Abstract: This paper presents a heating control system designed for a ruggedized computer operating in low-temperature environments. The system comprises a wide-temperature power supply module, an 89220501 microcontroller, a DS1620 digital temperature control chip, and solid-state relays. This circuit controls the operation of each heating plate, enabling the ruggedized computer to operate normally in low-temperature environments. The corresponding software design flow is also presented. Keywords : ruggedization; temperature sensor; solid-state relay; electric heating plate 0 Introduction With the increasing informatization, digitalization, and modernization of national defense, military, and industrial control fields, the demand for high-performance, specially developed ruggedized computers resistant to harsh environments is constantly growing. Ordinary computers simply cannot operate in harsh environments such as high temperature, low temperature, humidity, mold, rain, dust, strong vibration and shock, and electromagnetic interference. Therefore, it is necessary to select, apply, and develop high-performance, specially developed computers resistant to harsh environments, commonly referred to as "ruggedized computers." Conventional computer motherboards (including industrial control motherboards), backplanes, hard drives, power supplies, and especially LCD screens, cannot meet the environmental requirements under harsh conditions. Tests have shown that ordinary commercial computers generally cannot function properly below -10℃, requiring hardening measures to enable them to operate in extremely low temperature environments. Therefore, we designed a temperature control system to enable the computer to operate normally at low temperatures such as -25℃ and -40℃. [b]1 System Hardware Design 1.1 Composition of the Temperature Control System[/b] The temperature control system consists of a temperature control board and an electric heating plate. The system circuit diagram is shown in Figure 1. The 220V AC input is fed into a wide-temperature AC/DC power module. This is converted to a +5V DC power supply by a temperature control circuit. A DS1620 temperature sensor automatically monitors the temperature inside the chassis. When the temperature drops below 3℃, the microcontroller activates the heating plate via an AC solid-state relay to heat the internal environment of the chassis, and the heating indicator light illuminates. Once the temperature reaches 5℃, the heating plate automatically deactivates, and the indicator light turns off. During computer operation, if the temperature continues to drop below 3℃, the heating plate is activated again, and the cycle continues. 1.2 Brief Introduction to the Working Principle of the Temperature Control Board The main control chip for the temperature control board is the ATMEL 89C2051. It is compact, and its port count and ROM meet the functional requirements of this circuit. A 6MHz clock speed was chosen. To reduce the number of resistive components and improve reliability, a MAX813L is used as the reset signal for the 89C2051. The temperature sensor selected is the DS1620, a digital temperature measurement and control device from Dallas Semiconductor. It outputs a digital temperature value, operates on a 2.7V to 5.0V power supply, and measures temperatures from -55℃ to +125℃. It uses a 9-bit digital representation of the temperature value with a resolution of 0.5℃. The accuracy is 0.5℃ from 0℃ to +70℃, 1℃ from -40℃ to 0℃ and +70℃ to +85℃, and 2℃ from -55℃ to -40℃ and +85℃ to +125℃. It can convert the measured temperature value within 1 second. The temperature alarm limit settings in the TH and TL registers are stored in non-volatile memory and are not lost after power failure. It connects to the three ports P1.5, P1.6, and P1.7 of the 89C'2051 microcontroller via a three-wire serial interface to read the temperature value and set the TH and TL registers. [b][align=center]For more details, please click: Design of a Ruggedized Computer Temperature Control System[/align][/b]