Initially, when the water level is below the L1 strip, supplying electrical oscillation frequency is not transferred to the diode D1. Thus the low output and LED1 does not light. Also, because the base voltage of the transistor T1 is low, it is in a state of cut-off and the collector voltage is high, which enables to produce melody IC1 (UM66) and the alarm is sounded.

When the water is just touching the L1 level detector strip, the oscillation frequency of the supply transferred to the diode D1. This straightening supply voltage and positive DC voltage developing capacitor C1, which is lit LED1. At the same time the base voltage of the transistor T1 becomes high, which makes forward bias and collector voltage falls to near ground potential. Disabling IC1 (UM66) and the alarm is inhibited.

Depending on the quantity of water present in the tank, which shows the level of the corresponding LED lights up. It thus showing medium level of water in the tank with a bar-chart style.

When the water in the tank just touching the highest level detector lines L12, DC voltage developed in capacitor C2. This makes it possible to produce a melody IC1 (UM66) and the alarm sounds again.

Here the circuit diagram of low cost water pump controller. The automatic pump controller minimizes the need for any manual switching of water pumps installed for the functionality of pumping water from a reservoir to an overhead tank . It instantly switches on the pump once the water level within the tank falls below a specific low level (L), provided the water level in the reservoir is above a specific level (R). Subsequently, because the water level in the tank increases to an upper level (M), the pump is turned off instantly. The pump is turned on again only if the water level once again falls beneath level L in the tank, provided the level inside the reservoir is above R. This automated action
continues.

The circuit is intended to “overlook” the transient oscillations of the water level that would otherwise trigger the logic to modify its state rapidly and unnecessarily. The circuit works by using a single CMOS chip (CD4001) for logic processing.

No utilization of any moving electromechanical elements within the water-level sensor has been made. This assures fast reaction, no wear and tear, and no mechanical problems. The circuit diagram can be seen on above image. The unit performed satisfactorily on a test run in conjunction with a 0.5 HP motor and pump.

The sensors applied to the circuit could be any two conducting probes, preferably resistant to electrolytic corrosion. For example, in the easiest case, a appropriately sealed audio jack could be utilized to operate as the sensor.

The circuit may also be utilized like a constant fluid level maintainer. For this objective, the probes M and L are brought pretty near to one another to make sure that the fluid level is maintained within the M and L levels.

The benefit of this system is that it could be applied to tanks/reservoirs of any volume whatsoever. Even so, the circuit can’t be applied for purely non-conducting fluids. For non-conducting fluids, some modifications have to be prepared in the fluidlevel sensors. The circuit can on the other hand be kept intact.