1. Project introduction
The current article introduces the design process of a thermistor temperature measurement system based on 51 single-chip microcomputer, which is used to monitor the ambient temperature in real time and give an alarm when the temperature exceeds the preset threshold. Because the thermistor temperature measurement technology is used, no external temperature sensor is needed, which makes the system have the advantages of simple structure and low cost.
The main control chip adopts STC89C52, which has good stability and reliability, and is suitable for the application needs of industrial control and other fields. The ADC acquisition module adopts the PCF8591 module, which can conveniently realize the conversion and acquisition of the temperature data of the thermistor, which improves the accuracy and practicability of the system.
The system displays the temperature value through the 4-digit digital tube, and at the same time sets the temperature upper limit threshold value through the button. When the temperature exceeds the threshold value, it will alarm through the buzzer to remind the user to pay attention to the change of the ambient temperature.
The thermistor and PCF8591 module are mainly used in the project.
(1) Introduction of thermistor
A thermistor is a material-based resistive element whose resistance changes with temperature. Normally, the resistance value of a thermistor decreases as the temperature increases, and vice versa increases as the temperature decreases. This characteristic is called negative temperature coefficient (NTC) or positive temperature coefficient (PTC).
The operating principle of a thermistor is based on the temperature sensitive nature of the material. In the thermistor, there are many conductive particles. When the temperature rises, the degree of ion excitation between the conductive particles and the material increases, resulting in an increase in the number of conductive particles, so the resistance value decreases; conversely, when the temperature decreases, the conductive particles The number becomes smaller and the resistance value increases.