Design of Low-Power Electronic Thermometer

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2011 3rd International Conference on Computer Modeling and Simulation (ICCMS 2011)

Design of Low-power Electronic Thermometer

W.C. Wang

L. Wang

College of Information and Control Engineering
Weifang University
Weifang, China
wwcwfu@126.com

School of Control Science and Engineering
Shandong University
Jinan, China
wangleitongxing@mail.sdu.edu.cn

Abstract—To the characteristics of traditional temperature measuring system, a design method of low-power electronic
thermometer is proposed based on single chip machine and
digital temperature sensor in this paper. Firstly, the working principle of 1-wire digital temperature sensor is introduced in details. Then, the overall framework of system and the unit
modules are presented, which mainly realized the functions
such as temperature measurement, data processing, data
display and alarming. Finally, the software is designed and the main program flowchart is presented. Experiment shows that
the thermometer is simple, low power consumption, easy to use and with high precision.
Keywords- SCM; thermometer; DS18B20; alarming

I.

INTRODUCTION

Temperature is one of the most common parameters
which need to be measured in people’s productions and lives. So, the temperature detection system has been widely
applied in many areas. Currently, there are many methods
are used to measure temperature, such as the thermocouple
or RTD. The working principle of the thermocouple is
converting the temperature into electromotive force. While
the temperature measurement of thermal resistance is based
on the thermal resistance effect, that is, the resistance of resistors changes with temperature characteristics. Both
methods all need to convert from analog to digital, that needs more external components, and the hardware circuit will
more complexly and production cost will relatively higher.
Especially, it is susceptible to external interference and lead to considerable error when in the processes of analog signal transmission. In addition, when the system is conducting
multi-point temperature measurement, the increasing use of
analog temperature sensor and the tasks of microcontroller
conversion will make the system become more complex and
power consumption. And the increase in power consumption
will bring a range of issues, such as circuit parameters
drifting, reliability decreasing continuous working time
reduction of battery-powered systems. Therefore, the
system's power consumption in the overall system design is
very important.
For such problems, a design method of low-power
temperature measurement system based on digital
temperature sensor and low-power microcontroller is
proposed. The controller is selected MSP430, temperature

978-1-4244-9243-5/11/$26.00

C

2011 IEEE

sensors is DS18B20, the display device is LCD screen and
the thermometer has the functions of keyboard setting and
alarming. Compared with traditional thermometer, the
introduced digital thermometer is accurate, easy reading, and has a wide range of temperature measurement.
The rest of this paper is organized as follows. Section 2
introduces the principle of digital temperature sensor.
Section 3 described the framework of hardware and unit
circuits in details. After that, the flowchart of main program is presented in section4. Finally, the last section gives some concluding remarks.
II. DIGITAL SENSOR DS18B20
The outputting of commonly used analog temperature
sensor is analog quantity. So, in the measuring circuit, it
must be converted to digital quantity which computer can
handle through A/D converter. In the front of temperature
measurement system, we use DS18B20 digital temperature
sensor, it will directly receive the digital temperature. The DS18B20 digital thermometer provides 9-bit to 12-bit
Celsius temperature measurements and has an alarm function
with nonvolatile user-programmable upper and lower trigger
points. It has an operating...
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