Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

MINOR PROJECT

259 views

Published on

  • Be the first to comment

MINOR PROJECT

  1. 1. “DEVELOPMENT BOARD” A Minor Project Report submitted to CHHATTISGARH SWAMI VIVEKANAND TECHNICAL UNIVERSITY, BHILAI (C.G.), INDIA in partial fulfillment for requirement of degree of Bachelor of Engineering in Electronics & Telecommunication Engineering By DEEPA BHATIA 3292811023 DEPARTMENT OF ELECTRONICS & TELECOMMUNICATION RSR RUNGTA COLLEGE OF ENGINEERING & TECHNOLOGY, Kohka, Kurud Road, Bhilai. Submission Date: 14/11/2014
  2. 2. CERTIFICATE OF SUPERVISOR This is to certify that the report of the minor project work submitted entitled “DEVELOPMENT BOARD” carried out by DEEPA BHATIA bearing Roll No. : 3292811023 Enrollment No. AJ8501 carried out under my guidance and supervision for the award of Degree in Bachelor of Engineering in Electronics & Telecommunication of Chhattisgarh Swami Vivekananda Technical University, Bhilai (C.G.), India. To the best of my knowledge the report i) Embodies the work of the candidate herself/himself, ii) Has duly been completed, iii) Fulfills the requirem.ent of the Ordinance relating to the BE degree of the University and iv) Is up to the desired standard for the purpose of which is submitted. Mr. C.H Kranthi Kiran Mr. Satya Prakash Singh Bisen Assistant Professor Assistant Professor HOD ,ET&T,RSR RCET ET&T,RSR RCET Forwarded to Chhattisgarh Swami Vivekananda University Bhilai(C.G.) Dr. P.S. Bokare Principal RSR RCET, BHILAI (C.G.) i
  3. 3. CERTIFICATE BYTHE EXAMINER This is to certify that the minor project work entitled “DEVELOPMENT BOARD” Submitted by DEEPA BHATIA bearing Roll No. 3292811023 Enrollment No. AJ8501 has been examined by the undersigned as a part the examination for the award of Bachelor of Engineering degree in Electronics & Telecommunication of Chhattisgarh Swami Vivekananda Technical University, Bhilai(C.G.),India. Internal examiner External examiner Date: Date: ii
  4. 4. ACKNOWLEDGEMENT A formal statement of acknowledgment is hardly sufficient to express my gratitude towards the personalities who have helped me to undertake and complete this project. Project in an organization like RSRRCET which is fuelled by the individuals with so much zest and energy, “teaming” up to form a formidable force, was in itself a true learning experience which is going to help me immensely in my career. I hereby convey my thanks to all those who have rendered their valuable help, support and guidance. I am also thankful to Mr. Satya Prakash Singh Bisen, Assistant Professor for the valuable help gave to gather the insight knowledge which otherwise would not have been there. I am highly thankful to Mr. CH Kranthi Kiran, HOD for helping me to undertake a project in Embedded Systems and providing highly valuable technical knowledge, constructive criticism and moral support. Lastly, I bow before the almighty with folded hands. DEEPA BHATIA Roll No.-3292811023 7th SEM, ET&T RSR RCET iii
  5. 5. ABSTRACT In modern technology most of the Industrial & Commercial applications uses an embedded system. An embedded system is a system which performs a define works accurately .Most of the embedded system usually use the microcontrollers to control various operations. A development board is designed in a Printed Circuit Board (PCB) having microcontrollers with its minimum circuits & also some peripheral devices on board which gives various option to practice interfacing with different modules such as seven segment display, LED & switches relays etc. The main purpose of design this minor project i.e. Development Board is not only to design Development Board but also to learn the basic of designing circuits in printed circuit board (PCB) these enhance the technical skills which is required for an Electronics engineers such as PCB layout designing using EDA softwares here we use Dip Trace then after this etching , drilling , soldering testing interfacing and programming. Firstly we have study about the basic of soldering and how power supply is design. Which is to provide power supply to microcontrollers & different peripherals on board. Also an LDR is used in light dependent circuit to sense the light. The development board consists of different modules has been design and of all the modules present in a single PCB board which help us to design in major project in future. I had completed my minor project in given duration of time. iv
