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This circuit
gives out an alarm when its sensor is wetted by water.
A 555 astable multivibrator is used here which gives a tone of
about 1kHz upon detecting water.
The sensor when wetted by water completes the circuit and makes
the 555 oscillate at about 1kHz. The sensor is
also shown in the circuit diagram.
It has to placed making an angle of about 30 - 45 degrees to the
ground. This makes the rain water to flow through it to the ground
and prevents the alarm from going on due to the stored water on
the sensor.
The metal used to make the sensor has to be aluminium and not
copper. This is because copper forms a blue oxide on its layer on
prolonged exposure to moisture and has to be cleaned regularly.
The aluminium foils may be secured to the wooden / plastic board
via epoxy adhesive or small screws.
The contact X and Y from the sensor may be obtained by small
crocodile clips or you may use screws.
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