Water Level Alarm Using
555 Timer

How many times did your overhead water tank overflows due to your forgetfulness? It is a frequent problem in all homes where people turn ON the water pump and forget to turn it off when the water is filled. This project is made to solve this problem.

Important Post:
Water Level Indicator Project

In this project, we are using a water level
alarm using simple and low cost hardware using a 555 timer circuit. The aim of this project is to make a water level detecting alarm with simple and low cost hardware without compromising on the performance of
the device.

Water Level Alarm Using 555
Timer Circuit Diagram:


The circuit uses a 555 timer in astable mode
with R1=220 ohms, R2= 150 ohms and C1=1
uF. As we know, the frequency of operation of
the IC 555 in astable mode depends on the
values of R1, R2 and C1. By calculating the
frequency of the given astable circuit, we get
the frequency to be around 1.18KHz. The
frequency at which it operates is in the audio

The 1K Resistor R3 whose ends are
connected to pin-4 and ground disables the
circuit by default and it enables when the
water reaches its full level when the probes
get dipped in water.

The two probes which are shown in the
circuit should be kept at the high level for the
water. The astable multivibrator in the circuit
is normally disabled and it gets enabled only
when the probes touch the water. The
distance between the probes should be less
than a few centimeters to ensure that the
conduction between the probes will take
place when water is touched to these probes.
When the water level rises to the height of
the probes, then the 555 circuit will get
enabled and the output of the 555 timer
produces a square wave output with a
frequency of about 1.18Khz. This output is
given to the mini loudspeaker which then
beeps at an audio frequency of 1.18KHz.

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