Project Report On
“TRANSISTOR BASED TOUCH ON OFF SWITCH” Submitted as a part of course curriculum for
Diploma
In Electronics & Communication Engineering
Under the guidance of
Submitted By:
Jaskaran singh ECE (4th sem) 6116/2k9
Dept. of Electronics and Communication Engineering Chandigarh College of Engg. and Technology
Sector-26, Chandigarh. UT – 160026, (India)
Certificate Certified that this project entitled “Transistor Based Touch ON OFF Switch” submitted by JASKARAN SINGH (6116/2k9) student of Electronics & Communication Engineering Department, Chandigarh College OF Engineering and Technology, sector26, Chandigarh , as a part of course curriculum for Diploma (Electronics & Communication Engineering), is a record of students own study carried under our supervision & guidance.
This report has not been submitted to any other institute for the award of any diploma.
Ms. Sunita Mehta (H.O.D) Ms. Sarabjeet Kaur (Lecturer) Ms. Bharti (Lecturer)
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Acknowledgement Technology is like an ocean & engineer is like a pearl driver in search of a treasure beneath the sea. Today technology is very vast and there is no end of technical studies. I am submitting my report on the project entitled “Transistor Based Touch ON OFF Switch”.
I am very thankful to all the persons who with their views and participation helped me to carry this project and report successfully. It is with pleasure that I find myself penning down these lines to express my sincere thanks to various people to help me along the way in completing the project.
With deep sense of gratitude, I express my sincere thanks to Ms. Sunita Mehta (H.O.D), Ms. Sarabjeet kaur and Ms. Bharti for their precious guidance and for taking extra pain to seek through my problems. They were always a pillar of strength to infuse encouragement during our disheartening failures.
I thank all my friends who helped me readily and most gladly as when requires.
Jaskaran singh
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Contents
I. Certificate II. Acknowledgement III. Contents 1.
Introduction
2.
Component List
3.
Circuit diagram
4.
Circuit Diagram Description
5.
Component Description
6.
PCB Designing and Soldering
7.
Conclusion
8.
Application and cost
9.
Reference
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CHAPTER 1 Introduction
To understand the concept of computer hardware the knowledge of electronics is must. The project that I have chosen for understanding the concept of electronics is a Transistor Based Touch ON-OFF Switch. Apart from being exposed towards the working of the various parts of the electronics systems, the project has the significance that it can be used in places where regular switches would not last, such as wet or very dusty areas.
A touch switch is a switch that is turned on and off by touching a plate, instead of flicking a lever like a regular switch. Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches.
The Transistor Based Touch ON-OFF Switch works on the dc voltage. The main part of the Touch ON-OFF Switch is the TOUCH PLATE. A TOUCH PLATE is classified as a high impedance device (or high impedance circuit) as the effect of a finger will be detected by the circuit connected to the plate.
There are a number of different types of TOUCH PLATES and different effects can be created by the circuit:-
1) Touch a set of pads and the project turns on. When the finger is removed, the circuit turns off. The finger can touch the pads for any length of time.
2) Touch a set of pads fairly quickly and the project turns on. Touch the pads again for a short period of time and the circuit turns off. This is called the "Flip-Flop" effect. If the finger is kept on the pads, the circuit will turn on-off-on-off at a rate of about once per second.
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3) Touch one set of pads to turn the circuit on and another set of pads to turn the circuit off.
In this, there are 2 touch pads. One is used to turn on the switch and the other one is used to turn off the switch.
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CHAPTER 2 Component List Components Required & Their Values:-
S.NO.
1.
Parts list
Value
Capacitor : C1
2.
1000µF 16V
Transistor: T1,T2,T3,T4,T5
3.
BC557
Diode: D1,D2
4.
5.
IN4007
Resistance: R1,R3,R5,R6,R9
10 K
R2,R4,R7,R8
220K
Transformer: TXR
6.
Relay:
7.
AC Main Lead
8.
