1. By: Asad Ahmed Khan Muhammad Ali

2. Introduction: This circuit is designed to determine the water level especially in a water tank.  As the water level increases from the base of the tank the number of glowing LEDS increases subsequently.  Amount of water present in a water tank can be easily measured.

3. Bridge Rectifier AC  DC Step-Down Transformer 220 V AC  12 V AC N F Transistor A1015

4. Components List: Circuit elements used are as follow:  A1015 Transistor.  470 ohm Resistor.  1 k ohm Resistor.  Sound Buzzer.  Bridge Rectifier.  Transformer.  LEDs.  220 V AC Source.

5. About Circuit Elements: Transistor A1015: This is key element in circuit. It is used as switch. The important property of this Transistor Is, this transistor give out put from collector only when its base voltage is at some –ve potential than its emitter. 1 k ohm Resistors: As described before, Transistor A 1015 can only be turned on if base is at low voltage than emitter. In order to set the voltage bellow 12 V we put 1 k ohm resistor, setting base to some low voltage.

6. Bridge Rectifier: Bridge Rectifier is actually a bridge of Diodes 1N4007.This is used to convert 12 V AC (coming from Transformer) to 12 V DC which is supplied to circuit. LEDs: Light Emitting Diodes, Placed in circuit, to show level of water in Tank. These diodes are operated at 1.5 V 470 ohm Resistors: 470 ohm Resistors are installed in the circuit because LED is Operated at 1.5 V, and we are having 4.7 V there, so in order to decrease the voltage across LED we placed 470 ohm resistors

7. Working of Circuit: When any wire is dipped in water that wire will be connected to wire N through water, establishing a negative voltage across the base of transistor. Current begins to flow from collector. In this way, LED glows. After successive connections of wires with N, respective LEDs will glow, and when wire F will be connected to N, then there will be sound alarming you that water has attained maximum level and after this water will flow over.

8. N F

9. Applications of Circuit: This Circuit has a number of practical uses in daily life.  Now no need to go on the roof to check the water level.  Can be used to measure underground storage of water.  Water level Indicator works to maintain a constant water level. (Used in different Plants and Industries)  Alarm starts ringing as soon as tank becomes full. It helps to check overflow and wastage of water by warning the person when the tank is about to brim.  It can also be used to calculate incoming and out going water in large reservoirs.  It is used to predict the arrival of floods.