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Door knock alarm with timer

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It is a minor project on how a dook knock alarm works.Is shows how one form of energy is transferred to another form of energy which follows the law of conservation of energy

It is a minor project on how a dook knock alarm works.Is shows how one form of energy is transferred to another form of energy which follows the law of conservation of energy

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  • 1. Door Knock Alarm With Timer DOOR KNOCK ALARM WITH TIMER A Project Report Submitted in partial fulfillment of the requirement for the award of Degree of Bachelor of Engineering in Electronics & Communication Submitted to RAJIV GANDHI PROUDYOGIKI VISHWAVIDHYALAYA, BHOPAL(M.P.) MINOR PROJECT REPORT Submitted by 1.Sandeep Ghosh (0157EC091075) 2. Ankush Shivhare (0157EC091013) 3.Zeyaur Rahman (0157EC091090) 4.Pathik Sonkar (0157EC091056) 5.Kishor Kumar(0157EC091038) Under the supervision of Prof. Avinash Rai Prof.Priyanka Dubey Department of Electronics and Telecommunication Engineering LAKSHMI NARAYAN COLLEGE OF TECHNOLOGY & SCIENCES,BHOPAL SESSION-2011-2012 Department Of Electronics And Communication Engineering 1
  • 2. Door Knock Alarm With Timer LAKSHMI NARAIN COLLEGE OF TECHNOLOGY & SCIENCE, BHOPAL (M.P.) Department of Electronics and Telecommunication Engineering CERTIFICATE This is to certify that the work embodied in this thesis entitled “DOOR KNOCK ALARM WITH TIMER” has been satisfactorily completed by Sandeep Ghosh,Ankush Shivara,Pathik Sonkar,Zeyaur Rahaman of pre final year. It is a bonafied piece of work carried out under the supervision and guidance in the Department Of Electronics And Communication Engineering in LAKSHMI NARAYAN COLLEGE OF TECHNOLOGY AND SCIENCES for partial fulfilment of the Bachelor Of Engineering In ELECTRONICS AND COMMUNICATION AND ENGINEERING,during the academic year 2012. Under the supervision of …......................................... ………………………. Prof. AVINASH RAI Prof. PRIYANKA DUBEY (Project Guide) (Project Incharge) Approved by ………………………………. Prof. Soni Changlani (Head Of Department) Forwarded by …………………… ( Principal ) Department Of Electronics And Communication Engineering 2
  • 3. Door Knock Alarm With Timer LAKSHMI NARAIN COLLEGE OF TECHNOLOGY & SCIENCE, BHOPAL Department Of Electronics And Telecommunication Engineering CERTIFICATE OF APPROVAL This foregoing minor project work is hereby approved as a creditable study of Engineering carried out and presented in a manner satisfactory to warranty its acceptance as a prerequisite to the degree for which it has been submitted. It is understood that by this approval the undersigned do not necessarily endorse or approve any statement made, opinion expressed or conclusion drawn therein, but approve the thesis only for the purpose for which it has been submitted. Department Of Electronics And Communication Engineering 3
  • 4. Door Knock Alarm With Timer LAKSHMI NARAIN COLLEGE OF TECHNOLOGY & ,…………… SCIENCE, BHOPAL (M.P.) Department of Electronics and Telecommunication Engineering DECLARATION Sandeep Ghosh,Ankush Shivhare,Pathik Sonkar,Zeyaur Rahaman and Kishore Kumar students of bachelor of engineering,branch Electronics And Communication Engineering LAKSHMI NARAYAN COLLEGE OF TECHNOLOGY AND SCIENCE,BHOPAL,hereby declare that the work presented in this minor project report entitled “Door Knock Alarm With Timer”outcome of our own work,is bonafide,correct to best of our knowledge.This work has been carried out takink care of Engineering Ethics.This work presented does not infringe any patented work and has not been submitted to any university for the award of any degree or any professional diploma. ……………………….. ………………………. Sandeep Ghosh Ankush Shivhare (0157EC091075) (0157EC091013) …………….................... ………………………… Pathik Sonkar Zeyaur Rahaman (0157EC091057) (0157EC091090) .......................................... Kishore Kumar (0157EC091038) DATE-.............................. Department Of Electronics And Communication Engineering 4
  • 5. Door Knock Alarm With Timer ACKNOWLEDGEMENT Any work started and carried out with systemic approach turns out to be a success. Any accomplishment requires the effort of many people and this work is outcome of such one strenuous effort.The project was a challenge and was made more difficult due to a number of varied reasons. Some of which were beyond our capability.At time we were left with no options reguarding whwt to do next. It was then the very assistance of the faculty members who helped us out of the quicksand. We would be grateful to them for their inspiration, encouragement and guidance in all stages of our project development process. We feel extremely gratified to express out hearties thanks to Prof. Soni Changlani HOD of Electronics and Communication Department for her constant encouragement and valuable advice during the project development stages. We wish to extend our thanks to all the faculty members who devoted their valuable time for our project development. Finally we would like to thank Prof. Priyanka Dubey mam and Prof. Avinash Rai sir who tremendously contributed in this project either directly or indirectly. We wish to express our sincere thanks to all those who may have contributed in the project completion plan. Department Of Electronics And Communication Engineering 5
  • 6. Door Knock Alarm With Timer CONTENTS: NAME OF TOPICS PAGE NO. A PHOTOGRAPH OF PROJECT 3 B ABSTRACT 4 C PROJECT SPECIFICATION 5 D LIST OF FIGURES 6 E LIST OF TABLES 7 CHAPTER 1: INTRODUCTION 8 CHAPTER 2: THEORY/PRINCIPLE 9 CHAPTER 3: CIRCUIT ANALYSIS 3.1 CIRCUIT DETAILS 10 3.2 CIRCUIT LAYOUT 11 3.3 COMPONENT LIST 12 CHAPTER 4: PCB ANALYSIS 4.1 PCB DETAILS 13 4.2 PCB DESCRIPTION 19 4.3 PCB DESIGNING 21 4.4 PCB LAYOUT COMPONENT SIDE 24 4.5 PCB LAYOUT SOLDERED SIDE 25 4.6 PCB PROTECTION AND PACKAGING 26 CHAPTER 5: ASSEMBLY AND TESTING 5.1 BREADBOARD IMPLEMENTATION 27 Department Of Electronics And Communication Engineering 6
  • 7. Door Knock Alarm With Timer NAME OF TOPIC PAGE NO. 5.2 PCB IMPLEMENTATION 33 CHAPTER 6: WORKING OF CIRCUIT 38 CHAPTER 8: EXPECTATION AND ACHIEVEMENTS 39 CHAPTER9: PROJECT COST 40 CHAPTER 10: COMPONENT DETAILS 10.1 PIEZOELECTRIC SENSORS 41 10.2 NE 555 IC 45 10.3 UM 66 MUSIC GENERATOR 48 10.4 RESISTOR 50 10.5CAPACITOR 52 10.6 VARIBLE RESISTOR 55 10.7 LOUDSPEAKER 58 10.8 ZENER DIODE 63 CHAPTER 11: SHORTCOMMINGS, LIMITATIONS AND REMEDIES 66 CHAPTER 12: FUTURE APPLICATION AND SCOPE OF PROJECT 67 CHAPTER 13: CONCLUSION 68 CHAPTER 14:REFERENCES AND BIBLIOGRAPHY 69 Department Of Electronics And Communication Engineering 7
  • 8. Door Knock Alarm With Timer A- PHOTOGRAPH OF PROJECT Department Of Electronics And Communication Engineering 8
  • 9. Door Knock Alarm With Timer B- ABSTRACT This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor. When the door is knocked music is heard from the speakerLS1. After the set time period, the melody sound stops. The circuit works off 5-12V DC. The music time can be adjusted through VR1 by changing the R-C time constant of the timer. This is the general functioning of the door knock alarm. We have chosen the project as in day to day life it is not possible to have a watch over every nook and corner. So to have a check on every aspect of a place we plan to device a detector which is able to alert us of some change in the prevailing system. There are many application of the concept behind the project. It can not only be used for military purpose but also can be used in day to day like door knock alarm, bugler alarm safety alarm. Department Of Electronics And Communication Engineering 9
  • 10. Door Knock Alarm With Timer C- PROJECT SPECIFICATION Serial Number Component description Reference Description Quantity 1 IC NE555 IC 1 1 2 Resistor 10 K R4,R5,R8 3 3 Resistor 2.2 M R1 1 4 Resistor 270 K R2 1 5 Resistor 3.3 K R3 1 6 Resistor 470 K R 6 1 7 IC’S BC 547,BG 549,UM66,NE555 4 8 Resistor 1 K R 7 1 9 Variable Resistor 100 K VR 1 1 10 9 Volt Battery - 1 11 Piezoelectric element - 1 12 Piezoelectriv buzzer - 1 Table 1 D- LIST OF FIGURES FIGURE NO. FIGURE NAME PAGE NO. Figure 1- Circuit Diagram 11 Department Of Electronics And Communication Engineering 10
  • 11. Door Knock Alarm With Timer Figure 2- General PCB solder and component side 13 Figure 3- PCB Layout Component Side 24 Figure 4- PCB Layout Solder Side 25 Figure 5- Breadboard 28 Figure 6- PCB with test connection pads 33 Figure 7- Piezoelectric element 41 Figure 8- Schematic symbol and electronic model of a piezoelectric sensor 42 Figure 9- Frequency response of a piezoelectric sensor; output voltage v/s applied force 43 Figure 10- NE 555 45 Figure 11- Pin diagarm of NE 555 IC 45 Figure 12- Schematic of a 555 in monostable mode 46 Figure 13- UM66 48 ..………………… ……….E- LIST OF TABLES TABLE NO. TABLE NAME PAGE NO. Table 1 Project Specification 5 Department Of Electronics And Communication Engineering 11
  • 12. Door Knock Alarm With Timer Table 2 Component List 12 Table 3 Project Cost 40 CHAPTER 1 INTRODUCTION This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor. The piezoelectric element plate is fixed at the centre of the door wing by using Department Of Electronics And Communication Engineering 12
  • 13. Door Knock Alarm With Timer a cello tape. Apply a small quantity of adhesive at the edges between the plate and the door. Extend wires about 1-1.5 meters from the piezoelectric to the circuit. IC NE555 (IC1) is configured in monostable mode. When it gets an input pulse its output goes high for a period set by VR1, resistor R5 and capacitorC3. IC UM66 (IC2) is used as a melody generator. When the door is knocked at, the piezoelectric plate generates an input pulse, which is amplified by transistor T1.The amplified signal triggers the timer IC NE555 and its output pin 3goes high to enable the melody generator. Music is heard from the speakerLS1. After the set time period, the melody sound stops. Assemble the circuit on a general purpose PCB and enclose in a suitable case. Fix the piezoelectric element at the door and place the speaker in a central room inside the house using long wires. The circuit works off 5-12V DC. The music time can be adjusted through VR1 by changing the R-C time constant of the timer. CHAPTER 2 THEORY/PRINCIPLE The basic principle behind operation of DOOR KNOCK ALAM WITH TIMER is conservation of energy and transformation of one form of energy to another form of Department Of Electronics And Communication Engineering 13
  • 14. Door Knock Alarm With Timer energy. The law of conservation of energy states that “ Energy Can Neither Be Created Nor Destroyed But It Can Be Changer From One Form To Another’’. In DOOR KNOCK ALAM WITH TIMER we have conservation as well as transformation of energy with of help of different type of transducers. A TRANSDUCER is a special type of device which has the feature of converting one form of energy to another form of energy. Initially the mechanical energy that is pressure applied on the piezoelectric element is converted into its electrical equivalent due to unique characteristic of the piezoelectric .Then the electrical energy is again converted into sound energy with the help of UM66 IC which has the special characteristic of converting electrical energy to its sound energy equivalent. This successive transformation of energy takes place due to special type of transducers i.e.UM66 (electrical to sound) and piezoelectric element (mechanical to electrical energy) . CHAPTER 3 3.1 CIRCUIT DETAILS Department Of Electronics And Communication Engineering 14
