Municipal corporations in many cities supply water during early morning hours. So, you have to wake up early, just to switch on your motor pump and wait till your water tank is filled up. Further, there is no control for overflow of the tank. Many times you come to know of your overflowing tank only when your neighbour informs you.
Here is a low-cost and simple automatic water pump controller circuit (Fig. 1) to avoid the aforesaid problem. You just have to set your quartz alarm clock (connected to this system) at the appropriate time of water supply. Keep the clock nearby your sleeping bed and switch on the circuit before going to sleep. In the morning, as the alarm rings, you can switch off the alarm and, if you like, go to sleep again. The controller system will automatically switch on the pump motor immediately at the predetermined time. When the overhead tank is full, the pump motor will get switched off automatically, preventing overflow of the tank. The controller system works with a water-level sensor assembly. The sensor assembly has to be fixed up properly inside your overhead water tank.
You can assemble a simple water-level sensor (Fig. 2) at home. Take an empty cylindrical plastic vial having outer diameter smaller than 1.3 cm (0.5 inch), which is commonly used for dispensing medicines. Make it opaque by pasting a piece of black paper or PVC tape on its inner side. Fix up the vial’s lid firmly with a suitable material to make it airtight.
Now take a 15.2cm (6-inch) piece of opaque PVC conduit pipe having inner diameter of 1.3 cm (0.5 inch). Ensure that the vial can freely slide along the axis inside the conduit pipe; else use a PVC pipe having larger inner diameter. Drill two through-holes (of diameter 3.5 mm) along the diameter of the PVC pipe, at least 15 mm away from each end. Also drill two 5mm dia. through-holes along the diameter of the PVC pipe, 25-30 mm away from one end.
Insert the airtight plastic vial inside the PVC pipe and fix up two screws (M3x25mm) through 3.5mm dia. holes with suitable M3 nuts near the ends. These screws will restrict sliding of the vial within the PVC pipe.
Then fix up a 5mm red LED perpendicular to 5mm dia. hole, on the outer surface of PVC pipe, using suitable adhesive like M-seal. Also, opposite to this, fix up a light-dependent resistor (LDR) in similar way as shown in Fig. 1. Ensure that both the LDR and the LED are firmly placed outside the PVC pipe and they don’t interrupt movement of the vial inside the PVC pipe. Also ensure that the maximum light produced by the LED falls on the surface of the LDR through 5mm dia. holes along the diameter of the PVC pipe. Then plug the open ends of PVC pipe with dark-coloured (preferably black) sponge pieces, to avoid ambient light entering inside the pipe.
Solder the leads of LDR and LED with connecting wires of required length, according to the location of your overhead water tank. Then fix up this water-level sensor assembly vertically at a suitable height along the inner wall of the overhead water tank, as shown in Fig. 3.
Remove 1.5V (AA size) battery from the quartz alarm clock. Carefully open the back lid of the clock using a small screwdriver. Solder a braided pick-up wire parallel to the connected points of your alarm buzzer (clock). Make a small hole on the back lid of the clock and pull out free ends of the pick-up wire through this hole. Then, carefully fix up the back lid in proper position, without disturbing any mechanical part of the clock. Solder the free ends of pick-up wire on the PCB at input terminals. This pick-up wire will provide trigger pulses from the alarm clock to water pump motor controller system. Then set the time and place the battery in alarm clock.