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Almost all restaurants have handwash sink for the use of their customers. Since it is used by numerous people, the tap stops working properly after some time and starts leaking, leading to wastage of water. This circuit can prevent the problem as it lets the water flow from the tap automatically only when a person comes before the sink.
The circuit is built around a DC barrel jack (J1), PIR sensor HC-SR501 (MS1), transistor BD139 (T1), a normally-closed solenoid valve (SV1), and a few other components. The circuit can be powered by a 12V battery or an external 12V DC adaptor.

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