automatic solar led street light automation by using rtc and i2c protocols doccument

Automatic Solar Led Street Light Using RTC & I2C Protocol

LIET, ECE Department

CHAPTER-1

INTRODUCTION

INTRODUCTION

From olden days we are using non renewable sources of energy in excess mount for

our needs. As this type of minerals like coal etc are exhausting so we have to depend on the

renewable sources of energy like solar, wind, etc. For smaller application it is better to use

renewable energy. As this project is based on streetlight automation and required AC

supply. So for this particular application we are using solar panels to charge the DC battery

and the power from the battery can be used for this application. Advertising hoardings,

commercial sign boards, and street lights are generally switched on at 6:30 pm and

switched off at 10:00 am because nobody is available at the place in the morning to switch

it off. But actual required time is 6:30pm to 11:30pm and 4:30am to 6:30am. Meantime

i.e., from 11:30pm to 4:30am is not required, because the public flow on the roads is

almost nil in this time. And from 6:30am to 10:00am is also not required as the sun light is

available during this time. That means every day around nine hours of power is wasted.

This project gives the best solution for electrical energy wastage. Also the manual

operation of the lighting system is completely eliminated. The Project AT89S52

Microcontroller Based Energy saver for Commercial Lighting system with RTC DS1307

Interfacing is an interesting project which uses AT89S52 microcontroller as its brain. This

project is very useful for commercial sign boards, advertising boards, street lights for

automation lighting system. This system switches on the lights only at preprogrammed

timings. As the DS1307 Real Time Clock chip with battery back-up is used, there will be

no disturbances for the programmed on/off timings even in power failures. Control switch

set is provided for entering the required timings. 4-digit seven segment display is provided

to display the alarm times and current time. DS1307 is interfaced to the microcontroller for

real timing performance. A 3V battery can be connected to DS1307 to avoid time

disturbances caused by power failures. AT89S52 has inbuilt flash EPROM. Data stored

remains in the memory even after power failure, as the memory ensures reading of the

latest saved settings by the micro controller. It can retain data for more than ten years.



CHAPTER-2

EMBEDDED SYSTEMS

2.1 Embedded System Introduction

An Embedded System is a combination of computer hardware and software, and

perhaps additional mechanical or other parts, designed to perform a specific function. A

good example is the microwave oven. Almost every household has one, and tens of

millions of them are used every day, but very few people realize that a processor and

software are involved in the preparation of their lunch or dinner.

This is in direct contrast to the personal computer in the family room. It too is

comprised of computer hardware and software and mechanical components (disk drives,

for example). However, a personal computer is not designed to perform a specific function

rather; it is able to do many different things. Many people use the term general-purpose

computer to make this distinction clear. As shipped, a general-purpose computer is a blank

slate; the manufacturer does not know what the customer will do wish it. One customer

may use it for a network file server another may use it exclusively for playing games, and a

third may use it to write the next great American novel

If an embedded system is designed well, the existence of the processor and

software could be completely unnoticed by the user of the device. Such is the case for a

microwave oven, VCR, or alarm clock. In some cases, it would even be possible to build

an equivalent device that does not contain the processor and software. This could be done

by replacing the combination with a custom integrated circuit that performs the same

functions in hardware. However, a lot of flexibility is lost when a design is hard-cooled in

this way. It is mush easier, and cheaper, to change a few lines of software than to redesign

a piece of custom hardware.

2.2 History and Future

Given the definition of embedded systems earlier is this chapter; the first such

systems could not possibly have appeared before 1971. That was the year Intel introduced



the world's first microprocessor. This chip, the 4004, was designed for use in a line of

business calculators produced by the Japanese Company Busicom. In 1969, Busicom asked

Intel to design a set of custom integrated circuits-one for each of their new calculator

models. The 4004 was Intel's response rather than design custom hardware for each

calculator, Intel proposed a general-purpose circuit that could be used throughout the entire

line of calculators. Intel's idea was that the software would give each calculator its unique

set of features.

2.3 Tools

Embedded development makes up a small fraction of total programming. There's

also a large number of embedded architectures, unlike the PC world where 1 instruction set

rules, and the Unix world where there's only 3 or 4 major ones. This means that the tools

are more expensive. It also means that they're lower featured, and less developed. On a

major embedded project, at some point you will almost always find a compiler bug of

some sort.

Debugging tools are another issue. Since you can't always run general programs on

your embedded processor, you can't always run a debugger on it. This makes fixing your

program difficult. Special hardware

such as JTAG ports can overcome this issue in part. However, if you stop on a

breakpoint when your system is controlling real world hardware (such as a motor),

permanent equipment damage can occur. As a result, people doing embedded

programming quickly become masters at using serial IO channels and error message style

debugging.

2.4 Resources

To save costs, embedded systems frequently have the cheapest processors that can

do the job. This means your programs need to be written as efficiently as possible. When

dealing with large data sets, issues like memory cache misses that never matter in PC

programming can hurt you. Luckily, this won't happen too often- use reasonably efficient

algorithms to start, and optimize only when necessary. Of course, normal profilers won't

work well, due to the same reason debuggers don't work well. So more intuition and an



understanding of your software and hardware architecture is necessary to optimize

effectively.

Memory is also an issue. For the same cost savings reasons, embedded systems

usually have the least memory they can get away with. That means their algorithms must

be memory efficient (unlike in PC programs, you will frequently sacrifice processor time

for memory, rather than the reverse). It also means you can't afford to leak memory.

Embedded Application

2.5 Real Time Issues

Embedded systems frequently control hardware, and must be able to respond to them in

real time. Failure to do so could cause inaccuracy in measurements, or even damage

hardware such as motors. This is made even more difficult by the lack of resources

available. Almost all embedded systems need to be able to prioritize some tasks over

others, and to be able to put off/skip low priority tasks such as UI in favor of high priority

tasks like hardware control.

2.6 Characteristics

Embedded systems are designed to do some specific task, rather than be a general-

purpose computer for multiple tasks. Some also have real-time performance constraints

that must be met, for reasons such as safety and usability; others may have low or no

performance requirements, allowing the system hardware to be simplified to reduce costs.

Embedded systems are not always standalone devices. Many embedded systems

consist of small parts within a larger device that serves a more general purpose. For

example, the Gibson Robot Guitar features an embedded system for tuning the strings, but

the overall purpose of the Robot Guitar is, of course, to play music.[10] Similarly, an

embedded system in an automobile provides a specific function as a subsystem of the car

itself.

The program instructions written for embedded systems are referred to as firmware,

and are stored in read-only memory or Flash memory chips. They run with limited

computer hardware resources: little memory, small or non-existent keyboard or screen.

https://en.wikipedia.org/wiki/Embedded_system#cite_note-10



2.7 Need For Embedded Systems

2.7.1 Debugging

Embedded debugging may be performed at different levels, depending on the facilities

available. From simplest to most sophisticated they can be roughly grouped into the

following areas:

1. Interactive resident debugging, using the simple shell provided by the embedded operating

system (e.g. Forth and Basic)

2. External debugging using logging or serial port output to trace operation using either a

monitor in flash or using a debug server like the Remedy Debugger which even works for

heterogeneous multicore systems.

3. An in-circuit debugger (ICD), a hardware device that connects to the microprocessor via

a JTAG or Nexus interface. This allows the operation of the microprocessor to be

controlled externally, but is typically restricted to specific debugging capabilities in the

processor.

4. An in-circuit emulator (ICE) replaces the microprocessor with a simulated equivalent,

providing full control over all aspects of the microprocessor.

5. A complete emulator provides a simulation of all aspects of the hardware, allowing all of it

to be controlled and modified, and allowing debugging on a normal PC. The downsides are

expense and slow operation, in some cases up to 100X slower than the final system.

6. For SoC designs, the typical approach is to verify and debug the design on an FPGA

prototype board. Tools such as Certus are used to insert probes in the FPGA RTL that

make signals available for observation. This is used to debug hardware, firmware and

software interactions across multiple FPGA with capabilities similar to a logic analyser.

Unless restricted to external debugging, the programmer can typically load and run

software through the tools, view the code running in the processor, and start or stop its

operation. The view of the code may be as HLL source-code, assembly code or mixture of

both.

https://en.wikipedia.org/wiki/High-level_programming_language



Because an embedded system is often composed of a wide variety of elements, the

debugging strategy may vary. For instance, debugging a software- (and microprocessor-)

centric embedded system is different from debugging an embedded system where most of

the processing is performed by peripherals (DSP, FPGA, co-processor). An increasing

number of embedded systems today use more than one single processor core. A common

problem with multi-core development is the proper synchronization of software execution.

In such a case, the embedded system design may wish to check the data traffic on the

busses between the processor cores, which requires very low-level debugging, at signal/bus

level, with a logic analyser.



CHAPTER-3

BLOCK DIAGRAM

Figure 3.1 Block Diagram.



3.1 BLOCK DIAGRAM DESCRIPTION

The solar energy is converted into electrical energy by photo-voltaic cells. This

energy is stored in batteries during the day time for it to be utilized to on the street light.

This project deals with a controlled charging mechanism with protections for over charge,

deep discharge and under voltage of the battery. It overcomes the difficulties of switching

the street light ON/OFF manually. This proposed system has an inbuilt real time clock

(RTC) to keep tracking the time and thus to switch ON/OFF the pump accordingly.

This project consisting of a real-time clock (RTC) is interfaced to a microcontroller

of the PIC series family. While the set time equals to the real time, then microcontroller

gives command to the corresponding relay to turn on the load, and then another command

to switch off as programmed by the user. Multiple on/off time entry is the biggest

advantage with this project. A matrix keypad helps entering different time slots. A LCD

display is interfaced to the microcontroller to display time. In this project, a solar panel is

used to charge a battery. A set of op-amps are used as comparators to continuously monitor

panel voltage, load current, etc. Indications are also provided by a green LED for fully

charged battery while a set of red LEDs to indicate under charged, overloaded and deep

discharge condition. Charge controller also uses MOSFET as power semiconductor switch

to ensure cutting of the load in low battery or overload condition. A transistor is used to

bypass the solar energy to a dummy load while the battery gets fully charged. This protects

the battery from getting over charged.



CHAPTER-4

SCHEMATIC DIAGRAMS

Figure 4.1 Schematic Diagram-1.

4.1 Schematic Description-1

In this Solar Charging Circuit we are using SOLAR PANEL. Here we are using

MOSFET whose gate is connected to emitter of the transistor (BC547) drain is connected

to +VE terminal & source is connected to GND is parallel to MOSFET a battery of 12V is

connected collector of transistor is connected to +ve terminal with resistor R1 of 18K.

Whose base is connected to o/p of 1st op-amp (LM324) through resistor R3 of 100K. Pin

11 is connected to GND Pin 4 is connected to VCC for both op-amps’ known as U1: A &

U1B. 2nd Pin of U1:A is connected to Pin 1 of op-amp through two resistors R4 of 330K

R5 of 330k. Pin 3 and Pin 5 all shorted and connected to POT of 5K 6th Pin is connected to

GND through resistor R10 of 120K. And 7th Pin is o/p Pin with resistor R7 of 2K & LED.

VI:C is also an op-amp is whose 10th Pin is connected to POT of 5K whose one of the

terminal is also connected to 2nd Pin of U1:A where 9th Pin is connected to GND 4th & 11th

Pin are VCC and GND. Where 8th Pin is o/p Pin which is connected to Gate of MOSFET



Q2 through Diode IN4148 where 9th Pin is also connected to drain of MOSFET whose gate

is also connected to POT of RV1 who will get another o/p of U1:D known as Pin 14.