  6. 6. TABLE OF CONTENT CONTENT PAGE NO. CERTIFICATE OF SUPERVISIOR i CERTIFICATE BY EXAMINER ii ACKNOWLEDGMENT ii ABSTRACT iv LIST OF TABLES vi LIST OF FIGURES vii ABBREVATION viii CHAPTER 1 INTRODUCTION 1 CHAPTER 2 SOLDERING 2 2.1 Introduction 2 2.2 Soldering Equipment 2 2.3 Soldering Technique 3-4 CHAPTER 3 POWER SUPPLY 5 3.1 Introduction 5 3.2 Working of Power Supply 6 CHAPTER 4 LDR CIRCUIT 7 4.1 Introduction 7 4.2 Basic LDR Circuit 7 4.3LDR Circuit Working 8 4.4Application of LDR 9 CHAPTER 5 DIPTRACE 10 5.1Introduction 10 5.2Module 10 5.3 Features 10 5.4 Dip Trace Software 11
  7. 7. CHAPTER 6 Printed Circuit Board 12 6.1Introduction 12 6.2Steps of PCB Etching 13-15 CHAPTER 7 DEVLOPMENT BOARD 16 7.1Introduction 16 7.2Feature 16 7.3Component used 17-20 CHAPTER 8 CONCLUSIONS &FUTURE SCOPE 21 REFERENCE 22 v
  8. 8. LIST OF TABLES TABLES TITLE PAGE NO. 3.1 Component Used in 5 Power Supply 4.1 Component Used in 8 LDR Circuit vi
  9. 9. LIST OF FIGURES FIGURES TITLE PAGE NO. 2.1 Soldering Iron 2 2.2 Solder 2 2.3 Flux 2 3.1 Circuit Diagram of Power Supply 5 3.2 Power Supply 6 4.1 LDR 7 4.2 LDR Circuit with Split Circuit 7 4.3 LDR Circuit 9 5.1 PCB Layout 11 7.1 Basic Development Board 16 7.2 Microcontroller 17 7.3 LCD 17 7.4 MAX232 18 7.5 Crystal Oscillator 18 7.6 PCB Layout of Development Board 20 7.7 Development Board 20 vii
  10. 10. ABBREVATIONS IC- Integrated Circuit CMOS- Complementary Metal Oxide Semiconductor MOSFET- Metal Oxide Semiconductor Field Effect Transistor PCB- Printed Circuit Board LDR- Light Dependent Resistor DC- Direct Current AC- Alternating Current LED- Light Emitting Diode EDA- Electronic Design Automation LCD- Liquid Crystal Display TTL- Transistor Transistor Logic viii
  11. 11. Chapter - I Introduction
  12. 12. INTRODUCTION A Development Board is a minimum circuit hardware which is designed in a printed circuit board containing an 8051 microcontroller with some peripherals which can be interfaced with different circuit. In our own development board we use relay, pull up resistor, switches, transistors etc. It has the ability to accept and run the supplied program. Initially technique of soldering should be learned which is done to assemble the components on PCB. Firstly we designed Power Supply and LED glowing which give us suppply of 5V and 12V. Power Supply uses a transformer for the supply. I had learned to make circuits in simple circuit of glowing LDR all these are done in zero PCB board. To prepare development board firstly we design the circuit PCB layout in the dip trace software & trace it in a copper or glass PCB then the etching process is done by dippingthe board in strong acid or moderate i.e FeCl3 to cut into the unprotected parts of a metal surface to create a design in the metal. Now finally we drill the holes to solder the required components in it respective positions. Also the used microcontroller is an Atmel microcontroller AT889S52 . 1
  13. 13. Chapter - II Soldering
  14. 14. SOLDERING 2.1 INTRODUCTION Soldering was employed as early as 5000 year ago in Mesopotamia. Soldering is defined as “the joining of metals by a fusion of alloys which have relatively low melting points”. In other words ,we use a metal that has a low melting point adhere the surface to be soldering together. Considering the soldering is more like gluing with molten metal, unlike welding where the base metal actually melted and combined. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and develop with practice. Soldering was historically used to make jewelry item, cooking ware and tools as well as other uses such as in assembling stained glass. 2.2 SOLDERING EQUIPMENTS  Soldering Iron- The soldering iron of the 15W to 30W range are good for most electronic printed circuit board work .A soldering iron suited for printed circuit board should be small tip and low heat capacity. Fig-2.1 Soldering Iron  Solder:-For most PCB work, a solder with a diameter of 0.75MM to 1.00MM is desirable .Thicker solder maybe used and will allow we to solder layer joint more quickly. Fig-2.2 Solder  Flux:-Purpose of flux is to facilitate the soldering process. One of the obstacle to a successful solder joint is an impurities at the site of joint like dirt, oil etc. One of the earlier form of flux was char-coal. Fig-2.3 Flux 2
