Egg heating control circuit

The circuit is shown in the figure.
    (1) The DC power circuit turns on the power switch S3, and the AC 220v voltage is stepped down by T, rectified by UR, and filtered by C3 and C4 to generate
a +9V working voltage, which is supplied to the drive control circuit, buffer amplifier circuit and automatic egg-turning circuit of Kl . +9V voltage also passes through RJ. After current limiting and voltage reduction,
Cz filtering and vs voltage stabilization, it provides +5V working voltage for the temperature detection control circuit.
    (z) Automatic egg-turning circuit The automatic egg-turning circuit is composed of resistor R. . ~R. , potentiometer RP6, capacitor G,6, time base integrated circuit IC2,
transistor VT3, diode VD2, relay K2, limit switch S1, trigger switch S4 and DC motor M2. Among them, IC2 and peripheral
resistor-capacitor components form an astable circuit fVT3, R1l, and RI. , VD2, K2 and Sl form the control circuit of M2 .
+ (3) Temperature setting VT1 is used as a temperature sensor to detect the temperature in the incubator. The voltage
of its emitter junction (between b and e electrodes) decreases as the temperature increases (temperature coefficient is - 2mV/℃). RP4 is used to set and control the temperature. Adjusting the resistance values ​​of 'RP1 and RP2 can change
the slope of the voltage on the emitter junction of VT1 as it changes with temperature.
    (4) During the working process, when the ambient temperature in the incubator is low and reaches the set control temperature of RP4, the amplifiers Nl and N3 output high level ,
causing VT2 to saturate and conduct, Kl is energized and closed, and its normally open contact is connected. The fan motor M1 and the heater EH are powered on. When the ambient temperature in the incubator
exceeds the set control temperature, both amplifiers Nl and N3 output low level, causing VT2 to cut off. Kl is released, its normally open contact
is disconnected, and the fan motor Ml and heater 'EH stop working. This process repeats itself to keep the temperature in the incubator constant at the set temperature. Adjust
the resistance values ​​of RP3 and RP5 to adjust the accuracy of the displayed temperature.
    At the moment when the power is turned on, since the voltage at both ends of G cannot change suddenly, pins ② and ⑥ of IC2 are low level, pin ③ outputs high level, VT3 is cut off
, K2 is in the release state, and M2 does not work. Then G is charged through R1, RP6 and Ru, causing the potential of pin ② and pin ⑥ of 1C2 to gradually
increase. When the voltage at both ends of c7 is charged to above 6V (about 2h), the circuit in IC2 flips over, and pin ③ becomes low level, causing VT3 to conduct. K2 is
electrified and closed, and its normally open contact is connected, causing M2 to be energized and rotated. Through the deceleration and pulling device, the hatching plate holding the hatching eggs is tilted in one direction to
complete the egg turning process. Adjusting the resistance of RP6 can change the automatic egg-flying time. j
    When the incubation tray tilts to a certain angle (about 70°), the trigger mechanism installed on the deceleration traction wheel connects the normally open contact of Sl and
disconnects the normally closed contact, changing the polarity of the power supply applied to M2. change, and at the same time, S4 is turned on momentarily to make the discharge output circuit inside pin ⑦ of 1C2
work , and G is discharged quickly. When the voltage at both ends of G is lower than 3V, pin ③ of IC2 becomes high level, causing VT3 to cut off. When K2 is released, its normally open contact
is disconnected, causing M2 to stop rotating. Then G is slowly charged through Ris, RP6 and Ris. When the voltage at both ends of G is charged to above 6V,
the circuit in IC2 flips again, and pin ③ outputs a low level, causing VT3 to conduct, and K2 is powered on and closed, and its normally open contact Turn on the head, make M2 energized and rotate, and use
the deceleration and traction device to tilt the hatching plate on which the hatching eggs are placed in the opposite direction to complete the egg turning action.
    When the hatching plate tilts to a certain angle, the trigger mechanism installed on the deceleration traction wheel disconnects the normally open contact of Sl and
connects causing the polarity of the power supply applied to M2 to change, and at the same time, the It is triggered and turned on to make the internal discharge output circuit of IC2 pin ⑦ work,
G discharges quickly. When the voltage at both ends of S7 is lower than 3V, IC2 pin ③ becomes high level , causing VT3 to cut off and K2 to release. The normally open contact
is disconnected, causing M2 to stop rotating again.