  • 15. Door Knock Alarm With Timer In DOOR KNOCK ALAM WITH TIMER we have conservation as well as transformation of energy with of help of different type of transducers. A TRANSDUCER is a special type of device which has the feature of converting one form of energy to another form of energy. Initially the mechanical energy that is pressure applied on the piezoelectric element is converted into its electrical equivalent due to unique characteristic of the piezoelectric .Then the electrical energy is again converted into sound energy with the help of UM66 IC which has the special characteristic of converting electrical energy to its sound energy equivalent. This successive transformation of energy takes place due to special type of transducers i.e.UM66 (electrical to sound) and piezoelectric element (mechanical to electrical energy) . This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor. The piezoelectric element plate is fixed at the centre of the door wing by using a cello tape. Apply a small quantity of adhesive at the edges between the plate and the door. Extend wires about 1-1.5 meters from the piezoelectric to the circuit. IC NE555 (IC1) is configured in monostable mode. When it gets an input pulse its output goes high for a period set by VR1, resistor R5 and capacitorC3. IC UM66 (IC2) is used as a melody generator. When the door is knocked at, the piezoelectric plate generates an input pulse, which is amplified by transistor T1.The amplified signal triggers the timer IC NE555 and its output pin 3goes high to enable the melody generator. Music is heard from the speakerLS1. After the set time period, the melody sound stops. Assemble the circuit on a general purpose PCB and enclose in a suitable case. 3.2 CIRCUIT LAYOUT Department Of Electronics And Communication Engineering 15
  • 16. Door Knock Alarm With Timer Figure 1 1)T1,T2-TRANSISTORS 8)IC1 NE555-TIMER 2)GND-GROUND(0 VOLTS) 9)VR1-VARIABLE RESISTOR 3)C1,C2,C3-CAPACITORS 10)LS1-LOUDSPEAKER 4)R1,R2,R3,R4,R5,R6,R7,R8-RESISTORS 11)PZ1-PIEZOELECTRIC ELEMENT 5)ZD1-ZENNER DIODE 6)IC2 UM66-MELODY GENERATOR 3.3 COMPONENT LIST Department Of Electronics And Communication Engineering 16
  • 17. Door Knock Alarm With Timer Serial Number Component description Reference Description 1 IC NE555 IC 1 2 Resistor 10 K R4,R5,R8 3 Resistor 2.2 M R1 4 Resistor 270 K R2 5 Resistor 3.3 K R3 6 Resistor 470 K R 6 7 IC’S BC 547,BG 549,UM66,NE555 8 Resistor 1 K R 7 9 Variable Resistor 100 K VR 1 10 9 Volt Battery - 11 Piezoelectric element - 12 Piezoelectriv buzzer - Table 2 CHAPTER 4 4.1 PCB DETAILS MANUFACTURING A PCB as a design on a computer (left) and realized as a board assembly populated with components (right). The board is double sided, with through-hole plating, green solder resist, and white silkscreen printing. Both surface mount and through-hole components have been used. Department Of Electronics And Communication Engineering 17
  • 18. Door Knock Alarm With Timer The Component Side of a PCB in a computer mouse; some examples for common components and their reference designation on the silk screen. Figure 2 General PCB solder and component side Conducting layers are typically made of thin copper foil. Insulating layers dielectric are typically laminated together with epoxy resin prepreg. The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue, black, white and red. There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. PATTERNING(ETCHING) The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, (creating a "blank PCB") then removing unwanted copper after applying a temporary mask (e.g., by etching), leaving only the desired copper traces. A few PCBs are made by adding traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex process of multiple electroplating steps. The PCB manufacturing method primarily depends on whether it is for production volume or sample/prototype quantities. Double-sided Department Of Electronics And Communication Engineering 18
  • 19. Door Knock Alarm With Timer boards or multi-layer boards use plated-through holes, called vias, to connect traces on either side of the substrate. • Silk screen printing–the main commercial method. • Photographic methods–used when fine linewidths are required. • Print onto transparent film and use as photomask along with photo-sensitized boards. (i.e., pre-sensitized boards), then etch. (Alternatively, use a film photoplotter). • Laser resist ablation: Spray black paint onto copper clad laminate, place into CNC laser plotter. The laser raster-scans the PCB and ablates (vaporizes) the paint where no resist is wanted. Etch. (Note: laser copper ablation is rarely used and is considered experimental.) • Use a CNC-mill with a spade-shaped (i.e., a flat-ended cone) cutter or miniature end-mill to rout way the undesired copper, leaving only the traces. HOBBYIST • Laser-printed resist: Laser-print onto transparency film, heat-transfer with an iron or modified laminator onto bare laminate, touch up with a marker, then etch. • Other labor-intensive techniques exist, only suitable for one-off boards (vinyl film and resist, non-washable marker, and others). There are three common "subtractive" methods (methods that remove copper) used for the production of printed circuit boards: • SILK SKIN PRINTING:uses etch-resistant inks to protect the copper foil. Subsequent etching removes the unwanted copper. Alternatively, the ink may be conductive, printed on a blank (non-conductive) board. The latter technique is also used in the manufacture of hybrid -aided manufacturing circuit. • PHOTOENGRAVING uses a photomask and developer to selectively remove a photoresist coating. The remaining photoresist protects the copper foil. Subsequent etching removes the unwanted copper. The photomask is usually prepared with a photoplotter from data produced by a technician using CAM, or compute software. Laser-printed transparencies are typically employed for phototools; however, direct laser imaging techniques are being employed to replace phototools for high-resolution requirements. • PCB MILLING uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine (referred to as a 'PCB Prototyper') operates in a similar way to a plotter, receiving commands Department Of Electronics And Communication Engineering 19
  • 20. Door Knock Alarm With Timer from the host software that control the position of the milling head in the x, y, and (if relevant) z axis. Data to drive the Prototyper is extracted from files generated in PCB design software and stored in HPGL or Gerber file format. "Additive" processes also exist. The most common is the "semi-additive" process. In this version, the unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive process mask, this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas; copper may be plated to any desired weight. Tin-lead or other surface platings are then applied. The mask is stripped away and a brief etching step removes the now-exposed original copper laminate from the board, isolating the individual traces. Some boards with plated through holes but still single sided were made with a process like this.General electric made consumer radio sets in the late 1960s using boards like these. The additive process is commonly used for multi-layer boards as it facilitates the plating-through of the holes (to produce conductive vias) in the circuit board. The dimensions of the copper conductors of the printed circuit board is related to the amount of current the conductor must carry. Each trace consists of a flat, narrow part of the copper foil that remains after etching. Signal traces are usually narrower than power or ground traces because their current carrying requirements are usually much less. In a multi-layer board one entire layer may be mostly solid copper to act as a ground plane for shielding and power return. For printed circuit boards that contain microwave circuits, transmission line can be laid out in the form of stripline and microstrip with carefully controlled dimensions to assure a consistent impedence. In radio-frequency circuits the inductance and capacitance of the printed circuit board conductors can be used as a deliberate part of the circuit design, obviating the need for additional discrete components. CHEMICAL ETCHING Chemical etching is done with ferric chloride, ammonium persulfate, or sometimes hydrochloric acid. For PTH (plated-through holes), additional steps of electroless deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes the resist leaving the bare copper to be etched away. The simplest method, used for small-scale production and often by hobbyists, is immersion etching, in which the board is submerged in etching solution such as ferric Department Of Electronics And Communication Engineering 20
  • 21. Door Knock Alarm With Timer chloride. Compared with methods used for mass production, the etching time is long. Heat and agitation can be applied to the bath to speed the etching rate. In bubble etching, air is passed through the etchant bath to agitate the solution and speed up etching. Splash etching uses a motor-driven paddle to splash boards with etchant; the process has become commercially obsolete since it is not as fast as spray etching. In spray etching, the etchant solution is distributed over the boards by nozzles, and recirculated by pumps. Adjustment of the nozzle pattern, flow rate, temperature, and etchant composition gives predictable control of etching rates and high production rates. As more copper is consumed from the boards, the etchant becomes saturated and less effective; different etchants have different capacities for copper, with some as high as 150 grams of copper per litre of solution. In commercial use, etchants can be regenerated to restore their activity, and the dissolved copper recovered and sold. Small-scale etching requires attention to disposal of used etchant, which is corrosive and toxic due to its metal content. The etchant removes copper on all surfaces exposed by the resist. "Undercut" occurs when etchant attacks the thin edge of copper under the resist; this can reduce conductor widths and cause open-circuits. Careful control of etch time is required to prevent undercut. Where metallic plating is used as a resist, it can "overhang" which can cause short-circuits between adjacent traces when closely spaced. Overhang can be removed by wire-brushing the board after etching. A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic component using conductiv pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly or PCB Assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices. Alternatives to PCBs include wire wrap and point to point construction PCBs are often less expensive and more reliable than these alternatives, though they require more layout effort and higher initial cost. PCBs are much cheaper and faster for high- volume production since production and soldering of PCBs can be done by automated equipment. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization. Department Of Electronics And Communication Engineering 21
  • 22. Door Knock Alarm With Timer Conducting layers are typically made of thin copper foil. Insulating layers dielectric are typically laminated together with epoxy resin prepreg. The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue, black, white and red. There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluroethene(Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known prepreg materials used in the PCB industry are FR-2(Phenolic cotton paper), FR-3 (Cotton paper and epoxy), FR-4(Woven glass and epoxy), FR-5 (Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Non-woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven glass and polyester). Thermal expansion is an important consideration especially with ball grid array(BGA) and naked die technologies, and glass fiber offers the best dimensional stability.FR-4 is by far the most common material used today. The board with copper on it is called "copper-clad laminate". Copper foil thickness can be specified in ounces per square foot or micrometres. One ounce per square foot is 1.344 mils or 34 micrometres The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, (creating a "blank PCB") then removing unwanted copper after applying a temporary mask (e.g., by etching), leaving only the desired copper traces. A few PCBs are made by adding traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex process of multiple electroplating steps. The PCB manufacturing method primarily depends on whether it is for production volume or sample/prototype quantities. Double-sided boards or multi-layer boards use plated-through holes, called vias, to connect traces on either side of the substrate. Department Of Electronics And Communication Engineering 22