Whose 12th Pin is connected to RV5 22K PRESET 13th Pin is connected to 4diodes in

series known as D5, D6, D7,D8 source is connected to GND.

SCHEMATIC DIAGRAM

Figure 4.2 Schematic Diagram-2.



.4.2 Schematic Description-2

The o/p of the power supply which is +5V is connected to 11th&32th Pin of

Microcontroller & 12th &31th is connected to ground operate in this project “auto” Here we

are using 3x4 keypad. Whose Pins are connected to Pin D4 to D7 Pin of PIC

Microcontroller and for display purpose we are using 16x2 LCD whose data Pins from 27

to 30 is connected to Pin 2.0 to 2.7 which belongs to Port 2 of Microcontroller where as

4,5,6 Pin of LCD is connected to 19th 21 & 22th Pin of PIC MC. Buzzer is connected to Pin

2.

Pin 23,18 of PIC Microcontroller is connected to 6 & 5 Pin of DS1307 IC which

provide (Real Time Signal) 1st and 2nd Pin is connected to crystal of 32.765Khz of

reference frequency 3rd is connected to GND through capacitor 8th is connected to Vcc and

4th is connected to GND.

Working

The project uses one RTC (Real Time Clock) for Real Time Reference duly interfaced to

Pin 18 & 23 of PIC Microcontroller. A Matrix Telephone keypad is used to enter multiple

Timings for multiple medicines as per the program displayed on the LCD. First we have to

enter /set the time for RTC. after that we have to set the medicine times. When the

programmed times of the clock reaches the set time and o/p is logic 1 at Pin No.2 to sound

a Buzzer which is amplified by Q1 to draw the attention of the person to view the name of

the medicine on the LCD for taking the same in right time. The ckt is powered by a battery

and a voltage regulator for desired voltage operations.



CHAPTER-5

HARDWARE

5.1 COMPONENTS USED

1. MICROCONTROLLER PIC (16F877A)

2. SOLAR CELLS/SOLAR PANEL

3. BATTERY

4. KEYPAD

5. LCD

6. RTC

7. LM324

8. MOSFET

9. BC547

10. 1N4007 DIODE

11. RESISTORS

12. CAPACITORS

13. LED’S

14. PUSH BUTTON



5.2 MICROCONTROLLER- PIC16F877A

5.2.1 Micro Controller Core Features

1. High performance RISC CPU.

2. The instruction set has only 35 instructions.

3. Operating speed of DC-20MHz clock input.

4. Flash program memory of 8K x 14-bit words.

5. Data Memory (RAM) of 368 x 8 bytes.

6. EEPROM data memory of 258 x 8 bytes.

7. Power On reset (POR).

8. Power- up timer (PWRT).

9. Oscillator Start-up timer (OST).

10. Watchdog Timer (WDT) with its own On-chip RC oscillator for reliable operation.

11. Power saving SLEEP mode.

12. Low power, high speed CMOS FLASH/EEPROM technology.

13. In circuit serial programming (ICSP) via two pins.

14. Single 5V In-circuit Serial programming capability.

15. Wide operating voltage range: 2.0V to 5.5V.

16. Low power consumption.

17. High sink/source current: 25mA.

Peripheral Features

1. Timer0: 8-bit timer/counter with 8-bit pre scaler.

2. Timer1: 16-bit timer/counter with pre scaler, can be incremented during SLEEP via

external crystal/clock.

3. Timer2: 8-bit timer/counter with 8-bit period register, pre scaler and post scaler.

4. Two capture, compare, PWM modules.

- Capture is 16-bit, max. resolution is 12.5ns.

- Compare is 16-bit, max. resolution is 200ns.

- PWM max. resolution is 10-bit.

5. 10-bit multi- channel Analog-to-Digital converter.



Synchronous serial port (SSP) with SPI™ (Master mode) and I2C™ (Master/Slave).

6. Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI) with 9-

bit address detection.

7. Parallel slave port (PSP) 8-bits wide, with external Read, write and chip select

controls.

8. Brown out detection circuitry for brown out reset (BOR).

Analog Features

1. 10-bit, up to 8-channel Analog-to-Digital Converter (A/D)

2. Brown-out Reset (BOR)

3. Analog Comparator module with:

i) Two analog comparators.

ii) Programmable on-chip voltage reference (VREF) module.

iii) Programmable input multiplexing from device inputs and internal voltage reference.

iv) Comparator outputs are externally accessible.

High Performance RISC CPU

1. Only 35 single-word instructions.

2. All single-cycle instructions except for program branches, which are two cycle.

3. Operating speed: DC – 20 MHz clock input DC – 200 ns instruction cycle

4. Up to 8K x 14 words of Flash Program Memory, Up to 368 x 8 bytes of Data

Memory (RAM), Up to 256 x 8 bytes of EEPROM Data Memory.

5. Pin out compatible to other 28-pin or 40/44-pin, PIC16CXXX and PIC16FXXX

microcontrollers.

CMOS Technology

1. Low-power, high-speed Flash/EEPROM technology.

2. Fully static design.

3. Wide operating voltage range (2.0V to 5.5V).

4. Commercial and Industrial temperature ranges.



5.2.2 Comparison Chart Of Different Pic Microcontrollers

Table 5.1 Comparison of Different microcontrollers.

Device

Program

Memory

Data

SRAM

(Bytes)

EEPR

OM

(Byte

s)

I/O

10-bit

A/D

(ch)

CCP

(PWM

)

MSSP USAR

T

Timers

8/16-

bit

Co

mpa

rato

rs

Bytes

Single

Word

Instructio

ns

SPI

Master I2C

PIC16F873

A

7.2K 4096 192 128 22 5 2 Yes Yes Yes 2/1 2

PIC16F874

A

7.2K 4096 192 128 33 8 2 Yes Yes Yes 2/1 2

PIC16F876

A

14.3K 8192 368 256 22 5 2 Yes Yes Yes 2/1 2

PIC16F877

A

14.3K 8192 368 256 33 8 2 Yes Yes Yes 2/1 2

PIC16F873A/876A devices are available only in 28-pin packages, while

PIC16F874A/877A devices are available in 40-pin and 44-pin packages. All devices in

the PIC16F87XA family share common architecture with the following differences:

• The PIC16F873A and PIC16F874A have one-half of the total on-chip memory of the

PIC16F876A and PIC16F877A.

• The 28-pin devices have three I/O ports, while the 40/44-pin devices have five.

• The 28-pin devices have fourteen interrupts, while the 40/44-pin devices have fifteen.

• The 28-pin devices have five A/D input channels, while the 40/44-pin devices have eight.

• The Parallel Slave Port is implemented only on the 40/44-pin devices.



5.2.3 Instruction Set

Table 5.2 List of Instructions.



5.2.4 Pin Diagram

Figure 5.1 Pin Diagram Of PIC16F877A.



5.2.4.1 Pin Out Description

Table 5.3 List of Pins and Function.



5.2.5 Block Diagram

Figure 5.2. Block Diagram of PIC.



5.2.6 Block Diagram Description

PIC16F877A consists of the following main functional blocks:

Three Timers.

Capture/ Compare/ PWM module.

Master Synchronous Serial Port (MSSP) module.

Addressable Universal Synchronous Asynchronous Receiver Transmitter (USART).

Analog- to- Digital Converter (A/D) module.

Comparator module.

Comparator Voltage Reference module.

5.2.6.1 Timer Module

PIC16F877A has got three timers namely Timer0, Timer1 and Timer 2.

Timer0 Module

The Timer0 module timer/counter has the following features:

8-bit timer/counter

Readable and writable

8-bit software programmable prescaler

Internal or external clock select

Interrupt on overflow from FFh to 00h

Edge select for external clock

Timer1 Module

The Timer1 module is a 16-bit timer/counter consisting of two 8-bit registers

(TMR1H and TMR1L) which are readable and writeable. The TMR1 register pair

(TMR1H:TMR1L) increments from 0000h to FFFFh and rolls over to 0000h. The TMR1

interrupt, if enable, is generated on overflow which is latched in interrupt flag bit, TMR1F

(PIR1<0>). This interrupt can be enabled/disabled by setting/clearing TMR1 interrupt

enable bit, TMR1E (PIE<0>).

Timer2 Module



Timer2 is an 8-bit timer with a prescaler and a postscaler. It can be used as the

PWM time base for the PWM mode of the CCP modules. The TMR2 register is readable

and writable and is cleared on any reset. The input clock (Fosc/4) has a prescale option of

1:1, 1:4 or 1:16 selected by control bits T2CKPS1:T2CKPS0 (T2CON<1:0).

5.2.6.2 Capture/ Compare/ Pwm Modules

Each Capture/ Compare/ PWM (CCP) module contains a 16-bit register which can

operate as a:

16-bit capture register

16-bit compare register

PWM Master/Slave duty cycle register

Both the CCP1 and CCP2 modules are identical in operation, with the exception being the

operation of the special event trigger.

5.2.6.3 Master Synchronous Serial Port (MSSP) Module

The Master Synchronous Serial Port (MSSP) module is a serial interface, useful for

communicating with other peripheral or microcontroller devices. These peripheral devices

may be serial EEPROMs, Shift registers, display drivers, A/D converters etc. The MSSP

module can operate in one of the two modes:

Serial Peripheral Interface (SPI).

Inter- Integrated Circuit (𝐼2𝐶)

- Full Master Mode

- Slave mode (with general address call)

The I2C interface supports the following modes in hardware:

Master mode

Multi-master mode

Slave mode

SPI Mode



The SPI mode allows 8 bits of data to be synchronously transmitted and received

simultaneously. All four modes of SPI are supported. To accomplish communications,

typically three pins are used:

Serial Data Out (SDO)- RC5/SDO

Serial Data In (SDI)- RC4/SDI/SDA

Serial Clock (SCK)- RC3/SCK/SCL

Additionally, a fourth pin may be used when in a slave mode of operation:

Slave select (𝑆𝑆̅̅ ̅)- RA5/AN4/𝑆𝑆̅̅ ̅?C2OUT

I2C Mode

The MSSP module in I2C mode fully implements all master and slave functions

and provides interrupts on start and stop bits in hardware to determine a free bus. The

MSSP module implements the standard mode specifications, as well as 7-bit and 10-bit

addressing.

Two pins are used for data transfer:

Serial Clock (SCL)- RC3/SCK/ SCL

Serial Data (SDA)- RC4/SDI/ SDA

The user must configure these pins as inputs or outputs through TRISC <4:3> bits.

5.2.6.4 Addressable Universal Synchronous Asynchronous Receiver Transmitter

(Usart)

The Universal Synchronous Asynchronous Receiver Transmitter (USART) module

is one of the two serial I/O modules. The USART can be configured in the following

modes:

Asynchronous (full-duplex)

Synchronous- Master (half- duplex)

Synchronous- Slave (half-duplex)



The USART can be configured as a full-duplex asynchronous system that can

communicate with peripheral devices, such as CRT terminals and personal computers, or it

can be configured as a half-duplex synchronous system that can communicate with

peripheral devices such as A/D or D/A integrated circuits, serial EEPROMs etc.

5.2.6.5 Analog To Digital Converter (A/D) Module

The Analog-to-digital (A/D) converter module has five inputs for the 28-pin

devices and eight for the 40/44-pin devices.

The conversion of an analog input signal results in a corresponding 10-bit digital

number. The A/D module has high and low-voltage reference input that is software

selectable to some combination of Vdd, Vss, RA2 or RA3.

