Infrared remote control intelligent solar water heater control system based on STC89C52

0 Preface

With the continuous reform and innovation of energy-saving technology in society, solar energy has become a green label in the sustainable development strategy of the new era, and solar water heaters have become an indispensable device in our daily life. However, the solar water heaters sold in shopping malls now generally have problems such as complex circuits, high costs, no protection functions, easy to cause pipe freezing and cracking, heating belts are prone to fire, and cumbersome operation, which makes solar water heaters prone to fire, leakage and waste of electricity in winter. The system function has a lot of new pipe freezing and cracking, and heating belts are prone to fire. The advanced technologies introduced by this system, such as automatic water supply, automatic emptying, infrared remote control, etc., just solve the above-mentioned series of safety hazards such as pipe freezing and cracking, easy to cause fire, leakage and waste of electricity, which is convenient to use and saves energy.

1 Basic structure and function of the system

The system hardware design selects STC89C52 as the main control chip. The hardware design involves the following aspects: temperature sensor information acquisition circuit, water level simulation circuit, reset button circuit, AD conversion circuit, clock display circuit and infrared remote control receiving circuit, etc. The temperature sensor is used to collect circuit information, the water level sensor collects water level information, the AD converter transmits the information to the single-chip microcomputer for transmission, and the clock chip displays the clock on the LCD screen. We can also use the infrared remote control to adjust the time and alarm, automatically fill water and other functions, and can also save electricity by turning off and on the LCD screen at any time. As shown in Figure 2, the functions that the system can achieve are as follows: accurate temperature and water level display function; LCD display time and date; low water level automatic alarm and automatic water filling function; automatic emptying function; infrared remote control control solar water heater function.

2 System Hardware Design

2.1 Acquisition Circuit

The acquisition circuit is divided into water level and temperature acquisition circuit and AD conversion circuit. The temperature acquisition circuit uses NTC series MF11 type 101. The temperature acquisition circuit includes a temperature thermistor and a conditioning circuit, as shown in Figure 4. The water level measurement circuit uses a resistive water level sensor connected to a conditioning circuit, as shown in Figure 4. OP07 is an operational amplifier, which we use as a follower here to improve the anti-interference ability and the ability to protect the circuit. The AD circuit uses the ADC0832 dual-channel 8-bit analog-to-digital conversion chip.

2.2 Main control circuit

We chose the simplest and most practical control chip STC89C52 microcontroller, and the system function pin allocation diagram is shown in Figure 4. [page]

2.3 Display Circuit

The display circuit includes an indicator light circuit, an LED liquid crystal display circuit, a buzzer alarm circuit, and a clock display circuit. The indicator light circuit is shown in C in Figure 4. P1.0 to P1.3 respectively display insufficient water, moderate, saturated, and alarm. The LED liquid crystal display circuit is shown in A in Figure 4. The liquid crystal adopts 1602 type, and 6 to 14 of the liquid crystal are connected to P0.0 to P0.7 of the single chip computer. The clock display circuit is shown in B in Figure 4, and 5 to 7 are connected to P1.4 to P1.6.

2.4 Automatic water pipe emptying circuit

2.4.1 Automatic water supply circuit

As shown in Figure 5, when the water tank needs to be filled with water, the microcontroller gives IR VLAVEN a low level, which is driven and amplified by ULN2803 (as shown in part D in Figure 4), so that the relay is turned on, the LED tube is lit, the switch is closed to turn on the 220V voltage, and the solenoid valve A works. The function of automatic water filling is realized. When IR VLAVE IN is a high level, the solenoid valve A does not work and stops filling water. In this way, the function of automatic water filling is realized.

2.4.2 Automatic drain circuit

Under normal circumstances, the drain solenoid valve B is closed, and the drain switch is also closed. The pipeline is equivalent to a vacuum pipe with water inside. When the weather is cold in winter, the water in the pipeline is easy to freeze, causing the pipeline to crack. As shown in Figure 5, when we open the upper drain solenoid valve B and the lower drain switch, a lot of air suddenly enters the pipeline, and the water in our pipe flows down due to the characteristics of air convection. Since the lower drain switch is indoors, we can use a manual switch, and the water outlet switch is only controlled by a solenoid valve B.

3 System Software Design

The system software is written in C language, compiled by Keil uVision4, and debugged and run after simulation by Protues. The software is mainly designed for the information acquisition unit, host computer part, display part, and infrared remote control part of the system. The information acquisition includes temperature, water level, and AD conversion program. The host computer part includes automatic emptying part and automatic water filling part. The display part mainly operates the clock and LCD program. The temperature and water level programs adopt the table lookup method design idea, and the voltage values ​​corresponding to different temperatures are made into tables and compared in turn. This article mainly introduces the software design ideas of infrared and automatic actuators.

3.1 Infrared software design

The software part adopts NEC protocol, which includes: boot code, 16-bit user code (address code), 8-bit command code (data code) and its inverse code. The boot code consists of a 9ms carrier waveform and a 4.5ms off time. The user code is 16 bits in total, the lower 8 bits are output first, the higher 8 bits are output later, and the 8-bit key data code and its inverse code. The system determines the difference of the remote control buttons according to the different data codes, and sets different key functions according to the different buttons.

3.2 Automatic control unit software design

The automatic control unit includes automatic water filling, automatic emptying, automatic alarm, automatic water level display light, etc. The switch function is mainly realized by changing the state of the IO port of the single-chip microcomputer. When the water level is lower than 25%, low-voltage automatic water filling is adopted, the buzzer alarms, and the insufficient water light is on. When the water level is higher than 25% and lower than 50%, the automatic water filling light is off, and the insufficient water light is on. When the water level is higher than 50% and lower than 75%, the moderate light is on, and when the water level is higher than 75% and lower than 100%, the full water level light is on and the automatic water filling is stopped. The automatic control function is realized by controlling the state of the water filling solenoid valve by the single-chip microcomputer.

4 Summary

The solar controller designed in this paper is green and environmentally friendly. It uses the cheapest NTC thermistor MF11 and 101 water level resistor sensor to measure temperature and water level information: it receives signals through the single-chip microcomputer STC89C52, adds the DS1302 clock display function; it displays a series of information such as temperature, water level, time, etc. through the LCD, saving costs. In view of the fact that traditional solar designers cannot automatically fill water and are prone to freezing in winter, the features of automatic filling and automatic emptying are added. According to people's usage habits, a humanized design idea is adopted, and infrared remote control technology is used to achieve artificial short-distance wireless control to prevent electric shock.