  • 23. Door Knock Alarm With Timer 4.2 PCB DESCRIPTION FR-4 (or FR4) is a grade designation assigned to glass-reinforced epoxy laminate sheets, tubes, rods and printed circuit boards (PCB)fiberglass. FR-4 is a composite material composed of woven cloth with an epoxy resin binder that is flame resistant (self-extinguishing). FR-4 glass epoxy is a popular and versatile high-pressure thermoset plastic laminate grade with good strength to weight ratios. With near zero water absorption, FR-4 is Department Of Electronics And Communication Engineering 23
  • 24. Door Knock Alarm With Timer most commonly used as an electrical insulator possessing considerable mechanical strength. The material is known to retain its high mechanical values and electrical insulating qualities in both dry and humid conditions. These attributes, along with good fabrication characteristics, lend utility to this grade for a wide variety of electrical and mechanical applications.NEMA is the regulating authority for FR-4 and other insulating laminate grades. Grade designations for glass epoxy laminates are: G10, G11, FR4 and FR5. Of these, FR4 is the grade most widely in use today. G-10, the predecessor to FR-4, lacks FR-4's self-extinguishing flammability characteristics. Hence, FR-4 has since replaced G-10 in most applications. FR-4 epoxy resin systems typically employ bromine, a halogen, to facilitate flame- resistant properties in FR-4 glass epoxy laminates. Some applications where thermal destruction of the material is a desirable trait will still use G-10 non flame resistant PRINTED CIRCUIT BOARD FR-4 is the primary insulating backbone upon which the vast majority of rigid printed circuit board (PCBs) are produced. A thin layer of copper foil is laminated to one, or both sides of an FR-4 glass epoxy panel. These are commonly referred to as "copperclad laminates." FR-4 copper-clad sheets are fabricated with circuitry etched into copper layers to produce printed circuit boards. More sophisticated and complex FR-4 printed circuit boards are produced in multiple layers, aka "multilayer circuitry". SPECIFICATION In the USA, copper foil thickness is specified in units of ouncpeesr square foot (oz/ft2 ). One ounce copper foil has a weight of one oz/ft2 . This works out to a thickness of 34.1 µm (1.34 mils). Some PCB manufacturers refer to one ounce copper foil as having a thickness of 35 µm this may also be referred to as 35μ, 35 micron, or 35 mic. Two ounce would be 70 μ and half ounce would be 17.5 μ or thereabouts. 1/0 - denotes 1 ounce (28.3 gram) copper one side / with no copper on the other side. 1/1 - denotes 1 ounce copper on both sides. Similarly: H/0 or H/H - denotes Department Of Electronics And Communication Engineering 24
  • 25. Door Knock Alarm With Timer half ounce copper on one and both sides, respectively. 2/0 or 2/2 - denotes 2 ounce copper on one and both sides respectively. 4.3 PCB DESIGNING Printed circuit board design was initially a fully manual process, where an initial schematic diagram was converted into a layout of parts, then traces were routed between package terminals to provide the required interconnections. Pre-printed non- reproducing mylar grids assisted in layout, and rub-on dry transfers of common arrangements of circuit elements (pads, contact fingers, integrated circuit profiles, and so on) helped standardize the layout. The finished layout "artwork" wasn then photographically reproduced on the resist layers of the blank coated copper-clad boards. Department Of Electronics And Communication Engineering 25
  • 26. Door Knock Alarm With Timer Modern practice is less labor intensive since computers can inexpensively and accurately perform many of the layout steps. The general progression for a commercial printed circuit board design would include: • Schematic capture through an Electronic design specification tool. • Card dimensions and template are decided based on required heat sinks circuitry and case of the PCB. Determine the fixed components anh heif required. • Deciding stack layers of the PCB. 4 to 12 layers or more depending on design complexity. Ground plane and power plane are decided. Signal planes where signals are routed are in top layer as well as internal layers. • Line impedence determination using dielectric layer thickness, routing copper thickness and trace-width. Trace separation also taken into account in case of differential signals. Microstrip, stripline or dual stripline can be used to route signals. • Placement of the components. Thermal considerations and geometry are taken into account. Vias and lands are marked. • Routing the signal trace. For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes as power plane behaves as ground for AC. • Gerber file generation for manufacturing. In layout of the board, a power plane is the counterpart to the ground plane and behaves as an AC signal ground, whilst providing DC voltage for powering circuits mounted on the PCB. Where possible it is good to have a power plane for each ground plane on a board (known as a "plane pair"), as this reduces power supply impedence to the components on the board. In electronic design automation(EDA) design tools, power planes (and ground planes) are usually drawn automatically as a negative layer. Adding primitive layout shapes (for example, a donut pad) on such a layer automatically produces a negative of those primitives, placing copper wherever there is no track or via. After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly, or PCA (sometimes called a "printed circuit board assembly" PCBA). In through-hole construction, component leads are inserted in holes. In surface mount construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, Department Of Electronics And Communication Engineering 26
  • 27. Door Knock Alarm With Timer component leads are electrically and mechanically fixed to the board with a molten metal solder. There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with SMT placement machine and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for instance 0201 packages which are 0.02 in. by 0.01 in. by hand under microscope, using tweezers and a fine tip soldering iron,for small volume prototypes. Some parts may be extremely difficult to solder by hand, such as BGA packages. Often, through-hole and surface-mount construction must be combined in a single assembly because some required components are available only in surface-mount packages, while others are available only in through-hole packages. Another reason to use both methods is that through-hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface-mount techniques. After the board has been populated it may be tested in a variety of ways: • While the power is off, visual inspection,automated optical,inspection. JEDEC guidelines for PCB component placement, soldering, and inspection are commonly used to maintain quality control in this stage of PCB manufacturing. • While the power is off, analog signature analysis,power off testing • While the power is on, in circuit testing, where physical measurements (i.e. voltage, frequency) can be done. • While the power is on, functional test, just checking if the PCB does what it had been designed to do. To facilitate these tests, PCBs may be designed with extra pads to make temporary connections. Sometimes these pads must be isolated with resistors. The in-circuit test may also exercise boundary scan test features of some components. In-circuit test systems may also be used to program nonvolatile memory components on the board. In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group (JTAG)standard. The JTAG test architecture provides a means to test interconnects between integrated circuits on a board without using physical test probes. JTAGtool vendors Department Of Electronics And Communication Engineering 27
  • 28. Door Knock Alarm With Timer provide various types of stimulus and sophisticated algorithms, not only to detect the failing nets, but also to isolate the faults to specific nets, devices, and pins. When boards fail the test, technicians may desolder and replace failed components, a task known as rework. 4.4 PCB LAYOUT COMPONENT SIDE Department Of Electronics And Communication Engineering 28
  • 29. Door Knock Alarm With Timer Figure 3 4.5 PCB LAYOUT SOLDER SIDE Department Of Electronics And Communication Engineering 29
  • 30. Door Knock Alarm With Timer Figure 4 4.6 PROTCTION AND PACKAGING PCBs intended for extreme environments often have a conformal coating, which is applied by dipping or spraying after the components have been soldered. The coat prevents corrosion and leakage currents or shorting due to condensation. The earliest Department Of Electronics And Communication Engineering 30
  • 31. Door Knock Alarm With Timer conformal coats were wax; modern conformal coats are usually dips of dilute solutions of silicone rubber, polyurethane, acrylic, or epoxy. Another technique for applying a conformal coating is for plastic to be sputtered onto the PCB in a vacuum chamber. The chief disadvantage of conformal coatings is that servicing of the board is rendered extremely difficult. Many assembled PCBs are static sensitive, and therefore must be placed in antistatic bags during transport. When handling these boards, the user must be grounded(earthered). Improper handling techniques might transmit an accumulated static charge through the board, damaging or destroying components. Even bare boards are sometimes static sensitive. Traces have become so fine that it's quite possible to blow an etch off the board (or change its characteristics) with a static charge. This is especially true on non-traditional PCBs such as MCMs and microwave PCBs. CHAPTER 5 ASSEMBLY AND TESTING 5.1 BREADBOARD IMPLEMENTATION Department Of Electronics And Communication Engineering 31
  • 32. Door Knock Alarm With Timer A breadboard (protoboard) is a construction base for prototyping of electronics. The term is commonly used to refer to solderless breadboard (plugboard). Because the solderless breadboard does not require soldering, it is reusable. This makes it easy to use for creating temporary prototypes and experimenting with circuit design. Older breadboard types did not have this property. A stripboard(veroboard) and similar prototyping printed circuit board, which are used to build permanent soldered prototypes or one-offs, cannot easily be reused. A variety of electronic systems may be prototyped by using breadboards, from small analog and digital circuits to complete central processing units (CPUs). In the early days of radio, amateurs nailed bare copper wires or terminal strips to a wooden board (often literally a cutting board for bread) and soldered electronic components to them. Sometimes a paper schematic diagram was first glued to the board as a guide to placing terminals, then components and wires were installed over their symbols on the schematic. Using thumbtacks or small nails as mounting posts was also common. Breadboards have evolved over time, with the term now being used for all kinds of prototype electronic devices. For example, US Patent 3,145,483, filed in 1961 and granted in 1964, describes a wooden plate breadboard with mounted springs and other facilities. US Patent 3,496,419, filed in 1967 and granted in 1970, refers to a particular printed circuit board layout as a Printed Circuit Breadboard. Both examples refer to and describe other types of breadboards as prior art. The breadboard most commonly used today is usually made of white plastic and is a pluggable (solderless) breadboard. It was designed by Ronald J Portugal of EI Instruments Inc. in 1971. SOLDERLESS BREADBOARD TYPICAL SPECIFICATION: Department Of Electronics And Communication Engineering 32
  • 33. Door Knock Alarm With Timer A modern solderless breadboard consists of a perforated block of plastic with numerous tin plated phospher bronze or nickle silver alloy spring clips under the perforations. The clips are often called tie points or contact points. The number of tie points is often given in the specification of the breadboard. The spacing between the clips (lead pitch) is typically 0.1" (2.54 mm). Integrated circuit(ICs) in dual in package (DIPs) can be inserted to straddle the centerline of the block. Interconnecting wires and the leads of discrete components (such as capacitors, resistors, and inductor) can be inserted into the remaining free holes to complete the circuit. Where ICs are not used, discrete components and connecting wires may use any of the holes. Typically the spring clips are rated for 1 ampere at 5 volts and 0.333 amperes at 15 volts (5 watts). Figure 5 Breadboard Example breadboard drawing. Two bus strips and one terminal strip in one block. 25 consecutive terminals in a bus strip connected (indicated by gaps in the red and blue lines). Four binding posts depicted at the top. Close-up of a solderless breadboard. An IC straddling the centerline is probed with an oscilloscope probe. The solderless breadboard is mounted on a blue painted metal Department Of Electronics And Communication Engineering 33
