Step 2: The Circuit

It has numerous transistors acting as a switch and the switch gets activated when the sensors tell them to. 

The heart of the circuit is the transistors BC 547. There are total 7 transistors in the circuit and each one will be sensing the level of water present in the overhead water tank. There is one extra power LED without a transistor and that is because this Red LED will be telling us two things. Firstly when you power the unit it will be monitoring the power present in the unit and secondly it is also the indicator telling you that there is no water at all present in the tank. As because the water level is below the No. 1 (as shown in the circuit) sensor, no LED's will be lighting up, but only for the one Red LED. Therefore when you switch on your unit if you see only one Red LED lighting up then you know that the is no water present in the tank and therefore you should make you water pump on.
Then as shown in the figure i have given all the LED's in various color. Starting from the beginning is 
  1. Red LED (Indicating no water in the tank as none of the sensors are getting contact with the water)
  2. Red LED ( Level 1, indication very low water in the tank )
  3. Yellow LED (Level 2, indication of low water)
  4. Yellow LED (Level 3, indication of 1/4 of water in the tank)
  5. Green LED (Level 4, indication of half of water in the tank)
  6. Green LED (Level 5, indication of more than half of water)
  7. Green LED (Level 6, indication of nearing filling up the tank)
  8. Blue LED (Level 7, Full indication of tank and buzzer comes on)
Now as the water starts to rise up the sensors starts to get in contact with the water and the transistors are activated and there is a flow of current in the transistors making the LED's light up. Here in between the transistor and the LED there is a current limiting resistor 470 ohms, the job of the resistor is to checks that the LED does not get over voltage and destroy the LED. The transistor is biased by a 470K resistor with the ground and the sensing part is taken from the collector with a 33 ohms resistor going directly to the tank. As i have shown in the diagram the signals are drawn in the Green color. There by you can follow the LED's as they light up from Red to Yellow and then Green and finally to Blue making a sound.  

The Buzzer Part
Here you can add any of the normal buzzers that are readily available in the market and if  it is not then you can make yourself with a simple 555 IC. I am giving a small circuit diagram, it is really simple to make and there are minimum parts. It is a simple audio oscillator. I have also provide a circuit diagram here but if you are able to manage a buzzer then no need to assemble this circuit.

The Power Supply
This section contains a transformer converting the mains voltage 220V bring down to 9V. There is a bridge rectifier containing 4 diodes and making the Alternating current to Direct Current. After the filtering the voltage is then directly fed to the voltage regulator (7805) with a filtering capacitor. From the regulator IC the output voltage is then again filtered with a capacitor and is fed to the circuit. This comprises the power supply of the device.