Neon
6-0-6V 500MA
12v 200E
Lamp
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CHAPTER 3 Circuit diagram
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CHAPTER 4 Circuit Diagram Description
A touch switch is a switch that is turned on and off by touching a plate, instead of flicking a lever like a regular switch. Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches.
The main part of the Touch ON-OFF Switch is the TOUCH PLATE. A TOUCH PLATE is classified as a high impedance device (or high impedance circuit) as the effect of a finger will be detected by the circuit connected to the plate.
The schematic diagram of touch switch circuit is shown. Separate ON and OFF switch improves the ergonomics for safety, since the touching off button when the state is off doesn’t make the system acts in the opposite way: turning ON the system. This accident usually happens when we make wrong assumption of the current state about ON or OFF of the system while the function of the switch depends on its previous state.
As shown in the circuit diagram it consists of 5 transistors (BC557), 2 touch plates (one to turn the circuit ON and other to turn the circuit OFF), 2 diodes (IN4007), capacitor (1000µf, 16V), transformer, relay, resistors and a neon lamp.
The ON plate is connected to the base of the transistor (T2)and OFF plate is connected to the base of the transistor (T1). The collector of the transistor T1 and T2 are connected to each other. The resistors work as the biasing circuit for the transistors and make the emitter terminals grounded.
The AC supply (220V) is given at the primary of the transformer. And one terminal of the neon lamp is directly connected to the AC supply and other terminal is grounded through the relay terminal2. AC supply is also given to the terminal4 of the
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relay. The terminal3 of the relay is left open. The secondary of the transformer is connected to the circuit through the capacitor C1 and diode D1.diode D2 is connected between the terminal1 and terminal 5 of the relay.
The circuit turned on when the base of the transistor T2 receives a very small current detected from the skin resistance of a finger. To keep the circuit remains ON, the neon lamp is connected to the AC supply so that it can take the place of the finger. When a finger touches the OFF plate, the first transistor T1 will be activated and the voltage will be decreased and the circuit will turn OFF.
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CHAPTER 5 Component Description
Transformer: A Transformer is a device used for transferring power from one circuit to another circuit without change in frequency. It can raise or lower the voltage with corresponding increase or decrease in the current. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
For testing:
1. Set the multimeter range to 1Kohm. 2. There should be no continuity between primary and secondary windings.
Diode: The diode is unidirectional semiconductor device which only conducts when it is forward biased. It allows a electric current to flow in one direction, but blocks the flow of current in opposite direction. Diodes are used for rectification.
For testing:
1. Set the multimeter on diode range. 2.
In forward biased it will show the continuity and in reverse it will not show the
continuity.
Capacitor: A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric,
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causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. The capacitor used in the circuit is an electrolytic capacitor.
For testing:
1. Fix the given capacitor on the breadboard. 2. Set the meter in the highest ohm’s range. 3. Connect the ohmmeter leads across the capacitor. 4.
For a good capacitor the meter will show low resistance initially and then to higher
resistance. 5. Infinite/zero resistance in the meter shows open/short of the capacitor.
Printed circuit board: The printed circuit board is a sheet of insulating, material (Bakelite) on which a copper clad coating is done. It is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate.
Resistor: A resistor is a passive component. It introduces resistance i.e. opposition to the flow of current in a circuit. It is a two terminal component that resists an Electric current by producing a voltage drop between its terminals in accordance with “Ohm’s law”. Resistors may be connected either way round. They are not damaged by heat when soldering. The unit of resistance is ohms. Resistor
values
are
normally
shown
Each color represents a number as shown in the table. Most resistors have 4 bands: •
The first band gives the first digit.
•
The second band gives the second digit.
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using
colored
bands.
•
The third band indicates the number of zeros.
•
The fourth band is used to shows the tolerance (precision) of the resistor, this may be ignored for almost all circuits.
For testing:
1. Fix the given resistor on the breadboard. 2.
Set the multimeter in ohmmeter range and connect the ohmmeter leads across the
resistor. 3. open/short of the resistor is shown by infinite/zero resistance in the meter.
