Hello guys, hope you are enjoying there. Here I present a switch designed using a BJT and a relay. This switch is used to avoid overflow of water in a water tank. The importance of this simple gadget is quite obvious, that's conservation of water. I noticed all around in my colony that water from tanks flow for hours wasting a lot of water. So, I designed this switch. When water reaches the top level of the tank a cotton ball(or clothe) soaks water. Two wires (one from base of bjt and the other from Vcc) are packed in the ball( or clothe) making sure that they don't touch each other. The reason behind this setup is soaked water will dry-up slowly so that the water motor don't start suddfter r level goes down. This is necessary because otherwise motor will switch on an off throughout the time. This is not good for motor as well. When water is soaked in the cotton material the base is connected to Vcc via Rb. This switches the bjt on. One of the coil-terminal of the relay is connected to collector terminal of the bjt. I used relay to connect or disconnect wire coming out of motor.
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