Simple water pump automatic controller circuit

(1) Power supply circuit: It consists of transformer T, rectifier diode VD, one VD4, three-terminal
voltage stabilizing block IC , (7812), and capacitors C1 and C2 to form a bridge rectifier filter stabilized power supply
circuit; resistor R. And light-emitting tube LED. Acts as a power indicator.
  (2) Start and stop control circuit: The main controller
is composed of IC2 (NE555) integrated block and peripheral components R3, R4, C3, C4, and c5. Water level detection consists of reed switches S1 (normally
closed), S2 (normally open), magnet F and resistor Rz, and is composed of triode VT. , relay
K, and peripheral components wind and VDs perform shoulder stop tasks. The function of the resistor and the light-
emitting diode LEDz is to indicate the operation of the circuit . When the water level drops to S. When , magnet F
disconnects S1, pin 2 of IC 2 (NE555) changes to low level , pin 3 outputs high level,
the indicator LED2 lights up, and the high level passes through the water inlet resistor Rz to turn on the transistor VT2.
Relay K. Pull-in, its normally open contact K. Close and start the water pump or solenoid valve (
when the water pump capacity is large, the water pump must be started through an intermediate relay). When the water level rises to S2,
magnet F closes S2, pin 6 of Icz becomes high level to flip it over, pin 3 becomes
low level , transistor VT1 is cut off, and relay K1 loses power and stops the pump.