Relay: It is an electrically operated switch. The current flowing through the coil of relay
creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off.
Transistor: A transistor is a semiconductor device used to amplify and switch electronic
signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. It can be used with other components to make an amplifier or switching circuit. There are two types of transistor NPN and PNP. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon. The leads are labelled base (B), collector (C) and emitter (E).
Lamp: Lamp emits light when an electric current passes through them. Lamps have a
thin wire filament which becomes very hot and glows brightly when current passes through it.
CHAPTER 6 13
PCB Designing and Soldering PCB designing of the system Printed circuit board (PCB) is an integral part of any electronic product, and its design plays an important role in the design of the product. Design and quality are an integral part of a product. The instrument should have an appealing color for good aesthetic view and surface finish.
Basic Designing Phases of Electronic Equipment Designing is the heart of any electronic equipment. Before designing electronic equipment, the detailed specifications of the product must be known. The designed instrument should be handy, portable, light in weight, small in size and extremely easy to use by the people of any age. The following three aspects/phases are used in designing of a product: •
Aesthetic Design Phase: Aesthetic is the outlook of the equipment i.e. first
impression of quality. •
Engineering Design Phase: The translation of the plan prepared during the
designing process into a production prototype and evaluating it as per the target specifications is the engineering design. The electronic module, mechanical parts and sub assemblies are fabricated as per drawings and prototype is assembled from the modules. The following tasks performed during this phase are:
Circuit design, bread boarding and testing of the electronic functional modules, which eventually were converted into individual PCB’s.
Design of PCB layouts and the preparation of fabrication drawings.
Fabrication process used in PCB fabrication.
Design of power supply for the equipment and for different modules used in the terminal.
Design of software (algorithm, flowcharts, simulation and coding).
Functional and result testing of module.
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•
Ergonomic Design Phase : It is the functional design of the equipment e.g.
interface design i.e. display and controls, safety, handling etc. that helps in making the system user friendly.
Soldering Soldering is an alloying process b\w two meters or soldering as a method of making reliable joints is one of the widely practiced production techniques.
Soldering equipments If the number of PCBs and components to be soldered are less, hands soldering process is used. Following are the tools used: •
Soldering Iron
•
Solder
•
Soldering Fluxes
•
Tools
Soldering iron: It supplies sufficient heat transformer when the iron tip is applied to
connection to be soldered. Soldering irons are of different Temperature ranges. Soldering irons are divided in two groups:
Soldering iron or pencils
Soldering guns
Solder: It is the oldest and most widely used alloy. It is a genes name representing a host
of alloys of raw melting materials like tin, lead, cadmium, bismuth, sodium silver and many more. Other solders:
Tin lead antimony
Tin lead silver
Tin silver
Tin zinc
Fluxes: During soldering operations an auxiliary medium is most commonly used to
increase the flow properties of molten solder to improve the degree of melting and remove the oxide film from the base metal which prevents the film from reforming so
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that the liquid solder can display the flux and react with the base metal to form a bond characteristics of flux.
Soldering techniques Mass soldering incorporates these techniques by which large no of joints are made simultaneously using a solder bath, bather as the source of the heat as well as of refill material or metal. Mass soldering is classified as follows: •
Drag soldering
•
Dip soldering
•
Wave soldering
•
Ultrasonic soldering
Precautions •
The tip of the soldering iron is very hot therefore proper care should be taken when handling the iron.
•
The direction of the notch of the base IC should be taken care of.
•
Make sure that no two isolated paths should be short circuited during soldering.
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CHAPTER 7 Conclusion •
It is very simple.
•
It is cheap.
•
It takes only 100ns to operate the circuit.
•
It is used in various applications due to its quicker response.
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CHAPTER 8 Application and Cost
This project of mine, being compact, can be installed anywhere.
One can use it in a place where regular switches would not last, such as wet or very dusty areas. Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches.
The cost of this project is Rs.250/-
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References •
www.senix.com
•
www.google.com
•
www.electronics4u.com
•
Electronics makers
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