  • 34. Door Knock Alarm With Timer sheet. Red and black binding posts are present. The black one partly obscured by the oscilloscope probe. Solderless breadboards are available from several different manufacturers, but most share a similar layout. The layout of a typical solderless breadboard is made up from two types of areas, called strips. Strips consist of interconnected electrical terminals. Terminal strips The main areas, to hold most of the electronic components. In the middle of a terminal strip of a breadboard, one typically finds a notch running in parallel to the long side. The notch is to mark the centerline of the terminal strip and provides limited airflow (cooling) to DIP ICs straddling the centerline. The clips on the right and left of the notch are each connected in a radial way; typically five clips (i.e., beneath five holes) in a row on each side of the notch are electrically connected. The five clip columns on the left of the notch are often marked as A, B, C, D, and E, while the ones on the right are marked F, G, H, I and J. When a "skinny" Dual In-line Pin package (DIP) integrated circuit (such as a typical DIP-14 or DIP-16, which have a 0.3 inch separation between the pin rows) is plugged into a breadboard, the pins of one side of the chip are supposed to go into column E while the pins of the other side go into column F on the other side of the notch. Bus strips To provide power to the electronic components. A bus strip usually contains two columns: one for ground and one for a supply voltage. However, some breadboards only provide a single-column power distributions bus strip on each long side. Typically the column intended for a supply voltage is marked in red, while the column for ground is marked in blue or black. Some manufacturers connect all terminals in a column. Others just connect groups of, for example, 25 consecutive terminals in a column. The latter design provides a circuit designer with some more control over crosstalk (inductively coupled noise) on the power supply bus. Often the groups in a bus strip are indicated by gaps in the color marking. Bus strips typically run down one or both sides of a terminal strip or between terminal strips. On large breadboards additional bus strips can often be found on the top and bottom of terminal strips. Some manufacturers provide separate bus and terminal strips. Others just provide breadboard blocks which contain both in one block. Often breadboard strips or blocks of one brand can be clipped together to make a larger breadboard. In a more robust variant, one or more breadboard strips are mounted on a sheet of metal. Typically, that backing sheet also holds a number of binding posting. These posts provide a clean way to connect an external power supply. This type of Department Of Electronics And Communication Engineering 34
  • 35. Door Knock Alarm With Timer breadboard may be slightly easier to handle. Several images in this article show such solderless breadboards. DIAGRAM A "full size" terminal breadboard strip typically consists of around 56 to 65 rows of connectors, each row containing the above mentioned two sets of connected clips (A to E and F to J). Together with bus strips on each side this makes up a typical 784 to 910 tie point solderless breadboard. "Small size" strips typically come with around 30 rows. Miniature solderless breadboards as small as 17 rows (no bus strips, 170 tie points) can be found, but these are less well suited for practical use. JUMP WIRES Jump wires for solderless breadboarding can be obtained in ready-to-use jump wire sets or can be manually manufactured. The latter can become tedious work for larger circuits. Ready-to-use jump wires come in different qualities, some even with tiny plugs attached to the wire ends. Jump wire material for ready-made or homemade wires should usually be 22 AWG (0.33 mm²) solid copper, tin-plated wire - assuming no tiny plugs are to be attached to the wire ends. The wire ends should be stripped 3/16" to 5/16" (approx. 5 mm to 8 mm). Shorter stripped wires might result in bad contact with the board's spring clips (insulation being caught in the springs). Longer stripped wires increase the likelihood of short-circuits on the board. Needle nose pliers and tweezers are helpful when inserting or removing wires, particularly on crowded boards. Differently colored wires and color coding discipline are often adhered to for consistency. However, the number of available colors is typically far fewer than the number of signal types or paths. Typically, a few wire colors are reserved for the supply voltages and ground (e.g., red, blue, black), some are reserved for main signals, and the rest are simply used where convenient. Some ready-to-use jump wire sets use the color to indicate the length of the wires, but these sets do not allow a meaningful color-coding schema. ADVANCED SOLDRERLESS BREADBOARD Department Of Electronics And Communication Engineering 35
  • 36. Door Knock Alarm With Timer Some manufacturers provide high-end versions of solderless breadboards. These are typically high-quality breadboard modules mounted on a flat casing. The casing contains additional equipment for breadboarding, such as a power supply, one or more signal generators, serial interfaces, LED or LCD modules, and logic probes. Solderless breadboard modules can also be found mounted on devices like microcontroller evaluation boards. They provide an easy way to add additional periphery circuits to the evaluation board. LIMITATIONS Due to large stray capacitance(from 2-25 pF per contact point), high inductanceof some connections and a relatively high and not very reproducible contact resistance, solderless breadboards are limited to operation at relatively low frequencies, usually less than 10 MHz, depending on the nature of the circuit. The relative high contact resistance can already be a problem for DC and very low frequency circuits. Solderless breadboards are further limited by their voltage and current ratings. Solderless breadboards usually cannot accommodate surface mount technology devices (SMD) or components with grid spacing other than 0.1" (2.54 mm). Further, they cannot accommodate components with multiple rows of connectors if these connectors don't match the dual in line layout—it is impossible to provide the correct electrical connectivity. Sometimes small PCB adapters called breakout adapters can be used to fit the component to the board. Such adapters carry one or more components and have 0.1" (2.54 mm) connectors in a single in line or dual in-line layout. Larger components are usually plugged into a socket on the adapter, while smaller components (e.g., SMD resistors) are usually soldered directly onto the adapter. The adapter is then plugged into the breadboard via the 0.1" connectors. However, the need to solder the components onto the adapter negates some of the advantage of using a solderless breadboard. Complex circuits can become unmanageable on a breadboard due to the large amount of wiring required. Alternative methods to create prototypes are point to point construction, reminiscent of the original breadboards, wirw wrap, wiring pencil, and boards like the stripboard. Complicated systems, such as modern computers comprising millions of transistors, diodes, and resistors, do not lend themselves to prototyping using breadboards, as their complex designs can be difficult to lay out and debug on a breadboard. Modern circuit designs are generally developed using a schematic capture and simulation system, and tested in software simulation before the first prototype circuits are built Department Of Electronics And Communication Engineering 36
  • 37. Door Knock Alarm With Timer on a PCB. IC designs are a more extreme version of the same process: since producing prototype silicon is costly, extensive software simulations are performed before fabricating the first prototype. 5.2 PCB IMPLEMENTATION Department Of Electronics And Communication Engineering 37
  • 38. Door Knock Alarm With Timer Figure 6 PCB with test connection pads After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly,or PCA (sometimes called a "printed circuit board assembly" PCBA). In through hole construction, component leads are inserted in holes. In mount surface construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, component leads are electrically and mechanically fixed to the board with a molten metal solder. There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with SMT placement machine and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for instance 0201 packages which are 0.02 in. by 0.01 in.by hand under a microscope, using tweezers and a fine tip soldering iron for small volume prototypes. Some parts may be extremely difficult to solder by hand, such as BGA packages. Often, through-hole and surface-mount construction must be combined in a single assembly because some required components are available only in surface-mount packages, while others are available only in through-hole packages. Another reason to use both methods is that through-hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface-mount techniques. After the board has been populated it may be tested in a variety of ways: • While the power is off virtual inspection,automated optical inspection. JEDEC guidelines for PCB component placement, soldering, and inspection are commonly used to maintain quality contral in this stage of PCB manufacturing. • While the power is off,analog signature analysis ,power off testing. • While the power is on,in circuit testing,where physical measurements (i.e. voltage, frequency) can be done. Department Of Electronics And Communication Engineering 38
  • 39. Door Knock Alarm With Timer • While the power is on,functionality test , just checking if the PCB does what it had been designed to do. To facilitate these tests, PCBs may be designed with extra pads to make temporary connections. Sometimes these pads must be isolated with resistors. The in-circuit test may also exercise boundary scan test features of some components. In-circuit test systems may also be used to program nonvolatile memory components on the board. In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group (JTAG) standard. The JTAG test architecture provides a means to test interconnects between integrated circuits on a board without using physical test probes.JTAG tool vendors provide various types of stimulus and sophisticated algorithms, not only to detect the failing nets, but also to isolate the faults to specific nets, devices, and pins. When boards fail the test, technicians may desolder and replace failed components, a task known as rework. Lamination: Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are formed by bonding together separately etched thin boards. Drilling: Holes through a PCB are typically drilled with small-diameter drill bits made of solid coated tungsten carbide. Coated tungsten carbide is recommended since many board materials are very abrasive and drilling must be high RPM and high feed to be cost effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling with high-speed-steel is simply not feasible since the drill bits will dull quickly and thus tear the copper and ruin the boards. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer- generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB. When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Department Of Electronics And Communication Engineering 39
