The disinfection cabinet control board is the core control unit of the equipment, responsible for driving disinfection components such as ultraviolet lamps, ozone generators, and heating tubes, as well as processing signals from sensors and human-computer interaction modules. Its circuit layout directly affects the stability, anti-interference performance, and safety of the entire disinfection cabinet. This article sorts out the key points of circuit layout for disinfection cabinet control boards, aiming to provide reference for R&D and production personnel.

1. Partition Layout by Functional Modules to Reduce Mutual Interference

The control board of the disinfection cabinet integrates multiple functional modules, and reasonable partition layout is the basis for avoiding signal crosstalk.

Power supply module partition: The power supply module includes AC-DC conversion circuits, voltage stabilization circuits, and filter circuits. It should be arranged independently at the edge of the board, away from the sensitive signal area. The high-voltage input part and low-voltage output part (such as 5V, 12V) need to be separated by isolation slots or insulating partitions to prevent high-voltage interference from affecting low-voltage control signals.

Control core module partition: The MCU (microcontroller unit) and its peripheral circuits (crystal oscillator, reset circuit, memory) are the "brain" of the control board. This area should be placed in the central position of the board to shorten the connection distance with each functional module and reduce signal transmission loss. The crystal oscillator circuit, which is highly sensitive to interference, should be placed close to the MCU’s clock pin, and ground wires should be laid around it to improve stability.

Load driving module partition: The load driving module is used to control high-power components such as heating tubes and ultraviolet lamps, and the circuit has large current and strong electromagnetic interference. This module should be arranged at the position close to the wiring port of the cabinet body, and a certain distance should be kept from the MCU module. Optocoupler isolation devices can be added between the driving circuit and the control circuit to cut off the interference path.

Sensor and human-computer interaction module partition: Sensors (temperature sensor, door switch sensor, ozone concentration sensor) and human-computer interaction components (display screen, buttons) belong to weak current signal modules. The layout should be close to the corresponding installation position of the cabinet, and the signal lines should be short and straight to avoid parallel wiring with the high-current lines of the driving module.

2. Reasonable Wiring to Ensure Signal Integrity and Current Stability

Wiring is the key link of circuit layout, and different types of lines need to adopt targeted wiring strategies.

Power line wiring: The power line carries large current, so it should use wide copper foil to reduce line resistance and avoid heating due to excessive current density. The main power line should be laid as directly as possible, and bypass capacitors (such as 100μF electrolytic capacitor + 0.1μF ceramic capacitor) should be added near the power pin of each chip to filter out high-frequency interference and stabilize the power supply voltage.

Signal line wiring: The signal line should be short and straight, avoiding sharp bends (the angle should be greater than 90°) and cross-over as much as possible. For high-frequency signal lines such as crystal oscillator signals, impedance matching should be considered, and the line width should be adjusted according to the board material and thickness to prevent signal reflection. The signal lines of the same group should be kept consistent in length to ensure synchronous transmission of signals.

Ground wire layout: Ground wire layout is crucial to improving the anti-interference performance of the control board. The single-point grounding method can be adopted for the weak current signal module to avoid the formation of ground loops and cause interference; the multipoint grounding method can be used for the high-power driving module to quickly discharge the large current to the ground. In addition, a ground plane can be designed on the PCB (printed circuit board) to cover the entire board, which can not only reduce the loop area of the signal but also shield external electromagnetic interference.

3. Safety Layout to Meet Electrical Safety Standards

The disinfection cabinet works in a humid environment for a long time, and the circuit layout must comply with electrical safety standards to prevent electric leakage and short circuit.

Creepage distance and clearance control: Creepage distance refers to the shortest path between two conductors along the surface of the insulator; clearance refers to the shortest straight-line distance between two conductors in the air. For the parts where high voltage and low voltage coexist on the control board, the creepage distance and clearance must meet the requirements of national standards (such as GB 4706.1), generally not less than 3mm, to prevent insulation breakdown caused by moisture and dust accumulation.

Isolation of live parts: The live parts of the control board (such as AC input terminals) should be isolated from the touchable parts (such as button interfaces) by insulating materials or structural design to avoid electric shock hazards. The welding points of high-voltage components should not be exposed, and protective covers can be added if necessary.

Waterproof and moisture-proof design: The control board should be coated with a waterproof and moisture-proof coating (such as conformal coating) to isolate the circuit from the humid air in the cabinet. In the layout, the key components (such as MCU, optocoupler) should be arranged on the side away from the air outlet of the cabinet to reduce the impact of water vapor.

4. Consideration of Maintainability and Compatibility in Layout

In addition to performance and safety, the layout should also take into account the convenience of subsequent production, maintenance, and model compatibility.

Reserved test points: Test points should be reserved at key nodes of the circuit (such as the output end of the power supply, the input and output ends of the sensor, the I/O port of the MCU) to facilitate debugging and fault detection after production. The test points should be arranged in a centralized manner and marked clearly to improve the efficiency of maintenance personnel.

Standardization of component layout: The components should be arranged neatly, and the direction should be consistent (such as the polarity direction of capacitors and diodes) to facilitate automatic soldering and manual inspection in the production process. The spacing between components should be appropriate to avoid mutual interference during heat dissipation and ensure sufficient operation space for maintenance.

Compatibility with multiple models: When designing the layout, the installation hole positions and wiring ports can be standardized to adapt to the control board installation requirements of different disinfection cabinet models. The reserved positions of expansion interfaces (such as the interface of the Internet of Things module) can be added to facilitate the subsequent function upgrade of the product.

5. Heat Dissipation Layout to Prevent Component Overheating

Some components on the control board (such as power transistors, voltage regulators) will generate heat during operation. If the heat cannot be dissipated in time, it will affect the service life and stability of the components.

Heat dissipation of high-power components: High-power components should be arranged in the area with good air circulation on the board, and heat sinks can be installed if necessary. The heat dissipation pad of the component should be closely connected with the copper foil of the board, and the copper foil area should be increased to enhance the heat dissipation effect.

Avoid heat accumulation: Components with large heat generation should not be concentrated layout, and a certain distance should be kept between them to avoid heat accumulation. Sensitive components to temperature (such as sensors, electrolytic capacitors) should be placed away from high-temperature components to prevent their performance from being affected by high temperature.

In summary, the circuit layout of the disinfection cabinet control board needs to comprehensively consider the factors of anti-interference, safety, maintainability, and heat dissipation. Only by strictly following the above key points can we ensure that the control board operates stably and reliably in the complex working environment of the disinfection cabinet, and then guarantee the overall performance of the disinfection cabinet.

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