Single-phase electric water pump water level control point card

Working principle of the circuit: When the water level is lower than the lowest limit point, electrodes B and C are disconnected,
the base of transistor VT is open and cut off, VT2 and VT3 are turned on, and relay K. The coil is
electrically attracted, the normally open contact switch KI is closed, and the motor is electrically pumped. At this time VT is deeply
saturated and its dagger. . ≤0 1 V; when the water level rises beyond the ￡ point, although electrodes B and C are connected
, due to the small Vce, value of VT3, the Vbe value of VT, is ≤0.1 V, VT, still remains cut off
, and the motor continues to pump water. ; When the water level rises beyond the sun point, electrodes A and C are connected, and
the transistor VT. The base is electrically connected, VT2 and VT3 are cut off, K is released, the motor is powered off
, and water pumping stops. At this time, VTl is also deeply saturated, and the V boom value of VT3 is ≤0.1 V; when the water
level drops below the day point, due to When electrode day and C are connected (from K coil), VT. It is still
saturated and conductive, and continues to stop pumping until the next pumping cycle.