The three sensor points A, B and C are shown in the circuit, which will be placed in the water tank. The sensor C should be placed at the bottom of the tank. The sensor B will be placed on the level from which you want to start the pump to fill water in the tank and the sensor A should be placed at the at the upper level of the tank at the point where you want to stop the pump.
For powering the circuit a 230V to 9V or 12V 100 to 200mA transformer can be used. The circuit can also be operated with 5V or 6V for doing so use a 5V or 6V supply or transformer. The relay value should also be replaced according to the operating voltage.
This is a low cost project of an automatic water pump controller using some transistors, a relay, a BT139 triac, transformer and few other discrete components. The circuit is completely automatic and can control any water and liquid pump according to the desired upper and lower level of the tank.
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