Design of self-adaptive electric water boiler based on single chip microcomputer

Abstract: This electric water machine adopts an adaptive method to simulate the manual summary of the user's water use rules, reasonably determine the water boiling time and water volume, stop heating in the non-water use period, solve the problem of mixed water and dry boiling water, and achieve the dual effects of health and energy saving.
Keywords: adaptive; circuit design; electric water machine; single chip microcomputer

0 Introduction
Electric water machines have the characteristics of cleanliness, high efficiency, and easy installation. Therefore, they are widely used in schools, factories, offices, hotels and other places, providing convenience for people to drink water. The electric water machines currently on the market are usually composed of water storage tanks, heaters, water inlet valves and other components, with simple structures and single functions. There may be two serious consequences of using these electric water machines. One is the existence of yin and yang water (water mixed with raw water and boiled water), and the other is the existence of dry boiling water (water that is repeatedly boiled). The problem of yin and yang water has been solved in most water machines through some special separation structures, but there is no better solution to the problem of dry boiling water. When
the water dispenser is turned on for a long time, especially in the standby period when no water is used, the water in the hot tank will be repeatedly heated to form "dry boiling water". At the same time, most of the water dispensers sold on the market are water dispensers with a tank, which heats the water. The material of the tank is mostly stainless steel or aluminum shell. If it is heated repeatedly, the content of nitrites such as iron, aluminum, and ammonium in the water will increase significantly, thereby increasing the concentration of harmful substances in the "dry boiling water". Experiments show that the chemical composition of "dry boiling water" has changed greatly, breeding harmful substances such as heavy metals, and long-term drinking will affect people's gastrointestinal function.

1 System Overview
The water dispenser designed in this paper stops heating during the non-water use stage, such as at night. Before going to work in the morning, the water dispenser automatically drains the remaining water in the water tank and adds new water to reheat until it boils. During the daytime working hours, the amount of water boiled in each time period can be adjusted according to the water use of each user, achieving the dual effects of health and energy saving. Since the water use of each user in each time period is different, but there is usually a certain regularity, the electric water system designed in this paper adopts an adaptive method to simulate the manual summary of the user's water use rules, determine the water boiling time and water boiling amount, and achieve better health and energy saving effects.

2 Mechanical structure
Figure 1 Mechanical structure of electric water boiler. To completely solve the problem of yin and yang water, this device uses two water tanks and heating pipes. Water tank 1 is used to boil water, water tank 2 is used to store boiled water, and heating pipe 2 is used for heat preservation. When the water inlet valve is opened, tap water can be put into water tank 1. When the water in water tank 1 is boiled, the water is injected into water tank 2 through the connecting valve. The water outlet valve is used to supply water to the user, and the drain valve is used to drain the remaining water in water tank 2.

3 Hardware circuit design
Figure 2 shows the hardware circuit structure. The hardware circuit is based on a microcontroller and includes two water level sensors, two heating tubes, an inlet valve, a connecting valve, a drain valve, and an outlet valve, as well as a DC power supply, a human-machine exchange device, and a real-time clock circuit. The water level sensor uses a high-temperature immersion liquid level sensor. If the cost is to be reduced, a self-made graded liquid level switch can be used instead. The inlet and drain valves use high-temperature solenoid valves. The display uses a 12864-type LCD screen with a Chinese character library. If the cost is considered, a digital tube or a simple LCD screen can also be used. The
real-time clock uses the SD2058 chip, which is a real-time clock chip with a standard IIC interface. The CPU can use this interface to read and write the data of the 64-byte register on the chip through 6-bit address addressing. SD2058 has a built-in single-channel timing/alarm interrupt output, and the alarm interrupt time can be set up to 100 years; the built-in clock precision digital adjustment function can correct the clock deviation in a wide range (-189ppm~+189ppm, resolution 3.05ppm), and the adjustment value that adapts to temperature changes can be set through an external temperature sensor to achieve high-precision timing function in a wide temperature range; the chip also has an independent 32768Hz square wave pulse output pin.
In this system, the main task of the microcontroller is to record the water consumption per unit time, summarize the water consumption rules, and determine the water consumption and boiling time for the next stage. Therefore, the memory space of the microcontroller is mainly considered when selecting. This system uses the latest product STC12C5A16S2 from Hongjing Technology Co., Ltd. The chip has 16k Flash program memory, 1280 bytes SRAM, 45k EEPROM, 8-channel 10-bit A/D converter, LQFP44 package, and only RMB 5.

4 Software Design
The microcontroller records the water consumption every ten minutes, and 144 bytes are required to store the water consumption every day. The STC12C5A16S2 microcontroller has a 45k EEPROM, which can record the water consumption in each time period for about 3 months.
When the system is running for the first time, there is always enough boiled water in the water tank 2. When it runs to the second day, the control system first determines the water boiling situation of the day based on the water consumption of the previous day. When the system has been running for many days, the control piano determines the water boiling time and water boiling amount based on the daily water consumption curve of the previous stage and the water consumption of the previous day. The system tries to summarize the water use rules on a weekly basis. In order to cope with the sudden increase in water consumption when users increase water consumption, the system water storage has a certain margin, which can be adaptively produced or manually set. The margin should be moderate, and too much will cause waste of boiled water. The system also designs manual forced water boiling for special situations, and the water consumption of this situation is also included in the adaptive sampling data.

5 Conclusion
In the early stage of operation, this system may leave a large amount of water surplus, resulting in a large waste of water resources. After stable operation, the waste will be reduced to a minimum. The more regular the place, the better the effect of this system. In places with greater mutation, there will be a certain amount of resource waste, but it also has the effect of health and energy saving.