God teaches you: The design of DS18B20 water temperature control system

one. introduction

In some temperature control system circuits, widely used is through the thermocouple, RTD or PN junction temperature measurement circuit through the appropriate signal conditioning circuit, converted into A / D converter can receive analog, and then through the sample / hold circuit Perform A/D conversion, and finally send it to the SCM and its corresponding peripheral circuits to complete monitoring. However, traditional signal conditioning circuits are complex, susceptible to interference, difficult to control and have low precision. This paper introduces the design of SCM and DS18B20 water temperature control system. Therefore, the system uses a new type of programmable temperature sensor (DS18B20), which can complete data acquisition and processing directly with SCM without complex signal conditioning circuit and A/D conversion circuit. Easy to implement, high precision, can be used for various occasions according to different needs.

God teaches you: The design of DS18B20 water temperature control system

table of Contents

one. introduction

two. aim of design

three. System functions

four. System equipment

Fives. Overall plan and principle of temperature control

1. System module diagram

2. System module total diagram

six. Temperature conversion core and its algorithm

1. Principle and characteristics of temperature sensor DS18B20

Pins and Characteristics of DSl8B20

The internal structure of DS18B20

DS18B20 memory structure

DS18B20 temperature measurement function

DSl820 working process agreement

Temperature sensor and microcontroller communication timing

2. Temperature conversion algorithm and analysis

Seven. Hardware design instructions

1. Overall system circuit diagram

2. Each module circuit diagram

Input system

Output system

Chip system

Eight. Software Design Description

1. General module flow chart

2. The flow chart of each module

Reading the temperature of the DS18B20 module

Keyboard scan processing flow

nine. Operating instructions

Key Function

Display temperature

set temperature

ten. references

Program source code

two. aim of design

Design and produce a water temperature automatic control system, the control object is 1 liters of clean water, the container is enamelware. The water temperature can be manually set within a certain range, and can be automatically controlled when the ambient temperature decreases to keep the set temperature substantially constant.

The use of single-chip AT89S52 intelligent control of water temperature, so that the water temperature can be achieved in the 40-90 degrees control temperature adjustment. Use the instrument to read the water temperature, and adjust the water temperature to the temperature that we input through the keyboard (in the form of heating or cooling) and display the temperature on our seven-segment LED board.

three. System functions

1. The temperature can be set freely. At that time, it must be within 0-100 degrees Celsius. When setting, it can display the set temperature value in a timely manner. The temperature can be freely set, the sensor's detection value and setting. The temperature comparison can be displayed on seven segments of light emitting diodes.

2. The temperature is achieved by a 1000w electric furnace. If the temperature is not between 40-90 degrees, "8888" is displayed on the LED, indicating an error.

3. The water temperature can be continuously displayed, and the number of digits displayed is four hundred, one hundred, one, ten, and decimal digits. (But because the rule does not exceed 90 degrees, 100 is not implemented, the default 100 is not displayed)

four. System equipment

ME300B Minimum System Board

DS18B20 Digital Temperature Sensor (Integrated A/D Conversion Function)

1000W electric furnace

thermometer

Relay

fan

Water container

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