  • 40. Door Knock Alarm With Timer Laser-drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias. It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried vias when they connect two or more internal copper layers and no outer layers. The walls of the holes, for boards with 2 or more layers, are made conductive then plated with copper to form plated-through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. Removing (etching back) the smear also reveals the interior conductors as well. Exposed conductor plating and coating PCBsare plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper. After PCBs are etched and then rinsed with water, the soldermask is applied, and then any exposed copper is coated with solder, nickel/gold, or some other anti-corrosion coating. Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface. This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium. It is important to use solder compatible with both the PCB and the parts used. An example is Ball Grid Array (BGA) using tin-lead solder balls for connections losing their balls on bare copper traces or using lead-free solder paste. Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold plating (over nickel). Edge connectors, placed along one edge of some boards, are often nickel plated then gold plated. Another coating consideration is rapid diffusion Department Of Electronics And Communication Engineering 40
  • 41. Door Knock Alarm With Timer of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating or leaving voids. Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias. Silver, zinc, and aluminum are known to grow whiskers under the influence of an electric field. Silver also grows conducting surface paths in the presence of halide and other ions, making it a poor choice for electronics use. Tin will grow "whiskers" due to tension in the plated surface. Tin-Lead or Solder plating also grows whiskers, only reduced by the percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress lowers whisker incidence. Another coating issue is tin pest, the transformation of tin to a powdery allotrope at low temperature. Solder resist: Areas that should not be soldered may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and creating short circuits. Solder resist also provides some protection from the environment. Solder resist is typically 20–30 micrometres thick. Screen printing: Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board. Screen print is also known as the silk screen, or, in one sided PCBs, the red print. Lately some digital printing solutions have been developed to substitute the traditional screen printing process. This technology allows printing variable data onto the PCB, including serialization and barcode information for traceability purposes. Testing: Unpopulated boards may be subjected to a bare-board test where each circuit connection (as defined in a netlist) is verified as correct on the finished board. For high-volume production, a bed of nails tester, a fixture or a rigid needle adapter is used to make contact with copper lands or holes on one or both sides of the board to facilitate testing. A computer will instruct the electrical test unit to apply a small voltage to each contact point on the bed-of-nails as required, and verify that such voltage appears at other appropriate contact points. A "short" on a board would be a connection where there should not be one; an "open" is between two points that should be connected but are not. For small- or medium-volume boards, flying probe and flying-grid testers use moving test heads to make contact with the Department Of Electronics And Communication Engineering 41
  • 42. Door Knock Alarm With Timer copper/silver/gold/solder lands or holes to verify the electrical connectivity of the board under test. Another method for testing is industrial CT scanning, which can generate a 3D rendering of the board along with 2D image slices and can show details such a soldered paths and connections. CHAPTER 6: Department Of Electronics And Communication Engineering 42
  • 43. Door Knock Alarm With Timer WORKING OF CIRCUIT This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor. When the door is knocked music is heard from the speakerLS1. After the set time period, the melody sound stops. The circuit works off 5-12V DC. The music time can be adjusted through VR1 by changing the R-C time constant of the timer. This is the general functioning of the door knock alarm. We have chosen the project as in day to day life it is not possible to have a watch over every nook and corner. So to have a check on every aspect of a place we plan to device a detector which is able to alert us of some change in the prevailing system. There are many application of the concept behind the project. It can not only be used for military purpose but also can be used in day to day like door knock alarm, bugler alarm safety alarm. Alternative methods to create prototypes are point to point construction, reminiscent of the original breadboards, wirw wrap, wiring pencil, and boards like the stripboard. Complicated systems, such as modern computers comprising millions of transistors, diodes, and resistors, do not lend themselves to prototyping using breadboards, as their complex designs can be difficult to lay out and debug on a breadboard. Modern circuit designs are generally developed using a schematic capture and simulation system, and tested in software simulation before the first prototype circuits are built on a PCB. IC designs are a more extreme version of the same process: since producing prototype silicon is costly, extensive software simulations are performed before fabricating the first prototype. Department Of Electronics And Communication Engineering 43
  • 44. Door Knock Alarm With Timer CHAPTER 8: EXPECTATION AND ACHIEVEMENTS The project is easy and can be implemented on both pcb and breadboard within stipulated time. Minimal idea of circuit implementation on breadboard and pcb is required for successfully carrying out the development process of the circuit. As we had an idea of pcb and breadboard implementation we could easily carry out the designing of the circuit. After the implementation of circuit on breadboard the main hurdle was carrying out the fabrication process of the circuit on printed circuit board. Initially we carried out the process of circuit layout manually. Later on we carried out the process on special software called DIPTRACE.With the help of it we could easily manage the layout diagram of the circuit. During the process we came to know about the working of new software called DIPTRACE.Later on the fabrication process on the pcb was carried out by us manually. We drew the layout on the unitched pcb and then later on itched it to remove excess copper off the pcb board. The circuit was ready for the drilling process. After the drilling process the components were placed at their respective location and soldering of the components was carried out.After the soldering process the development process was successfully carried out and the circuit was tested. The project was a success at last. Department Of Electronics And Communication Engineering 44
  • 45. Door Knock Alarm With Timer CHAPTER 8: PROJECT COST Serial Number Component description Reference Description Cost 1 IC NE555 IC 1 10/- 2 Resistor 10 K R4,R5,R8 2/- (EACH) 3 Resistor 2.2 M R1 2/- 4 Resistor 270 K R2 2/- 5 Resistor 3.3 K R3 2/- 6 Resistor 470 K R 6 2/- 7 IC’S BC 547,BG 549,UM66,NE555 15/- (EACH) 8 Resistor 1 K R 7 2/- 9 Variable Resistor 100 K VR 1 5/- 10 9 Volt Battery - 20/- 11 Piezoelectric element - 25/- 12 Piezoelectriv buzzer - 35/- Table 3 CHAPTER 10: COMPONENT DETAILS 10.1 PIEZOELECTRIC SENSORS Department Of Electronics And Communication Engineering 45
  • 46. Door Knock Alarm With Timer Figure 7 A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated) A piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration strain and force by converting them to an electrical charge. Principle of operation: Depending on how a piezoelectric material is cut, three main modes of operation can be distinguished: transverse, longitudinal, and shear. Transverse effect A force is applied along a neutral axis (y) and the charges are generated along the (x) direction, perpendicular to the line of force. The amount of charge depends on the geometrical dimensions of the respective piezoelectric element. When dimensions apply, , where is the dimension in line with the neutral axis, is in line with the charge generating axis and is the corresponding piezoelectric coefficient. Longitudinal effect The amount of charge produced is strictly proportional to the applied force and is independent of size and shape of the piezoelectric element. Using several Department Of Electronics And Communication Engineering 46
  • 47. Door Knock Alarm With Timer elements that are mechanically in series and electrically in parallel is the only way to increase the charge output. The resulting charge is , where is the piezoelectric coefficient for a charge in x-direction released by forces applied along x-direction. is the applied Force in x-direction [N] and corresponds to the number of stacked elements . Electrical properties Figure 8 Schematic symbol and electronic model of a piezoelectric sensor A piezoelectric transducer has very high DC output impedance and can be modeled as a proportional voltage and filter network.The voltage V at the source is directly proportional to the applied force, pressure, or strain.The output signal is then related to this mechanical force as if it had passed through the equivalent circuit. Figure 9 Frequency response of a piezoelectric sensor; output voltage vs applied force Department Of Electronics And Communication Engineering 47
  • 48. Door Knock Alarm With Timer A detailed model includes the effects of the sensor's mechanical construction and other non-idealities. The inductance Lm is due to the seismic mass and inertia of the sensor itself. Ce is inversely proportional to the mechanical elasticity of the sensor. C0 represents the static capacitance of the transducer, resulting from an inertial mass of infinite size Ri is the insulation leakage rsistance of the transducer element. If the sensor is connected to a load resistance, this also acts in parallel with the insulation resistance, both increasing the high-pass cutoff frequency. In the flat region, the sensor can be modeled as a voltage source in series with the sensor's capacitance or a charge source in parallel with the capacitance.For use as a sensor, the flat region of the frequency response plot is typically used, between the high-pass cutoff and the resonant peak. The load and leakage resistance need to be large enough that low frequencies of interest are not lost. A simplified equivalent circuit model can be used in this region, in which Cs represents the capacitance of the sensor surface itself, determined by the standard formula for capacitance of parallel plate.It can also be modeled as a charge source in parallel with the source capacitance, with the charge directly proportional to the applied force, as above. Sensor design Metal disks with piezo material, used in buzzers or as contact microphones. Based on piezoelectric technology various physical quantities can be measured; the most common are pressure and acceleration. For pressure sensors, a thin membrane and a massive base is used, ensuring that an applied pressure specifically loads the elements in one direction. For accelerometer,aseismometer is attached to the crystal elements. When the accelerometer experiences a motion, the invariant seismic mass loads the elements according to Newton’s second law of motion . The main difference in the working principle between these two cases is the way forces are applied to the sensing elements. In a pressure sensor a thin membrane is used to transfer the force to the elements, while in accelerometers the forces are applied by an attached seismic mass.Sensors often tend to be sensitive to more than one physical quantity. Pressure sensors show false signal when they are exposed to vibrations. Department Of Electronics And Communication Engineering 48