The A/D converter has a unique feature of being able to operate while the device is

in sleep mode. To operate in sleep, the A/D clock must be derived from the A/D’s internal

RC oscillator.

The A/D module has four registers. These registers are:

A/D Result High Register (ADRESH)

A/D Result Low Register (ADRESL)

A/D Control Register 0 (ADCON0)

A/D Control Register 1 (ADCON1)

5.2.6.6 Comparator Module

The comparator module contains two analog comparators. The inputs to the

comparators are multiplexed with I/O port pins RA0 through RA3, while the outputs are

multiplexed to pins RA4 and RA5. The on-chip voltage reference can also be an input to

the comparators.

The CMCON register controls the comparator input and output multiplexers.

Comparator Voltage Reference Module



The comparator voltage reference generator is a 16-tap resistor ladder network that

provides a fixed voltage reference when the comparators are in mode ‘110’. A

programmable register controls the function of the reference generator. The resistor ladder

is segmented to provide two ranges of CVref values and has a power-down function to

conserve power when the reference is no being used.

The comparator reference supply voltage comes directly from Vdd. It should be

noted, however, that the voltage at the top of the ladder is CVrsrc-Vsat, where Vsat is the

saturation voltage of the power switch transistor. This reference will only be as accurate as

the values of CVrsrc and Vsat.

The output of the reference generator may be connected to the RA2/AN2/Vref-

/CVref pin. This can be used as a simple D/A function by the user if a very high impedance

load is used.

5.2.7 Special Features of the CPU

PIC16F877A have a host of features intended to maximize system reliability,

minimize cost through elimination of external components, provide power saving operating

modes and offer code protection. These are:

Oscillator Selection

Reset

- Power-On reset (POR)

- Power- Up Timer (PWRT)

- Oscillator Start- Up timer (OST)

- Brown-Out Reset (BOR)

Interrupts

Watch dog Timer (WDT)

Sleep

Code Protection

ID locations

In- Circuit Serial Programming



Low- Voltage In-Circuit Serial Programming

In- Circuit Debugger

The watchdog timer which can be shut-off only through configuration bits. It runs off

its own RC oscillator for added reliability.

There are two timers that offer necessary delays on power-up. One is the oscillator

Start-Up timer (OST), intended to keep the chip in reset until the crystal oscillator is

stable. The other is the power-up timer (PWRT), which provides a fixed delay of 72ms on

power-up only. It is designed to keep the part in reset while the power supply stabilizes.

With these two timers on-chip, most applications need no external reset circuitry.



5.2.8 Register File Map

Figure 5.3 Register File Map.



5.2.8.1 Special Function Registers

PIC16F877A has got 64 Special Function Registers (SFRs).

1. These registers are used by CPU and peripheral modules for controlling the desired

operation of the device.

2. These registers are implemented as static RAM.

Table 5.4 Special Function Register.



5.2.9 Memory Organization

There are three memory blocks in each of the PIC16F87XA devices. The

0program memory and data memory have separate buses so that concurrent access

can occur and is detailed in this section. The EEPROM data memory block is detailed in

Section 3.0 “Data EEPROM and Flash Program Memory”. Additional information on

device memory may be found in the PIC micro Mid-Range MCU Family Reference

Manual (DS33023).

Data Memory Organization

The data memory is partitioned into multiple banks which contain the General

Purpose Registers and the Special Function Registers. Bits RP1 (Status<6>) and RP0

(Status<5>) are the bank select bits. Each bank extends up to 7Fh (128 bytes). The lower

locations of each bank are reserved for the Special Function Registers. Above the Special

Function Registers are General Purpose Registers, implemented as static RAM. All

implemented banks contain Special Function Registers. Some frequently used Special

Function Registers from one bank may be mirrored in another bank for code reduction and

quicker access.

Program Memory Organization

The PIC16F87XA devices have a 13-bit program counter capable of

addressing an 8K word x 14 bit program memory space. The PIC16F876A/877A

devices have 8K words x 14 bits of Flash program memory, while

PIC16F873A/874A devices have 4K words x 14 bits. Accessing a location above

the physically implemented address will cause a wrap around.



The Reset vector is at 0000h and the interrupt vector is at 0004h.

Figure 5.4 Memory Organization.

5.2.10 I/O Ports

In this microcontroller, we have got 4 I/O ports namely PORTA, PORTB, PORTC

and PORTD. Some pins of these I/O ports are multiplexed with an alternate function for

the peripheral features on the device. In general, when a peripheral is enabled, that pin may

not be used as a general purpose I/O pin.

5.2.10.1 PORTA and the TRISA Register

PORTA is a 6-bit wide, bi-directional port. The corresponding data direction

register is TRISA. Setting a TRISA bit (=1) will make the corresponding PORTA pin an



input. Clearing a TRISA bit (=0) will make the corresponding PORTA pin an output.

Reading the PORTA registers reads the status of the pins, whereas writing to it will write

to the port latch. All write operations are read-modify-write operations. Therefore, a write

to a port implies that the port pins are read, the value is modified and then written to the

port data latch.

Pin RA4 is multiplexed with the Timer0 module clock input to become the

RA4/T0CKI pin. The RA4/T0CKI pin is a Schmitt trigger input and open-drain output. All

the other PORTA pins have TTL input levels and full CMOS output drivers.

Figure 5.5 Block Diagram Figure 5.6 Block Diagram

of Ra3-Ra0 Pins. of Ra4-T0 Pin.



Figure 5.7 Block Diagram of RA5 Pin.

Table 5.5 Port A Functions.

Table 5.6 Registers Associated With Port A.



5.2.10.2 PORTB and TRISB Register

PORTB is an 8-bit wide, bi- directional port. The corresponding data direction

register is TRISB. Setting a TRISB bit (=1) will make the corresponding PORTB pin an

input. Cleating a TRISB bit (=0) will make the corresponding PORTB pin an output.

Three pins of PORTB are multiplexed with the In-Circuit Debugger and Low-

Voltage Programming function: RB3/PGM, RB6/PGC and RB7/PGD. Each PORTB pins

has a weak internal pull-up. A single control bit can turn all the pull-ups. This is performed

by clearing bit RBPU. The weak pull-up is automatically turned off when the port pin is

configured as an output. The pull-ups are disable on a power-on reset.

Figure 5.8 Block Diagram of Figure 5.9 Block Diagram

RB3-RB0 Pins. of RB7-RB4 Pins.



Table 5.7 Port B Functions.

Registers Associated With Port B:

Table 5.8 Registers Associated With Port B.

5.2.10.3 PORTC and the TRISC Register

PORTC is an 8-bit wide, bi-directional port. The corresponding data direction

register is TRISC. Setting a TRISC bit (= 1) will make the corresponding PORTC pin an

input (i.e., put the corresponding output driver in a High-Impedance mode). Clearing a a

TRISC bit (=0) will make the corresponding PORTC pin an output (i.e., put the contents of

the output latch on the selected pin).



PORTC is multiplexed with several peripheral functions. PORTC pins have

Schmitt trigger input buffers.

Figure 5.10 PortC Block Diagram-1. Figure 5.11 PortC Block Diagram-2.

Port C Functions

Table 5.9 Port C Functions.



Registers associated with PORTC

Table 5.10 Registers Associated With Port C.

In PORTC, three pins are used for two different purposes. They are:-

RC4/SDI/SDA i.e., pin23 of the microcontroller is used as Enable 2 (EN2) for the

motor driver.

RC6/TX/CK and RC7/RX/DT i.e., pin25 and pin26 of the microcontroller

respectively are used for the communicating serially (USART) with the Bluetooth module.

Universal Synchronous Asynchronous Receiver Transmitter (USART)

The USART module is one of the two serial I/O modules.

USART is also known as a Serial communications Interface (SCI).

The USART can be configured as a full-duplex asynchronous system that can

communicate with peripheral devices, such as CRT terminals and personal computers, or it

can be configured as a half-duplex synchronous system that can communicate with

peripheral devices such as A/D or D/A integrated circuits, serial EEPROMs etc.

The USART can be configured in the following modes:

Asynchronous (Full-duplex).

Synchronous – Master (Half-duplex).

Synchronous – Slave (Half-duplex).

Bit SPEN (RCSTA <7>) and bits TRISC <7:6> have to be set in order to configure

pins RC6/TX/CK and RC7/RX/DT as Universal Synchronous Asynchronous Receiver

Transmitter.

The Special functions registers used by USART are TXSTA and RCSTA. The

format and bit definition of the these registers is given below.



Format Of TXSTA: Transmit Status And Control Register (Address 98H)



Format Of RCSTA: Receive Status And Control Register (Address 18H)

5.2.10.4 PORTD and TRISD Registers

PORTD is an 8-bit port with Schmitt trigger input buffers. Each pin is individually

configurable as an input or output.

PORTD can be configured as an 8-bit wide microprocessor port (Parallel Slave

port) by setting control bit, PSPMODE (TRISE <4>). In this mode, the input buffers are

TTL.



Figure 5.12 PORTD Block Diagram (in I/O mode).

Port D Functions

Table 5.11 Port D Functions.

Registers Associated With PORTD

Table 5.12 Registers Associated With Port D.



In PORTD, five pins are used for driving the motor driver. They are:-

RD6/PSP6, RD7/PSP7, RD3/PSP3 and RD4/PSP4 i.e., pin29, pin30, pin22 and pin27 of

the microcontroller respectively are used as General purpose I/O pins and are used as

inputs to the motor driver.

RD5/PSP5 i.e., pin28 of the microcontroller is used as Enable 1 (EN1) for the motor driver.

List Of Pins Used

Table 5.13 List of Pins Used.

Pins Name Function

1 MCLR/Vpp To reset the signal

13 OSC1/CLKIN Oscilator input/ clock input

14 OSC2/CLKOUT Oscillator output/clock

output

18 RC3/SCL/SCL Serial clock input

connected to rtc

23 RC4/SDI/SDA Serial data input/output

List Of Ports Used

Table 5.14 List Of Ports Used.

Ports Pins Name Funtion

A 2 RA0 Input of led lights

B 33,34,35,36,

37,38,39

RB0-RB6 Input from Matrix

KEYPAD.

D 19,21,22,

27,28,29,30.

RD0,

RD2-RD7

Digital Output from

LCD



5.2.11 REGISTERS

SSPCON



PIE1

The PIE1 register contains the individual enable bits for the peripheral interrupts.



PIR1

The PIR1 register contains the individual flag bits for the peripheral interrupts.



PIE2

The PIE2 register contains the individual enable bits for the CCP2 peripheral

interrupt, the SSP bus collision interrupt, and the EEPROM write operation interrupt.

PIR2

The PIR2 register contains the flag bits for the CCP2 interrupt, the SSP bus

collision interrupt and the EEPROM write operation interrupt.



5.3 Solar Cells/Photovoltaic Cells

How Solar Panels Work?

1. Rays of sunlight hit the solar panel (also known as a photovoltaic/ (PV) cells) and

are absorbed by semi-conducting materials such as silicone.

2. Electrons are knocked loose from their atoms, which allow them to flow through

the material to produce electricity. This process whereby light (photo) is converted into

electricity (voltage) is called the photovoltaic (PV) effect.

3. An array of solar panels converts solar energy into DC (direct current) electricity.

4. The DC electricity then enters an inverter.

5. The inverter turns DC electricity into 120-volt AC (alternating current) electricity

needed by home appliances.

