(1) Refrigeration characteristic curves of the freezing compartment and the refrigerating compartment;
(2) Pipeline characteristic parameters and leakage characteristics of pipeline devices such as evaporators and capillary tubes;
(3) Electrical performance parameters of various electrical components;
(4) Complete identification information of the product, etc.
The latest theoretical research results of pipeline leakage characteristics and a new digital temperature sensor featuring first-line bus technology, coupled with a sophisticated distributed computer automatic measurement and control system, enable the automatic detection of the design of the refrigerator and its components, engineering implementation And the operation of the system shows obvious advantages in terms of investment, construction, operation and reliability.
1 system composition
1.1 System Structure
The system consists of the upper computer (PC-586), the lower computer (including the distributed temperature acquisition module based on single-chip microcomputer, the refrigerator electrical performance parameter test module, the refrigerator pipeline characteristics and leakage characteristic detection module) and the test management software, as shown in Figure 1. Show. The upper computer of the system communicates with the lower computer through the RS485 serial bus. The distributed temperature acquisition module is connected to the digital temperature sensor DSl8B20 distributed in each refrigerator through the one-line data bus to complete the data collection and processing of the refrigeration characteristic curve of the online refrigerator.
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1.2 Introduction of automatic inspection line station
The actual refrigerator test line has bar code reading artificial position; refrigerator pipe characteristics and leakage characteristic test station; refrigerator electrical performance parameter test station; and 6 refrigeration characteristic test lines (each refrigeration characteristic test line has 25 refrigerator workers) Bits, each station has 2 digital temperature sensors), as shown in Figure 2.
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The refrigerator to be assembled is first read into the station by the barcode, and the product identification information is read by the barcode reader; thereafter, in the pipeline characteristic and leakage characteristic station of the refrigerator, the AT89C52 single chip microcomputer is taken as the core component, including the electromagnetic valve and the temperature measuring platinum. Peripheral devices such as resistors, flow transmitters, pressure transmitters, and pneumatic actuators form a comprehensive test bench for refrigerator evaporators (including capillaries). Through the automatic detection of the temperature, pressure and flow of the gas flowing through the evaporator, the measured data is obtained to judge whether the evaporator is qualified; then, in the electrical performance parameter test station of the refrigerator, the AT89C52 single-chip microcomputer is also used as the lower position machine, and the electronic switch and the micro-computer are used. The relay constitutes an electrical component performance test bench that automatically detects short-circuits, open circuits, and insulation defects in a complete set of electrical components (including 14 electrical components such as compressors, solenoid valves, fans, door lights, and temperature sensors) in the refrigerator. If all the above tests are qualified, the refrigerator can complete the final assembly, and then the upper computer sends a command to the PLC according to the type information of the refrigerator contained in the barcode, and the PLC controls the transfer plate chain to send the refrigerator to a certain refrigeration characteristic test station. After the digital temperature sensor is manually placed in the freezer compartment and the refrigerating compartment, the refrigeration characteristic parameters are collected.
2 Multi-point temperature measurement system consisting of DSl8B20 and single chip microcomputer
2.1 System characteristics
DSl8B20 is a digital temperature sensor introduced by DALLAS in recent years. The die of the device integrates temperature sensitive components, data conversion chip, memory chip and computer interface chip. The device can then directly output a binary temperature sensitive signal and communicate with the microcontroller via a serial output. There are only 3 pins on the outside, of which VDD and GND are power supplies, and the other DO pin is used as a bus (Data In/Out), which is called a one-line data bus. It only needs to occupy one interface when interfacing with the microprocessor. I/O port; the temperature range of the device is 55~+125°C; the temperature measurement accuracy is 0.5°C; the temperature can be directly converted into 9~12 digit binary serial output by programming preset method; The temperature conversion time is only 750ms. The emergence of this new type of digital temperature sensor has revolutionized the traditional temperature measurement interface circuit and brought significant economic benefits.
