Microwave oven control circuit

Circuit composition The microwave control switch circuit consists of a local oscillator, amplifier, double-limit voltage comparator and control execution circuit. The
    local oscillation circuit consists of transistor VT1, inductor L, capacitor C. , C2, resistors Ri, Ra, potentiometer RP1 and antenna.
    The amplifier consists of transistor VT2, capacitors C3, G, and resistors fR and Rs.
    The double-limited voltage comparator circuit is composed of an operational amplifier integrated circuit IC, resistors R6, R, diodes VD1, VD2 and potentiometer RP2.
    The control execution circuit is composed of transistor VT3, resistor B, capacitor C, diode VD3 and relay K.
    (2) Circuit principle VT1 generates self-excited oscillation under the positive feedback of Cl. The high-frequency electromagnetic waves generated by the oscillation are radiated from the antenna to the surrounding
space, creating a three-dimensional microwave field around the antenna. When an object moves in this microwave field, the electromagnetic waves reflected by the object's movement are
received by the antenna, causing VT1. The amplitude and frequency of self-oscillation change, and this change is converted into a
voltage signal that fluctuates with the movement of the object through the integral circuit composed of R and C7. After the voltage signal is amplified by VT2, it generates 2.5 to 6.7 on the collector of VT2. The changing voltage of V (
the changing voltage is proportional to the speed of the object moving and the distance from the antenna). After this changed voltage is compared and processed by the IC, a control high level is generated to
turn on VT3. K pulls in, and the controlled circuit (alarm or lighting, etc.) is powered on.
    Adjusting the capacity of c] can change the operating frequency of the self-oscillator. Adjusting the resistance of RP1 and RP2 can change
the sensitivity of the microwave control switch action.