This can be used as an alarm when filling overhead tanks. Quite some time ago, I used it as an indication when the municipal water used to start flowing to my pipeline. When I built this project, happiest one was my mother. Municipal water used to be pumped in the midnighl at unearthly hours and my mother used to wake up now and then to check if the water started pouring in.
With half wave power supply already built, connect the buzzer as shown in the schematic and fix the wires. As the water level rises to touch the wires, the buzzer gives out a loud alarm. I used to put these wires in a plastic bucket under the tap. When municipal water flows down, it indicates an alarm. It is one of those most useful and easiest projects I ever built.
You may use this as a rain alarm particularly if the lady of the house dries up clothes or grain in the open yard or even as bed wetting alarm for the baby ((Use only batter}/” power!!)).You can try this as a steady hand testing game. You may use this for a continuity tester but do not use this on live wires.
Bring two wires and keep them at the desired level in the tank with a little separating distance between them. You can use fairly long wires and run them along into the house. Needless to say scrap and expose the copper wires a little. Connect one of these wires to the trigger terminal (generally yellow) of the buzzer and the other to the positive terminal (red wire). Black wire goes to the negative.
If you want battery operation, use two battery cells (1.5V each). Use more cells for more sound. If you want to use mains supply, half wave circuit description is given above. Use a transformer with 12V or 6-0-6V at the secondary. Screw the secondary ends to the terminal strip; screw diode (Dl, IN 4003) CI is an electrolytic capacitor of 1000 mfd and 16V rating. Please follow the polarity marked on the can. Light emitting diode is optional. Use with resistor (Rl, IK). It gives an indication that the power supply is OK. You may use the mains plug mounted power supplies or eliminators and mount all the parts on it.
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