The control board is the core control unit of a disinfection cabinet, which integrates power supply, signal acquisition, logic operation, load drive and safety protection circuits. It realizes automatic control of ultraviolet disinfection, ozone sterilization, high-temperature drying, timing operation and door interlock protection. Working in a closed environment with humidity, ozone and high temperature, the circuit design requires reliable isolation, strong anti-interference and perfect safety mechanisms. This article systematically introduces the overall hardware architecture, each functional module composition, circuit working principle and signal transmission logic of the disinfection cabinet control board.

Overall, the control board adopts a modular circuit design, which is divided into seven core functional units: power supply module, main control MCU minimum system, human-computer interaction module, signal detection module, load drive module, safety interlock protection module and auxiliary circuit. All modules work collaboratively under the scheduling of the main control chip. The weak current circuit completes signal collection and logic judgment, and the drive circuit controls the on-off of high-power loads, realizing the separation of strong and weak currents to ensure electrical safety and operational stability.

The power supply module provides stable DC voltage for the entire control board and is the basis for normal operation of all circuits. The 220V AC mains first passes through a fuse and a varistor. The fuse provides over-current and short-circuit protection. The varistor absorbs surge voltage to prevent instantaneous high voltage from damaging the rear-stage circuit. Then the current enters the EMI filter circuit composed of common-mode inductors and safety capacitors to suppress electromagnetic interference from the power grid and prevent the equipment itself from generating harmonic pollution. After filtering, the AC power is divided into two paths: one directly supplies power to high-power loads such as ultraviolet lamps, ozone generators and heating tubes; the other is converted into low-voltage DC power through a step-down circuit.

Most household disinfection cabinets adopt the resistance-capacitance step-down scheme for cost control, while mid-to-high-end and commercial models use isolated switching power supplies for higher safety. The power module outputs two groups of common voltages: +12V supplies power to relays, buzzers and cooling fans; +5V is used for the main control MCU, sensors, key circuits and display units. Multiple electrolytic capacitors and ceramic capacitors are connected in parallel at the output terminal to filter high and low frequency ripples, ensuring stable voltage output and avoiding abnormal operation of the chip caused by voltage fluctuation.

The main control MCU minimum system is the logic operation center of the control board, mainly composed of an 8-bit dedicated household appliance single-chip microcomputer, crystal oscillator circuit and reset circuit. The crystal oscillator provides a stable operating clock for the MCU to determine the program running speed. The reset circuit completes system initialization at power-on, and can automatically reset when the program runs away or crashes. The built-in I/O ports, AD conversion interfaces, timers and interrupt ports of the MCU are connected to each functional module respectively. Its working logic is as follows: scan and receive user operation instructions in real time, collect temperature and door state signals, perform logical judgment and operation according to preset programs, and send control level signals to the drive module to turn on or off corresponding loads, so as to execute disinfection, drying, timing and other functions. A watchdog circuit is usually integrated to monitor the operating state of the program all the time and improve the overall anti-jamming capability.

The human-computer interaction module realizes man-machine command interaction and status display, including key circuit, display circuit and acousto-optic prompt circuit. The key circuit is divided into traditional mechanical tact keys and capacitive touch keys. The independent I/O or matrix scanning mode is adopted. When a key is pressed, the level of the corresponding pin changes, and the MCU identifies the function instruction. For touch keys, a special touch detection chip is matched, with peripheral filter resistors and capacitors to prevent false triggering caused by humidity and static electricity. The display circuit uses LED indicator lights, digital tubes or segment code LCD screens, which are directly driven by the MCU or a dedicated display driver chip to display working modes, remaining time, gear levels and fault codes. The acousto-optic prompt circuit is composed of triodes and buzzers. The MCU outputs level signals to control the buzzer to sound prompts for power-on confirmation, key response, work completion and fault alarm.

