Design and production of automatic deodorizer for refrigerator

The traditional refrigerator "deodorizer" uses the porous adsorption of activated carbon to absorb the odor in the refrigerator. This deodorizer has no sterilization effect, and the activated carbon or the entire finished product needs to be replaced frequently, which is very inconvenient to use and increases economic expenditure. Here is an electronic deodorizer that can automatically remove the odor of the refrigerator. It uses corona discharge to ionize the air, generating a large amount of air negative ions (mainly negative ions) and a certain amount of ozone. After diffusion, it can quickly remove the odor and maintain the original flavor of the food to prevent cross-flavoring. Ozone is a strong oxidant with extremely strong sterilization and disinfection functions, while negative oxygen ions can also inhibit the biochemical process inside vegetables and fruits, playing a certain role in preservation. The electronic deodorizer integrates deodorization, sterilization, and preservation functions. It has the characteristics of simple circuit, easy use, and extremely low power consumption (about 1W). Therefore, it is very suitable for amateurs to make and use, and can also be used as a reference for small household appliance manufacturers.

　　Working principle The device is mainly composed of two parts: light control, delay circuit and negative ion generator. The circuit is shown in Figure 1 (click here to download the schematic diagram). The light in the refrigerator is used to control the start of the device. When the refrigerator is opened to take out food, the light turns on, the photoelectric tube VT1 is turned on, the ② pin of the time base circuit IC1 is instantly low, and the ③ pin immediately outputs a high level, the bidirectional thyristor VS is triggered to turn on, and the negative ion generator starts to work. The working voltage of the light control and delay control circuit is provided by 220V AC after being stepped down by C1, rectified by VD1, stabilized by VDW, and filtered by C2. While the negative ion generator is working, the DC power supply is charged through R2 and capacitor C3. When the voltage across C3 reaches 2/3 of the power supply voltage, the ③ pin returns to a low level, the thyristor VS is turned off, the negative ion generator stops working, and the charged voltage of C3 is quickly discharged through the discharge tube in the IC. In this cycle, the deodorizer automatically works for 8-10 minutes every time the refrigerator door is opened. The length of the delay time can be adjusted by changing the value of R2.
 

The working principle of the negative ion generator circuit is relatively simple. When VS is turned on, the 220V AC is rectified and limited by VD2, VD3, R4, and R5. The unidirectional pulsating current controls the on and off of VS, generating oscillations. After being stepped up by transformer T and rectified by VD4, tens of thousands of volts of negative high voltage are generated. The discharge is directed to the air to ionize the air and generate negative ions. R6 is a protective resistor designed to prevent electric shock . Selection and production of
components
See the attached table for component selection.
 No. Name Model Quantity R1 Resistor 20K1 R2 Resistor 1M1 R3 Resistor 240Ω1 R4 Resistor 22K1 R5 Resistor 27K1 R6 Resistor 2-4M1 C1, C5 Metallized paper dielectric capacitor 0.1u/400V2 C2, C3 Electrolytic

capacitance

220u/25V2C4 polyester capacitor 0.01u1VD1-VD3 rectifier

diode

IN40073VD4 Silicon Stack 18kV1VDW Zener Diode 2CW21H1VT1 Phototransistor TLP1071VS1

Bidirectional thyristor

1A/400V1VS2 unidirectional thyristor 1A/400V1IC1 time base ICNE5551T

switch

Transformer self-made (see text after the table) 1
Transformer T can be modified from a 35cm black and white TV line output transformer. Remove all low-voltage winding coils and use Φ＝0.35mm enameled wire or silk-covered wire to wind 28 turns as L1. The original high-voltage package is L2. If it is modified from an integrated line output transformer, the whole machine will be smaller. Two thumbtacks are used as discharge needles. The tip of the thumbtack should be trimmed as sharp as possible with an assorted file to facilitate tip discharge. All components can be installed in a plastic box as small as possible, and the AC output line is connected to points A and B of the lighting control circuit in the temperature control box. The whole machine can be placed under the control box, and the photoelectric tube is aimed at the lighting in the refrigerator. The deodorizer can work automatically under the control of the lighting.