  15. 15. 2.3 SOLDERING TECHNIQUE  SURFACE PREPARATION A clean surface is very important if we want a strong , low resistance soldering joint. All surfaces to be soldered should be cleaned well 3m scotch brite pads are a good choice as quickly remove surface tarnish but will not abrade the pcb material.If we have particularly tough deposits on over board, then a fine grade of steel wool is acceptable.  COMPONENTS PLACEMENT After the component and board have been cleaned , we are ready to place the components onto the board. Unless our components ,we will probably not be placing all the components onto the board and soldering them at once. Most likely we will be soldering a few components at a time before turning the board over and placing more.  APPLY HEAT Apply a very small amount of solder to the tip of the iron.This helps conduct the heat to the component and board ,but it is not the solder that will make up the joint.To heat the joint we will lay the tip of the iron so that is rests against both the component lead and the both. If we see the area under the pad starting to bubbled, stop heating and remove the soldering iron because we are over heating the pad and it is in danger of lifting.  APPLY SOLDER TO THE JOINT Once the component lead and solder pad has heated up, we are ready to apply the solder .If everything is hot enough, the solder should flow freely around the lead and pad .We will see the flux melt liquefy as well, bubble around the joint, flow out and release smoke .Continue to add solder to the joint until the pad is completely coated. Once the surface of the pad completely coated we can stop adding solder and remove the soldering iron .  INSPECT THE JOINT AND CLEANUP Once the joint is made we should inspect it. Check the joints, shorts with the adjacent pads or poor flow. If the joint checks out, now trim the lead use a small set of side cutter and cut at the top of the solder joint.  TIPS AND TRICKS  Use heat sinks- Heat sinks are must for the leads of sensitive components such as IC’s and transistors.  Keep the iron tip clean- A clean iron tip means better heat conduction and a better joint. Keep the tip well tinned.  Double check joints-when assembling complicated circuits, it is good practice to check joints after soldering them 3
  16. 16.  Solder small parts first-Solder resistors, jumper leads, diodes and any other small parts before we solder large part like capacitor and transistors. This makes assembly much easier.  Install sensitive components last-Install CMOS ICs , MOSFETs and other static sensitive components last to avoid damaging them during assembly of other part. 4
  17. 17. Chapter III Power Supply
  18. 18. POWER SUPPLY 3.1. INTRODUCTION Virtually every piece of electronic equipment in the world today is powered from a DC source; this DC source may be either a battery or a power supply. Most electronic equipment requires not only a DC power source but one that is well filtered and well regulated as well three types of electronics power conversion devices in common use today: the AC/DC power supply, the DC/DC convertor and the DC/AC invertors. The mostly used power supply is AC/DC power supply. A Power supply is an electronics device that supplies electrical energy to an electrical load. The primary function of a power supply is to convert one form of electrical signal to another form and result, power supplies are sometimes referred to as electric power convertors. Some power supply are discrete, stand alone devices, whereas other are built into larger devices along with their loads. Examples of the latter include power supplies found in desktop computers and consumer electronics devices. Fig 3.1:- Circuit Diagram of 5V & 12V Power Supply A 5V & 12V DC is most commonly used. The above circuit shown in the figure, uses a cheap integrated three-terminal positive regulator LM7805, and LM7812 and provides high-quality voltage stability and quite enough current to enable the microcontroller. TABLE -3.1 COMPONENTS USED:- S.NO COMPONENTS QUANTITY 1. Step down transformer (1A). 1 2. Diodes IN4007 4 3. Capacitors 470µf ,1000µf,10µf 1,1,1 4. Voltage regulator for 12V LM7812 1 5. Voltage regulator For 5V LM780 1 6. Resistor 220Ω 1 7. LED 1 5
  19. 19. 3.2 WORKING OF POWER SUPPLY:- To provide a usable low voltage are the following conditions:  Reduce the mains ac (alternating current) voltage to lower level.  Convert this lower voltage from ac to dc (direct current)  Regulate the dc output to compensate for varying load(current demand)  Provide protection against excessive input/output voltages. Fig 3.2- Power Supply 6
  20. 20. Chapter IV Light Dependent Resistor