6. The AC power enters the utility panel in the house.

7. The electricity (load) is then distributed to appliances or lights in the house.

8. When more solar energy is generated that what you’re using – it can be stored in a

battery as DC electricity. The battery will continue to supply your home with electricity in

the event of a power blackout or at nighttime.

9. When the battery is full the excess electricity can be exported back into the utility

grid, if your system is connected to it.

10. Utility supplied electricity can also be drawn from the grid when not enough solar

energy is produced and no excess energy is stored in the battery, i.e. at night or on cloudy

days.

11. The flow of electricity in and out of the utility grid is measured by a utility meter,

which spins backwards (when you are producing more energy that you need) and forward

(when you require additional electricity from the utility company). The two are offset

ensuring that you only pay for the additional energy you use from the utility company. Any

surplus energy is sold back to the utility company. This system is referred to as “net-

metering”.

Solar Energy is measured in kilowatt-hour. 1 kilowatt = 1000 watts.

1 kilowatt-hour (kWh) = the amount of electricity required to burn a 100

watt light bulb for 10 hours.



According to the US Department of Energy, an average American

household used approximately 866-kilowatt hours per month in 1999 costing them $70.68.

About 30% of our total energy consumption is used to heat water.

The Sun produces radiant energy by consuming hydrogen in nuclear fusion

reactions. Solar energy is transmitted to the earth in portions of energy called

photons, which interact with the earth’s atmosphere and surface. It takes

about 8 minutes and 20 seconds for the sun’s energy to reach the earth.

The Earth receives and collects solar energy in the atmosphere, oceans, and

plant life. Interactions between the sun’s energy, the oceans, and the

atmosphere, for example, create winds, which can produce electricity when

directed through aerodynamically designed wind machines.

Solar Photovoltaic Cells convert solar radiation into electricity

(photovoltaic literally means “light energy”; “photo” = light, “voltaic” =

energy). Individual cells are packaged into modules, like the one shown at

the right; groups of modules are called arrays. Photovoltaic arrays act like a

battery when the sun is shining, producing a stream of direct current (DC)

electricity and sending it into the building or sharing it with the grid.

The Dc Disconnect Switch allows professional electricians to disconnect the

photovoltaic array from the rest of the system. With the switch in the “off”

position, workers can safely perform maintenance on other system

components.

The Inverter converts direct current (DC) electricity generated by the array

into alternating current (AC) electricity for use in the building. Most

electrical loads (energy-consuming devices like lights, motors, computers,

and air conditioners) in schools, homes and businesses use AC electricity.



The Transformer ensures that the voltage of the electricity coming from the

inverter is compatible with the voltage of the electricity in the building.

The Ac Disconnect disconnect switch allows professional electricians to

disconnect the building’s electrical system from the solar photovoltaic

system. With the AC disconnect switch in the “off” position, workers can

safely perform maintenance on the solar photovoltaic system’s components.

The Electric Meter keeps track of the amount of electrical energy produced

by the solar photovoltaic system and sends electronic signals to the data

acquisition system where they are recorded. Electrical energy is measured in

kilowatt-hours. How much energy is contained in a kilowatt-hour? We’re

glad you asked. Use our calculator to find out.

5.3.1 Photovoltaic Cells: Converting Photons To Electrons

Photovoltaic (PV) cells are made of special materials called semiconductors such as

silicon, which is currently the most commonly used. Basically, when light strikes the cell, a

certain portion of it is absorbed within the semiconductor material. This means that the

energy of the absorbed light is transferred to the semiconductor. The energy knocks

electrons loose, allowing them to flow freely. PV cells also all have one or more electric

fields that act to force electrons freed by light absorption to flow in a certain direction. This

flow of electrons is a current, and by placing metal contacts on the top and bottom of the

PV cell, we can draw that current off to use externally. For example, the current can power

a calculator. This current, together with the cell’s voltage (which is a result of its built-in

electric field or fields), defines the power (or wattage) that the solar cell can produce.



Figure 5.13 Working of Solar Panel.

5.4 Battery

An electrical battery is a combination of one or more electrochemical cells,

used to convert stored chemical energy into electrical energy. The battery has become a

common power source for many household and industrial applications.

Batteries may be used once and discarded, or recharged for years as in standby

power applications. Miniature cells are used to power devices such as hearing aids and

wristwatches; larger batteries provide standby power for telephone exchanges or computer

data centers.

Working of Battery

A battery is a device that converts chemical energy directly to electrical energy.

It consists of a number of voltaic cells; each voltaic cell consists of two half cells

connected in series by a conductive electrolyte containing anions and cat ions. One half-

cell includes electrolyte and the electrode to which anions (negatively-charged ions)

migrate, i.e. the anode or negative electrode; the other half-cell includes electrolyte and the

electrode to which cat ions (positively-charged ions) migrate, i.e. the cathode or positive

electrode. In the red ox reaction that powers the battery, reduction (addition of electrons)

occurs to cat ions at the cathode, while oxidation (removal of electrons) occurs to anions at

the anode. The electrodes do not touch each other but are electrically connected by the



electrolyte. Many cells use two half-cells with different electrolytes. In that case each half-

cell is enclosed in a container, and a separator that is porous to ions but not the bulk of the

electrolytes prevents mixing.

Each half cell has an electromotive force (or emf), determined by its ability to

drive electric current from the interior to the exterior of the cell. The net emf of the cell is

the difference between the emfs of its half-cells. Therefore, if the electrodes have emfs and,

in other words, the net emf is the difference between the reduction potentials of the half-

reactions.

The electrical driving force or across the terminals of a cell is known as the

terminal voltage (difference) and is measured in volts. The terminal voltage of a cell that is

neither charging nor discharging is called the open-circuit voltage and equals the emf of

the cell. Because of internal resistance, the terminal voltage of a cell that is discharging is

smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is

charging exceeds the open-circuit voltage. An ideal cell has negligible internal resistance,

so it would maintain a constant terminal voltage of until exhausted, then dropping to zero.

If such a cell maintained 1.5 volts and stored a charge of one Coulomb then on complete

discharge it would perform 1.5 Joule of work. In actual cells, the internal resistance

increases under discharge, and the open circuit voltage also decreases under discharge. If

the voltage and resistance are plotted against time, the resulting graphs typically are a

curve; the shape of the curve varies according to the chemistry and internal arrangement

employed.

An electrical battery is one or more electrochemical cells that convert stored chemical

energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in

1800 by Alessandro Volta, batteries have become a common power source for many

household and industrial applications. According to a 2005 estimate, the worldwide battery

industry generates US$48 billion in sales each year, with 6% annual growth. There are two

types of batteries: primary batteries (disposable batteries), which are designed to be used

once and discarded, and secondary batteries (rechargeable batteries), which are designed to

be recharged and used multiple times. Miniature cells are used to power devices such as

hearing aids and wristwatches; larger batteries provide standby power for telephone

exchanges or computer data centres.



Principle of Operation

A battery is a device that converts chemical energy directly to electrical energy. It

consists of a number of voltaic cells; each voltaic cell consists of two half cells connected

in series by a conductive electrolyte containing anions and cations. One half-cell includes

electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the

anode or negative electrode; the other half-cell includes electrolyte and the electrode to

which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In

the redox reaction that powers the battery, cations are reduced (electrons are added) at the

cathode, while anions are oxidized (electrons are removed) at the anode. The electrodes do

not touch each other but are electrically connected by the electrolyte. Some cells use two

half-cells with different electrolytes. A separator between half cells allows ions to flow, but

prevents mixing of the electrolytes.

Each half cell has an electromotive force (or emf), determined by its ability to drive

electric current from the interior to the exterior of the cell. The net emf of the cell is the

difference between the emfs of its half-cells, as first recognized by Volta. Therefore, if the

electrodes have emfs and , then the net emf is ; in other words, the net emf

is the difference between the reduction potentials of the half-reactions. The electrical

driving force or across the terminals of a cell is known as the terminal voltage

(difference) and is measured in volts. The terminal voltage of a cell that is neither charging

nor discharging is called the open-circuit voltage and equals the emf of the cell. Because of

internal resistance, the terminal voltage of a cell that is discharging is smaller in magnitude

than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the

open-circuit voltage. An ideal cell has negligible internal resistance, so it would maintain a

constant terminal voltage of until exhausted, then dropping to zero. If such a cell

maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it

would perform 1.5 joule of work. In actual cells, the internal resistance increases under

discharge, and the open circuit voltage also decreases under discharge. If the voltage and

resistance are plotted against time, the resulting graphs typically are a curve; the shape of

the curve varies according to the chemistry and internal arrangement employed.

As stated above, the voltage developed across a cell's terminals depends on the energy

release of the chemical reactions of its electrodes and electrolyte. Alkaline and carbon-zinc



cells have different chemistries but approximately the same emf of 1.5 volts; likewise

NiCad and NiMH cells have different chemistries, but approximately the same emf of 1.2

volts. On the other hand the high electrochemical potential changes in the reactions of

lithium compounds give lithium cells emfs of 3 volts or more.

The battery capacity that battery manufacturers print on a battery is usually the product of

20 hours multiplied by the maximum constant current that a new battery can supply for 20

hours at 68 F° (20 C°), down to a predetermined terminal voltage per cell. A battery rated

at 100 A·h will deliver 5 A over a 20 hour period at room temperature. However, if it is

instead discharged at 50 A, it will have a lower apparent capacity.

The relationship between current, discharge time, and capacity for a lead acid battery is

approximated (over a certain range of current values) by Peukert's law:

Where

QP is the capacity when discharged at a rate of 1 amp.

I is the current drawn from battery (A).

t is the amount of time (in hours) that a battery can sustain.

k is a constant around 1.3.

For low values of I internal self-discharge must be included.

In practical batteries, internal energy losses, and limited rate of diffusion of ions through

the electrolyte, cause the efficiency of a battery to vary at different discharge rates. When

discharging at low rate, the battery's energy is delivered more efficiently than at higher

discharge rates, but if the rate is too low, it will self-discharge during the long time of

operation, again lowering its efficiency.

Installing batteries with different A·h ratings will not affect the operation of a device rated

for a specific voltage unless the load limits of the battery are exceeded. High-drain loads

like digital cameras can result in lower actual energy, most notably for alkaline batteries.

For example, a battery rated at 2000 mA·h would not sustain a current of 1 A for the full

two hours, if it had been rated at a 10-hour or 20-hour discharge.



Fastest Charging, Largest, And Lightest Batteries

Lithium iron phosphate (LiFePO4) batteries are the fastest charging and discharging, next

to super capacitors. The world's largest battery is in Fairbanks, Alaska, composed of Ni-

Cdcells. Sodium-sulfur batteries are being used to store wind power. Lithium-sulfur

batteries have been used on the longest and highest solar powered flight. The speed of

recharging for lithium-ion batteries may be increased by manipulation.

5.5 Keypad

Figure 5.14 Keypad.

A keypad is a set of buttons arranged in a block or "pad" which usually bear digits,

symbols and usually a complete set of alphabetical letters. If it mostly contains numbers

then it can also be called a numeric keypad. Keypads are found on many alphanumeric

keyboards and on other devices such as calculators, push-button telephones, combination

locks, and digital door locks, which require mainly numeric input.

Keypads are a part of HMI or Human Machine Interface and play really important

role in a small embedded system where human interaction or human input is needed.

Matrix keypads are well known for their simple architecture and ease of interfacing with

any microcontroller.

Figure 5.15 Matrix Keypad.



