Pump Motor Automation
Pump Motor Automation
Here’s a automatic water pump controller circuit that controls the water pump motor. The motor gets automatically switched on when water in the overhead tank (OHT) falls below the lower limit. Similarly, it gets switched off when the tank is filled up. Built around only one NAND gate IC (CD4011), the circuit is simple, compact and economical. It works off a 12V DC power supply and consumes very little power.
Circuit operation
If the tank is filled below probe A, transistors T1 and T2 do not conduct and the output of N3 goes high. This high output energises relay RL2 to drive the motor and it starts pumping water into the tank.
When the tank is filled above probe A but below probe B, water inside the tank provides base voltage to drive transistor T1 and relay RL1 energises to make pin 13 of gate N3 high. However, water inside the tank does not provide base voltage to transistor T2, so it does not conduct and the logic built around NAND gates N1 and N2 outputs low to pin 12 of gate N3. The net effect is that the output of N3 remains high and the motor continues pumping water into the tank.
Circuit operation
When the tank is filled up to probe B level, water inside the tank still provides base voltage to transistor T1 and relay RL1 energises to make pin 13 of gate N3 high. At the same time, water inside the tank also provides base voltage to drive transistor T2 and the logic built around NAND gates N1 and N2 outputs high to pin 12 of gate N3. The net effect is that the output at pin 11 of N3 goes low and the motor stops pumping water into the tank.
Circuit operation
When water level falls below probe B but above probe A, water inside the tank still provides base voltage to transistor T1 and relay RL1 remains energised to make pin 13 of gate N3 high. However, transistor T2 doesn’t conduct and the logic built around NAND gates N1 and N2 outputs high to pin 12 of N3. As a result, the output of N3 remains low and motor remains stopped.
When water level falls below probe A, both transistors T1 and T2 do not conduct. NAND gate N3 gives a high output to drive relay RL2 and the motor restarts pumping water into the tank.
