TOUCH SWITCH

Part 1 of project

For complete project go to http://electronicsforengineers.blogspot.com/search/label/TOUCH%20SWITCH%20PROJECT

INTRODUCTION

Touch switch is a device which produces high output(led glow) when its plate is touched. It is basically used for security systems. The actual concept behind touching the plate of touch alarm is its grounding. It glows led only for the time for which it is in contact with the ground.

The main component used in touch switch is 555 timer. The 555 timer has high output for certain time interval which depends upon the triggering of device. This output is used to glow the led.

PRINCIPLE

The touch switch is based on the principle of triggering of 555 timer by a negative pulse which is given by touching its touch-pad. Once triggering is done, then oscillations are produced and circuit starts working. When it stops working after some specific time interval, it will not start again by itself, until a new trigger is given.

COMPONENTS USED

a) Resistance :

Here two resistances are used of 100 k and 4.7 M Ω as shown in circuit diagram. The function of the 4.7 M Ω resistance is to control the sensitivity of the touch switch.

b) Voltage Source :

The 9 V DC battery is used to provide electrical energy to the circuit.

c) 555 Timer :

The 555 timer is the main component used. It is a pulse-generating circuit consisting of 8 pins. Pin 1 and pin 2 act as a touch plate of the touch alarm and the battery is connected to the 8^th pin.

d) Led: Led glows when plate is touched.

continued to TOUCH SWITCH 2