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 total7 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
- Red LED (Indicating no water in the tank as none of the sensors are getting contact with the water)
- Red LED ( Level 1, indication very low water in the tank )
- Yellow LED (Level 2, indication of low water)
- Yellow LED (Level 3, indication of 1/4 of water in the tank)
- Green LED (Level 4, indication of half of water in the tank)
- Green LED (Level 5, indication of more than half of water)
- Green LED (Level 6, indication of nearing filling up the tank)
- 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.