Introduction: Saving Water Using LEDs

This Instructable describes about conservation of water which get wasted due to overflowing of tanks using few LEDs and Transistor.Hope you would enjoy making it.

Step 1: Problem:

I live in India where most of the people have overhead tanks at their houses which they fill with the help of submersible pumps.Most of the time they are on the rooftop of second floor or even higher so monitoring the water level during filling of the tank is quite difficult as one have to go all up to the top floor to monitor the water level.As a result many times thousand of gallons of water is wasted everyday throughout my locality because of overflowing of these tanks. So having some knowledge of Electronics I have decided to design some very cheap and effective Solution to monitor the water level.

Step 2: Solution:

So I decided to make a water level indicator by just using some very basics electronic items like wires,transistors,resistor,general purpose board,buzzers and few different color led.Yes that's all you need for the tasks.These all items are quite cheap and it has to be as people in India are quite cost conscious!

Step 3: Tools and Supplies


  • Soldering Iron
  • Screw Driver


  • 3 LED of different Colour
  • 3 Transistor(BC547)
  • 6 Resistor
  • 1 General purpose board
  • 1 buzzer
  • 1 9V Battery
  • Few meters wire
  • Soldering wire
  • 1 9V battery connector
  • 1 Switch

The cost of all the supplies is only about 5$.

Step 4: Details of the Component

    1. LED(Light Emitting Diode):- Three LED of different color are required.I have used LED of RED,BLUE and Green color.While connecting LED care should be taken that the longer leg of the LED should be connected to the positive terminal(Anode) and the shorter leg should be connected to the negative leg(Cathode).

    2. Resistor:-There are 3 220 Ohm Resistor which are used in this project.See the color code in the above figure.

    3. Transistor:-3 BC547 transistor are required for this project. BC547 is a NPN transistor.Make sure you connect the transistor according to its pin configuration as shown in the figure.

    Look here for the data sheet of BC 547 transistor.

    Step 5: Details of Component(Contd)

    4. Battery:- One 9V battery is used to provide power to this project.

    5.Battery Connector:- One battery connector is used to connect the battery to the project.

    6.Piezoelectric Buzzer:-One buzzer is used to give indication of full tank using sound.It is optional.

    7. Switch:-One switch is required to turn off the circuit when not in use.

    8. GPB:- One General Purpose Board(GPB) is required to solder all the component on it.

    Step 6: Circuit

    The circuit connection of the water level sensor is as shown in the figure.As you can see in the circuit a resistor and a led is connected in series with the emitter of the transistor.A wire from the base of the transistor is kept at different water level in the tank.

    Step 7: Breadboard Implementation

    As shown in the figure the circuit of the water level sensor is mounted on the breadboard.Take care of the polarity of the component (which terminal is positive and which terminal is negative) when making the connections among various component.

    Step 8: Working of the Project

    As seen in the figure the wire from the bases of the transistor is kept at different height in the tank.Also one terminal from the positive end of the battery is kept at the bottom of the tank.When water reaches the level of the wire connected to the base of the transistor the led glows and you can get idea of the water level.

    In my case following is the output:-

    1.Water at the bottom(LOW LEVEL) :-Only RED LED glows.

    2.Water filled up to the middle(MIDDLE LEVEL):- RED and BLUE LED glows

    3.Tank is fully filled(HIGH LEVEL):- RED,BLUE and GREEN LED glows and also the buzzer rings.

    The transistor act as a switch in this case.When water reaches up to the wire connected to the base of the transistor a base current flows due to its connection with the positive terminal located at the bottom of the tank(and because tap water is conductive) and as a result transistor acts as a closed switch and the current flows through its emitter and the LED glows.

    Step 9: Practical Implementation of the Project

    The Picture shows some of the Pics of the implementation of this project at my house.I have been successfully using this project since last few week without any problem and thus SAVING WATER from being wasted.

    Some points you should consider while making the project:-

    • First make the project on the breadboard before actually soldering on the GPB.
    • Connect the battery only when entire circuit is ready.
    • Make sure that the two terminal of the battery do not touch each other otherwise the battery would drain and may reach a very high temperature.
    • You can monitor more number of level instead of three that I have used by just using few more LED,Transistor,resistor and wire
    • Make sure the wire does not slip inside the tank thereby indicating false reading.Therefore attach the wire firmly at the top of the tank.

    Some points you should keep in mind while using the project:

    • Switch off the circuit when the water pump is not running or when you do not want to monitor as it will save the battery power.

    I have been thinking about this project since a very long time and now I have done it!!

    Hope you love it and will certainly make it to preserve water.

    LED Contest

    Participated in the
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    Lamps and Lighting Contest 2016

    Participated in the
    Lamps and Lighting Contest 2016