For the supply of water it is very common method to use an overhead tank to which water is pumped from a ground level tank. Generally a person has to manually switch on the water pump when the overhead tank is running low of water. Also when the tank is filled a person has to switch off the water pump manually. This process is inefficient because the person has no idea about the current water level in the tank. Therefore it cannot be known when the water is going to run out and when the tank is filled up, until the actual thing occurs. This may cause unexpected cut off of water supply. Also when the water is being pumped up the person has to wait until water overflows and then switch off the water pump. To improve this to certain extent sensors can be placed in the tank to measure the water level. Then the person can monitor the water level in the tank and can take necessary actions. In this system sensors are used to measure the water level in the tank and the water pumped is automatically switched on and switched off as required. This system minimizes human intervention and eliminates the inefficiencies described above.1.1 REQUIREMENTS OF THE SYSTEM:
Ø The system should minimize user intervention.
Ø The water level of the overhead tank should be monitored using sensors and when water level drops below a threshold level the water pump should be turned on. When the level of water is above a predefined level the pump should be turned off.
Ø When the pump is turned on the water level in the ground tank should be monitored. If that level drops a below a defined value the pump should be turned off.
Ø A user should be able to disable the whole automatic system and switch on or switch off the pump manually.
Ø A display system should be used to indicate the water level in the tanks. However for the convenience of the user the display system should not display the level of water in the overhead tank when the pump controlling system is operating in the automatic mode. Otherwise the user will become confused. In the automatic mode only the level of water in the ground level tank should be displayed.
Ø Sometimes the levels of water in both the overhead tank and the ground level tank will be below their lower thresholds. At this situation the pump should not be turned on and the system should indicate that the water level is low in both the tanks.
Ø In the manual mode the water level in both tanks should be displayed so that the user can operate the motor by observing the indications of the display.
1.4 INPUTS TO THE SYSTEM:
L0 - Lower threshold level of over head tank
L1 - Higher threshold level of overhead tank
L2 - Lower threshold level of ground level tank
M - Select the mode automatic or manual from Switch. When manual is selected its output is logic1 and else the output is logic 0.
Note: If the water level is higher than threshold level the inputs to the system is logic1.Otherwise logic is 0.
1.5 OUTPUTS FROM THE SYSTEM:
D0 – Indicates the lower threshold of the overhead tank. LED lights up when water level is below the lower threshold
D1 - Indicates the higher threshold of the overhead tank. LED lights up when water level is above the higher threshold
D2 – Indicates the water level of the ground tank. The LED lights up when water is below the lower threshold
P- Objective output to the water pump of the control system
The control circuits in the controller are implemented as a synchronous sequential circuit.
2. SYSTEM DESIGN (AUTOMATIC):
2.1 STATE DIAGRAM:
Input sequence - L0, L1, L2
Output sequence – PD0
STATES
| States | Binary Assignment | Description |
| S0 | 00 | The pump is turned off |
| S1 | 01 | The pump is turned on |
| S2 | 10 | Pump is turned off. Water level is below the lower threshold in both tanks |
2.3 TRUTH TABLE:
| Present state AB | Inputs L0L1L2 |  Next state AB |  A JA KA |  B JB KB |
| 00 | 000 | 10 | 1 X | 0 X |
| 00 | 001 | 01 | 0 X |  1 X |
| 00 | 010 | 10 | 1 X | 0 X |
| 00 | 011 | 01 | 0 X | 1 X |
| 00 | 100 | 00 | 0 X | 0 X |
| 00 | 101 | 00 | 0 X | 0 X |
| 00 | 110 | 00 | 0 X | 0 X |
| 00 | 111 | 00 | 0 X | 0 X |
| 00 | 000 | 10 | 1 X | X 1 |
| 01 | 001 | 01 | 0 X | X 0 |
| 01 | 010 | 00 | 0 X | X 1 |
| 01 | 011 | 00 | 0 X | X 1 |
| 01 | 100 | 00 | 0 X | X 1 |
| 01 | 101 | 01 | 0 X | X 0 |
| 01 | 110 | 00 | 0 X | X 1 |
| 01 | 111 | 00 | 0 X | X 1 |
| 10 | 000 | 10 | X 0 | 0 X |
| 10 | 001 | 01 | X 1 | 1 X |
| 10 | 010 | 10 | X 0 | 0 X |
| 10 | 011 | 01 | X 1 | 1 X |
| 10 | 100 | 00 | X 1 | 0 X |
| 10 | 101 | 00 | X 1 | 0 X |
| 10 | 110 | 00 | X 1 | 0 X |
| 10 | 111 | 00 |  X 1 |  0 X |
6. CONCLUSION:
For the supply of water it is very common method to use an overhead tank to which water is pumped from a ground level tank. The controller is primarily used where water is stored in an underground tank & then lifted to an overhead tank. It automatically control water level of both the tanks. Auto starts the motor/pump when water in upper tank reaches low level provided water is available in lower tank. Auto switch off when upper tank becomes full or lower tank gets empty. It is suitable where water is stored in an underground tank & then lifted to an overhead tank. Automatically controls water level of both the tank simultaneously.
The automatic pump controller eliminates the need for any manual switching of pumps installed for the purpose of pumping water from a reservoir to an overhead tank (refer Fig. 1). It automatically switches on the pump when the water level in the tank falls below a certain low level (L), provided the water level in the reservoir is above a certain level (R). Subsequently, as the water level in the tank rises to an upper level (M), the pump switched off automatically. The pump is turned on again only when the water level again falls below level L in the tank, provided the level in the reservoir is above R. This automated action continues. The circuit is designed to ‘overlook’ the transient oscillations of the water level which would otherwise cause the logic to change its state rapidly and unnecessarily. The circuit uses a single CMOS chip (CD4001) for logic processing. No use of any moving electro-mechanical parts in the water-level sensor has been made. This ensures quick response, no wear and tear, and no mechanical failures. The circuit diagram is shown in Fig. 2. The device performed satisfactorily on a test run in conjunction with a 0.5 HP motor and pump. The sensors used in the circuit can be any two conducting probes, preferably resistant to electrolytic corrosion. For instance, in the simplest case, a properly sealed audio jack can be used to work as the sensor. The circuit can also be used as a constant fluid level maintainer. For this purpose the probes M and L are brought very close to each other to ensure that the fluid level is maintained within the M and L levels. The advantage of this system is that it can be used in tanks/reservoirs of any capacity whatsoever. However, the circuit cannot be used for purely non-conducting fluids. For non-conducting fluids, some modifications need to be made in the fluid-level sensors. The circuit can however be kept intact.
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