Based on a single chip a medical sterilizer control system development

Introduction

Sterilizer is to protect human life and health of vital equipment, developed both domestic sterilizer or commercial sterilizers are very popular.

The sterilizer is qualified majority depends on the reliability of the control system, a medical equipment factory sterilizer control system instability, man-machine interface is friendly, practical problems, the author adopts 80C196KB MCU for plant design and sterilization control system to eliminate the defects of the original system and the corresponding increase in the number of functions, compared to 51 series microcontrollers, 96 series on resources, it is relatively easy to design the system.

1, sterilizer control analysis

The sterilizer main class parcels, instruments, LaTeX class, liquid class and other classes of five for sterilization, its process largely the same, the difference can be made by the program.

Through its operating principle (Figure 1) shows that, according to the outside temperature and pressure pot meets the provisions of the various actions carried out in accordance with the value of control.

Analog input volume 4: temperature TW, Pan Pan pressure cooker in PW, TL PL, in pot pressure; control output of 16: pan into the steam valve switch IW, Pan exhaust valve switch OW, pot into the steam valve switch IL, Pan exhaust valve switch OL, vacuum valve switch ZK, dry air valve switch GZ, oil pump relay switching YB, vacuum pump relay switching ZB, electromagnetic hydraulic valves (high pressure valve GF, rack valve CF, bolt valve MF), signal indication (power indicates PowerL, total power indicates PowerZ, fault indication ERR, beep beep ALARM).

Figure 1

The figure above shows the body of the sterilizer as a jacket and seal the door of a pressure vessel, equipped with a vacuum pump, vacuum valves, steam valves, controllers and sensors for temperature, pressure, work process, as shown in Figure 2.

Figure 2

2. control system hardware structure

Control system hardware structure as shown in Figure 3 below:

Figure 3 hardware circuit diagrams

The control system hardware circuit consists of data acquisition, control output, clock module, and HMI hardware components, such as.

Sterilization room actual temperature and pressure values from semiconductor AD590JH integrated temperature sensor and the integrated pressure sensor MPX5500D measurement, sampling of 2-channel temperature signal and 2-way pressure signal fed by P0.0 ~ P0.3 80C196CKB chip.

In 80C196CKB, there is an 8-channel 10-bit A/D converter, suitable for multi-channel data acquisition system. Once A/D conversion required 88 State cycle (when using 12MHz Crystal 22 μ s). Its advantages are in meet the technological requirements greatly simplifies hardware circuit, good for circuit reliability.

The digital 80C196CKB via digital filtering, on the one hand, the scaling transformation through the LCD display, on the other hand is compared with the set, get deviation E and deviation rate EC, to provide a basis for the subsequent control.

Parallel output interface circuit 8255A to achieve nearly 20 channels for on/off control of output control. Temperature control is by regulated steam valves open to implementation, control of the D/A conversion to analog output, power amplification control steam valve openings. User via the keyboard setting sterilization temperature, time and frequency pulsating vacuum, meet a variety of disinfection requirements.

Use DS12887 parallel clock module.

Man-machine interface including keyboard, display, and micro-printer interface circuit.

The keyboard uses the soft keyboard, the procedure for the identification of key code, go to jitter and confirm; by a 8255A enables keyboard and printer hardware interface. Monitor with built-in T6963C controller with LCD display module (and CPU to direct connection) for dynamic display of temperature, pressure, time and action prompts, etc. The printer used to print the relevant process parameters. User interface software implementation is dispersed and not a set of software modules to achieve (see next section).

All devices of the system are made of a single + 5V power supply, because of the practical application of, data acquisition, signal vulnerable to interference, signal input and output contacts Department take optocoupler circuits, and to take measures such as shielding resistance guarantees the stability of the system.

3. software design

Many of the functions of the system, in order to facilitate the design and maintenance, use of top-down gradually to refine the design of structured module, will have a separate method function subroutines are set to sub module, related functionality provided by the corresponding function subprogram.

The main program by initialization, sterilizing category selection and related shows, parameter comparison, actuator output control, whose core is the temperature and pressure parameters of comparison and the corresponding output control; time of dynamic displays timer 1 overflow interrupt handler implementation; 4 channels of temperature and pressure data acquisition and processing, and dynamic display A/d conversion end interrupt handler. Because the display program is relatively large, placed in the interrupt handler to run in the background is simple, to the reliability of the software is running. Program flow shown in Figure 4.

Figure 4

Program the basic procedure is running: initialize after A/D conversion to acquisition of temperature, pressure signal, processed, such data and user settings of the operating parameters of comparison, and then determine the system executing agencies of different actions to meet the operating parameters are controlled at the technological requirements.

This control system software are all used in Assembly language, perform efficient, reliable, and limited to

Limited space, not a presentation.

Conclusions:

This is a utility for core 80C196KB embedded control systems, its function is complete, the relative simplicity of design.

The actual application indicates that the entire system running smooth, reliable sterilization control. Relative to have the same function and sterilization of PLC-based control system, it's cheap, friendly man-machine interface, easy operation, with a very good promotional value.

Reference documents:

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