1. Design requirements and goals
Specific functions:
1. The first line of LCD1602 display shows the temperature and timing time, the second line displays the upper and lower temperature limits;
2. The button can set the upper and lower limits of temperature and the timing time; the timing is up to start heating
3. Two water level detection sensors are used to detect the water level: when the water level lower limit sensor detects water, the relay starts to control the water addition; when the water level upper limit sensor detects water, it stops adding water;
4. When the temperature is lower than the set lower limit temperature value, The relay starts to control the heating; when the temperature is higher than the set upper limit temperature value, the heating is stopped.
2. Design ideas and plans
The hardware system of the system is based on the STC89C51 single-chip microcomputer, which is mainly divided into two parts: DC stabilized power supply and intelligent electric water heater control circuit. The schematic diagram is shown in Appendix 2. The DC stabilized power supply consists of a transformer, a rectifier bridge, a filter circuit, and a stabilized circuit. The intelligent electric water heater system is composed of clock circuit, reset circuit, alarm circuit, keyboard, temperature detection circuit and display interface circuit.
3. Hardware circuit
