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Choosing a Microcontroller
 As it provides on chip microprocessor, RAM, ROM, Parallel I/O port, Serial I/O port etc. hence its cost is less, size is less, power consumption is less and speed is more.
 Software development tools like assembler, C compilers etc are easily available and are easy to upgrade.

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1. INTRODUCTION
This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full. The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs.
When the water is empty the wires in the tank are open circuited and the 180K resistors pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the tank connected to S1 and the + supply are shorted by water. This closes the switch S1 and turns the LED1 ON. As the water continues to fill the tank, the LEDs2 , 3 and 4 light up gradually. The no. of levels of indication can be increased to 8 if 2 CD4066 ICs are used in a similar fashion. When the water is full, the base of the transistor BC148 is pulled high by the water and this saturates the transistor, turning the buzzer ON. The SPST switch has to be opened to turn the buzzer OFF. Remember to turn the switch ON while pumping water otherwise the buzzer will not sound!
2. WORKING PRINCIPLE
One electrode probe is with 6V AC is placed at the bottom of tank. Next probes are placed step by step above the bottom probe. When the water/liquid comes in contact with the electrode tip, a conductive path is established between the sense electrode and the tank wall/reference electrode, which in turn makes the transistors conduct to glow LED and indicate the level of water. The ends of probes are connected to corresponding points in the circuit as shown in circuit diagram. Insulated Aluminum wires with end insulation removed will do for the probe. Arrange the probes in order on a PVC pipe according to the depth and immerse it in the tank. AC voltage is use to prevent electrolysis at the probes.
3. BREADBOARD
A breadboard (proto board) is a construction base for a one-of-a-kind electronic circuit, a prototype. In modern times the term is commonly used to refer to a particular type of breadboard, the solder less breadboard (plug board).
Because the solder less breadboard does not require soldering, it is reusable, and thus can be used for temporary prototypes and experimenting with circuit design more easily. Other, often historic, breadboard types don't have this property. This is also in contrast to strip board (veroboard) and similar prototyping printed circuit boards, which are used to build more permanent soldered prototypes or one-offs, and cannot easily be reused.