Introduction to Industrial Control Systems: Building a Simple Temperature and Humidity Control System

Introduction to Industrial Control Systems: Building a Simple Temperature and Humidity Control System

Hello everyone, I am an engineer with over ten years of experience in the field of industrial automation control. Today, I would like to share a very practical project experience – how to use the DVP-ES2 PLC to build a temperature and humidity control system. This project is very suitable for friends who are new to the industrial control field to learn, and it can also be directly applied in actual work.

1. Project Background and Value

I remember when I first started in the industry, my first independent project was to renovate the temperature and humidity control system of a material storage room. At that time, I felt a lot of pressure, but this project gave me a comprehensive understanding of PLC control. The solution I am sharing today is a summary of my experiences over the years.

The typical application scenarios for this system include:

• Industrial raw material storage rooms
• Laboratory environment control
• Agricultural greenhouse control
• Small constant temperature and humidity test chambers

2. Hardware Configuration List

Main equipment:

• DVP-ES2 series PLC (recommended model 16TX11R)
• Temperature and humidity sensor (e.g., AM2302)
• Heater (select power based on actual needs)
• Humidifier (ultrasonic humidification)
• Fan (for forced convection)
• Distribution box and wiring

Tip: When purchasing hardware, it is recommended to have some redundancy, for example, it is advisable to reserve about 30% of the PLC’s I/O points for future expansion.

3. System Design Approach

3.1 Control Principle

We use the classic PID control algorithm to achieve closed-loop control of temperature and humidity:

• Temperature loop: implemented with heater + fan
• Humidity loop: achieved through humidifier and exhaust
• Both loops work in complementary coordination

3.2 Program Framework

Mainly includes the following functional modules:

1. Data acquisition module
2. PID computation module
3. Actuator control module
4. Alarm protection module
5. Human-machine interaction module

4. Core Code Implementation

Below is the core code snippet for the temperature control loop:

// Temperature PID control program block
LD M8000
MOV D100 D0    // Current temperature value
MOV D101 D1    // Target temperature value
DPID D0 K0     // PID computation
MOV D10 Y0     // Output to heater

// Fan control program block
LD M8000
OUT Y1         // Fan always on

Here are some suggestions to note:

1. PID parameter tuning should be gradual
2. Add soft start function to avoid impact
3. Set reasonable deadband to avoid frequent actions

5. Debugging Tips

Here are a few pitfalls I have encountered:

1. Sensor placement: I remember once, because the sensor was installed in a dead corner of airflow, the measurement value was severely delayed. It is recommended to install the sensor:

• At an appropriate distance from the actuator
• Avoid airflow dead zones
• Keep away from interference sources

1. PID parameter tuning: My experience is:

• First set Ki and Kd to zero, adjust Kp
• After the system stabilizes, gradually add integral
• Finally, fine-tune the differential parameter
• Adjust one parameter at a time, and do not make large adjustments

6. Frequently Asked Questions

Q1: Why is the system response particularly slow?

• Check if the PID parameters are appropriate
• Confirm if the actuator power is sufficient
• Investigate if the sensor placement is reasonable

Q2: Why is the temperature and humidity display unstable?

• Check if the sensor is being interfered with
• Increase sampling filtering
• Adjust the PID deadband parameters

7. Project Practice Case

Last year, we undertook a renovation project for a Chinese medicinal material storage room, with the requirements being:

• Temperature: 20±2℃
• Humidity: 60±5%RH
• Continuous operation for 24 hours

Through this solution, we successfully achieved:

• Temperature control accuracy ±1℃
• Humidity control accuracy ±3%RH
• System stable operation for over six months

8. Experience Summary

1. Design Recommendations

• Reserve sufficient system redundancy
• Focus on safety protection functions
• Implement anti-interference measures

1. Implementation Key Points

• Conduct thorough on-site inspections
• Carefully verify equipment parameters
• Record debugging data in detail

Finally, I want to say that while industrial control systems may not be as fashionable as IT, they are the foundation of industrial production. I hope this article can help more friends who want to enter this field. If you have any questions, feel free to leave a message for discussion!

Tomorrow, I will share some more in-depth technical details, including:

• Multi-zone coordinated control
• Remote monitoring solutions
• Data recording and analysis. Stay tuned!