Refrigerator air cooling power saving automatic controller circuit

Practice has proven that using an electric fan to dissipate heat in a refrigerator is an effective way to save electricity. When the fan is working continuously, the power consumption per month is only about 2 degrees, and if the fan stops, the power consumption is only 0.7 degrees. The automatic controller introduced in this article, when the temperature rise of the refrigerator compressor reaches a predetermined value, the electric fan automatically supplies air to assist heat dissipation, improves work efficiency, and prevents the refrigerator from starting frequently. Working Principle    　　The working principle of the device circuit is shown in Figure 1.

It is mainly composed of high-power switch integrated circuit IC2 and thermal element Rt. When the temperature of the refrigerator compressor increases, the resistance of the thermistor Rt decreases, causing the voltage at point A of the circuit (i.e., pin ① of IC2) to rise above 1.5V. At this time, the drive tube inside IC2 8752 is turned on. , relay J is excited and closed, and turns on the power supply of the micro fan to rotate and supply air. Once the temperature of the compressor drops, the resistance of the thermistor Rt also increases, causing the voltage at point A to drop below 1.5V. At this time, the drive tube inside IC2 is cut off and the micro fan stops rotating. This not only compresses The machine is cooled, and the electric fan itself also saves energy consumption and extends its service life. The component selection and production component list is shown in the table below. No. Name Model Quantity R Carbon film resistor 300Ω 1 RP Trimming resistor 2.2K 1 Rt Thermistor 1K Negative temperature coefficient 1 C1 Electrolytic capacitor 220u/25V 1 VD1--VD5 Rectifier diode IN4001 5 IC1 Three-terminal voltage regulator LM7806 1 IC2 Large Power switch IC 8752 or 8751 1 J Relay 1A 6V any model 1 T Power transformer 12V 2--3W 1 Thermistor Rt is fixed on the metal shell of the compressor with tape or strong heat-resistant glue. When debugging, use a cup of warm water (about 40℃), adjust the RP to stop running below body temperature, and then immerse the thermistor in hot water higher than human body temperature. At this time, be careful not to immerse the thermistor lead in water. When thermal balance is reached (Rt rises to the hot water temperature), the motor runs, and the circuit is successfully debugged and can be put into use.