One of the transistor-type water level automatic control circuits (fill-in type) a

The simple irrigation transistor water level automatic control circuit
is shown in Figure 11-2. Three electrodes
(metal rods such as copper or stainless steel can be used) A, B, and C are introduced into the upper part of the water tank.
The A pole is placed at the highest water level allowed, the B pole is placed at
the lowest water level allowed, and the C pole is placed at the bottom of the water tank. The water
level will be controlled between electrode A and plate C.
    If the automatic fails, the transfer switch can be turned to the manual position, and the start and stop buttons of the start button SBi and the stop button can be used to manually control
the start and stop of the water pump.
    Electrode C is only required when the water tank is made of non-metallic material. If the water tank is of metal construction, the entire water tank can be used
instead of electrode C.