PLC based automatic Tank Filling Demo:
When the lower level is reached (%I0.1), the upper level contact is not activated (%I0.0), and the pump output (%Q0.0) is activated.
The contact %Q0.0 can be used to keep the pump active until the upper level is reached.
When the upper level is reached (%I0.0), this contact cuts off the power to the pump output and the pump stops.