This thermostat uses a vertically-phase method of power control in the heating element. The comparator VT1 compares shifted by 90 El.degrees the voltage from the secondary winding of the transformer TR1 and the DC voltage offset of the bridge, amplified by defcustom VT4, VT5, through the repeater VT3. At the moment of equality of the signals through the amplifier VT2, the current control opens the thyristor VD4. The thermistor R12 is located in the housing of the incubator, in place of laying eggs, and protected from radiation radiation heater. Thanks to the feedback through the thermistor, the temperature in the incubator to stabilize. Unlike key schemes, change the power in the heating element is proportional to the temperature deviation.
The controller uses one half cycle of the mains voltage, so the power of the heater (typically use incandescent lamps) must be doubled, in relation to sufficient to achieve the desired temperature in your design incubator. During the initial inclusion of the incubator the process of establishing the working temperature is decaying oscillatory in nature, due to the inertia of feedback through the air and the sensor. After warming up capture and proportionate regulation. Due to galvanic coupling with the mains supply circuit must be isolated from the user (and the thermistor is the same). Do not rush to lay eggs run the incubator for at least a day, and during that time programfree scale of the potentiometer using a laboratory thermometer. Yes and unexpected failure of unreliable elements often occurs in the first hours of operation (true for any schemes).
If you need to have a large range of operating temperature, it is necessary to increase the value of the potentiometer R14. Alternatively, the value change of the thermistor is proportional to the bridge R9, R11, R14, R15. The maximum power of the heater is determined by the type applied to the thyristor. When you install a more powerful thyristor necessary current control pick up the resistor R7. Small heatsink for thyristor usually required. The coincidence of the phases of management and the anode voltage of the thyristor until swapping the ends of the primary winding TP1, if it does not open immediately upon a cold sensor. Ku-ka-re-ku!
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