Scanning of Matrix Keypad

There are many methods depending on the connection keypad with micro

controller, but the basic logic is same the columns are made as input and drive the rows

making them as output; this whole procedure of reading the keyboard is called scanning. In

order to detect which key is pressed from the matrix, the row lines are to be made low one

by one and read the columns. Assume that if Row1 is made low, then read the columns. If

any of the key in row1 is pressed then correspondingly the column 1will give low that is if

second key is pressed in Row1, then column2 will give low. This is how Scanning is done.

So to scan the keypad completely, we need to make rows low one by one and read the

columns. If any of the buttons are pressed in a row, it will take the corresponding column

to a low state which shows that a key is pressed in that row. If button 1 of a row is pressed

then Column 1 will become low, if button 2 then column2 and so on...this is the way of

working by a keypad.

5.6 LCD

Description

This is the example for the Parallel Port. This example doesn't use the Bi-

directional feature found on newer ports, thus it should work with most, if not all Parallel

Ports. It however doesn't show the use of the Status Port as an input for a 16 Character x 2

Line LCD Module to the Parallel Port. These LCD Modules are very common these days,

and are quite simple to work with, as all the logic required running them is on board.

Advantages

Very compact and light

Low power consumption

No geometric distortion

Little or no flicker depending on backlight technology

Not affected by screen burn-in

No high voltage or other hazards present during repair/service

Can be made in almost any size or shape

No theoretical resolution limit



LCD Background

Frequently, an 8051 program must interact with the outside world using input and

output devices that communicate directly with a human being. One of the most common

devices attached to an 8051 is an LCD display. Some of the most common LCDs

connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2

lines and 20 characters per line by 2 lines, respectively.

Fortunately, a very popular standard exists which allows us to communicate with

the vast majority of LCDs regardless of their manufacturer. The standard is referred to as

HD44780U, which refers to the controller chip which receives data from an external source

(in this case, the 8051) and communicates directly with the LCD.

Figure 5.16 LCD.

The 44780 standard requires 3 control lines as well as either 4 or 8 I/O lines for the

data bus. The user may select whether the LCD is to operate with a 4-bit data bus or an 8-

bit data bus. If a 4-bit data bus is used the LCD will require a total of 7 data lines (3 control

lines plus the 4 lines for the data bus). If an 8-bit data bus is used the LCD will require a

total of 11 data lines (3 control lines plus the 8 lines for the data bus).

http://upload.wikimedia.org/wikipedia/commons/2/24/LCD_display_16x2_alphanumeric.jpg



Figure 5.17 Pin Diagram of LCD.

The three control lines are referred to as EN, RS, and RW.

The EN line is called "Enable." This control line is used to tell the LCD that you

are sending it data. To send data to the LCD, your program should make sure this line is

low (0) and then set the other two control lines and/or put data on the data bus. When the

other lines are completely ready, bring EN high (1) and wait for the minimum amount of

time required by the LCD datasheet (this varies from LCD to LCD), and end by bringing it

low (0) again.

The RS line is the "Register Select" line. When RS is low (0), the data is to be

treated as a command or special instruction (such as clear screen, position cursor, etc.).

When RS is high (1), the data being sent is text data which should be displayed on the

screen. For example, to display the letter "T" on the screen you would set RS high.

The RW line is the "Read/Write" control line. When RW is low (0), the information

on the data bus is being written to the LCD. When RW is high (1), the program is

effectively querying (or reading) the LCD. Only one instruction ("Get LCD status") is a

read command. All others are write commands--so RW will almost always be low .Finally,

the data bus consists of 4 or 8 lines (depending on the mode of operation selected by the

user). In the case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2, DB3,

DB4, DB5, DB6, and DB7.



5.6.1 Pin Function of LCD

Table 5.15 Pin Function of Lcd.

NAME FUNCTION

01 Vss (ground) Ground (0V)

02 Vcc Supply voltage(5v)

03 Vee Contrast adjustment through

Variable resistor

04 Rs ( register select) Selects data register when low

Select command register when high

05 R/W Reads the data when low

Writes the data when high

06 E(Enable) Sends data to data pins when a

High to low pulse is given

07 DO

Data lines

08 D1

09 D2

10 D3

11 D4

12 D5

13 D6

14 D7

15 LED+ Backlight VCC(5V)

16 LED- Backlight ground(0V)



Logic Status On Control Lines

• E - 0 Access to LCD disabled

- 1 Access to LCD enabled

• R/W - 0 Writing data to LCD

- 1 Reading data from LCD

• RS - 0 Instructions

- 1 Character

Writing Data To LCD

1) Set R/W bit to low

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

Read Data From Data Lines (If It Is Reading) On LCD

1) Set R/W bit to high

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

5.6.3 LCD Commands

1. 38H-Select 8 bit mode

2. 28H-select 4 bit mode

3. 01H-Clear screen

4. 0EH-Turn the display, turn the cursor

5. 80H-Select top row

6. C0H-select bottom row

7. 06H-Cursor right shift

8. 1CH-for entire display left shift



5.7 RTC

The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded

decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are

transferred serially through an I²C, bidirectional bus. The clock/calendar provides seconds,

minutes, hours, day, date, month, and year information. The end of the month date is

automatically adjusted for months with fewer than 31 days, including corrections for leap

year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.

The DS1307 has a built-in power-sense circuit that detects power failures and

automatically switches to the backup supply. Timekeeping operation continues while the

part operates from the backup supply.

Features of DS1307

Real time clock counts seconds, minutes, hours, date of month, month, day of week

and year with leap year compensation valid up to 2100

56 byte nonvolatile RAM for general data storage

2-wrire interface (I2C)

Automatic power fail detect

Comsumes less than 500 nA for battery back-up at 25'C

Figure 5.18 Pin Diagram of RTC.



5.7.1 Pin Description

VCC, GND – DC power is provided to the device on these pins. VCC is the +5V

input. When 5V is applied within normal limits, the device is fully accessible and data

can be written and read. When a 3V battery is connected to the device and VCC is

below 1.25 x VBAT, reads and writes are inhibited. However, the timekeeping

function continues unaffected by the lower input voltage. As VCC falls below VBAT

the RAM and timekeeper are switched over to the external power supply (nominal

3.0V DC) at VBAT.

VBAT – Battery input for any standard 3V lithium cell or other energy source. Battery

voltage must be held between 2.0V and 3.5V for proper operation. The nominal write

protect trip point voltage at which access to the RTC and user RAM is denied is set by

the internal circuitry as 1.25 x VBAT nominal. A lithium battery with 48mAhr or

greater will back up the DS1307 for more than 10 years in the absence of power at

25ºC. UL recognized to ensure against reverse charging current when used in

conjunction with a lithium battery.

SCL (Serial Clock Input) – SCL is used to synchronize data movement on the serial

interface.

SDA (Serial Data Input/Output) – SDA is the input/output pin for the 2-wire serial

interface. The SDA pin is open drain which requires an external pullup resistor.

SQW/OUT (Square Wave/Output Driver) – When enabled, the SQWE bit set to 1,

the SQW/OUT pin outputs one of four square wave frequencies (1Hz, 4kHz, 8kHz,

32kHz). The SQW/OUT pin is open drain and requires an external pull-up resistor.

SQW/OUT will operate with either Vcc or Vbat applied.

X1, X2 – Connections for a standard 32.768kHz quartz crystal. The internal oscillator

circuitry is designed for operation with a crystal having a specified load capacitance



(CL) of 12.5pF.

The DS1307 can also be driven by an external 32.768kHz oscillator. In this

configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is

floated

Figure 5.19 Wire Timing Interface.

Start Data Transfer: A change in the state of the data line from high to low, while the

clock line is high, defines a START condition.

Stop Data Transfer: A change in the state of the data line from low to high, while the

clock line is high, defines the STOP condition.

Data Valid: The state of the data line represents valid data when, after a START

condition, the data line is stable for the duration of the high period of the clock signal. The

data on the line must be changed during the low period of the clock signal. There is one

clock pulse per bit of data. Each data transfer is initiated with a START condition and

terminated with a STOP condition. The number of data bytes transferred between the

START and the STOP conditions is not limited, and is determined by the master device.

The information is transferred byte–wise and each receiver acknowledges with a ninth bit.



Acknowledge: Each receiving device, when addressed, is obliged to generate an

acknowledge after the reception of each byte. The master device must generate an extra

clock pulse which is associated with acknowledge bit.

Figure 5.20 Data Flow.

Figure 5.21 Operating Circuit.

Operation

The DS1307 operates as a slave device on the serial bus. Access is obtained by

implementing a START condition and providing a device identification code followed by a

register address. Subsequent registers can be accessed sequentially until a STOP condition

is executed. When VCC falls below 1.25 x VBAT the device terminates an access in

progress and resets the device address counter. Inputs to the device will not be recognized



at this time to prevent erroneous data from being written to the device from an out of

tolerance system. When VCC falls below VBAT the device switches into a low-current

battery backup mode. Upon power-up, the device switches from battery to VCC when

VCC is greater than VBAT + 0.2V and recognizes inputs when VCC is greater than 1.25 x

VBAT. The block diagram in Figure 1 shows the main elements of the serial RTC.

5.8 Operational Amplifier Lm324

The LM158 series consists of two independent, high gain, internally frequency

compensated operational amplifiers which were designed specifically to operate from a

single power supply over a wide range of voltages. Operation from split power supplies is

also possible and the low power supply current drain is independent of the magnitude of

the power supply voltage.

Application areas include transducer amplifiers, dc gain blocks and all the

conventional op amp circuits which now can be more easily implemented in single power

supply systems. For example, the LM158 series can be directly operated off of the standard

+5V power supply voltage which is used in digital systems and will easily provide the

required interface electronics without requiring the additional ±15V power supplies.

The LM324 and LM2904 are available in a chip sized package (8-Bump micro

SMD) using National's micro SMD package technology.

Figure 5.22 Opamp LM324.

Features

• Available in 8-Bump micro SMD chip sized package, (See AN-1112)

• Internally frequency compensated for unity gain

http://www.national.com/images/pf/LM358/00778723.pdf



• Large dc voltage gain: 100 dB

• Wide bandwidth (unity gain): 1 MHz (temperature compensated)

• Wide power supply range:

o Single supply: 3V to 32V

o or dual supplies: ±1.5V to ±16V

• Very low supply current drain (500 µA)-essentially independent of supply voltage

• Low input offset voltage: 2 mV

• Input common-mode voltage range includes ground

• Differential input voltage range equal to the power supply voltage

• large output voltage swing.

5.9 MOSFET

The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or

MOS FET) is a device used for amplifying or switching electronic signals. The basic

principle of the device was first proposed by Julius Edgar Lilienfeld in 1925. In

MOSFET’s, a voltage on the oxide-insulated gate electrode can induce a conducting

channel between the two other contacts called source and drain. The channel can be of n-

type or p-type and is accordingly called an n-MOSFET or a p-MOSFET. It is by far the

most common transistor in both digital and analog circuits, though the bipolar junction

transistor was at one time much more common.

A variety of symbols are used for the MOSFET. The basic design is generally a line for the

channel with the source and drain leaving it at right angles and then bending back at right

angles into the same direction as the channel. Sometimes three line segments are used for

enhancement mode and a solid line for depletion mode.

