Description

Touch Free Timer Switch

Introduction

            This type of proximity based touch switches used in public places for the hygiene purpose. This switches are used in public drinking foundations and public washrooms. These devices uses infrared radiations to detect the person or object infront of it. This circuit’s used in public places by receiving the reflected infrared radiations which is present infront of the device. This touch free timer circuits works by simply moving the hand infront of the circuits.

Working

• When a short IR burst is received by IRX1 (as you wave your hand in front of the switch), the demodulated pulses are fed to the trigger input (pin 2) of the second LMC555 (IC2).
• This, in turn, triggers the monostable wired around IC2 and its output pin 3 goes high for a period determined by the 2.2-mega-ohm potentiometer and capacitor C5.
• This turns off the standby indicator (LED1) and transistor T1 conducts to drive the 5V relay (RL1). LED1 enables you to locate the switch in the dark.
• AC mains supply to the load to be switched-on is routed through the pole and normally-opened contacts of RL1 as shown in the diagram. The circuit works off regulated 5V DC.

Applications

• Automatic fluid dispensers
• Public water foundation
• Public washrooms