  21. 21. LIGHT DEPENDENT RESISTOR 4.1 . INTRODUCTION The “light dependent resistor” (LDR) is also known as photoconductor, photo resistor or photocell. It is a variable resistor whose value decreases with increasing incident light intensity. Basically LDR of 2 types: - intrinsic and extrinsic LDR. Basic LDR circuit is used to detect light which is used various application and various field. There are several method to made LDR circuit like LDR with relay; LDR without relay; LDR using transistor etc. The simplest method to design LDR circuit is by using IC 741 opamp and a split circuit. In this circuit split circuit is used to give supply to opamp of +12v and -12v to operate. This type of LDR circuit is used for detecting the change in light levels and determining if it is ‘dark’ or ‘light’. Fig-4.1 LDR 4.2 BASIC LDR CIRCUIT Basic LDR circuit is used to detect light or change in light level. Basic LDR circuit consist of op-amp 741 IC ,resistor ,split circuit etc The LDR circuit designed by using IC 741 is very easy and inexpensive and the result is satisfactory. The basic LDR circuit need some calibrated because it do not give accurate measurement of light level. The LDR circuit using op-amp needs +12v and - 12v supply so the split circuit is provided to give supply by power supply designed earlier. Fig-4.2 LDR Circuit With Split Circuit 7
  22. 22. TABLE 4.1COMPONENTS USED:- S.NO. COMPONENTS QUANTITY 1 LDR 1 2 Resistor-10kΩ 5 3 Variable Resistor 1 4 Capacitor-10µF 2 5 IC 741 op-amp 1 6 LED 1 4.3 LDR CIRCUIT WORKING:- Basic LDR circuit consist of Op-amp 741 and a variable resistor, LDR , and LED and split circuit. The Op-amp is used as comparator whose inverting terminal is parallel combination of 10k resistor and LDR and non inverting terminal is connected to 10K resistor and variable resistor. This Op-amp circuit is connected to split circuit for the supply split circuit consist of 2 resistor, 2 capacitor which split the supply in +12V and -12V which is connected to 7 and 4 pin of Op-amp and its output pin is connected to an LED through resistance. In the circuit, the Op-amp act as a comparator circuit i.e. for the high value of input on non-inverting and a zero value for both the input obtain a positive saturation and a high on the inverting input obtain a negative saturation voltage .The output is always either positive saturation or negative saturation. As the light fall over the LDR its resistance decreases and a voltage drop created across the resistance R1 of 10K, in the inverting terminal is kept open and this for a small rise in non-inverting terminal voltage the output would be at positive saturation and the LED is reversed biased. In the full darkness the resistance of LDR will be high and the voltage drops the maximized. Whenever the full voltage drop the LDR the Op-amp can switch to negative saturation and OFF the LED. Thus the circuit has a high sensitive to light a small variation in LDR resistance can switch the LED ON 8
  23. 23. Fig 4.3- LDR Circuit 4.4 APPLICATION OF LDR :- 1. Smoke and fire detector. 2. Camera light meter. 3. Security alarms, for street lamps and clock radio. 4. Light intensity meter, for counting the package moving in the conveyor belt. 9
  24. 24. Chapter V Dip Trace
  25. 25. PCB LAYOUT 5.1 INTRODUCTION Dip Trace is EDA software for creating schematic diagrams and printed circuit boards. The first version of Dip Trace was released in August, 2004. The latest version as of July 21, 2014 is Dip Trace version 2.4.0.2. The interface and tutorials are multi-lingual. In January of 2011, Parallax switched from Eagle to Dip Trace for developing its printed circuit boards. 5.2 MODULES  Schematic Design Editor  PCB Layout Editor  Component Editor  Pattern Editor  Shape-Based Auto router  3D PCB Preview, using Wings 3D format 5.3 FEATURES  Schematic and PCB Interaction  Advanced Verifications with real-time DRC  Real-Time 3D PCB Preview & STEP Export  Manufacturing output  Commitment to the future  Multi-sheet and hierarchical schematics  High-speed shape-based auto router  Smart manual routing tools  Wide import / export capabilities 5.4 DIPTRACE SOFTWARE: PCB LAYOUT PCB Layout is high-level engineering tool for board design with smart manual routing, shape-based auto router, advanced verification and wide import / export capabilities. Design requirements are defined by net classes, class-to- class rules and detailed settings by object types for each class or layer. Dip Trace features design process with real-time DRC, which reports errors on the fly before actually making them. Board can be previewed in 3D and exported for mechanical CAD modeling. 10