Comparison of enhancement-mode and depletion-mode MOSFET symbols, along with

JFET symbols (drawn with source and drain ordered such that higher voltages appear higher

on the page than lower voltages).

http://en.wikipedia.org/wiki/Signal_(electrical_engineering)

http://en.wikipedia.org/wiki/Julius_Edgar_Lilienfeld

http://en.wikipedia.org/wiki/Channel_(transistor)

http://en.wikipedia.org/wiki/Channel_(transistor)

http://en.wikipedia.org/wiki/N-type_semiconductor

http://en.wikipedia.org/wiki/N-type_semiconductor

http://en.wikipedia.org/wiki/P-type_semiconductor

http://en.wikipedia.org/wiki/Transistor

http://en.wikipedia.org/wiki/Digital_circuit

http://en.wikipedia.org/wiki/Bipolar_junction_transistor

http://en.wikipedia.org/wiki/Bipolar_junction_transistor

http://en.wikipedia.org/wiki/Field-effect_transistor#FET_operation

http://en.wikipedia.org/wiki/JFET



Figure 5.23 Mosfet.

Figure 5.24 Mosfet as Switch.

In this circuit arrangement an Enhancement-mode N-channel MOSFET is being

used to switch a simple lamp "ON" and "OFF" (could also be an LED). The gate input

voltage VGS is taken to an appropriate positive voltage level to turn the device and the lamp

either fully "ON", (VGS = +ve) or a zero voltage level to turn the device fully "OFF", (VGS

= 0).

If the resistive load of the lamp was to be replaced by an inductive load such as a

coil or solenoid, a "Flywheel" diode would be required in parallel with the load to protect

the MOSFET from any back-emf. Above shows a very simple circuit for switching a

resistive load such as a lamp or LED. But when using power MOSFET's to switch either



inductive or capacitive loads some form of protection is required to prevent the MOSFET

device from becoming damaged.

Driving an inductive load has the opposite effect from driving a capacitive load.

For example, a capacitor without an electrical charge is a short circuit, resulting in a high

"inrush" of current and when we remove the voltage from an inductive load we have a

large reverse voltage build up as the magnetic field collapses, resulting in an induced back-

emf in the windings of the inductor.

For the power MOSFET to operate as an analogue switching device, it needs to be

switched between its "Cut-off Region" where VGS = 0 and its "Saturation Region" where

VGS (on) = +ve. The power dissipated in the MOSFET (PD) depends upon the current

flowing through the channel ID at saturation and also the "ON-resistance" of the channel

given as RDS (on).

5.10 TRANSISTOR(BC547)

The BC547 transistor is an NPN Epitaxial Silicon Transistor. The BC547 transistor is a

general-purpose transistor in small plastic packages. It is used in general-purpose switching

and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.

Figure 5.25 Transistor.

The BC547 transistor is an NPN bipolar transistor, in which the letters "N" and "P"

refer to the majority charge carriers inside the different regions of the transistor. Most

bipolar transistors used today are NPN, because electron mobility is higher than hole

mobility in semiconductors, allowing greater currents and faster operation. NPN transistors

consist of a layer of P-doped semiconductor (the "base") between two N-doped layers. A



small current entering the base in common-emitter mode is amplified in the collector

output. In other terms, an NPN transistor is "on" when its base is pulled high relative to the

emitter. The arrow in the NPN transistor symbol is on the emitter leg and points in the

direction of the conventional current flow when the device is in forward active mode. One

mnemonic device for identifying the symbol for the NPN transistor is "not pointing in." An

NPN transistor can be considered as two diodes with a shared anode region. In typical

operation, the emitter base junction is forward biased and the base collector junction is

reverse biased. In an NPN transistor, for example, when a positive voltage is applied to the

base emitter junction, the equilibrium between thermally generated carriers and the

repelling electric field of the depletion region becomes unbalanced, allowing thermally

excited electrons to inject into the base region. These electrons wander (or "diffuse")

through the base from the region of high concentration near the emitter towards the region

of low concentration near the collector. The electrons in the base are called minority

carriers because the base is doped p-type which would make holes the majority carrier in

the base.

Whenever base is high, then current starts flowing through base and emitter and after that

only current will pass from collector to emitter. So that the LED which is connected to

collector will glow to indicate that transistor is ON.

An NPN Transistor Configuration

Figure 5.26 Transistor Configuration.



5.11 1N4007 DIODE

Diodes are used to convert AC into DC these are used as half wave rectifier or full

wave rectifier. Three points must he kept in mind while using any type of diode.

1.Maximum forward current capacity

2.Maximum reverse voltage capacity

3.Maximum forward voltage capacity

Figure 5.27 1N4007 Diodes.

The number and voltage capacity of some of the important diodes available in the

market are as follows:

Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007

have maximum reverse bias voltage capacity of 50V and maximum forward current

capacity of 1 Amp.

Diode of same capacities can be used in place of one another. Besides this diode of

more capacity can be used in place of diode of low capacity but diode of low capacity

cannot be used in place of diode of high capacity. For example, in place of IN4002;

IN4001 or IN4007 can be used but IN4001 or IN4002 cannot be used in place of

IN4007.The diode BY125made by company BEL is equivalent of diode from IN4001 to

IN4003. BY 126 is equivalent to diodes IN4004 to 4006 and BY 127 is equivalent to diode

IN4007.



Figure 5.28 PN Junction Diode.

PN Junction Operation

Now that you are familiar with P- and N-type materials, how these materials are

joined together to form a diode, and the function of the diode, let us continue our

discussion with the operation of the PN junction. But before we can understand how the

PN junction works, we must first consider current flow in the materials that make up the

junction and what happens initially within the junction when these two materials are joined

together.

Current Flow in the N-Type Material

Conduction in the N-type semiconductor, or crystal, is similar to conduction in a

copper wire. That is, with voltage applied across the material, electrons will move through

the crystal just as current would flow in a copper wire. This is shown in figure. The

positive potential of the battery will attract the free electrons in the crystal. These electrons

will leave the crystal and flow into the positive terminal of the battery. As an electron leaves

the crystal, an electron from the negative terminal of the battery will enter the crystal, thus

completing the current path. Therefore, the majority current carriers in the N-type material

(electrons) are repelled by the negative side of the battery and move through the crystal

toward the positive side of the battery.



Current Flow in the P-Type Material

Current flow through the P-type material is illustrated. Conduction in the P material

isby positive holes, instead of negative electrons. A hole moves from the positive terminal

of the P materialto the negative terminal. Electrons from the external circuit enter the

negative terminal of the material andfill holes in the vicinity of this terminal. At the

positive terminal, electrons are removed from the covalentbonds, thus creating new holes.

This process continues as the steady stream of holes (hole current) movestoward the

negative terminal

5.12 RESISTORS

A resistor is a two-terminal electronic component designed to oppose an electric current by

producing a voltage drop between its terminals in proportion to the current, that is, in

accordance with Ohm's law:

V = IR

Resistors are used as part of electrical networks and electronic circuits. They are extremely

commonplace in most electronic equipment. Practical resistors can be made of various

compounds and films, as well as resistance wire (wire made of a high-resistivity alloy,

such as nickel/chrome).

The primary characteristics of resistors are their resistance and the power they

can dissipate. Other characteristics include temperature coefficient, noise, and inductance.

Less well-known is critical resistance, the value below which power dissipation limits the

maximum permitted current flow, and above which the limit is applied voltage. Critical

resistance depends upon the materials constituting the resistor as well as its physical

dimensions; it's determined by design.

Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits.

Size, and position of leads (or terminals) are relevant to equipment designers; resistors

must be physically large enough not to overheat when dissipating their power.



Figure 5.29 Resistors.

A resistor is a two-terminal passive electronic component which implements

electrical resistance as a circuit element. When a voltage V is applied across the terminals

of a resistor, a current I will flow through the resistor in direct proportion to that voltage.

The reciprocal of the constant of proportionality is known as the resistance R, since, with a

given voltage V, a larger value of R further "resists" the flow of current I as given by

Ohm's law :

Resistors are common elements of electrical networks and electronic circuits and

are ubiquitous in most electronic equipment. Practical resistors can be made of various

compounds and films, as well as resistance wire (wire made of a high-resistivity alloy,

such as nickel-chrome). Resistors are also implemented within integrated circuits,

particularly analog devices, and can also be integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than 9 orders of magnitude.

When specifying that resistance in an electronic design, the required precision of the

resistance may require attention to the manufacturing tolerance of the chosen resistor,

according to its specific application. The temperature coefficient of the resistance may also

be of concern in some precision applications. Practical resistors are also specified as

having a maximum power rating which must exceed the anticipated power dissipation of

that resistor in a particular circuit: this is mainly of concern in power electronics

applications. Resistors with higher power ratings are physically larger and may require heat

sinking. In a high voltage circuit, attention must sometimes be paid to the rated maximum

working voltage of the resistor.



The series inductance of a practical resistor causes its behavior to depart from ohms

law; this specification can be important in some high-frequency applications for smaller

values of resistance. In a low-noise amplifier or pre-amp the noise characteristics of a

resistor may be an issue. The unwanted inductance, excess noise, and temperature

coefficient are mainly dependent on the technology used in manufacturing the resistor.

They are not normally specified individually for a particular family of resistors

manufactured using a particular technology. A family of discrete resistors is also

characterized according to its form factor, that is, the size of the device and position of its

leads (or terminals) which is relevant in the practical manufacturing of circuits using them.

Units

The ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg

Simon Ohm. An ohm is equivalent to a volt per ampere. Since resistors are specified and

manufactured over a very large range of values, the derived units of milliohm (1 mΩ =

10−3 Ω), kilohm (1 kΩ = 103 Ω), and megohm (1 MΩ = 106 Ω) are also in common usage.

The reciprocal of resistance R is called conductance G = 1/R and is measured in

Siemens (SI unit), sometimes referred to as a mho. Thus a Siemens is the reciprocal of an

ohm: S = Ω − 1. Although the concept of conductance is often used in circuit analysis,

practical resistors are always specified in terms of their resistance (ohms) rather than

conductance.

5.13 CAPACITORS

A capacitor or condenser is a passive electronic component consisting of a pair of

conductors separated by a dielectric. When a voltage potential difference exists between

the conductors, an electric field is present in the dielectric. This field stores energy and

produces a mechanical force between the plates. The effect is greatest between wide, flat,

parallel, narrowly separated conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is

measured in farads. This is the ratio of the electric charge on each conductor to the

potential difference between them. In practice, the dielectric between the plates passes a



small amount of leakage current. The conductors and leads introduce an equivalent series

resistance and the dielectric has an electric field strength limit resulting in a breakdown

voltage.

The properties of capacitors in a circuit may determine the resonant frequency and quality

factor of a resonant circuit, power dissipation and operating frequency in a digital logic

circuit, energy capacity in a high-power system, and many other important aspects.

Figure 5.30 Capacitors.

A capacitor (formerly known as condenser) is a device for storing electric charge.

The forms of practical capacitors vary widely, but all contain at least two conductors

separated by a non-conductor. Capacitors used as parts of electrical systems, for example,

consist of metal foils separated by a layer of insulating film.

Capacitors are widely used in electronic circuits for blocking direct current while

allowing alternating current to pass, in filter networks, for smoothing the output of power

supplies, in the resonant circuits that tune radios to particular frequencies and for many

other purposes.

A capacitor is a passive electronic component consisting of a pair of conductors

separated by a dielectric (insulator). When there is a potential difference (voltage) across

the conductors, a static electric field develops in the dielectric that stores energy and

produces a mechanical force between the conductors. An ideal capacitor is characterized



by a single constant value, capacitance, measured in farads. This is the ratio of the electric

charge on each conductor to the potential difference between them.

