TOUCH CONTROLLED LOAD SWITCH Project Title TOUCH CONTROLLED LOAD SWITCH Under the Guidance of Submitted by

ABSTRACT In this project a switch is implemented that is turned on and auto off by touching a wire contact, instead of a regular switch. Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches. Touch switches can be used in places where regular switches would not last, such as wet or very dusty areas. This is achieved by operating a 555 Timer in monostable mode while its trigger point is connected to a touch pad. Human body induced mains supply develops a voltage on the touch pad to trigger the monostable of 555 Timer, the output of which drives a relay for time period as decided by the time constant formed by R and C of the monostable.

PROJECT BLOCK DIAGRAM

555 TIMER BATTERY LED 1N4007 BC547 RELAY LAMP LOAD RESISTOR CAPACITOR HARDWARE REQUIREMENTS POWER SUPPLY BLOCK 555 TIMER BATTERY LED 1N4007 BC547 RELAY LAMP LOAD RESISTOR CAPACITOR

POWER SUPPLY Bridge rectifier 5v Regulator 230 V AC 50 Hz 5V DC Filter(470µf) 12V step down transformer

555 TIMER The 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and multivibrator applications The 555 has three operating modes: Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) etc. 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 position modulation, etc. 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, etc.

Internal architecture of 555 timer 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 VCC). 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.

RELAY IT IS A ELECTRO MAGNETIC SWITCH USED TO CONTROL THE ELECTRICAL DEVICES COPPER CORE MAGNETIC FLUX PLAYS MAIN ROLE HERE

The relay's switch connections are usually labeled COM, NC and NO: COM = Common, always connect to this; it is the moving part of the itch. NC = Normally Closed, COM is connected to this when the relay coil is off. NO = Normally Open, COM is connected to this when the relay coil is on

BC547 (NPN –Transistor) The BC547 transistor is an NPN Epitaxial Silicon Transistor. It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors. The ratio of two currents (Ic/Ib) is called the DC Current Gain of the device and is given the symbol of hfe or nowadays Beta, (β).

The current gain from the emitter to the collector terminal, Ic/Ie, is called Alpha, (α), and is a function of the transistor itself

Lamp Load There are many types of lamp loads such as tungsten filament, fluorescent, mercury-vapour, and other exotic gas lamps. The loads we normally concern ourselves with are tungsten filament. Tungsten filament lamps, when first turned on, will draw an inrush current of 10-15 times of the steady-state current After the lamp filament has heated up, the current will drop to its normal level. Most tungsten filament lamp load ratings are 20% of a resistive load

WORKING OF PROJECT In this project we are using 555 timer in mono stable mode. In normal conditions 2pin of 555 timer is high. So the O/P pin 3 is low. When ever we touched the plate then the 2 pin becomes low. So the O/P pin 3 is high which gives logic high at the base of transistorQ1 so it starts conducting so that relay will ON up to particular duration. The ON time is 1.1RC.D3 LED is used to indicate power supply. D1 LED will ON when ever relay is ON or to indicate that the load is ON.

Software Requirements Keil an ARM Company makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, integrated environments, evaluation boards, and emulators for ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families. Compilers are programs used to convert a High Level Language to object code. Desktop compilers produce an output object code for the underlying microprocessor, but not for other microprocessors.

i.e the programs written in one of the HLL like ‘C’ will compile the code to run on the system for a particular processor like x86 (underlying microprocessor in the computer). For example compilers for Dos platform is different from the Compilers for Unix platform  So if one wants to define a compiler then compiler is a program that translates source code into object code.

BIBILOGRAPHY www.electronicsforu.com www.alldatasheets.com www.scribd.com www.extremecircuit.com

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