With EasyARM1138 processor as the core of detection and control, the real-time display and control functions of time, temperature and water level are realized, and the functions of time setting, temperature setting and control are also realized. Fuzzy control is used in temperature control. The controller can use auxiliary heating device to make the water temperature in the storage tank reach the pre-set temperature at the set time according to the weather conditions. The controller integrates many functions such as constant temperature heating, regular water supply, heat preservation cycle, pressurization of water supply, temperature difference cycle, low pressure water supply, temperature control water supply, leakage protection and so on. It can fully meet the needs of users. And the price is low, in vigorously promoting energy-saving, environmental protection in our country, will have broad market prospects. With the development of society, the awareness of energy conservation and environmental protection has been deeply rooted in the hearts of the people. On the one hand, solar energy, wind energy and other clean energy are becoming more and more popular. On the other hand, low-power products are also becoming more and more popular. Solar water heaters, as the best combination of these two products, have developed at an alarming rate [2].
Market research shows that at present, the demand for electricity saving and water-saving products is booming, and the demand for solar water heaters and other products of city consumers is becoming more and more obvious. [3] has led manufacturers to develop new products, [4]. Not only foreign brand TV brands, Panasonic and other new products have been launched to seize the market, Konka, China and other domestic brands have launched a new product [5].
However, the solar water heater controllers currently used in the market generally have large, thick and heavy shortcomings [6]. Some controllers only have the function of temperature and liquid level display, and can only provide users with a general range for sectional display, which has a large display error. According to the survey, such control shows that the temperature display error is 10%, and the water level display error is 25%[7]. When the light intensity is insufficient due to weather, thermostatic element it will lead to the problem of insufficient hot water supply. Even if the water heater has auxiliary heating function, overheating will occur because the heating time can not be controlled.
On the one hand, it will damage the service life of the water heater, on the other hand, it will waste a lot of electric energy [8]. Developing a controller with safe performance, compact and delicate, convenient installation, elegant appearance, environmental protection and energy saving will surely be welcomed by consumers. In this paper, EasyARM1138 processor is used as the detection and control core to realize real-time display and control functions of time, temperature and water level parameters. It integrates many functions such as constant temperature heating, timing water supply, thermal insulation cycle, water pressurization, temperature difference cycle, low pressure water supply, temperature control water supply, leakage protection and so on. It can fully meet the needs of users. And the price is low, in vigorously promoting energy-saving, environmental protection in our country, will have broad market prospects. Easy ARM1138 processor is used as the control core. Real-time parameters of the water heater are converted into digital signals by various sensors, which are sent to the ARM processor for analysis and calculation, and then corresponding signals are sent to the control unit to realize various control functions of the water heater.
The overall design is shown in Figure 1. With the function of man-machine conversation, users can operate by menu and keyboard, which greatly reduces the difficulty of operation and makes the operation process more humanized and powerful. Using temperature sensor to collect the temperature, the controller can display the temperature of the water tank in real time. When the temperature exceeds or falls below the set value of the user, the controller will make the corresponding water inlet, outlet or heating equipment heated or stop working. If the user chooses the memory mode, the controller will start the corresponding equipment (such as heater) at a specific time according to the rules of the user’s use. Do. The water level sensor can measure the water level of the water tank in real time and continuously display the water level of the water tank. When the water level is below or above the specified water level, the water adding and discharging equipment will be activated through the controller.
If there is a malfunction alarm device will start the alarm. Leakage protection devices installed in heating and other high-intensity electrical equipment can ensure that the equipment quickly cuts off the power supply when leakage occurs, so as to ensure the safety and reliability of the person and equipment. In temperature acquisition, the method of multi-point acquisition is adopted. When heating, the water heated parts are not uniform, which will result in different local temperatures. Therefore, it is necessary to install multiple temperature sensors to collect the temperature of different parts [9]. Because the designed product requires higher precision (temperature resolution is less than 1 C), so the selected temperature sensor should also have higher precision, but also considering the cost of the product, comprehensive consideration, decided to use the latest improved temperature sensor S18B20 introduced by DALLAS Semiconductor Company of the United States to collect the temperature of the water tank. The water level detection uses the LM1042 integrated liquid level sensor integrated circuit, and its internal structure is shown in Figure 2. [10]. LM1042 liquid level sensor integrated circuit can be adapted to two thermistors to measure liquid level, of which probe 1 is the main probe. Probe 2 is an auxiliary probe. The circuit can directly input a linear change signal. The upper and lower parts of the thermistor probe are placed in air and liquid respectively, and the working current of the probe is put on.
Because the thermal resistance of air is much larger than that of liquid, the temperature, resistance and voltage variations of upper and lower parts are different, so the height of liquid surface can be measured. In this paper, EasyARM1138 processor is used as the detection and control core to realize the real-time display and control functions of time, temperature and water level. It also has the functions of time setting, temperature setting and control. Fuzzy control is used in temperature control. The controller can use auxiliary heating device to make the water temperature in the storage tank reach the pre-set temperature at the set time according to the weather conditions. The controller integrates many functions such as constant temperature heating, regular water supply, heat preservation cycle, pressurization of water supply, temperature difference cycle, low pressure water supply, temperature control water supply, leakage protection and so on.
It can fully meet the needs of users. The designed controller has powerful human-computer interaction mode, and adopts menu control system. Users can set various functions freely through menu, such as temperature control. LCD can display real-time information of water temperature and temperature, user status and so on. Temperature control realizes the accurate control of temperature, and the accuracy of the target temperature control is less than 1 C.
In water level setting, the accurate control of water level and alarm water level control are realized. In determining the volume of small water tank, the minimum amount of water used for bathing is given, which saves water resources.
While measuring the water temperature, the temperature is measured, and on the basis of the data obtained, according to the health standards, the user can be provided with the best water temperature suggestions, which is more humanized. In terms of cost, due to the adoption of digital control technology, the production cost has been greatly reduced [14]. The development of solar water heater controller is closely related to the development of solar water heater. The solar water heater controller with reliable quality and powerful function can promote the promotion of solar water heater and greatly promote the progress of solar energy industry. This device is designed for energy saving of water heater.