Automatic Fan Controller Temperature

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WATER LEVEL INDICATOR

This water level indicator can intimate the low and high water levels in the overhead tank through audible beeps. Dual operational amplifier has two Op-Amps inside which can be controlled independently. Both the Op-Amps have inverting and non-inverting inputs and separate outputs. The inverting input of first Op-Amp is pin2 and that of the second is pin6. The non-inverting input of first Op-Amp is pin3 and that of the second is pin5.When the non-inverting inputs 3 and 5 gets higher voltage than the inverting inputs, the outputs 1 and 7 becomes high.

The inverting inputs(pin2) of Op-Amp 1 is connected to a potential divider R3 and R4 while its non- inverting input(pin3) is connected to a probe B ( metal rod) which is placed in contact with the upper water level. The non- inverting input (pin5) of second Op-Amp is connected to another potential divider R1 and R2 while its inverting input (pin6) is connected to another probe(C) which makes contact with the lower water level in the bottom of tank. A common probe A is also placed in the middle water level and it provides current through the probes. When the water level in the tank reduces below the probe C, the electrical contact between probes A and C brakes and the non- inverting input 5 gets more current than the inverting input6. As result output pin7 becomes high and buzzer beeps and Red LED lights indicating that the tank is going to be empty. This is the time for pumping water. When the water level rises and makes contact with probe C, buzzer stops beeping and Red LED turns off. When the water tank is almost full, probe B makes contact with water. At this time the non- inverting input 3 gets more current than inverting input2. As a result output 1 becomes high and Green LED lights indicating that tank is full. This is the time to switch off pump. The green LED remains on until the water level goes below probe B.

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