Water Activated Sensor Alarm Using 555

Here is a circuit diagram of water activated sensor alarm using 555 IC.We may use this circuit for the following applications:

•  Water leakage detection from water tank and can be used as a water leak alarm
•  To detect presence of rain outside the room
•  Do detect the presence of moisture or water molecules on a substance
•  Used as detector of water in water overflow alarm

 Also we can fix this circuit anywhere in the basements and roof parts to detect any type of water leakage.

 Circuit Diagram of  Water Activated Sensor Alarm : Click  to enlarge

The circuit comprises a 555 IC as the core. This is designed to work as an astable multivibrator. When we connect a positive 9 volt to pin no. 8, the circuit will produce a sound through speaker.  But here the connection to pin 8 goes through the transistor BC 109c or BC 548. In this condition, the base of the NPN transistor haven't any positive voltage. But when the resistance between the "contacts" is lower due to water, the transistor get it base voltage and the circuit will produce a sound.

Working

We can connect the the 555 output pin no. 3 to loudspeaker through a 100uF electrolytic capacitor. The resistors, R1 and R2 are used for IC biasing. We can change the tone of the sound coming from the speaker by changing the value of capacitor C1.

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