microcontroller cannot provide this much of current. In normal practice, it desirable to draw 60 to 600µA current from the Microcontroller, as the output to load current requirement is very high a transistor driver is required. This driver circuit is configured with a integrated Darlington pair of transistors (TIP122). The common emitter amplification factor is approximately 200x50 for TIP 122. The load current is considered about 40mA then, the base current will be around = 500/(200x50)= 500x10-3 /(200x50) = 50 micro A. In this arrangement the base current is design for200 micro Amp. Appling KVL, 5-Rb Ib-0.7-0.7=0 Rb= 22k( max) Rb= 2.2k 34
  • 35. Whenever the relay driver section receives a signal from the controller, the driver transistor driven into saturation, on removal of signal the driver transistor will be driven into cut-off. BUZZER DRIVER This section interfaces one audible piezo electric buzzer with the controller. The controller activates the buzzer whenever there is any fault appears in any of the channel. This buzzer driver section is also one darling ton pair integrated circuit. A single transistor BC547 is used for this purpose PIEZO ELECRTIC BUZZER: It is a device that converts electrical signal to an audible signal (sound signal).The Microcontroller cannot drive directly to the buzzer, because the Microcontroller cannot give sufficient current to drive the buzzer for that we need a driver transistor (BC547), which will give sufficient current to the buzzer. Whenever a signal received to the base of the transistor through a base resistance (1.5k) is high, the transistor comes to saturation condition i.e. ON condition thus the buzzer comes to on condition with a audible sound. Similarly, whenever the signal is not received to the base of the transistor, thus the transistor is in cut-off state i.e. is in OFF state thus the buzzer does not gets activated 35
  • 36. P3.6 VCC=+12V 1.5k BUZZER&RELAYDRIVER P3.7 BC547 1.5k VCC=+12V RELAY BC547 36
  • 37. e) COMPARATOR SECTION: - In this section our aim is to detect the line voltage varying current. Introduction: This section is configured with a quad comparator LM393 (is a dual comparator integrated circuit. All the comparators are receiving a common input signal from the signal conditioning section. The comparator is designed with hysterias, to avoid fluctuation at the equal set values. All the four comparators are set with different reference value; each corresponds to a particular current value. Whenever the input to this comparator from the signal section, gives beyond the set value, then the comparator toggles. As the input is given at the non–inverting terminal as the output of the comparator goes to positive saturation voltage. As the reference voltage are set in a increasing order, When the comparator set for highest value is driven into positive saturation. All the comparator must be driven into saturation. So LED s connected to the each comparator section indicates the level of different parameter. The line voltage (230vac) coming from the mains is given to the one end of primary of the current transformer-1 and another end through a load (1KW) of the one end and another end to the another current transformer-2 primary and another end to the neutral. That current/voltage is step down at the secondary winding of the current transformer due to the mutual induction. If the load varies, the step down voltage also varies in accordance with the input voltage. Due to the mutual induction of the transformer, if the primary winding of the transformer voltage is more the flux induced is more and the secondary voltage is more. Similarly, if the primary winding of the transformer voltage is less the flux induced is less and the secondary voltage is less. In this way under/over voltage occurs. At present we can′t vary the line voltage manually, 37
  • 38. for that we needs to vary the load to vary manually. But in our project we can vary the current/voltage by converting it to AC to DC voltage.The above figure shows a half-wave rectifier, in which it will converts ac to dc voltage. We can vary the voltage with the variable load resistance (10k) by varying the load resistance we can make under/over voltage manually; otherwise we have to vary the line voltage. Operation: The output of the signal sampling voltage (3v) goes to the input of both of the comparator. In the first comparator we have set the voltage say 3.5Vto the non-inverting terminal. In this case non-inverting terminal is greater than the inverting terminal. That means output of the first comparator is LOW. At present under temperature can′t be done because the room temperature will be always available If we want′s to do under temperature, we have to vary or change the set point which is connected to the inverting terminal of that comparator. Similarly, for the second comparator we have set the voltage say 4V to the inverting terminal. In this case inverting terminal is greater than the non-inverting terminal that means output of the second comparator is HIGH. If the voltage increases, the corresponding voltage will increase say 4.5V. That voltage goes to the input of both of the comparator. In the first comparator we have set the voltage say 3.5Vto the non-inverting terminal. In this case inverting terminal is greater than the non- inverting terminal. That means output of the first comparator is HIGH this means that over temperature has occurred. Similarly, for the second comparator we have set the voltage say 4V to the inverting terminal. In this case non- inverting terminal is greater than the inverting terminal that means output of the second comparator is LOW. That output signal is not compatible with the µ-controller because as we know that the controller takes input signal as 5V and gives output as 5V. For this reason we needs a signal 38
