AUTOMATIC WATER TAP SYSTEM INTRODUCTIONAutomatic water tap controller is an Infrared based system that detects any interruption of the IR rays by our hands or utensils and water automatically starts flowing out of the tap.

The circuit mainly comprises Transmitter & Receiver which are built with the 555 Timer. Both require 5 volts D.C. Supply. The IR rays continuously emitted by the transmitter fall on the receiver. We have used an IR sensor TSOP1738 and an infra-red LED. A relay is used in the circuit along with the free-wheeling diode to drive the solenoid. Solenoid is used to lift up the valve fitted in the pipe to let the water flow out of the tap. The circuit is simple, economical and finds wide application in daily life.

The aim of this project is to design an Automatic Water Tap Controller using 555 timer, IR LED and infrared sensor. The overall module should be miniature to allow portability and should be economical.

CIRCUIT COMPONENTS 555 Timer ICThe 555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a capacitor. 555 is very commonly used for generating time delays and pulses. Infrared LEDAn IR LED, also known as IR transmitter, is a special purpose LED that transmits infrared rays in the range of 760 nm wavelength. Such LEDs are usually made of gallium arsenide or aluminum gallium arsenide. They, along with IR receivers, are commonly used as sensors. Transistor BC548BC548 is general purpose silicon, NPN, bipolar junction transistor. It is used for amplification and switching purposes. The current gain may vary between 110 and 800. The maximum DC current gain is 800. BC548 is used in common emitter configuration for amplifiers. ResistorResistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits. CapacitorCapacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycle of charging and discharging in AC circuits where the voltage and current across it depends on the RC time constant. For this reason, capacitors are used for smoothing power supply variations. WORKINGThe circuit comprises a transmitter and a receiver, both are built around 555 timer. The IR rays continuously emitted by the transmitter fall on the receiver. As soon as an obstacle comes in between the receiver and the transmitter, interrupting the IR rays, the output of the IR rays sensor goes momentarily low to trigger the timer circuit in the receiver and water comes out through the tap.

TRANSMITTER

It is built around timer IC 555 which is used as an astable multivibrator to generate around 38 kHz of frequency .The timer output is fed to transistor T 1 which drives the IR LED (LED 1).Its transmission wavelength of 900- 1100 nm lies in the peak receptivity range of TSOP1738 receiver module.

RECEIVER

It comprises the sensor module, monostable timer and relay driver circuit. The sensor module TSOP1738 is sensitive to IR radiation modulated at 38 kHz. Its normally high output goes momentarily low when any IR radiation detected or interrupted, it triggers the timer IC 555 (IC2). The output of timer goes high for 11 seconds and relay drives the solenoid .During this time period, energization of solenoid lifts up the valve fitted in the pipe to let water flow out of the tap.

The relay driver circuit consists of resistor R8, transistor BC548 (T2) and free-wheeling diode D1. Diode protects the relay from damage by high voltages generated by the back emf when the relay is de- energized. When we put our hands between IR LED and IR sensor, the relay energizes to make the solenoid open up the valve and water flows out of the tap.

APPLICATIONS

This circuit finds wide applications in our daily life. This circuit is not only used for automatically controlling the tap of wash-basin but it can be used for controlling the dryers ,blowers and door opening and closing by replacing the solenoid.

The key learning of the project is to understand the basic working of the IC 555 timer, in monostable and astable mode and IR TSOP1738 sensor. REFERENCES http://www.technologystudent.com/elec1/5554.htm http://www.allaboutcircuits.com/vol_6/chpt_8/4.html http://www.doctronics.co.uk/555.htm http://www.answers.com/topic/infrared-receiver http://en.wikipedia.org/wiki/Solenoid_valve https://www.futureelectronics.com/en/optoelectronics/infraredreceivers.aspx