  26. 26. Fig-5.1 PCB Layout 11
  27. 27. Chapter – VI Printed Circuit Board
  28. 28. PRINTED CIRCUIT BOARD 6.1 INTRODUCTION: Etching is the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal (the original process—in modern manufacturing other chemicals may be used on other types of material). As an intaglio method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains in wide use today 6.2 STEPS OF PCB ETCHING PROCESS: Step 1: Design First we need to design the board using a service like Dip trace or we can even just use Adobe Illustrator if you know exactly what we want. And remember to flip the design once you have it complete before you print it out. Step 2: Print out the design onto the shiny side of the glossy photo paper 12
  29. 29. Step 3: Sand the copper plate so there is a rough surface for the design to stick to when transferred Starting from this point on we should use surgical gloves to handle the copper plate and etching solution, this helps avoid getting oils on the copper and chemicals on your hands. Step 4: Wash the copper with some water and let it dry Step 6: Run the copper plate with the design face down through a iron 5-7 times until the plate is hot This step is not as complicated as the title says. Switch on your cloths iron and turn it to its highest setting. Place the printed paper over the board and start moving the iron over it for 2-3 minutes. Now drop the board into a mug of water and peel off the glossy paper. 13
  30. 30. Step 7: After running the plate through iron place the plate into a cold bath and agitate until the paper floats off Step 8: Place the PCB into the etching solution and agitate for 25-30 minutes or until all the copper has dissolved around the design Step 9: Once all the copper is gone rinse it in the water bath, let it dry and use rubbing alcohol to whip off the ink transferred onto the PCB 14
  31. 31. Step 10: And now you have a etched PCB board but you still need to drill the holes 15
  32. 32. Chapter VII Development Board
  33. 33. DEVELOPMENTBOARD 7.1 INTRODUCTION A general purpose 40 pin 8051 development board with onboard 16X2 LCD support, 4 X general purposes LEDs, 4 X general purposes switches, RS232 Port for serial interface with computer & other serial devices, reset switch, power status LED. The board provides port extensions for all ports & also provides an empty hole for each IO pin Further these board is perfect for learning, testing & development. The board is compatible with the AT89S51/52, and the P89V51RD2 microcontrollers. The P89V51RD2 allows serial programming and can be programmed directly with this board through a serial or USB connection without the need for an external programmer. 7.2 FEATURES OF DEVELOPMENT BOARD  AT89S52 included (AT89S51 and P89V51RD2 also supported)  5V voltage regulator.  On/Off switch.  Power indicator LED.  Reset Button.  MAX232 based TTL to RS232 Adaptor.  9 PIN D Type Female Connector for RS232 Communication.  24MHz Crystal.  10 PIN FRC Box Header for In Circuit Programming.  Pull ups on PORT0.  Free Protyping Area. Fig 7.1- Basic Development Board 16
  34. 34. 7.3 COMPONENTS USED IN BOARD:  Microcontroller- A microcontroller is compact ‘microcomputer’ designed to govern the operation of ‘embedded systems’ in motor vehicles, robots, office machines, complex medical devices, mobile radio transceiver, vending machines, home appliance, and various other devices. A typical Fig 7.2- Microcontroller  LCD (LIQUID CRYSTAL DISPLAY):- An LCD display is specifically manufactured to be used with microcontrollers, which means that it cannot be activated by standard IC circuits. It is used for displaying different messages on a miniature liquid crysal display. Fig 7.3-LCD The onboard potentiometer below the LCD (labelled as LCD Contrast in the board overview) controls the contrast of the LCD. Adjust it until the characters on the LCD appear clearly by rotating the shaft of the potentiometer with a screw driver. The characters on the LCD will be faint and not visible if the contrast is not set correctly.  Serial Connections The board provides an industry standard RS232 interface circuit which can be used to connect the board to an external device with serial interface or to a computer through a serial cable 17
