Circuit Analysis of Drum Washing Machine

1. Principle of laundry

A drum washing machine mainly places clothes in the drum, partially immersing them in water. When the motor drives the drum to rotate, the protrusions inside the drum can drive the clothes to roll up and down, thus achieving the purpose of washing clothes.

(Typical drum washing machine control schematic diagram)

2. Control circuit Analysis

The coordinated work of various components of a drum washing machine is achieved through the main control circuit. The control schematic diagram of a typical drum washing machine is shown in the figure below.

1. Power supply part

Working process: The AC 220V voltage connectors IF1 and IF2 provide power to the switching power supply on the main control board . After the switching power supply works, the DC current Vcc is output to provide working conditions for the entire working system of the washing machine.

2. Water inlet control part

Working process: The main wash water inlet valve VW, pre-wash water inlet valve VPw and hot water inlet valve VHF form a water inlet system. Water is added through the control of the main control circuit board. When the water level reaches the preset height, the internal contacts of the water level switch act to input the water level high and low signal to the main control circuit , and the main control circuit outputs a stop signal, and the water inlet solenoid valve stops water inlet.

3. Washing control part

Working process: After the water is added, if the added water is cold water, the cold water will be heated. This function is completed by the heating tube HB and the temperature sensor NTC. After the preset temperature is set, the main control circuit controls the heating tube to start heating the cold water. When the temperature reaches the preset value, the temperature sensor NTC sends the temperature detection signal to the main control circuit, and the main control circuit drives the motor to start the washing operation.

4. Drainage control part

Working process: The drain pump DP is the main component of the drainage system. Its main function is to drain the water in the drum, which is the opposite of the work of the water inlet system. When washing is completed, the main control circuit controls the washing system to stop working, and at the same time controls the start of the drain pump DP to work, and discharges the water in the drum to the outside of the machine through the water outlet.

5. Dehydration control part

Working process: After drainage is completed, the main control circuit controls the washing machine to automatically enter the dehydration work. The washing motor drives the inner barrel to rotate at high speed. The moisture adsorbed on the clothes is thrown out of the barrel through the drainage holes on the inner barrel wall under the action of centrifugal force, realizing the dehydration function.

Note: During the operation of the drum washing machine, there will be different status indications on the operation display panel. When the dehydration is completed, the washing of the clothes is completed. The safety door switch plays a protective role in the drum washing machine. When the washing machine is in operation, the safety door cannot be opened; it can only be opened when the washing machine stops running.