Design of automatic control system for ironing machine based on single chip microcomputer

    With the increasing demand in the garment market in recent years, small garment manufacturing enterprises have developed very rapidly, and the demand for small ironing systems has increased. Most of the original small ironing machines are manually controlled devices, which require high operating experience of operators. Due to the different operating levels of operators, product quality problems often occur, and the damage rate is very high. In order to meet user needs, we designed an ironing control system by ourselves.
    1 Overall requirements of the system
    The control machine uses ATMEL89C51 to form a single-machine control system. Each ironing process is roughly divided into the following steps: mold closing, hot pressing (2 times), upper steam spraying, exhaust, lower steam spraying, mold opening, etc. Sometimes in a process, the execution times of a step may be different. The system should flexibly adjust the starting time and duration of each step. The system should also have a temperature control system so that the ironing temperature can be controlled as required to avoid damaging the fabric.

    The ironing machine uses AT89C51 as the main controller and DMF50174 as the display module. It can store and modify 10 ironing programs. It can change the operating parameters according to the process and fabric, and can display the parameter settings of the ironing program in a graphical way. The system is also equipped with a temperature control system, which uses a TLC549 serial A/D converter and a linear temperature sensor to collect and control the temperature. The system can control the temperature valve according to the temperature range preset in the ironing program. During the ironing process, the system displays the parameter settings of each solenoid valve in a graphical way on the LCD screen, and indicates the current system operation process with a highlighted scan line.

    2. Overall system design
    2.1 Solenoid valve control part
    Each working step of the ironing machine is controlled by a different control valve. The system has: mold closing valve, pressurizing valve, steam injection valve, steam extraction valve, temperature control valve and other valves. In order to facilitate expansion, the system has enough expansion space. This system uses P1 port as the control port, and also expands a 74LS377 for backup. It can control up to 16 solenoid valves to meet system requirements.

    Each control valve in this system is an AC solenoid valve. In order to avoid electromagnetic interference, photoelectric isolation is adopted.

    2.2 Temperature Control Section
    In order to control the temperature, a temperature acquisition section is designed, which uses the resistive temperature sensor PT100 and the A/D converter TLC549 with serial control from TI to realize temperature acquisition.

    The TLC549 is a CMOS A/D converter based on an 8-bit switched capacitor successive approximation A/D converter. It is designed to interface with a microprocessor or peripheral device serially through 3-state data output and analog input. The TLC549 uses only the input/output clock (I/O CLOCK) and chip select (CS) input for data control. The I/O CLOCK input frequency of the TLC549 can reach up to 1.1MHz. [page]

    The TLC549 provides an on-chip system clock that typically operates at 4MHz and does not require external components. The on-chip system clock makes the operation of internal devices independent of the serial input/output timing and allows the TLC549 to operate as required by many software and hardware. The I/O CLOCK and the internal system clock together can achieve high-speed data transfer and a conversion speed of 40,000 conversions per second for the TLC549. [page]

    Other features of the TLC549 include universal control logic, on-chip sample-and-hold circuits that can operate automatically or under microprocessor control, high-speed converters with differential high-impedance reference voltage inputs, scaling, and circuits that isolate the circuits from logic and power supply noise. The design of the entire switched capacitor successive approximation converter circuit allows conversions to be achieved in less than 17μs with a maximum total error of ±0.5 least significant bit (LSB).

    2.3 LCD display

    The system is equipped with a membrane keyboard to facilitate modification of the control program and system settings. For ease of operation, the system uses an independent LCD display system that can display the system temperature, the status of each control valve, the system operating status, etc. in real time.

    The system adopts the advanced dot matrix LCD module DMF50174NB-FW produced by Japan OPTREX Company and the SED1330 LCD controller produced by Japan SEIKO EPSON Company.

    The DMF50174NB-FW LCD display module has the characteristics of high sensitivity, high reliability, low power consumption, long life, high brightness, etc. It has a 320×240 dot matrix. The module has two display modes: character and graphic. The display font is 8×8 dot matrix, which fully meets the requirements of industrial production.

    SED1330 is an advanced character and graphic LCD display controller, and is the most powerful one among similar products. It has the following features:
    SED1330 is not only suitable for 8080 series MPU interface, but also for M6800 series MPU interface. It has two pins, SEL1 and SEL2, in the interface part as the interface function conversion settings of MPU.

    SED1330 has a powerful I/O buffer at the interface of MPU, avoiding the status check items of general controllers. MPU can access SED1330 at any time without asking for the "busy" flag.

    SED1330 has a rich instruction set, and most instructions have parameters, up to 10 parameters. SED1330 instructions can not only realize the synthesis of the contents of two display areas according to different logical relationships, but also the synthesis of the contents of three display areas. Through the synthesis display, character and graphic mixed display, character text feature display, flashing display and half-color tone display can be realized.
    The display data sent by SED1330 to the LCD module is transmitted in 4-bit parallel mode, which greatly improves the ability to control the dot matrix LCD display device.

    3. System software design

    The system software adopts a modular design and is divided into the following parts: LCD display control module, parameter setting module, ten separate ironing program settings and parameter display modules, machine operation status display module and temperature acquisition, control and display module.

    In summary, the ironing machine control system designed and implemented in this paper has high practical value. At the same time, the functions and usage methods of DMF50174 LCD, SED1330 LCD controller and serial A/D converter TLC549 are introduced. This system is now in use in Shanghai Weijie Garment Equipment Factory. After a long period of actual testing, the system performance is good.