This completes the electronic part of the project and now i will be going to the sensor part, which is also made easily.
<p>the power supply is 9v or 5v ?</p>
<p>You can use either 5V or 9V...:)</p>
What if i use a12v adapter
<p>can any one please tall me the exact materials i am going to use and how many of them because im gonna try to do this project </p><p>thanks :)</p>
<p>what if we don't use Power Regulater 7805????</p>
<p>thanks raikut for this project.. ive made every exactly you have written but the sensors in overhead tank gets corroded in just two weeks . after that the buzzer sound gets low and some LED's start flickering. pls telll m some solution on this.</p>
Hm I also have same issue , what I do is cleanup wires every month :(
<p>Hi,</p><p>Have you tried anti-corrosive(AC) materials like AC paint or AC powder which are available in market. I am also planning to make one for my home.</p>
<p>This can cured by using a float that is sealed and designed to be in water. It acts as a switch. I have two 2500 gallon water tanks with 5 floats attached to it. No problems and works flawlessly. Electronics submerged in water will only last for so long due to electrolysis, the same phenomenon on outboard motors which is why they have zinc plate that is softer than the metal for the motor. So it eats away slowly at that instead. Email if you want help.</p>
<p>Hello Jason,<br>Can you provide the details on how to construct the floats?<br><br>Will be much obliged :)</p>
<p>can you pls send pic of tht switch?? or its web link.</p>
<p>Hi! Can I ask what is the value of the capacitor and the wattage? Do we use 2 or just 1 capacitor?</p>
9v adapter
can use 5v adapter
<p>can i use 560k ohm resistor in place of 470k ohm resistor for biasing the transistor and also i am applying 12v dc current to the circuit?????</p>
<p>can i use 560k ohm resistor in place of 470k because it is not available in my place and also i am applying 12v dc to this circuit..</p>
<p>i am so much impressed by this project i just love it and im going to make it for my class project.</p>
<p>i have made it but my family is afraid of installing it they are afraid if it will very dangerous to work with taps when this circuit is in on condition</p>
Don't worry... This circuit uses 5V DC which will not give you an electric shock. It is perfectly safe.
What is the longevity of the probe ? Sooner or later it is going to rust and it will be virtually cut off from the water... So which material should we use ?
<p>Hi friends,</p><p>One of my friend has build this Water level indicator to keep at his home. But the water seems to be non-conductive. Its acts as an insulator. Even We did check with multi-meter on the continuity mode. but still no conduction is happening. I am not able to resolve his problem. Could anyone help me on this... </p>
Most probably there's a deposition of oxide layer over the probe... which is decreasing the conductivity drastically... Try rubbing the probe with a sand paper and see.
Nice One
Can i just use dc supply rather than ac supply?
<p>any one plz tell me the value of capacitor that we are using in bridge rectifire...</p>
<p>Use 100 micro farad capacitor</p>
<p>Can anyone help me with the terminals of BC547. I am a bit confused :/.</p>
<p>ls refer the snap shot below</p>
Can i please know how much did this cost approximately ?
<p>It will cost you around 150rs</p>
<p>instead of connecting to main power supply can i use 9v</p><p>is it work for large size tank</p>
<p>You can use either 5V or 9V...:)</p>
Hello sir pls give me your mobile no I have some doubts sir
Hi i made this ckt it work s perfect but when tank is full buZzer is not ring loudly.<br><br>When i short comon wire n last led wire it rings loudly.<br><br>Any one can help me to solve my problem.<br><br>Thanks in advance.
<p>i also want to design pcbs so i will be very thankful if anyone can tellme all the requirements for designing and printing of pcbs at home</p>
<p>i want to know any good microcontroller programmer hardware and software as i want to learn to program and burn almost every kind of microcontroller so can anyone please tell me name of a goof microcontroller programmer device that supports almost every microcontroller...</p>
<p>can i use 400k ohm and 47 ohm resistors</p>
<p>Hi can any one tell me how to get rid of electrolysis problem which break wires in water tank </p>
hei i just connected the relay directly to the last output, i have given the relay a 12 v supply directly, and the neutral is via the master ckt, relay seems to work, can i connect it to motor???
Hei thanks for this simple circuit, i just made it, I just want to know if i can drive a relay to stop the motor. My logic is , 'take the output of the last level give it to a driver IC like L293D, get a 12v output frm IC andr drive the relay, its a 1/2 h.p 240v motor, I wanto connect it directly between phase lines, like a switch' is there any flaw??? help me out
There is mistake in showing collector and emitter of the transistors. Collector should go to positive hence LEDs cathode should be connected to collector of BC547 and emitter should go to common negative line.
This issue has been discussed earlier, please go through the comment section and watch the given video<br> <br> <div class="media_embed"> <iframe frameborder="0" height="315" src="http://www.youtube.com/embed/mb66rti1Qx8" width="420"></iframe></div>
Transister will work though biased collector emitter inversely . Collector is lightly doped in order to have high voltage withstand capability. However, one major advantage of operating the npn transistor with its emitter and collector roles reversed is that the saturation voltage drop across collector and emitter is lower than that obtained in the normal mode, inspite of having lower current gain. This is why such devices were used as analog switches in low voltage control electronics in discrete applications. So no problem we can go head with this collector emitter inverse connection as this circute is operated by low voltage. No much power gain . So there wont be much heat to dissipate . I think for buzzer it is better to connect load in the collector line . <br>information courtesy :-Sujit K. Biswas &middot; Jadavpur University.
<p>Use aluminum foil (2 pcs) glued to a plastic backing as an electrode plate. will weather far longer than just wires.</p>
<p>hey guys could someone explaine the circuit analysis</p>
<p>I have doubt whether this will have electric leakage in water tank leading to shockage. Kindly clear my doubt</p>
<p>Nice one. However, one problem with such circuits is the corrosion of electrodes due to the high current. I've been using this <a href="http://www.electronic-circuits-diagrams.com/water-level-indicator-circuit-with-alarm/" rel="nofollow">water level indicator</a> circuit for several years and hardly needs cleaning. Maybe its the low current needed to trigger the CMOS IC switch.</p>
Which diode will i use as the full wave. Rectifier
Which diode will i use as the full wave. Rectifier
<p>can some one let me know the parts used</p>

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