Research and Design of a Constant Temperature Control System Based on DC PTC Thermistor 1

Introduction

Most existing heaters utilize traditional components such as electric heating tubes or heating wires for heating. The outer shell of an electric heating tube is made of stainless steel pipe, containing a resistive heating element inside. During operation, heat is transferred to the external environment through the resistive wire and the steel pipe. When air is not in motion, the heat from the electric heating tube cannot dissipate, leading to a continuous rise in temperature. In severe cases, this may cause the heating tube to burn out or even trigger a fire.  In contrast, PTC thermistors, as heating materials, offer advantages such as energy efficiency, constant temperature regulation, no open flame, high safety, easy adjustment of heat output, minimal impact from power supply voltage fluctuations, and rapid heating. Therefore, designing a constant-temperature heating system using PTC thermistors as the heating material is highly significant for applications with stringent safety requirements.  diode

2. Overall System Design Plan

The system adopts the AT89C2051 as the control core, uses PTC thermistors to heat the target area, and employs the digital thermometer DS18B20 to collect temperature data in real time. The external keyboard sets the upper and lower limits of the desired heating temperature. By comparing the real-time temperature readings with the set temperature values, the system determines whether the target range is achieved. The AT89C2051 controls multiple relays to switch the operating states of several PTC thermistors (one relay controls one PTC thermistor), maintaining the heating area's temperature within the specified range. The system schematic is shown in Figure 1.

3. Microcontroller-controlled heating

3.1 Microcontroller System

The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcontroller produced by the American company ATMEL. It is manufactured using ATMEL's high-density, non-volatile memory technology and is compatible with the MCS-51 instruction set. The chip features an integrated 8-bit general-purpose CPU, a 2K-byte Flash memory, 128 bytes of internal RAM, 15 I/O lines, two 16-bit timers/counters, a five-vector two-level interrupt structure, a full-duplex serial communication port, an on-chip precision comparator, and internal oscillator and clock circuits [1].diode