Design of intelligent clothes drying rack control system based on single chip microcomputer

Designing an intelligent clothes drying rack control system based on a single-chip microcontroller (MCU) involves integrating sensors, actuators, and control logic to automate and optimize the drying process. Below is a detailed design approach:

System Requirements

1. Core Functionality:

   • Automatically detect humidity levels to determine if clothes are dry.

   • Control heating and fan systems for efficient drying.

   • Provide user feedback (e.g., LED indicators, display).

   • Support manual override for user control.

2. Additional Features:

   • Energy efficiency (e.g., turn off heating when clothes are dry).

   • Safety features (e.g., overheat protection).

   • Wireless connectivity for remote monitoring (optional).

System Block Diagram

+-------------------+       +-------------------+       +-------------------+
| Humidity Sensor   |       | Temperature Sensor|       | User Interface    |
| (e.g., DHT22)     |       | (e.g., NTC Therm.)|       | (Buttons, Display)|
+--------+----------+       +--------+----------+       +--------+----------+
         |                           |                           |
         |                           |                           |
         v                           v                           v
+--------+-------------------------------------------------------+----------+
|                                                                          |
|                          Single-Chip Microcontroller                     |
|                          (e.g., STM32, ESP32, ATmega328)                |
|                                                                          |
+--------+-------------------------------------------------------+----------+
         |                           |                           |
         |                           |                           |
         v                           v                           v
+--------+----------+       +-------------------+       +-------------------+
| Heater Control    |       | Fan Control       |       | Power Supply      |
| (Relay/MOSFET)    |       | (Relay/MOSFET)    |       | (AC/DC Converter) |
+-------------------+       +-------------------+       +-------------------+

Hardware Design

1. Microcontroller:

   • Choose a low-cost MCU with sufficient GPIOs, ADC, and PWM (e.g., STM32, ESP32, or ATmega328).

   • ESP32 is a good choice if Wi-Fi connectivity is needed for remote monitoring.

2. Sensors:

   • Humidity Sensor: DHT22 or SHT31 for accurate humidity and temperature measurement.

   • Temperature Sensor: NTC thermistor or DS18B20 for monitoring rack temperature.

   • Optional: Load cell to detect the weight of clothes (to estimate drying progress).

3. Actuators:

   • Heater: Use a relay or MOSFET to control a heating element.

   • Fan: Use a relay or MOSFET to control a fan for air circulation.

   • Indicator LEDs: For system status (e.g., drying, dry, error).

4. Power Supply:

   • Use a 5V or 3.3V DC power supply for the MCU and sensors.

   • Use a relay or solid-state relay (SSR) to control AC-powered heaters and fans.

5. User Interface:

   • Buttons for manual control (e.g., start/stop, mode selection).

   • LCD or OLED display for showing status (e.g., humidity, temperature, drying time).

Software Design

1. Main Control Logic:

   • Read humidity and temperature data from sensors.

   • Compare humidity levels with a predefined threshold to determine if clothes are dry.

   • Control the heater and fan based on humidity and temperature readings.

2. Heater and Fan Control:

   • Use PWM to adjust heating intensity and fan speed for energy efficiency.

   • Implement a PID controller for precise temperature control (optional).

3. Safety Features:

   • Overheat protection: Turn off the heater if the temperature exceeds a safe limit.

   • Timeout: Stop the system after a predefined drying time to prevent over-drying.

4. User Interface:

   • Display real-time humidity, temperature, and system status on the LCD/OLED.

   • Use LEDs to indicate system states (e.g., red for heating, green for dry).

5. Optional Features:

   • Wi-Fi Connectivity: Use ESP32 to enable remote monitoring and control via a mobile app or web interface.

   • Data Logging: Store drying history in EEPROM or external flash memory.

Algorithm (Pseudocode)

void main() {
    initialize_sensors();
    initialize_actuators();
    initialize_user_interface();

    while (1) {
        float humidity = read_humidity_sensor();
        float temperature = read_temperature_sensor();

        if (humidity > HUMIDITY_THRESHOLD) {
            turn_on_heater();
            turn_on_fan();
            display_status("Drying...");
        } else {
            turn_off_heater();
            turn_off_fan();
            display_status("Dry");
        }

        if (temperature > MAX_SAFE_TEMP) {
            turn_off_heater();
            display_error("Overheat!");
        }

        check_user_input(); // Handle manual control
        delay(1000); // Wait for 1 second
    }
}

Prototype and Testing

1. Build a Prototype:

   • Assemble the hardware on a breadboard or PCB.

   • Connect sensors, actuators, and the MCU.

2. Test Functionality:

   • Verify sensor readings and actuator control.

   • Test the control logic under different conditions (e.g., wet clothes, dry clothes).

3. Optimize:

   • Adjust thresholds (e.g., humidity, temperature) for optimal drying.

   • Fine-tune PWM settings for heater and fan control.

Cost Optimization

1. Use low-cost components (e.g., DHT22 instead of SHT31).

2. Simplify the PCB design (e.g., 2-layer board).

3. Use open-source software tools and libraries.

Example Components

• MCU: ESP32 (~$5).

• Humidity Sensor: DHT22 (~$5).

• Temperature Sensor: NTC Thermistor (~$1).

• Heater: PTC Heater (~$10).

• Fan: 12V DC Fan (~$5).

• Display: 16x2 LCD (~$3).

By following this design, you can create an intelligent clothes drying rack control system that is cost-effective, energy-efficient, and user-friendly.