Simple water level controller circuit (2)

Working principle of the circuit: The working process of the entire circuit is that when the water level is lower than point C
, VT. The bias voltage is obtained and turned on, VT2 works, K pulls in, the load works, and
the water level increases. Due to the work of VTz, VT3 obtains sufficient forward bias through R2 and VD and
is turned on. C is charged at the same time. When the water level is higher than points B and C, VT is cut off,
the potential of VTz drops (pole B), and C3 is discharged. , VL continues to work, VTz cannot be cut off. When
the potential of point A is lower than the potential of point B, VDs is turned on, C2 is discharged
, and C is charged; when the potential of point A is equal to the potential of point B, VDs is turned off, C2 is charged, and C3 is discharged. When the next
cycle comes, C2 and C3 , VDs repeats the above action and keeps VT3 continuing to work. When the water level is at point A, C discharges to the ground through the water, and the potential
at point A 7 drops instantly. VT3 is cut off due to power loss, VT stops working, and the entire circuit is in a waiting state. When the water level is below point A and above point C, the circuit is also in a waiting state because there is no starting voltage.