  • 49. Door Knock Alarm With Timer Sophisticated pressure sensors therefore use acceleration compensation elements in addition to the pressure sensing elements. By carefully matching those elements, the acceleration signal (released from the compensation element) is subtracted from the combined signal of pressure and acceleration to derive the true pressure information.Vibration sensors can also be used to harvest otherwise wasted energy from mechanical vibrations. This is accomplished by using piezoelectric materials to convert mechanical strain into usable electrical energy. 10.2 NE555 IC Figure 10 Department Of Electronics And Communication Engineering 49
  • 50. Door Knock Alarm With Timer The 555 timer IC is an Integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip flop element. Derivatives provide up to four timing circuits in one package. Introduced in 1971 by Signetics the 555 is still in widespread use, thanks to its ease of use, low price and good stability, and is now made by many companies in the original bipolar and also in low-power CMOS types. PIN DIAGRAM: Figure 11 Pin Name Purpose 1 GND Ground, low level (0 V) 2 TRIG OUT rises, and interval starts, when this input falls below 1/3 VCC. 3 OUT This output is driven to +Vcc or GND. 4 RESET A timing interval may be interrupted by driving this input to GND. 5 CTRL "Control" access to the internal voltage divider (by default, 2/3) 6 THR The interval ends when the voltage at THR is greater than at CTRL. 7 DIS Open collector output; may discharge a capacitor between intervals. 8 V+, VCC Positive supply voltage is usually between 3 and 15 V. Modes: The 555 has three operating modes: • Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bounce free switches, and touch switches, frequency divider, capacitance measurement, pulse width modulation (PWM) and so on. • Astable free running mode: the 555 can operate as an oscillator Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse and so on. Selecting a thermistor as timing resistor allows the use Department Of Electronics And Communication Engineering 50
  • 51. Door Knock Alarm With Timer of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means. • Bistable mode or Schmitt trigger the 555 can operate as a flip flop if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches. Monostable Figure 12 Schematic of a 555 in monostable mode The relationships of the trigger signal, the voltage on C and the pulse width in monostable mode In the monostable mode, the 555 timer acts as a "one-shot" pulse generator. The pulse begins when the 555 timer receives a signal at the trigger input that falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, which consists of capacitor(C) and a resistor(R). The output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C. The output pulse width of time t, which is the time it takes to charge C to 2/3 of the supply voltage, is given by where t is in seconds, R is in ohms and C is in farads. While using the timer IC in monostable mode, the main disadvantage is that the time span between the two triggering pulses must be greater than the RC time constant Specifications These specifications apply to the NE555. Other 555 timers can have different specifications depending on the grade (military, medical, etc.). Department Of Electronics And Communication Engineering 51
  • 52. Door Knock Alarm With Timer Supply voltage (VCC) 4.5 to 15 V Supply current (VCC = +5 V) 3 to 6 mA Supply current (VCC = +15 V) 10 to 15 mA Output current (maximum) 200 mA Maximum Power dissipation 600 mW Power consumption (minimum operating) 30 mW@5V, 225 mW@15V Operating Temperature 0 to 70 °C 10.3 UM66 Music Generator Circuit Department Of Electronics And Communication Engineering 52
  • 53. Door Knock Alarm With Timer Figure 13 This is the UM66 music generator circuit, of course this circuit uses UM66 as the main component to generate the signal of music / melody. UM66 operates on a supply voltage of 3V. The required 3V supply is given through a zener regulator. The transistor Q1 and Q2 is a push pull amplifier to drive the loudspeaker, so the music signal from pin 1 IC UM66 can be heard loudly. A class A amplifier can be used before push pull amplifier to minimize the noise and improve the output sound quality. UM66 is a 3 pin IC package just looks like a BC547 transistor COMPONETS R1 = 4.7K Q1=SK100 SP=8 ohm C1 = 10uF-25v Q2=SL100 D1 = 3.3v Zener IC=UM66 UM66 PIN CONFIGURATIONS: • Output : Melody Output • +Vdd : Positive Power supply • -Vss : Negative Power supply UM66T FEATURES: • Voltage rating: 1.3V to 3.3 V • 62 Note ROM Memory • Power on reset An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range Department Of Electronics And Communication Engineering 53
  • 54. Door Knock Alarm With Timer of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain. The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels. While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts 10.4 RESISTOR A resistor Is s passive two terminal electrical compnent that implements electrical component as a circuit element. The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's terminals to the intensity of current through the circuit is called resistance. This relation is represented by ohm’s law: where I is the current through the conductor in units of ampers, V is the potential difference measured across the conductor in units of volts, and R is the resistance of Department Of Electronics And Communication Engineering 54
  • 55. Door Knock Alarm With Timer the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current. Resistors are common elements of electrical network and electronic circuits and are ubiquitous in 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 hybrid and printed circuit. The electrical functionality of a resistor is specified by its resistance: common commercial resistors are manufactured over a range of more than nine orders of magnitude. When specifying that resistance in an electronic design, the required precision of the resistance may require attention to manufacturing tollerance 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 sink. In a high-voltage circuit, attention must sometimes be paid to the rated maximum working voltage of the resistor. Practical resistors have a series inductance and a small parallel capacitance; these specifications can be important in high-frequency applications. In a low noise amplifier or pre-ampilfier, noise effect 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 the position of its leads (or terminals) which is relevant in the practical manufacturing of circuits using them The ohm 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), kiloohm (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. Hence, siemens is the reciprocal of an ohm: . 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. The behavior of an ideal resistor is dictated by the relationship specified by Ohm's law: Department Of Electronics And Communication Engineering 55
  • 56. Door Knock Alarm With Timer Ohm's law states that the voltage (V) across a resistor is proportional to the current (I), where the constant of proportionality is the resistance (R). Equivalently, Ohm's law can be stated: This formulation states that the current (I) is proportional to the voltage (V) and inversely proportional to the resistance (R). This is directly used in practical computations. For example, if a 300 ohm resistor is attached across the terminals of a 12 volt battery, then a current of 12 / 300 = 0.04 amperes (or 40 milliamperes) occurs across that resistor. 10.5 CAPACITOR A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); for example, one common construction consists of metal foils separated by a thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in many common electrical devices. When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric, causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. Department Of Electronics And Communication Engineering 56
  • 57. Door Knock Alarm With Timer 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. 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, in electric power transmission systems for stabilizing voltage and power flow, and for many other purposes. A capacitor consists of two conductors separated by a non-conductive region. The non-conductive region is called the dielectric. In simpler terms, the dielectric is just an electrical insulator. Examples of dielectric media 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. 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 of electric field 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: Department Of Electronics And Communication Engineering 57
  • 58. Door Knock Alarm With Timer 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. . 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 a magnetic field rather than an electric field. Its current-voltage relation is obtained by exchanging current and voltage in the capacitor equations and replacing C with the inductance L. The simplest capacitor consists of two parallel conductive plates separated by a dielectric with permittivity ε (such as air). The model may also be used to make qualitative predictions for other device geometries. The plates are considered to extend uniformly over an area A and a charge density ±ρ = ±Q/A exists on their surface. Assuming that the width of the plates is much greater than their separation d, the electric field near the centre of the device will be uniform with the magnitude E = ρ/ε. The voltage is defined as the line integral of the electric field between the plates Solving this for C = Q/V reveals that capacitance increases with area and decreases with separation .The capacitance is therefore greatest in devices made from materials with a high permittivity, large plate area, and small distance between plates. However solving for maximum energy storage using Ud as the dielectric strength per distance and capacitor voltage at the capacitor's breakdown voltage limit V = Vbd = Udd. Department Of Electronics And Communication Engineering 58
  • 59. Door Knock Alarm With Timer We see that the maximum energy is a function of dielectric volume, permittivity, and dielectric strength per distance. So increasing the plate area while decreasing the separation between the plates while maintaining the same volume has no change on the amount of energy the capacitor can store. Care must be taken when increasing the plate separation so that the above assumption of the distance between plates being much smaller than the area of the plates is still valid for these equations to be accurate. 10.6 VARIABLE RESISTOR Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available. Variable resistors may be used as a rheostat with two connections (the wiper and just one end of the track) or as a potentiometer with all three connections in use. Department Of Electronics And Communication Engineering 59
  • 60. Door Knock Alarm With Timer Miniature versions called presets are made for setting up circuits which will not require further adjustment. Variable resistors are often called potentiometers in books and catalogues. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm. The resistance and type of track are marked on the body: 4K7 LIN means 4.7 k linear track. 1M LOG means 1 M logarithmic track. Some variable resistors are designed to be mounted directly on the circuit board, but most are for mounting through a hole drilled in the case containing the circuit with stranded wire connecting their terminals to the circuit board. Linear (LIN) and Logarithmic (LOG) tracks Linear (LIN) track means that the resistance changes at a constant rate as you move the wiper. This is the standard arrangement and you should assume this type is required if a project does not specify the type of track. Presets always have linear tracks. Logarithmic (LOG) track means that the resistance changes slowly at one end of the track and rapidly at the other end, so halfway along the track is not half the total resistance! This arrangement is used for volume (loudness) controls because the human ear has a logarithmic response to loudness so fine control (slow change) is required at low volumes and coarser control (rapid change) at high volumes. It is important to connect the ends of the track the correct way round, if you find that turning the spindle increases the volume rapidly followed by little further change you should swap the connections to the ends of the track. RHEOSTAT This is the simplest way of using a variable resistor. Two terminals are used: one connected to an end of the track, the other to the moveable wiper. Turning the spindle changes the resistance between the two terminals from zero up to the maximum resistance. Department Of Electronics And Communication Engineering 60
