Design of medical temperature controller control system
Abstract: The medical temperature controller control system is an important part of the medical temperature control instrument. The temperature control of the medical temperature controller is realized by the temperature detection of each part of the refrigeration system and the setting of the temperature by the operator. Based on the research and reference to the domestic and international medical temperature control system, the article makes full use of the modern electronic, sensor, liquid crystal display and other technical achievements, and developed a more humanized and better medical temperature control system. The system not only has conventional functions such as temperature display and timing, but also has strong anti-interference ability, and also has more practical functions such as storage memory.
In recent decades, modern medicine has adopted sub-hypothermia treatment for many neurological diseases. Mild hypothermia treatment, also known as hibernation treatment or artificial hibernation, through manual intervention, the patient's body temperature is reduced, thereby achieving the purpose of treatment. The medical temperature controller designed in this paper is mainly applied to the hypothermia treatment in medical treatment, and belongs to the selective head cooling. By comparing various cooling modes, the vapor compression refrigeration cycle technology is applied for a long time and is widely used, and the safety, reliability and technical maturity are high, so this method is adopted. The circulation mode mainly comprises a compressor, a heat exchanger, a radiator and a drying filter. wherein the heat exchanger has a ring-shaped heat exchange tube inside, and the radiator has a plate structure and a cooling fan is arranged on a side thereof. The refrigerant removes heat from the heat exchanger through the refrigeration cycle, cooling the liquid cooling medium inside the heat exchanger. At the same time, there is a water pump outside the heat exchanger to circulate the internal liquid cooling medium through the ice cap, so that the internal temperature of the ice cap reaches a sub-low temperature state to treat the patient.
1 Overall design of medical temperature controller control system
The temperature controller control system takes the single-chip microcomputer as the core, and collects several temperature values ​​of the temperature sensor to control the start and stop of the refrigeration system and the circulation system to realize the temperature control of the controlled object. At the same time, the human-computer interaction is realized through the liquid crystal display and the keyboard. Make the operation process simple and convenient. The design of the medical temperature controller control system to achieve the above functions includes the following aspects:
1) Microcontroller system: The central part of the control system consists of a single-chip microcomputer and its minimum system. It is responsible for collecting sensor signals and key signals, realizing temperature control, outputting cooling control signals, realizing liquid crystal display, and realizing storage functions.
2) Temperature sensor module: measure the temperature of each channel and output the temperature value to the microcontroller;
3) Human-computer interaction channel: It consists of a liquid crystal display and buttons, which allows the user to operate the instrument more conveniently and comfortably;
4) Control output system: accept the output signal of the microcontroller, control the on/off of the refrigeration system, and isolate the weak current control system from the high-power refrigeration system to ensure the safety and reliability of the control system;
5) Data storage module: realize the memory function of the system, store the data in the module to save the data to prevent the power failure from disappearing;
6) Power module: Provide the required DC power for the entire system to prevent external power interference from affecting system operation.
The overall framework of the system is shown in Figure 1.
Figure 1 Overall framework of the medical temperature controller control system
2 hardware design of medical temperature controller control system
The AT89C55WD 8-bit microcontroller with low power consumption and high performance is produced by Atmel. The system temperature is collected by the digital temperature sensor AD7416, which has the advantages of small size and high resolution. The human-computer interaction mode adopts the function of inputting commands through the keys and displaying the system parameters through the liquid crystal module ET-240128AV7, and has the advantages of convenient operation, beautiful appearance and the like. The memory chip HK1225-7 is used to realize the function of the system to remember the working parameters when the power is off. The use of an integrated AC/DC power module not only reduces the size of the control system but also ensures a smooth system power supply. It also takes necessary anti-interference measures, such as: photoelectric isolation, button software debounce, adding decoupling capacitors, using a special watchdog chip, etc., to eliminate external interference to the system and improve system stability and reliability.
2.1 Temperature measurement circuit
The three-way measuring circuit is used to measure the temperature of the liquid cooling medium in the heat exchanger, the temperature of the liquid cooling medium in the ice cap, and the human body temperature. Taking into account the accuracy requirements of the system and the cost of the sensor, the AD7416 digital temperature sensor chip produced by ANALOG DEVICE is selected to collect the temperature. The temperature data can be collected in the field, and the temperature physical quantity is directly converted into a digital signal and transmitted to the single chip through I2C communication. data processing. It has the advantages of simple hardware circuit, small size, convenient use, etc. It has great advantages over other temperature sensors in terms of transmission distance, conversion time, resolution and temperature measurement accuracy, which brings more convenient use effect to users. It is widely used in automated test and control systems in various fields and environments.
The I2C serial bus interface SDA (1 pin) and SCL (2 pin) are connected to the P1 port of the MCU, and a 4.7 kΩ pull-up resistor is added to the signal line to ensure that the signal line remains high in the idle state. Since the P89 port of the AT89C55WD MCU has a 10 kΩ pull-up resistor inside, a 10 kΩ pull-up resistor is added externally, and the two resistors are connected in parallel so that the total resistance is close to 4.7 kΩ. The specific circuit is shown in Figure 2.
Figure 2 AD7416 circuit schematic
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