导语：该系统体积小、成本低、工作可靠，具有很高工程应用价值。系统稍加改动或扩展，还可以完成温度测量等功能。

摘要：本文介绍了一种应用LM35温度传感器开发的温控系统，重点阐述了系统结构、工作原理以及采样值量化。同时对LM35传感器特性、系统硬件电路设计、软件设计也作了介绍。该系统体积小、成本低、工作可靠，具有很高工程应用价值。系统稍加改动或扩展，还可以完成温度测量等功能。

关键词：温度传感器 工作原理 硬件设计 软件设计

引言

在各类民用控制、工业控制以及航空航天技术方面，温度测量和温度控制得到了广泛使用。在很多工作场合，元器件工作温度指标达不到工业级或普军级temperature要求，可以通过设计加温电路的办法得以解决。小型、高精度、高灵敏度且价格合适的temperature sensor已经越来越受到设计者的关注。本文介绍了一种基于LM35 temperature sensor开发的温控system hardware circuit及software design。

LM35 temperature sensor

LM35是NS公司生产的一款集成电路temperature sensor，它具有很高的working precision和较宽的linear working range，该device output voltage与摄氏度temperature线性成比例。因而，从使用角度来说， LM35与用开尔文standard of linear temperature sensors相比更有优越之处，因为它无需外部calibration or adjustment，只能提供±1/4℃of accuracy at 25℃.

• Working voltage: DC 4～30V;

• Working current: less than 133μA;

• Output voltage: +6V～-1.0V;

• Output impedance: 1mA load, 0.1Ω;

• Accuracy: ±0.5℃at +25℃;

• Leaking current: less than 60μA;

• Proportion factor: linear +10mV/℃;

Non-linearity value:+/-1/4℃;

Calibration method:Directly calibrated with Celsius temperatures;

Packaging type:

Sealed TO-46 transistor package or plastic TO-92 transistor package;

Pinout explanation:

① Positive power supply Vcc；②Output；③Output ground/power ground.

System structure and working principle

The control circuit is composed of a sensing circuit, signal conditioning circuit, A/D sampling circuit, single-chip microcomputer system, output control circuit, and heating circuit.

The basic working principle of the circuit is as follows:

Sensing Circuit converts the sensed temperature into an electrical signal in the form of a voltage which then goes to Signal Conditioning Circuit where it gets amplified and filtered out any noise that may be present in the input signal before being sent to A/D Sampling Circuit for conversion into digital format using Analog-to-Digital Converter (ADC). The converted data is then processed by Single-Chip Microcomputer System which compares it with a reference value set by user to decide whether or not to turn on Heating Circuit based on certain criteria such as threshold levels etc.. If the sensed temperature falls below this level (in our case we use -55°C), then Heating Circuit will be activated automatically until desired room temperature has been reached again otherwise it remains off till next time when needed due to sudden drop in ambient temperture around us because there are no other devices installed nearby like air conditioners & heaters so I don't want my device get damaged from overheating during extreme weather conditions outside!