The capacitance is greatest when there is a narrow separation between large areas

of conductor, hence capacitor conductors are often called "plates", referring to an early

means of construction. In practice the dielectric between the plates passes a small amount

of leakage current and also has an electric field strength limit, resulting in a breakdown

voltage, while the conductors and leads introduce an undesired inductance and resistance.

Figure 5.31 Charge of Capacitance.

Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric

(orange) reduces the field and increases the capacitance.

A Simple Demonstration of a Parallel-Plate Capacitor

A capacitor consists of two conductors separated by a non-conductive region. The non-

conductive region is called the dielectric or sometimes the dielectric medium. In simpler

terms, the dielectric is just an electrical insulator. Examples of dielectric mediums are

glass, air, paper, vacuum, and even a semiconductor depletion region chemically identical

to the conductors. A capacitor is assumed to be self-contained and isolated, with no net

electric charge and no influence from any external electric field. The conductors thus hold

equal and opposite charges on their facing surfaces, and the dielectric develops an electric

field. In SI units, a capacitance of one farad means that one coulomb of charge on each

conductor causes a voltage of one volt across the device.

http://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svg



The capacitor is a reasonably general model for electric fields within electric circuits. An

ideal capacitor is wholly characterized by a constant capacitance C, defined as the ratio of

charge ±Q on each conductor to the voltage V between them:

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to

vary. In this case, capacitance is defined in terms of incremental changes:

Energy storage:

Work must be done by an external influence to "move" charge between the conductors in a

capacitor. When the external influence is removed the charge separation persists in the

electric field and energy is stored to be released when the charge is allowed to return to its

equilibrium position. The work done in establishing the electric field, and hence the

amount of energy stored, is given by:

Current-voltage relation:

The current i(t) through any component in an electric circuit is defined as the rate of flow

of a charge q(t) passing through it, but actual charges, electrons, cannot pass through the

dielectric layer of a capacitor, rather an electron accumulates on the negative plate for each

one that leaves the positive plate, resulting in an electron depletion and consequent positive

charge on one electrode that is equal and opposite to the accumulated negative charge on

the other. Thus the charge on the electrodes is equal to the integral of the current as well as

proportional to the voltage as discussed above. As with any anti derivative, a constant of

integration is added to represent the initial voltage v (t0). This is the integral form of the

capacitor equation,

.

Taking the derivative of this, and multiplying by C, yields the derivative form,



.

The dual of the capacitor is the inductor, which stores energy in the magnetic field rather

than the electric field. Its current-voltage relation is obtained by exchanging current and

voltage in the capacitor equations and replacing C with the inductance L.

5.14 LED’S

Light Emitting Diodes (LED) have recently become available that are white and

bright, so bright that they seriously compete with incandescent lamps in lighting

applications. They are still pretty expensive as compared to a GOW lamp but draw much

less current and project a fairly well focused beam.

The diode in the photo came with a neat little reflector that tends to sharpen the

beam a little but doesn't seem to add much to the overall intensity.

When run within their ratings, they are more reliable than lamps as well. Red LEDs

are now being used in automotive and truck tail lights and in red traffic signal lights. You

will be able to detect them because they look like an array of point sources and they go on

and off instantly as compared to conventional incandescent lamps.

Figure 5.32 White Led Spectrum.

LEDs are monochromatic (one color) devices. The color is determined by the band

gap of the semiconductor used to make them. Red, green, yellow and blue LEDs are fairly



common. White light contains all colors and cannot be directly created by a single LED.

The most common form of "white" LED really isn't white. It is a Gallium Nitride blue LED

coated with a phosphor that, when excited by the blue LED light, emits a broad range

spectrum that in addition to the blue emission, makes a fairly white light.

There is a claim that these white LED's have a limited life. After 1000 hours or so

of operation, they tend to yellow and dim to some extent. Running the LEDs at more than

their rated current will certainly accelerate this process.

There are two primary ways of producing high intensity white-light using LED’S.

One is to use individual LED’S that emit three primary colours—red, green, and blue—and

then mix all the colours to form white light. The other is to use a phosphor material to

convert monochromatic light from a blue or UV LED to broad-spectrum white light, much

in the same way a fluorescent light bulb works. Due to metamerism, it is possible to have

quite different spectra that appear white.

LEDs are semiconductor devices. Like transistors, and other diodes, LEDs are

made out of silicon. What makes an LED give off light are the small amounts of chemical

impurities that are added to the silicon, such as gallium, arsenide, indium, and nitride.

When current passes through the LED, it emits photons as a byproduct. Normal

light bulbs produce light by heating a metal filament until it is white hot. LEDs produce

photons directly and not via heat, they are far more efficient than incandescent bulbs.

Figure 5.33 Symbol of Led.

Not long ago LEDs were only bright enough to be used as indicators on dashboards

or electronic equipment. But recent advances have made LEDs bright enough to rival

traditional lighting technologies. Modern LEDs can replace incandescent bulbs in almost

any application.

Types of LED’S

LEDs are produced in an array of shapes and sizes. The 5 mm cylindrical package is the

most common, estimated at 80% of world production. The color of the plastic lens is often the

same as the actual color of light emitted, but not always. For instance, purple plastic is often

http://www.bivar.com/bullethtml/bull-nov2.htm

http://en.wikipedia.org/wiki/Primary_color

http://en.wikipedia.org/wiki/Metamerism_(color)



used for infrared LEDs, and most blue devices have clear housings. There are also LEDs in

extremely tiny packages, such as those found on blinkers and on cell phone keypads. The main

types of LEDs are miniature, high power devices and custom designs such as alphanumeric or

multi-color.

Figure 5.34 Types of LED’s.

5.15 PUSH BUTTON

Figure 5.35 Push Buttons.

A push-button (also spelled pushbutton) or simply button is a simple switch

mechanism for controlling some aspect of a machine or a process. Buttons are typically

made out of hard material, usually plastic or metal. The surface is usually flat or shaped to

accommodate the human finger or hand, so as to be easily depressed or pushed. Buttons are

most often biased switches, though even many un-biased buttons (due to their physical

nature) require a spring to return to their un-pushed state. Different people use different

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

Uses

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

mechanical linkage so that the act of pushing one button causes the other button to be

http://en.wikipedia.org/wiki/File:Verschiedene_LEDs.jpg

http://en.wikipedia.org/wiki/File:Tactile_switches.jpg



released. In this way, a stop button can "force" a start button to be released. This method of

linkage is used in simple manual operations in which the machine or process have no

electrical circuits for control.

Red pushbuttons can also have large heads (mushroom shaped) for easy operation

and to facilitate the stopping of a machine. These pushbuttons are called emergency stop

buttons and are mandated by the electrical code in many jurisdictions for increased safety.

This large mushroom shape can also be found in buttons for use with operators who need

to wear gloves for their work and could not actuate a regular flush-mounted push button.

As an aid for operators and users in industrial or commercial applications, a pilot light is

commonly added to draw the attention of the user and to provide feedback if the button is

pushed. Typically this light is included into the center of the pushbutton and a lens replaces

the pushbutton hard center disk.

The source of the energy to illuminate the light is not directly tied to the contacts

on the back of the pushbutton but to the action the pushbutton controls. In this way a start

button when pushed will cause the process or machine operation to be started and a

secondary contact designed into the operation or process will close to turn on the pilot light

and signify the action of pushing the button caused the resultant process or action to start.

In popular culture, the phrase "the button" refers to a (usually fictional) button that

a military or government leader could press to launch nuclear weapons.

Push to ON button:

Figure 5.36 Symbol of Push Button.

Initially the two contacts of the button are open. When the button is pressed they

become connected. This makes the switching operation using the push button.



CHAPTER-6

SOFTWARE

6.1 Flowchart



6.2 PROGRAM CODE

#include<16f877a.h> //header file

#use delay(clock=4000000)

#byte PORT_B=6

#bit R1=0x6.0

#bit R2=0X6.1

#bit R3=0x6.2

#bit R4=0x6.4

#bit C1=0x6.5

#bit C2=0x6.6

#bit C3=0x6.7

#bit STREET LIGHT =0x5.0

#define RTC_SDA PIN_C4

#define RTC_SCLPIN_C3

#use i2c(master ,sda=RTC_SDA,scl=RTC_SCL,SLOW) //enable I2C protocol

#bit LCD_RS=0x8.2 //0x5.3 //RA3

#bit LCD_RW=0X8.0 //0X5.2 //RA2

#bit LCD_EN=0x8.3 //0x5.1 //RA1

#byte LCD_DATA=8

#define LCD_STROBE ((LCD_EN=1),(LCD_EN=0))

#define DS1307_WRITE_ADDRESS 0XD0

#define DS1307_READ_ADDRESS 0XD1

unsigned char second;



unsigned char minute;

unsigned char hour;

unsigned char day;

unsigned char month;

unsigned char year;

unsigned char day_of_week;

unsigned char Temp_buf[2],key,key1,I,b;ink_flag;

unsgined char hours1,minutes1,seconds1,date1,month1,year1;

unsigned char M1_hours,M2_hours,M3_hours,M1_minutes,M2_minutes,M3_minutes;

unsigned char str[]=”Enter Time”;

unsigned char str[]=”Enter Date”;

unsigned char str[]=”Enter ON Time”;

unsigned char str[]=”Enter OFF Time”;

unsigned char bin2bcd(unsigned char binary_value);

unsigned char bin2bcd(unsigned char bcd_value);

void lcd_string(char*s);

void lcd_write(unsigned char c);

void lcd_clear(void);

void lcd_string(char*s);

void lcd_character(char c);

void lcd_init();

unsigned char key_board();

void RTC_initialise();

void Enter_Street light();

void compare();

void ds1307_set d_date_time(unsigned char day, unsigned char mth, unsigned char year,

unsigned char dow, unsigned char hr, unsigned char min, unsigned char sec)

{

sec &=0x7F;

hr &=0x3F;

i2c_start();



i2c_write(0XD0); // I2C write address

i2c_write(0XD0); // Start at REG 0 - seconds

i2c_write(bin2bcd(sec)); //REG 0 i2c_write(bin2bcd(dow)); //REG3

i2c_write(bin2bcd(day)); //REG4

i2c_write(bin2bcd(mth)); //REG5

i2c_write(bin2bcd(mth)); //REG6

i2c_write(0x80); //REG7-disable squarewave output pin

i2c_stop();

}

Void ds1307_get_date(unsigned char&day, unsigned char &mth, unsigned char &year,

unsigned char &dow)

{

i2c_start();

i2c_write(0xD0);

i2c_write(0x03); //start at REG 3- Day ot week

i2c_start();

i2c_write(0xD1);

dow = bcd2bin(i2c_read() & 0x4f); //REG 3

day = bcd2bin(i2c_read() & 0x4f); //REG 4

mth = bcd2bin(i2c_read() & 0x6f); //REG 5

year = bcd2bin(i2c_read(0)): //REG 6

i2c_stop();

}

Void ds1307_get_time(unsigned char &hr , unsigned char &min , unsigned char &sec)

{i2c_write(0x00); //start at REG 0 - seconds

i2c_start();

i2c_write(0xD1);sec = bcd2bin(i2c_read() & 0x4f);

min = bcd2bin(i2c_read() & 0x4f);

hr = bcd2bin(i2c_read(0) & 0x6f);

i2c_stop();

}



unsigned char bin2bcd(unsigned char binary_value)

{

unsigned char temp;

unsigned char retval;

temp = binary_value;

retval = 0;

while(TRUE)

{

// Get the tens digit by doing multiple subtraction

// of 10 from the binary value

if(temp>=10)

{

temp - = 10;

else // Get the ones digit by adding the remainder.