  • 39. conditioning circuit which is given in the below figure-2. That output signal is compatible with the controller because the current will flows from the collector of the transistor whenever the base voltage is high due to the transistor action. Similarly the output is low in the absence of the input signal to the signal conditioning circuit from the comparators. BC547 1.5k 10k (1:0) VCC=+5vVCC=+5v (1:1) INPUT 1.5k SIGNAL CONDITIONING OUTPUT 10k OUTPUT BC547 INPUT in our section we are using fig1: 0, whenever the base voltage is HIGH the transistor comes to saturation condition i.e. the emitter current flows to the collector which gives a low voltage at the output corresponding to GND. The output is taken from the collector junction through a current limiting resistance and the output signal is given to the µ - controller or any other circuit which needs a compatible (5V/0V) voltage. Similarly, whenever the base voltage is LOW the collector current flows from the Collector junction of the transistor, which gives a high voltage at the output corresponding to Vcc. The output is taken from the emitter junction through a current limiting resistance and the output signal is given to the µ - controller or any other circuit which needs a compatible (5V/0V) voltage. 39
  • 40. 15k 10k VCC=+12v 470E 1.5k P3.1 10k CT - 02 + - LM393 6 5 7 84 - + LM393 3 2 1 84 1.5k P3.5 BC547 10k 470E P3.2 10k VCC=+5v 68k PHASE LED 1.5k BC547 COMPARATOR & SIGNAL CONDITIONING 10k OUTPUT-2 15k VCC=+5v VCC=+5v VCC=+5v 68k 68k 10k BC547 15k 1.5k BC547 VCC=+5v CT - 01 P3.0 10k - + LM393 3 2 1 84 BC547 VCC=+5v 10k BC547 NEUTRAL LED VCC=+5v BC547 470E 10k M.DLED 10k f) NEUTRAL TAMPERING: 40
  • 41. This is a very important and useful facility to restrict the Energy theft. In this section two numbers of CT (Current Transformer) is connected before and after the load i.e. one CT at the phase and other at the neutral. The voltage output of the CT is converted into DC using a half wave rectifier filtered with an electrolytic capacitor. The DC voltage produced in this manner adjusted to a level by using a voltage divider. Using two resistances in series forms the voltage divider, R1 (Fixed) R2 (Variable) the voltage outpu(Vs) is adjusted normally for a value bellow 5volt. While designing the voltage divider the care is taken to allow maximum 1mA current to the ground also the required voltage for sampling is also important. I= V/(R1+R2) =1m…………………………….(1) Vs = IxR2…..…………………………………..(2) R1 is assumed and R2 is decided for nearest available values. The voltage sampled feed to two comparators, the comparator set values are kept as low as possible, normally adjusted between 0v to 0.5 volt. If there is current in the CT then the CT out put feed to the comparator (Vs) drives the comparator into saturation. There are two comparator connected to the phase and neutral, if the system is normal the it is understood the phase current and neutral currents are same so both the comparator outputs are high. If any user uses the phase and run the load using the earth instead of using the neutral then the and comparator outputs are no longer remains high but the phase comparator output is high the neutral comparator output becomes low. When this combination is feed to the microcontroller after signal conditioning the microcontroller understands this as a fault condition. 41
  • 42. C.T-01 C.T-02 10K CURRENT SAMPLING CKT C NC N L1 P3.6 ENERGY METER L2 COMP..-2 1000W LOAD 100uF S2 10K P RELAY TIP122 10K 100uF IN4007 IN4007 VCC=+12V S1 1.5k 10K COMP..-1 g) OPTO-ISOLATOR: 42
  • 43. Introduction: The device is a simple isolating opt coupler show two other types of opt coupler. The device shown in Fig is known as a slotted opt coupler. And has a slot moulded into the package between the LED light source and the phototransistor light sensor. Here, light can normally pass from the LED to Q1 without significant attenuation by the slot. The optocoupling can, however, be completely blocked by placing an opaque object in the slot. The slotted opt coupler can thus be used in a variety of presence detecting applications, including end-of-tape detection, limit switching, and liquid-level detection. An opt Isolator is a device containing an infrared LED and a matching phototransistor, mounted close together (optically coupled) within a light-excluding package as shown in below figure. VCC R1 2 1 U2 MCT2E 1 2 5 4 SW1 1 2 R2 2 1 Here sw1 is normally open, so zero current flows through the LED: Q1 is thus in darkness and also passes zero current, so zero output voltage appears across R2. When sw1 is closed, however current flows through the LED via R1, thus illuminating Q1 and causing it to generate an R2 output voltage. The R2 output voltage can thus be controlled via the R1 input current, even though R1 and R2 are fully isolated electrically.In practice, the device can be used to 43
  • 44. optocouple either digital or analogue signals, and can provide hundreds or thousands of volts of isolation between the input and output circuits. FUTURE EXPANSION: This project can be expanded in the following directions. 1. The electromagnetic induction meter can be replaced with a Electronic meter. 2. Remote recharging can be implemented through telephone line or wireless network. 3. The protection against the power theft and energy meter tampering can incorporate in this project. 4. A mini printer can be interfaced to get a printed bill or details of billing. 5. Software can be modified to view the balance on request. CONCLUSION This project is performing satisfactory function in laboratory condition. The device designed is used in conjunction with an Induction Energy meter. With minor modification in the software and hardware this system can be used for field application. 44
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