  35. 35.  Max232: Fig 7.4- MAX 232  Crystal Oscillator The board by default comes with an onboard crystal oscillator circuit consisting of a 11.0952 MHz quartz crystal and the required capacitors. If you would like to use the microcontroller on a different speed, you may replace this crystal with the crystal of the required frequency. Make sure you replace the capacitors also to match the crystal you use. Fig 7.5- Crystal Oscillator  General Purpose Switches The onboard switches can be used to provide input signals to the microcontroller. Switch1 -> P0.0, Switch2-> P0.1, Switch3-> P0.2, Switch4-> P0.3. Every time the switch is pressed a low signal appears at the corresponding switch LED which at other times has a high signal.  Reset Button The board provides a reset switch which is connected such that it resets the microcontroller every time it is pressed. Upon reset, all registers are set to their default value and the program is executed from the beginning. The Reset switch is provided in right angled package below the LCD. 18
  36. 36.  External Pull-up Resistors for PORT0 All eight pins of PORT0 are by default connected to Vcc through a resistor of 10K Ohms.  Port Extensions All IO pins are brought out to male header pins for easy connections with external circuits. Two parallel empty holes are also provided to each IO pin, which can be used to solder in wires directly and provide easy expansion. The pin name and any dual functions of each pin are also printed on the board next to each pin for easy prototyping.  Programming the P89V51RD2 with the board If you are using a P89V51RD2, you can program the microcontroller without any external hardware programmer directly from Flash Magic programming software. To program theP89V51RD2, the following steps should be followed –  Once the required program to be uploaded is compiled and the hex file is generated, run Flash Magic and set the parameters on Flash Magic as follows:  Set COM port to the serial port to which the development board is Connected (usually COM1)  Set Baud Rate to 9600 bps  Set Device to 89V51RD2  Set Interface as None(ISP)  Check “Erase Blocks used by Hex File”  Check “Verify after programming”  Connect the board to the computer using a serial cable.  Apply power to the board. You should see the Green Power LED light up  Select the Hex File to be uploaded on Flash Magic and click on Start  When you get a message indicating you to Reset Device into ISP Mode, reset the microcontroller by pressing the Reset button on the development board  The Hex file will get uploaded to the microcontroller in a few seconds, after which we may execute the program by resetting the device again. 19
  37. 37. Fig 7.6 PCB Layout of Development Board Fig 7.7-Development Board 20
  38. 38. Chapter - VIII Conclusion & Future Scope
  39. 39. CONCLUSION On the completion of this project titled “Development Board“we can conclude that we have acquired much sophisticated knowledge regarding technical skills required for electronic engineers. The development board can be used to develop any embedded project based on 8051 microcontroller in a very much efficient way as the board is having different options to interface various modules with 8051 microcontrollers so the testing & debugging of hardware & firmware for any 8051 microcontroller based embedded projects can be done easily on the development board.. The embedded systems which have virtually entered every place of our life, sight from the time we work out on tread mills to the cases that we drive today. The possibilities in this field are only in our imagination. Many of the embedded systems are managed human controllers by some sort of man machine interface for example a TV screen & a PC interface. FUTURE SCOPE Various projects can be done using development board .we can interface different modules such as GSM modules, GPS modules etc.Also we can add other peripherals to extend our development board. By using same method other families of microcontroller can be implemented such as ARM and PIC controllers for developing & designing embedded system around the same controllers. The universal boards result for various applications as follows:  Countdown Timer 7-segment display.  Character Generator Display LCD.  Speed Measurement of the DC Motor.  LED Glows as per the programming. 21
  40. 40. REFRENCES 1. http://en.wikipedia.org/wiki/Soldering. 2. http://en.wikipedia.org/wiki/etching. 3. Diptrace tutorial from the software. 4. Muhammad Ali Mazidi, Janice Gillispie Mazidi and Rolin D. McKinlay “The 8051 microcontroller and embedded systems” pearson publication, second edition. 5. http://en.wikipedia.org/wiki/photoresistor 22

×