{

retval += temp;

break;

}

}

return(retval);

}

unsigned char bcd2bin(unsigned char bcd_value)

{

unsigned char temp;

temp = bcd_value; // Shifting upper digit right by 1 is same as multiplying by 8.

temp >>= 1; // Isolate the bits for the upper digit.

temp &=0x78; // Now return: (Tens*8) + (Tens *2) + ones

return(temp + temp << 2) + (bcd_value / 0x0f));

}

void ds1307_init(void)



{

i2c_start();

i2c_write(0xD0); //WR to RTC

i2c_write(0xD0); // REG 0

i2c_start();

i2c_write(0xD1); // RD from RTC

seconds = bcd2bin(i2c_read(0); // Read current “seconds” in DS1307

i2c_stop();

seconds &= 0x7F;

delay_us(3);

i2c_start();

i2c_write(0xD0); // WR to RTC

i2c_write(0x00); // REG 0

i2c_write(bin2bcd(seconds)); // Start oscillator with current “seconds” value

i2c_start();

i2c_write(0xD0); // WR to RTC

i2c_write(0x07); // Control register

i2c_write(0x80); // Disable the squarewave output pin

i2c_stop();

}

void display(unsigned char num)

{

char x,y;

y=num%10;

num = num/10;

x = num%10;

lcd_char(x+0x30);

lcd_char(y+0x30);

}

void main()



{

set_tris_d(0x00); // make port-d as output port

set_tris_b(0x0F); // make rb0,rb1,rb2,rb3 as input pins & rb4,rb5,rb6,rb7 as

output port pins

set_tris_a(0x00); // make port-a as output port

lcd_init(); // initialise the LCD

blink_flag = 0; // clear flag

RTC_initialise(); // initialise the RTC

delay_ms(1000); // delay 1sec

ds1307_init(); // initialise the DS1307

ds1307_set_date_time(date1,month1,year1,3,hours1,minutes1,seconds1); // set Date &

Time Enter street light(); // Enter the street light timings

while(TRUE)

{

ds1307_get_date(day,month,year,day_of_week); // get Date from DS1307

ds1307_get_time(hour,minute,second); // get Time from DS1307

lcd_write(0x80); //select lcd 1st line starting position

display(day); // Display Date

lcd_char(‘/’);

display(month); // Display month

lcd_char(‘/’);

display(year); // Display year

lcd_write(0x8b); // select lcd first line 11th position

display(hour); // Display hours

if (blink_flag == 0)

{

lcd_char(‘:’);

blink_flag = 1;

}

else

{



lcd_char(‘ ‘);

blink_flag = 0;

}

display(minute); // Display minutes

compare(); // compare the timing

lcd_write(0xc0); // select lcd 2nd line starting position

lcd_string(str8); // display string on LCD

delay_ms(500);

}

}

void compare()

{

if(hour ==M1_hours)

{

if(minute == M1_minutes)

{

if(second ==00)

{

lcd_write(0xc0); // select lcd 2nd line starting position

lcd_string(str9); // display string on the LCD

STREET LIGHT = 1; // street light ON

delay_ms(1000); // delay 1sec

STREET LIGHT = 1;

delay_ms(2000); // delay for 2sec

STREET LIGHT = 0; // street light OFF

}

}

}

if(hour==M2_hours)

{



if(minute==M2_minutes)

{

if(second==00)

{

Lcd_write(0Xc0)

Lcd_string(atr10);

STREET LIGHT=1;

Delay_ms(2000);

STREET LIGHT=0;

Delay_ms(1000);

STREET LIGHT=1;

Delay_ms(2000);

STREET LIGHT=0;

}

}

}

if(hour==M3_hours)

{

if(minute==M3_minutes)

{

if(second==00)

{

Lcd_write(0Xc0)

Lcd_string(str11);

STREET LIGHT=1;



Delay_ms(2000);

STREET LIGHT=0;

Delay_ms(1000);

STREET LIGHT=1;

Delay_ms(2000);

STREET LIGHT=0;

}

}

}

Void RTC_intialize()

{

Lcd_clear();

Lcd_write(0X80);

Lcd_string(str3);

Lcd_write(0Xc0);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;

Lcd_char(Tempbuf[i]+0X30);

}

Hours1=((Temp_buf[0]*10)+Temp_buf[i]);

Lcd_char(‘:’);

For(i=0;i<2;i++)



{

Key1=key_board();

Temp_buf[i]=key1;

Lcd_char(Temp_buf[i]+0X30);

}

minutes1=((Temp_buf[0]*10)+Temp_buf[1]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}

Seconds1=((Temp_buf[0]*10)+Temp_buf[i]);

Delay_ms(1000);

Lcd_clear();

Lcd_write(0X80);

Lcd_string(str4);

Lcd_write(0Xc0);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}



date1=((Temp_buf[0]*10)+Temp_buf[i]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}

month1=((Temp_buf[0]*10)+Temp_buf[1]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}

Year1=((Temp_buf[0]*10)+Temp_buf[1]);

Delay_ms(1000);

}

{

Lcd _clear();

Lcd_write (0X80);

Lcd_string(str5);

Lcd_write(0Xc0);



For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;

Lcd_char(temp_buf[i]+0x30);

}

M1_hours=((temp_buf[0]*10)+temp_buf[1]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;

Lcd_char(temp_buf[i]+0x30);

}

M1_minutes=((temp_buf[0]*10)+temp_buf[1]);

Delay_ms(1000);

Lcd_clear();

Lcd_write(0X80);

Lcd_string(str6);

Lcd_write(0Xc0);

For(i=0;i<2;i++)

{

Key1=key_board();



Temp_buf[i]=key1;


}

M2_hours=((Temp_buf[0]*10)+Temp_buf[1]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}

M2_minutes=((Temp_buf[0]*10)+Temp_buf[1]);

Delay_ms(1000);

Lcd_clear();

Lcd_write(0X80);

Lcd_string(str7);

Lcd_write(0Xc0);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}



M2_hourss=((Temp_buf[0]*10)+Temp_buf[1]);

Lcd_char(‘:’);

For(i=0;i<2;i++)

{

Key1=key_board();

Temp_buf[i]=key1;


}

M3_minutes=((Temp_buf[0]*10)+Temp_buf[1]);

Delay_ms(1000);

Lcd_clear();

Lcd_write(0X80);

Lcd_string(str8);

}

Unsigned char key_board()

{

While(TRUE)

{

Unsigned char k;

For(k=0;k<7;k++)

{

if((R1==0)&&(C1==0))

{

Key=1;

Delay_ms(400);



Return(key);

}

else if(R1==0)&&(C2==0))

{

Key=2;

Delay_ms(400);

Return(key);

}

else if(R1==0)&&(C3==0))

{

Key=3;

Delay_ms(400);

Return(key);

}

else if(R2==0)&&(C1==0))

{

Key=4;

Delay_ms(400);

Return(key);

}

else if(R2==0)&&(C2==0))

{

Key=5;

Delay_ms(400);

Return(key);



}

else if(R1==0)&&(C3==0))

{

Key=6;

Delay_ms(400);

Return(key);

}

else if(R3==0)&&(C1==0))

{

Key=7;

Delay_ms(400);

Return(key);

}

else if(R3==0)&&(C2==0))

{

Key=8;

Delay_ms(400);

Return(key);

}

else if(R3==0)&&(C3==0))

{

Key=9;

Delay_ms(400);

Return(key);

}



else if(R4==0)&&(C1==0))

{

Key=10;

Delay_ms(400);

Return(key);

}

else if(R4==0)&&(C2==0))

{

Key=0;

Delay_ms(400);

Return(key);

}

else if(R4==0)&&(C3==0))

{

Key=11;

Delay_ms(400);

Return(key);

}

}

}

}

Void lcd_write(unsigned char c)

{

Delay_us(40);

LCD_DATA=((c&0Xf0);



LCD_STROBE();

LCD_DATA=((c>>4)&0Xf0);

LCD_STROBE();

}

Void lcd_char(unsigned char c)

{

delay_us(40);

LCD_DATA=((c&0Xf0);

LCD_RS=1;

LCD_STROBE();

LCD_DATA=((c>>4)&0Xf0);

LCD_RS=1;

LCD_STROBE();

Void lcd_init()

{

Char init_value;

Init_value=0X03;

Set_tris_a(0X00);

Set_tris_d(0X00);

LCD_RS=0;

LCD_EN=0;

LCD_RW=0;

Delay_ms(15);

LCD_DATA=init_value;

LCD_STROBE();



Delay_ms(5);

LCD_STROBE();

Delay_ms(200);

LCD_STROBE();

Delay_ms(200);

LCD_DATA=0X02;

LCD_STROBE();

Lcd_write(0X38);

Lcd_write(0X0C);

Lcd_clear();

Lcd_write(0X06);

}



CHAPTER 7

RESULTS ANALYSIS

7.1 RESULT

1. After entering the real time using keypad.

Figure 7.1: Displaying Entered Real Time



2. After entering the date using keypad.

Figure 7.2: Displaying the Entered Date

3. After entering the ON time using keypad, it is displayed on the lcd screen as follows.

Figure 7.3: Displaying ON Time



4. After entering the OFF time using keypad, it is displayed on lcd as follows.

Figure 7.4: Displaying OFF Time

5. When the real time equals the entered ON time the led’s will glow as shown below.

Fig 7.5: Led’s ON



6. When the real time reaches the entered OFF time the leds will automatically OFF, which

can be shown as follows.

Figure 7.6: Led’s OFF

7.2 Applications

This system is designed for outdoor application in un-electrified remote areas. This

system is an ideal application for campus and village street lighting.

1. Solar Street lighting system is used for lighting on roads, yards, residential colonies

Town ships.

2. It can also be used for lighting in corporate offices, hospitals, educational institutions

and rural electrification.

7.3 Advantages

1. Solar street lights are independent of utility grid. Hence, the operation costs are

minimized.

2. Solar street lights require much less maintenance compared to conventional street

lights.

3. Since external wires are eliminated, risk of accidents is minimized.



4. This is a non-polluting source of electricity.

5. Separate parts of solar system can be easily carried to the remote areas.

7.4 Disadvantages

1. Initial investment is higher compared to conventional street lights.

2. Risk of theft is higher as equipment costs are comparatively higher.

3. Snow or dust, combined with moisture can accumulate on horizontal pv-panels and

reduce or even stop energy production.

4. Rechargeable batteries will need to replaced several times over the lifetime of the

fixtures adding to the total lifetime cast of the light.

5. The batteries have to be replaced from time to time.



CHAPTER-8

CONCLUSION

The project entitled “Automatic Solar Led Street Light Using RTC & I2C” mainly gives an

idea in saving power consumption by various devices in any field. Since it can switch

automatically in reference to real time it doesn’t waste power.

Usually most of the street lights run on the power generated by several power plants using

lots of resources. This project is designed in order to use the natural power generated from

solar rays. Also, it consumes very less power and works for a long time.

8.1 Future Scope

This project have much scope in future because we are having the scarcity of natural

resources like water, coal, steam used for power generation. This project has a huge

advantage, because it doesn’t require human interference, large number of times. This

project not only serves as street lights but also it can be used in home appliances.



BIBLIOGRAPHY

Text Books Referred

1. PIC16F877A Data Sheets.

Websites

www.atmel.com

www.beyondlogic.org

www.wikipedia.org

www.howstuffworks.com

www.alldatasheets.com