To design a automatic control of maintaining a level of a tank, First thing to consider from two option – Keep the tank empty – for dirty water, dirty wastage liquid.Keep the tank filled– for fresh water, fresh liquid.
Floating switch-What we need
Floating switch:Two types of float switch constructed-Filling – switched on when level is low and switched off when level is high.Emptying – switch on when level is high(pump out); switch off when level is low.
Signal:Only two level signal, Low level- also additional (very low level). High level(also very high level).An alarm system or start , stop of motor is actuated by this two level signal. Say if we consider fresh water tank, When water in tank is in low level float switch is in clinging downward sends low level signal and a motor starts to filling water.After reaching certain level float switch sends high level signal and an arrangement switch off the motor.
But If we consider dirty water tank, it must be kept at low level certainly. Then after reaching high level in dirty water tank, float switch send signal, that starts a motor. At reaching low level, float switch again sends signal, that initiates the stopping of the motor.