As soon as the water reaches the uppermost level of the tank, the last sensor positioned at the relevant point triggers a relay which in turn switches the pump motor for initiating the required water evacuating action.
The circuit is as simple as it could be. Use of just one IC makes the entire configuration very easy to build, install and maintain.
The fact that impure water which happens to be the tap water that we receive in our homes offers a relatively low resistance to electricity has been effectively exploited for implementing the intended purpose.
Here a single CMOS IC 4049 has been employed for the necessary sensing and executing the control function.
Another interesting associated fact that’s associated with CMOS ICs has helped in making the present concept very easy to implement.
It is the high input resistance and sensitivity of the CMOS gates which actually makes the functioning completely straightforward and hassle free.
As shown in the above water level indicator circuit figure, we see that the six NOT gates inside the IC 4049 are arranged in line with their inputs directly introduced inside the tank for the required sensing of the water levels.
The ground or the negative terminal of the power supply is introduced right at the bottom of the tank, so that it becomes the first terminal to come in contact with water inside the tank.
It also means that the preceding sensors placed inside the tank, or rather the inputs of the NOT gates sequentially come in contact or bridges themselves with the negative potential as the water gradually rises inside the tank.
We know that NOT gates are simple potential or logic inverters, meaning their output produces exactly the opposite potential to the one that’s applied to their input.
Here it means as the negative potential from the water bottom comes in contact with the inputs of the NOT gates through the resistance offered by the water, the output of those relevant NOT gates sequentially start producing opposite response, that is their outputs start becoming logic high or become at the positive potential.
This action immediately lights up the LEDs at the outputs of the relevant gates, indicating the proportionate levels of the water inside the tank.
Another point that’s to be noted is, all the inputs of the gates are clamped to the positive supply through a high value resistance.
This is important so that the gates inputs are initially fixed at the high logic level and subsequently their outputs generate a logic low level keeping all the LEDs switched off when there’s no water present inside the tank.
The last gate which is responsible for initiating the motor pump has its input positioned right at the brim of the tank.
It means when the water reaches t the top of the tank and bridges the negative supply to this input, the gate output becomes positive and riggers the transistor T1, which in turn switches the power to the motor pump through the wired relay contacts.
The motor pump stats and begin evacuating or releasing the water from the tank to some other destination.
This helps the water tank from overfilling and spilling, the other relevant LEDs which monitors the level of the water as it climbs also provides important indication and information regarding the instantaneous levels of the rising water inside the tank.
R1 to R6 = 2M2,
R7 to R12 = 1K,
All LEDs = Red 5mm,
D1 = 1N4148,
Relay = 12 V, SPDT,
T1 = BC547B
N1 to N5 = IC 4049
All the sensor points for this water level indicator circuit are ordinary brass screw terminals fitted over a plastic stick at the required measured distance apart and connected to the circuit through flexible conducting insulated wires (14/36).
The above circuit was successfully built and tested by Mr. E.Rama Murthy who is one of the regular and dedicated readers of this blog. The following pictures of the built prototype were sent by him, let's investigate the results closely.