introduction

　　With the development of information technology, modern industrial system is becoming more and more digital, intelligent and integrated, and modern mechanical equipment is increasingly tending to automatic control and management. In the field of automatic control, temperature detection and control plays an important role. With the development of modern information technology and the realization of traditional industrial transformation, temperature sensors are developing rapidly from analog to digital integration. The temperature control module is driven by a single chip computer. Because of its low power consumption, easy expansion and high reliability, the single chip computer has also become the goal of people.

　　Low voltage control cabinet is a series of intelligent transportation products, which is generally integrated with railing machine, lane traffic lights, audible and visual alarm and other modules, and is mainly used in the automatic management system of expressway toll gates. As there are many integrated circuits in the low-voltage control cabinet, it is very important to ensure the normal work of each module, and temperature control is the key point. The working environment required by each circuit module is different, and the requirements for temperature are also different. This paper designs a method to realize the temperature control in the low-voltage control cabinet, which can automatically collect the temperature and intelligently control the temperature within an ideal working range.

　　1 Overall system design

　　With the progress of society, intelligent transportation products are more and more used in the intelligent automatic control management system of expressway. A number of detection and control devices have been set up in the toll office of expressway. How to control these devices intelligently has become the focus of people's thinking. The lane control cabinet is integrated with industrial personal computer, weight charge display, lane access control entrance, signal light control circuit and other modules, which facilitates the control and management of road traffic products. The temperature control module is an automatic system applied in the lane control cabinet. It can automatically detect the temperature in the control cabinet and intelligently control the temperature within a range suitable for the circuit work.

　　The temperature control module mainly includes digital temperature sensor circuit, single-chip control circuit and digital display circuit. Integrating them in the same module can not only detect and control the temperature better, but also be easy to maintain and expand. The temperature sensor circuit is responsible for collecting the temperature information and transmitting the temperature information to the microcontroller; The microcontroller control circuit is responsible for receiving the external temperature information, and sending the corresponding instructions to the temperature control part to adjust the temperature after data processing; The digital display circuit displays the temperature information in real time, which is convenient for the working and maintenance personnel to view.

　　2 Temperature acquisition sensor

　　In the temperature acquisition part, DS18B20, a 1-wire sensor produced by DALLAS, is selected. The temperature measurement range of DS18B20 is - 55 ℃~+125 ℃. It can be programmed to 9 to 12 bit A/D conversion accuracy. The temperature measurement resolution can reach 0.0625 ℃. The measured temperature is serially output in the 16 bit digital quantity mode with symbol expansion; The working power supply can be introduced at the remote end or generated by parasitic power supply. The CPU can communicate with many DS18B20s with only one port cable, which takes up fewer ports of the processor and saves a lot of leads and logic circuits.

　　3 Temperature control chip

　　The temperature control part selects the optical coupler MOC3041M produced by FAIRCHILD Company. The MOC3041M is a zero crossing bidirectional silicon controlled optocoupler. The microcontroller changes the conduction angle of the bidirectional silicon controlled by controlling to change the voltage at the output end, thus changing the input voltage applied to the electric fan, so as to adjust the speed of the fan and realize intelligent speed regulation and temperature control.