Abstract : Traditional heating systems cannot control the temperature in a home; excessively high temperatures waste energy, while excessively low temperatures cause discomfort. Intelligent heating control systems allow for controlled heating flow, minimizing resource consumption and conserving energy while meeting daily needs.
Central heating remains the primary method of heating in northern China during winter. Currently, many residential communities are primarily comprised of young couples or three-person households, with parents at work and children at school during the day, leaving the home unattended. In these situations, the indoor heating temperature is no different from when someone is home. Traditional heating systems cannot control the indoor temperature; excessively high temperatures waste energy, while excessively low temperatures are uncomfortable. Furthermore, existing heating controllers only provide temperature control; to save energy, the temperature must be lowered. Especially today, with the increasing scarcity of non-renewable energy sources like coal and natural gas used for heating, we aim to minimize resource consumption while meeting people's daily needs. Therefore, we propose a design concept that makes heating systems like air conditioning, with adjustable temperatures and a timer system. Simultaneously, incorporating smart home design concepts, a remote control module is added, allowing for low-temperature heating when no one is home, and normal heating when people return. Using low-temperature heating for nearly one-third of the day can save significant amounts of coal and natural gas.
Some indoor heating temperature controllers on the market now use temperature sensors to measure indoor temperature and a microcontroller to regulate the opening and closing of solenoid valves to control the temperature. This system uses a stepper motor instead of a solenoid valve to control the amount of hot water flowing into the heating system. The stepper motor is self-locking after power-on and can withstand high pressure within the heating pipes. By using a stepper motor to control the valves, the flow rate of hot water in the pipes is precisely controlled, achieving temperature adjustment. This system also incorporates control via smartphones, computers, and other smart devices, allowing users to adjust the operating mode switching time anytime, anywhere based on their arrival time. This ensures maximum energy savings when returning home late and a comfortable environment when returning early.
The controller is customizable, including the temperature for different heating modes and the operating time for each mode. The development of IoT technology has enabled more flexible control methods for smart homes, allowing users to remotely modify parameters via mobile internet, such as changing the mode switching time anytime, anywhere when arriving home early or late. This achieves remote control, allowing for easy modification of settings and modes.
A temperature sensor measures the indoor temperature, and a fuzzy control algorithm adjusts the stepper motor angle to control the valve opening size. A GPRS module is used for communication between the user and the controller. The workflow of the intelligent heating control system is shown in Figure 1.
Figure 1. Workflow diagram of the intelligent heating control system
1. Overall circuit design
The overall circuit design components include: STM32F103CB minimum system MCU, power supply, I2C communication E2PROM, CAN bus, buzzer, temperature measurement, AD conversion, buttons, expansion ports, etc. The overall circuit diagram is shown in Figure 2.
Figure 2 Overall circuit diagram
The I/O ports and PWM ports of the microcontroller motherboard serve as the direction control interface and rotation distance control interface of the motor driver board, and the motor speed is controlled by the PWM frequency output by the microcontroller.
2. Stepper Motor Control System Design
The difference between a stepper motor and a regular electric motor lies in that it is an actuator that converts electrical pulse signals into angular displacement. It performs two functions simultaneously: transmitting torque and controlling angular position or speed. A stepper motor requires a driver and a controller to function properly. The driver's role is to distribute and amplify the control pulses in a circular manner, energizing the stepper motor windings in a specific sequence to control the motor's rotation.
Figure 3 Stepper motor control system diagram
3. GPRS module selection
Select the ATK-SIM900AGSM/GPRS module. The ATK-SIM900A module is equipped with SIMCOM's industrial-grade dual-band GSM/GPRS module: SIM900A, operating in dual-band (900/1800MHz). It can transmit voice, SMS (text messages, MMS not supported), data, and fax information with low power consumption. The module's functions are shown in Figure 4.
Figure 4 GPRS Module Function Diagram
4. Mobile Client Software Design
The mobile client software can utilize existing Lewei50 IoT software to achieve intelligent system control. Lewei50 (http://open.lewei50.com), through its open API, allows for easy connection of various sensors, measuring devices, or industrial instruments to the platform, and enables the development of applications to monitor and control them. Lewei50's platform provides sensor cloud services, eliminating the need for cumbersome programming and allowing users to quickly enable network functionality for their various measuring or control devices, thus launching IoT applications. Lewei50's main functions include a personal portal, data storage and analysis (extendable to an expert system when combined with industry experts), seamless integration of industrial instruments, and a mobile app.
The Internet of Things (IoT) architecture consists of three layers: "cloud server -> device -> sensor & controller". "Sensor & controller" refers to devices or instruments that can collect, measure, or be controlled. The role of the "device" is to send the collected data to the cloud server or return control data to the device. The front end of the "device" must be able to communicate with the measuring device (e.g., RS232 interface, RS485 interface), and the back end needs to have network capabilities (e.g., GPRS, Wi-Fi, and Ethernet). The "cloud server" deploys a database for data storage and analysis. Finally, users can access the database through a browser using a client (computer, mobile phone), enabling a wide variety of data-driven applications.
To illustrate with an example, as shown in Figure 5, if we want to collect temperature and humidity data from two greenhouses in Beijing and Shanghai and store it on a server for agricultural experts to query and analyze, thus providing guidance for planting, we first need to install measuring "sensors" in both greenhouses. Then, we connect these "sensors" to a network adapter module, i.e., a "device." This "device" will forward the collected data to a public network server, i.e., a "cloud server," for storage. End users can then access and analyze the data via a webpage.
Figure 5. Internet of Things Architecture Diagram
The intelligent heating control system can automatically adjust the size of the heating valve according to the set temperature to achieve controllable indoor temperature; the dual-pipe parallel connection ensures that the heating water supply between each household is independent and the system is balanced; when no one is home, a low-temperature mode is activated to save coal and natural gas energy; parameters can be remotely controlled via mobile phone or Internet.