The signal detection module mainly includes temperature sampling circuit and door switch detection circuit. The temperature sampling circuit uses NTC thermistors as temperature sensing elements. The thermistor forms a voltage division loop with a precision fixed resistor powered by +5V. The resistance of the thermistor changes with the internal temperature of the cabinet, resulting in continuous change of the division voltage. The analog voltage signal is transmitted to the MCU's AD port, and the chip converts it into digital quantity to obtain the real-time temperature. This circuit is used for high-temperature drying temperature control and over-temperature early warning. A filter capacitor is connected in parallel at the sampling terminal to eliminate signal jitter caused by interference.

The door interlock detection circuit is a unique design of disinfection cabinets. It adopts mechanical door switches connected to the I/O ports of the MCU. When the cabinet door is closed normally, the switch is turned on and the circuit is conducted; when the door is opened accidentally during operation, the switch is disconnected, and the MCU immediately captures the level change. Combined with the program logic, it forcibly cuts off the disinfection load to prevent ultraviolet rays and ozone from leaking out and hurting human bodies.

The load drive module is the execution unit for weak current to control strong current, responsible for driving ultraviolet lamp, ozone generator, heating tube and fan. It adopts the classic combination circuit of triode amplification, optocoupler isolation and relay switch. The weak control signal output by the MCU is amplified by the triode and then transmitted to the optocoupler. The optocoupler realizes complete electrical isolation between strong and weak current circuits, effectively isolating strong current interference and improving safety. The rear stage of the optocoupler drives the relay coil to pull in, and the relay contacts connect the 220V AC power to the corresponding load. Different loads are equipped with independent drive loops: ultraviolet lamps and ozone generators use small-power relays; high-temperature heating tubes use high-current relays. Some models use bidirectional thyristors for stepless power regulation of heating components to achieve constant temperature drying.

The safety interlock protection module is a key guarantee for the safe operation of disinfection cabinets, combining hardware forced protection and software logic protection. In terms of hardware protection, thermal fuses and mechanical temperature controllers are connected in series in the high-temperature heating circuit. When the internal temperature is abnormally overheated, the contacts are automatically disconnected to cut off the power supply, which can still work normally even if the MCU fails. The door lock switch mentioned above forms a physical interlock. Once the door is opened, all disinfection and heating loads are locked immediately. In terms of software protection, the MCU judges faults according to temperature signals and sensor states. When the temperature exceeds the limit or the sensor is open/short-circuited, the program stops all output and triggers an alarm. The power fuse at the input terminal realizes over-current and short-circuit protection for the whole machine.

The auxiliary circuits include anti-static circuit, wiring terminals and board protection components. ESD protection diodes are connected to key signal pins to release static electricity and prevent the chip from being broken down. Since the internal environment of the disinfection cabinet is humid, the entire circuit board is coated with three-proof paint to prevent condensation from causing creepage and short circuit. The wiring terminals adopt high-temperature and corrosion-resistant terminals to adapt to long-term humid and ozone environment.

The overall working flow of the circuit is as follows: After power-on, the power module outputs stable voltage, the MCU completes initialization and self-check of each module, and the equipment enters the standby state. The user selects the working mode and sets the timing through keys. The MCU receives the instruction and first detects the state of the cabinet door. Only when the door is closed tightly can it start the subsequent procedure. The system turns on corresponding loads such as ultraviolet lamps, ozone generators or heating tubes through the drive circuit according to the selected mode. During operation, the temperature and door state are monitored in real time. If an abnormal state is detected, the protection circuit acts immediately. When the set time ends, the MCU automatically cuts off all loads, and the buzzer sends a completion prompt. The whole circuit operates in a closed loop to complete the full process of disinfection and drying.

In conclusion, the disinfection cabinet control board takes the power supply and MCU as the core, and cooperates with detection, interaction, drive and protection circuits to form a complete strong and weak current control system. Aiming at the special environment of ultraviolet radiation, ozone, high temperature and humidity, the circuit adopts targeted designs such as electrical isolation, anti-interference, moisture-proof and multi-layer safety protection. Understanding the hardware composition and circuit principle is the basis for equipment debugging, fault maintenance and product function upgrading.