  • 61. Door Knock Alarm With Timer Rheostats are often used to vary current, for example to control the brightness of a lamp or the rate at which a capacitor charges. If the rheostat is mounted on a printed circuit board you may find that all three terminals are connected! However, one of them will be linked to the wiper terminal. This improves the mechanical strength of the mounting but it serves no function electrically. POTENTIOMETER Variable resistors used as potentiometers have all three terminals connected. This arrangement is normally used to vary voltage, for example to set the switching point of a circuit with a sensor, or control the volume (loudness) in an amplifier circuit. If the terminals at the ends of the track are connected across the power supply then the wiper terminal will provide a voltage which can be varied from zero up to the maximum of the supply. PRESET These are miniature versions of the standard variable resistor. They are designed to be mounted directly onto the circuit board and adjusted only when the circuit is built. For example to set the frequency of an alarm tone or the sensitivity of a light-sensitive circuit. A small screwdriver or similar tool is required to adjust presets. Department Of Electronics And Communication Engineering 61
  • 62. Door Knock Alarm With Timer Presets are much cheaper than standard variable resistors so they are sometimes used in projects where a standard variable resistor would normally be used. Multiturn presets are used where very precise adjustments must be made. The screw must be turned many times (10+) to move the slider from one end of the track to the other, giving very fine control. 10.7 LOUDSPEAKER A loudspeaker (or "speaker") is an electro acoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful. The most common form of loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a permanent magnet, but many other types exist. Where accurate reproduction of sound Department Of Electronics And Communication Engineering 62
  • 63. Door Knock Alarm With Timer is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range. Miniature loudspeakers are found in devices such as radio and TV receivers, and many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, and in public address systems. The term "loudspeaker" may refer to individual transducers (known as "drivers") or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a wide range of frequencies, most loudspeaker systems employ more than one driver, particularly for higher sound pressure level or maximum accuracy. Individual drivers are used to reproduce different frequency ranges. The drivers are named sub woofers (for very low frequencies); woofers (low frequencies); mid range speakers (middle frequencies);tweeters (high frequencies); and sometimes supertweeters, optimized for the highest audible frequencies. The terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter. Home stereos use the designation "tweeter" for the high frequency driver, while professional concert systems may designate them as "HF" or "highs". When multiple drivers are used in a system, a "filter network", called a crossover, separates the incoming signal into different frequency ranges and routes them to the appropriate driver. A loudspeaker system with n separate frequency bands is described as "n-way speakers": a two-way system will have a woofer and a tweeter; a three-way system employs a woofer, a mid-range, and a tweeter. Loudspeakers were described as "dynamic" to distinguish them from the earlier moving iron speakers, or speakers using piezoelectric or piezostatic systems as opposed to a voice call that moves through a steady magnetic field. Driver types Individual electrodynamic drivers provide optimal performance within a limited pitch range. Multiple drivers (e.g., subwoofers, woofers, mid-range drivers, and tweeters) are generally combined into a complete loudspeaker system to provide performance beyond that constraint. FULL RANGE DRIVERS A full-range driver is designed to have the widest frequency response possible. These drivers are small, typically 3 to 8 inches (7.6 to 20 cm) in diameter to permit reasonable high frequency response, and carefully designed to give low-distortion output at low frequencies, though with reduced maximum output level. Full-range (or more accurately, wide-range) drivers are most commonly heard in public address systems, in televisions (although some models are suitable for hi-fi listening), small Department Of Electronics And Communication Engineering 63
  • 64. Door Knock Alarm With Timer radios, intercoms, some computer speakers, etc. In hi-fi speaker systems, the use of wide-range drive units can avoid undesirable interactions between multiple drivers caused by non-coincident driver location or crossover network issues. Fans of wide- range driver hi-fi speaker systems claim a coherence of sound due to the single source and a resulting lack of interference, and likely also to the lack of crossover components. Detractors typically cite wide-range drivers' limited frequency response and modest output abilities (most especially at low frequencies), together with their requirement for large, elaborate, expensive enclosures—such as transmission lines, or horns—to approach optimum performance. Full-range drivers often employ an additional cone called a whizzer: a small, light cone attached to the joint between the voice coil and the primary cone. The whizzer cone extends the high-frequency response of the driver and broadens its high frequency directivity, which would otherwise be greatly narrowed due to the outer diameter cone material failing to keep up with the central voice coil at higher frequencies. The main cone in a whizzer design is manufactured so as to flex more in the outer diameter than in the center. The result is that the main cone delivers low frequencies and the whizzer cone contributes most of the higher frequencies. Since the whizzer cone is smaller than the main diaphragm, output dispersion at high frequencies is improved relative to an equivalent single larger diaphragm. Limited-range drivers, also used alone, are typically found in computers, toys, and clock radios. These drivers are less elaborate and less expensive than wide-range drivers, and they may be severely compromised to fit into very small mounting locations. In these applications, sound quality is a low priority. The human ear is remarkably tolerant of poor sound quality, and the distortion inherent in limited-range drivers may enhance their output at high frequencies, increasing clarity when listening to spoken word material. SUBWOOFER: A subwoofer is a woofer driver used only for the lowest part of the audio spectrum: typically below 200 Hz for consumer systems,[17] below 100 Hz for professional live sound,[18] and below 80 Hz in THX-approved systems.[19] Because the intended range of frequencies is limited, subwoofer system design is usually simpler in many respects than for conventional loudspeakers, often consisting of a single driver enclosed in a suitable box or enclosure. Department Of Electronics And Communication Engineering 64
  • 65. Door Knock Alarm With Timer To accurately reproduce very low bass notes without unwanted resonances (typically from cabinet panels), subwoofer systems must be solidly constructed and properly braced; good speakers are typically quite heavy. Many subwoofer systems include power amplifiers and electronic sub-filters, with additional controls relevant to low- frequency reproduction. These variants are known as "active" or "powered" subwoofers.[20] In contrast, "passive" subwoofers require external amplification. WOOFER: A woofer is a driver that reproduces low frequencies. The driver combines with the enclosure design to produce suitable low frequencies (see speaker enclosure for the design choices available). Some loudspeaker systems use a woofer for the lowest frequencies, sometimes well enough that a subwoofer is not needed. Additionally, some loudspeakers use the woofer to handle middle frequencies, eliminating the mid- range driver. This can be accomplished with the selection of a tweeter that can work low enough that, combined with a woofer that responds high enough, the two drivers add coherently in the middle frequencies. MID-RANGE DRIVER: A mid-range speaker is a loudspeaker driver that reproduces middle frequencies. Mid- range driver diaphragms can be made of paper or composite materials, and can be direct radiation drivers (rather like smaller woofers) or they can be compression drivers (rather like some tweeter designs). If the mid-range driver is a direct radiator, it can be mounted on the front baffle of a loudspeaker enclosure, or, if a compression driver, mounted at the throat of a horn for added output level and control of radiation pattern. TWEETER: A tweeter is a high-frequency driver that reproduces the highest frequencies in a speaker system. Many varieties of tweeter design exist, each with differing abilities with regard to frequency response, output fidelity, power handling, maximum output level, etc. Soft-dome tweeters are widely found in home stereo systems, and horn- loaded compression drivers are common in professional sound reinforcement. Ribbon tweeters have gained popularity in recent years, as their output power has been increased to levels useful for professional sound reinforcement, and their output pattern is wide in the horizontal plane, a pattern that has convenient applications in concert sound. CO-AXIAL DRIVER: A coaxial driver is a loudspeaker driver with two or several combined concentric drivers. Coaxial drivers have been produced by many companies, such as Altec, Tannoy, Pioneer, KEF, B&C Speakers, BMS, Cabasse and Genelec. Loudspeaker system design Department Of Electronics And Communication Engineering 65
  • 66. Door Knock Alarm With Timer Used in multi-driver speaker systems, the crossover is a subsystem that separates the input signal into different frequency ranges suited to each driver. The drivers receive power only in their usable frequency range (the range they were designed for), thereby reducing distortion in the drivers and interference between them. No crossover can be perfect (i.e., absolute block at the edges of the passband, no amplitude variation within the passband, no phase changes across the frequency band boundaries the crossover establishes, ..), so this is an idealized description. Crossovers can be passive or active. A passive crossover is an electronic circuit that uses a combination of one or more resistors, inductors, or non-polar capacitors. These parts are formed into carefully designed networks and are most often placed between the full frequency-range power amplifier and the loudspeaker drivers to divide the amplifier's signal into the necessary frequency bands before being delivered to the individual drivers. Passive crossover circuits need no external power beyond the audio signal itself, but have disadvantages: high cost, large components (inductors and capacitors), limited ability to adjust the circuit as desired due to limited choice of high power level components, etc. They also cause substantial overall signal loss and a significant reduction in damping factor between the voice coil and the crossover. An active crossover is an electronic filter circuit that divides the signal into individual frequency bands before power amplification, thus requiring at least one power amplifier for each bandpass. Passive filtering may also be used in this way before power amplification, but it is an uncommon solution, being less flexible than active filtering. Any technique that uses crossover filtering followed by amplification is commonly known as bi-amping, tri-amping, quad-amping, and so on, depending on the minimum number of amplifier channels. Some loudspeaker designs use a combination of passive and active crossover filtering, such as a passive crossover between the mid- and high-frequency drivers and an active crossover between the low-frequency driver and the combined mid- and high frequencies. Passive crossovers are commonly installed inside speaker boxes and are by far the most usual type of crossover for home and low-power use. In car audio systems, passive crossovers may be in a separate box, necessary to accommodate the size of the components used. Passive crossovers may be simple for low-order filtering, or complex to allow steep slopes such as 18 or 24 dB per octave. Passive crossovers can also be designed to compensate for undesired characteristics of driver, horn, or enclosure resonances, and can be tricky to implement, due to component interaction. Passive crossovers, like the driver units that they feed, have power handling limits, have insertion losses (10% is often claimed), and change the load seen by the amplifier. The changes are matters of concern for many in the hi-fi world. When high output levels are required, active crossovers may be preferable. Active crossovers may be simple circuits that emulate the response of a passive network, or may be more complex, allowing extensive audio adjustments. Some active crossovers, usually digital Department Of Electronics And Communication Engineering 66
