A simple circuit for detection of water level and indication with help of a buzzer without the use of any micro controller.

Step 1: Components Required

LED (any color)
IC 7404.
IC 4N35.
Buzzer.
Resisters x3 (100 ohms)
General purpose Board.
Float Switch.
Soldering Rod
.Diode

Step 2: Circuit Diagram

The above circuit is for simple water level buzzer. When water reaches a certain level the buzzer is switched on. Whole circuit is powered by a 9 Volt battery. A switch is used for actuating the circuit ON/OFF. A diode is provided to prevent reverse current to flow into the battery which may damage the battery.

IC 7404 requires a minimum of 5 volts supply to power. I have used a 9 volts power because its battery was more compact to use. The float switch is just like a normal ON/OFF switch but the position of the float triggers the switching action. It is a normally open switch i.e. it will pass current in normal position and block current when moved. When the float is in normal position the red LED glows indicating that the circuit is switched on. When the float is moved the current is blocked, so IC 7404 or inverter inverts this signal to a 5 volts signal. This signal is given to the optocoupler which passes 9 volts to the buzzer.

Always implement the circuit on breadboard first before mounting and soldering on PCB board.