2.2 Hardware Configuration
The system hardware consists of 89C2051 microcontroller and a small number of peripheral devices, as shown in Figure 3. Because the DSl8B20 uses a unique one-wire bus interface, multiple DSl8B20 devices can be mounted on a single-wire interface, and each device contains a unique 64b serial code that can be distinguished by identifying the code. The host selects the sensor by identifying the serial code, and performs operations such as reading, writing, starting conversion, setting an alarm threshold, and the like. At the same time, there are 9 B RAM and 3 B E2PROM in the device, which can set the working mode of the sensor and store the detected temperature for reading by the MCU. The chip MAX813 provides the monitoring function of the lower computer. When the power is turned on, the power is off, and the grid voltage is too low, the reset signal is output. At the same time, it can track the 1.6s timing signal to provide Watchdog protection for the software. The MAXl483 converts between TTL levels and RS485 electronics.
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3 parameter test software design
The lower position machine (89C2051) collects the temperature sensor data and sends the data to the upper PC through the RS485 serial bus port after a certain pre-processing. The detection software in the Windows environment developed by Microsoft Visual Basic 6.0 is run on a PC, and the data transmitted from the serial port is accepted, and the data processing result is printed and output in the form of a graphic. The main points of programming of the host computer are:
(1) SCOMM communication control settings for the serial port
The communication protocol is: baud rate 9 600, even parity, 8 data bits, 1 stop bit. The test command is sent by the host computer, and after receiving the command, the lower computer sends the detected data every 1rain to the host computer. The host computer cyclically receives and processes and displays data.
(2) Data display
The data display uses the MSFLex Grid control in VB 6.0 to define the row and column of the control as an array, so that the temperature data of the refrigerator freezer and the refrigerator in each station sent by the lower computer, the refrigerator compression The number of machine start and stop times is displayed, as shown in Figure 4.
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(3) Data storage
The system is mainly composed of two parts: parameter database and temperature sampling point database. The schematic diagram of its system data structure is shown in Figure 5. The parameter database includes system parameters, user-defined parameters, sensor calibration parameters, refrigerator model list and standard parameters. The temperature sampling point database records the model, detection date, detection time, temperature at each time, number of starts and stops, and so on. At the beginning of the system, the parameters set by the person are read from the parameter database for initialization, and the system can be updated and saved at any time when the user modifies the parameters. Before the test, the system creates a new data table with the name of the date, line number, station number and serial number, which is ready for the preservation of the test data. Each tested refrigerator has a unique number. You can view the detection curve of any refrigerator in the data retrieval interface. The data retrieval method is flexible, and it can search by number direction, and can also view data of a batch of refrigerators through various elements. If you check the test result of a certain model on a certain day, as long as you enter the date and model on the search interface, the table will immediately display the data of the refrigerator that meets the conditions. The currently selected refrigerator refrigeration curve is displayed in the drawing area below the interface.
The software design adopts a clear and modular programming method, and a large number of function functions and general processes are established to make the structure simple and convenient. This avoids a lot of code duplication, is conducive to software debugging, improves programming efficiency, and provides convenience for software development and database maintenance.
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4 actual application of the system
The above-mentioned distributed refrigerator refrigeration performance parameter sampling and processing system was put into use in a large refrigerator manufacturer at the end of 2001. 150 refrigerator compressors on site were randomly started/stopped, and there were serious electromagnetic interferences. Due to the use of digital temperature sensors and reasonable fieldbus technology, and the adoption of perfect software/hardware anti-jamming measures in the design of the lower-level system, The system has strong anti-interference ability. After more than one year of actual operation, it proves that the system has less investment, convenient installation and construction, small maintenance workload, high temperature measurement accuracy, stable and reliable operation, and far superior performance to the traditional analog circuit acquisition system. Recently, the temperature measurement station has been doubled. It can be seen that the system is effective and has broad application prospects.
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