  • 67. Door Knock Alarm With Timer loudspeaker management systems, may include facilities for precise alignment of phase and time between frequency bands, equalization, and dynamics (compression and limiting) control. Some hi-fi and professional loudspeaker systems now include an active crossover circuit as part of an onboard amplifier system. These speaker designs are identifiable by their need for AC power in addition to a signal cable from a pre-amplifier. This active topology may include driver protection circuits and other features of a digital loudspeaker management system. Powered speaker systems are common in computer sound (for a single listener) and, at the other end of the size spectrum, in modern concert sound systems, where their presence is significant and steadily increasing. 10.8 ZENER DIODE A conventional solid-state diode will not allow significant current if it is reverse-biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "zener knee voltage" or "zener voltage." The device was named after Clarence Zener, who Department Of Electronics And Communication Engineering 67
  • 68. Door Knock Alarm With Timer discovered this electrical property. Many diodes described as "zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used. Common applications include providing a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses. due to avalanche breakdown. Unless this current is limited by circuitry, the diode will be permanently damaged due to overheating. A zener diode exhibits almost the same properties, except the device is specially designed so as to have a greatly reduced breakdown voltage, the so-called zener voltage. By contrast with the conventional device, a reverse-biased zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the zener diode close to the zener breakdown voltage. For example, a diode with a zener breakdown voltage of 3.2 V will exhibit a voltage drop of very nearly 3.2 V across a wide range of reverse currents. The zener diode is therefore ideal for applications such as the generation of a reference voltage (e.g. for an amplifier stage), or as a voltage stabilizer for low-current applications.[1] Another mechanism that produces a similar effect is the avalanche effect as in the avalanche diode. [1] The two types of diode are in fact constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the zener effect is the predominant effect and shows a marked negative temperature coefficient. Above 5.6 volts, the avalanche effect becomes predominant and exhibits a positive temperature coefficient.[ In a 5.6 V diode, the two effects occur together and their temperature coefficients nearly cancel each other out, thus the 5.6 V diode is the component of choice in temperature-critical applications. Modern manufacturing techniques have produced devices with voltages lower than 5.6 V with negligible temperature coefficients, but as higher voltage devices are encountered, the temperature coefficient rises dramatically. A 75 V diode has 10 times the coefficient of a 12 V diode. All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of "zener diode". Construction The zener diode's operation depends on the heavy doping of its p-n junction. The depletion region formed in the diode is very thin (<0.000001 m)and the electric field is consequently very high (about 500000V/m) even for a small reverse bias voltage of about 5V, allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material. In the atomic scale, this tunneling corresponds to the transport of valence band electrons into the empty conduction band states; as a result of the reduced barrier between these bands and high electric fields that are induced due to the relatively high levels of dopings on both sides.[2] The breakdown voltage can be controlled quite Department Of Electronics And Communication Engineering 68
  • 69. Door Knock Alarm With Timer accurately in the doping process. While tolerances within 0.05% are available, the most widely used tolerances are 5% and 10%. Breakdown voltage for commonly available zener diodes can vary widely from 1.2 volts to 200 volts. In the case of a large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount of the voltage drop depends on the semiconductor material and the doping concentrations Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diode's reverse breakdown voltage. From that point on, the relatively low impedance of the diode keeps the voltage across the diode at that value. In this circuit, a typical voltage reference or regulator, an input voltage, UIN, is regulated down to a stable output voltage UOUT. The breakdown voltage of diode D is stable over a wide current range and holds UOUT relatively constant even though the input voltage may fluctuate over a fairly wide range. Because of the low impedance of the diode when operated like this, resistor R is used to limit current through the circuit. In the case of this simple reference, the current flowing in the diode is determined using Ohm's law and the known voltage drop across the resistor R. IDiode = (UIN - UOUT) / RΩ The value of R must satisfy two conditions: • R must be small enough that the current through D keeps D in reverse breakdown. The value of this current is given in the data sheet for D. For example, the common BZX79C5V6device, a 5.6 V 0.5 W zener diode, has a recommended reverse current of 5 mA. If insufficient current exists through D, then UOUT will be unregulated, and less than the nominal breakdown voltage (this differs to voltage regulator tubes where the output voltage will be higher than nominal and could rise as high as UIN). When calculating R, allowance must be made for any current through the external load, not shown in this diagram, connected across UOUT. • R must be large enough that the current through D does not destroy the device. If the current through D is ID, its breakdown voltage VB and its maximum power dissipation PMAX, then . A load may be placed across the diode in this reference circuit, and as long as the zener stays in reverse breakdown, the diode will provide a stable voltage source to the Department Of Electronics And Communication Engineering 69
  • 70. Door Knock Alarm With Timer load. Zener diodes in this configuration are often used as stable references for more advanced voltage regulator circuits. Shunt regulators are simple, but the requirements that the ballast resistor be small enough to avoid excessive voltage drop during worst-case operation (low input voltage concurrent with high load current) tends to leave a lot of current flowing in the diode much of the time, making for a fairly wasteful regulator with high quiescent power dissipation, only suitable for smaller loads. These devices are also encountered, typically in series with a base-emitter junction, in transistor stages where selective choice of a device centered around the avalanche or zener point can be used to introduce compensating temperature co-efficient balancing of the transistor PN junction. An example of this kind of use would be a DC error amplifier used in a regulated power supply circuit feedback loop system. Zener diodes are also used in surge protectors to limit transient voltage spikes. Another notable application of the zener diode is the use of noise caused by its avalanche breakdown in a random number generator that never repeats. CHAPTER 11 SHORTCOMMINGS, LIMITATIONS AND ...................... ...................REMEDIES The circuit was unable to detect mechanical force below a particular limit. Due to the fixed specifications of the components used in circuit. Special efforts have been made to enhance the sensitivity of the piezoelectric element used in the circuit. Many more implementation can be brought about to further enhance the working and performance of the circuit. By changing the capacitance and resistance used in the circuit with one with higher specification we can enhance the functionality of the Department Of Electronics And Communication Engineering 70
  • 71. Door Knock Alarm With Timer DOOR KNOCK ALARM WITH TIMER to a greater extent. We can also increase the time for which the alarm will ring in case of a door knock. But due to financial constraints we could not use component which has best specifications. Moreover due to some technical snag we were not able to fabricate the perfect combination of the capacitor, resistor and variable resistor due to which we failed to harness the efficacy of the DOOR KNOCK ALARM WITH TIMER to its optimum extent. However we tried our best with best of our knowledge to make our circuit work with the best possible condition keeping into mind all sort of technical and financial constraints. CHAPTER 12 FUTURE APPLICATION AND SCOPE OF PROJECT A)BUZZERS: Basically it will convert the pressure applied on the piezoelectric element to sound enegy. B)KNOCK ALARMS: Department Of Electronics And Communication Engineering 71
  • 72. Door Knock Alarm With Timer The concept is same as buzzer but the application criteria and characteristic are quite different. C)PRESSURE DETECTORS: Generally used in industries to detect the exact pressure of gases flowing via safety valves and tubes. D)BUGLAR ALARM: A traditional use of it can be to spot the thief at times when we are not aware of their presence around. E)MECHANICAL ENERGY TO SOUND ENERGY CONVERTORS Used in industries where the mechanical force is proportionally converted into equivalent sound energy and used for varied application. F)MECHANICAL SENSORS G)WEIGHT LIMIT DETECTORS: Can be used as a threshold weight detector where upto a limit the device allows the application of weight but above it the detector alerts the user. CHAPTER 13 CONCLUSION “NOTHING IS MORE SWEETER THAN SUCCESS” is a very well said quotation by someone.The successful execution of the project is of paramount joy.The entire journey from collection of the components for assembly of the project to the journey of implementing the circuit on the PCB was very interesting.But it was not a cake walk for us.During the course we had to face a number of hurdles but as it’s said God helps them those who help themselves.At last i would like to say that it was a great time for our team during the entire process of project completion plan. Department Of Electronics And Communication Engineering 72
  • 73. Door Knock Alarm With Timer CHAPTER 14 REFERENCES AND BIBLIOGRAPHY 1. www.google.co.in 2. www.en.wikipedia.org 3. www.en.wikipedia.org/wiki/Resistor 4. www.en.wikipedia.org/wiki/Capacitor Department Of Electronics And Communication Engineering 73
  • 74. Door Knock Alarm With Timer 5. www.datasheetcatalog.com/datasheets_pdf/A/T/8/9/AT89S52.shtml 6. www.en.wikipedia.org/wiki/Potentiometer 7. www.en.wikipedia.org/wiki/Diode 8. www.electronicsforu.com/electronicsforu/lab/ TECHNICAL INFORMATION FROM FOLLOWING BOOKS 1) Electronic devices and circuit theory By Robert.L.Boylestad, 4th edition, 2004 2) Microelectronic circuits .By Adel.S. Sedra 5th edition,2008 3) Electronics by R.S Sedha. 2nd edition,2002 Department Of Electronics And Communication Engineering 74
  • 75. Door Knock Alarm With Timer Department Of Electronics And Communication Engineering 75