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Automatic dishwasher Control System Design
Abstract: Based on the functional requirements of the automatic dishwasher, introduced by SCM AT89LS8252 and keyboard / display management chip designed automatic dishwasher HD7279A hardware control system design methods, using HD7279 is given control of the keyboard and display hardware circuit, while the system is functional software modules and software flow chart. After debugging test of the system, which can effectively achieve the control dishwasher complete automatic water, heating, cleaning and disinfection, and other functions.
???? Key words: dishwashers; controller; keyboard / display
1 Introduction
As digital application of information appliances, dishwashers have broad access to masses of people in the family, so that people can work from home in the complex gradually liberated.
MCU Sensor-Menci
Magnetic water level sensor
Influent solenoid valve
Temperature Control Protector
Switch 5 kw heater thermostat
Cleaning agents control box
Cleaning agents control box
Electric motors
Transmission trip switch 2
Analog Xiaodaishui temperature
Counter
Display Interface
Man-machine interface Keyboard Interface
Ringing Interface
Figure 1 Control of the dishwasher
As a home automation equipment, such as dishwashers generally need to achieve automatic control influent, automatic detergent, cold wash, automatic temperature washing, cleaning, drainage, Disinfection, and the timing and fault alarm functions. From the point of view of control, a dishwasher usually need to meet Figure 1 shows some of the specific requirements, which involves the switching of signals there are two kinds of sensors is high, low signal detection, such as doors Switch , the water level and temperature regulation for the protection of trip switches, etc.; another solid-state relay switching control signals by the strength of the signal voltage disconnect and loading, such as electromagnetic inlet valve opening and closing, opening and closing the heater thermostat , and instantly the heater to create a control box cleaning agents and disinfectants control box, and so on. Figure 1 in the analog signal used to achieve the following major aspects of functions:
(1) Temperature Sensor temperature / Xiaodaishui temperature detection;
(2) through the man-machine interface display, keyboard input and output, such as voice achieve temperature, washing process shows that the fault type and display;
(3) According to user needs by setting button to select washing mode, and through function keys launch-related functional;
(4) the use of statistical machine, cleaning agents and the use of disinfectants dose counting;
(5) Failure Alarm, as well as, washing complete the report.
2 dishwashers control system hardware design
To address the above function and reliability, cost and ease of use factors such as maintenance, and the author of the design shown in Figure 2 dishwashers control system.
SCM system is the smallest and MCS-51 compatible with the AT-MEL companies low-power high-performance CMOS chip design AT89LS8252, k-chip 8-byte programmable flash memory storage system for the procedures to be adopted by the SPI interface download programs; and 2 k bytes of EEPROM is used to store key parameters, such as the boot password maintenance, product serial number, the number of boot, washing setting parameters; 256 bytes of RAM used to store temporary variables.
In view of the dishwashers have more of the switching signal, therefore, the use of parallel design chips 8255 to expand the I / O interface, and to meet some of P1 and P3 I pin the use of its input and output ratio of 21 / 14, which buzzer from P1.3 control. From the reliability point of view, part of the input and output using photoelectric isolation measures. Consider that part of the drive signal required by the larger drive current, therefore, the design uses power-driven devices ULN2803 to drive.
There are two temperature acquisition programme: First, the use of thermal resistance with a MAX150 chip AD converter, and then deposited in the program memory in the form to achieve the current temperature; Second, the use of three-DS18B20 temperature sensor for acquisition, direct access to the temperature data . In contrast, after a simple programme more economical.
LED display and keyboard use HD7279A 3 to control, the circuit shown in Figure 3. HD7279A without external components can directly drive a total of eight vaginal LED digital pipe; corresponding pin DIG0 ~ 0 ~ 3 digital output driver; pin SA ~ SG and DP is a paragraph corresponding to ~ g and the decimal point drive output can be independently controlled to decode / decoding and attributes such as blanking and scintillation.
PO Bus Driver74LS245 DB 8255 Switch output
CB Buzzer
Address buffer74LS573 AB Switch Input
CPU AT89LS8252 Y8255 DB
P2 Address decoding74LS138 YMAX150 AD samplingMAX150
CB
Minimum System
CB Read / write control Keyboard and Four 8-segment LED
circuit continuity display management 4*4 keyboard
P1
Figure 2 controller hardware structure
The chip there are three types of instruction: The first one is without six of the eight data-orders, such as reduction, testing, left / right (cycle) and transposition; second is the 7 with 16 orders data , including downloading data by means 0 / 1 decoder, download not decoding, scintillation, blanking, paragraph lit, closed; third keyboard data is read instructions. Serial way they are used to communicate with AT89LS8252, DATA-pin serial data from the chip into by the CLK-synchronization. When the chip-select signal CS into low, the data on DATA-pin will be in the CLK pin at the rising edge of the buffer HD7279A was written into the register.
In addition, the chip contains HD7279A to jitter circuitry, which can be controlled 64 key keyboard matrix. Figure 2, components for the 4 × 4 JKEY keyboard interface, when a key is pressed, the output pin LOW KEY, LED1 bright light-emitting diodes, the state has been key to the release. If at this time to receive the "Reading keyboard" commands 15 H, in the first half of the directive, DATA pin will be in a high-impedance state to receive instructions from the microprocessor. In the latter half of the directive, the DATA input pins from state to state output for the output value of the code by pressing the button.
3 dishwasher Control System Software Design
Functional modules of the system by washing process can be divided into six stages: influent process, process heating, cleaning agents into the process, control motor rotating cleaning process, injected Xiaodaishui disinfection process and the drainage process. Dishwasher at the same time to ensure that the normal work of the process vulnerable to failure, the system also set up a fault alarm or shutdown feature. Dishwashers system software in accordance with the preparation of the work processes. The main software modules with power-on self test, state initialization, display the current default state, the state entered the keyboard scan button and wait for the press operation, as well as operating under the corresponding key into the process, and its main program flow as shown in Figure 3.
???? Users, dishwashers state should first check whether it is normal, if normal, press the power switch weak, according to wash requested washing mode (or use the default mode), Add to bowl cleaning room, and then close the doors, press start button. , The controller of water level and water temperature, to determine whether the water temperature and heating, bringing the preparatory work completed, motor start cleaning. Next then cleaning agent into the washing room, high and low level detection at the same time, if the lower water level, water immediately, in order to ensure cleaning effect. Upon completion of cleaning, such as a bowl of water on the air after a period of time, dishwasher temperature to be injected Xiaodaishui were disinfected. Upon completion of washing, buzzer call that washing completed on time and the initial controller settings to user mode. In the washing process and the keys were each corresponding to one of the bright light-emitting diodes eliminate, the process and to indicate whether or not the normal keys. Washing completed, the user opens doors, remove dishes, and then power to end the entire washing process.
In the system software subroutine, the need for keyboard / display module for the management, including the initialization subroutine, sent subroutine, receiving subroutine, interrupt subroutine, such as display subroutine. Keyboard settings through which users can be set washing mode modules, each process and the length of time washing dose, and may at any time by the corresponding button suspended or terminated washing process. Technical maintenance staff through keyboard / display module for entering the correct password to the use of machinery such as machine serial number, frequency of the use of machines, but also on the key parameters set according to the actual situation.
Start
Power-on self test state initialization / Display
N Check whether there is a bond?
Y
Judge keys
Set bond / Display Function keys
Whether the closed doors? N
Not influent
Heating temperature Y
Thermostat Temperature / Display Y Whether the low water level?
N N
Water temperature set to meet? Influent / Display
Water enough,
commissioner influent
Completion of the preparatory work at home signs
Delay ready to start second grade dishwasher
Injection cleaning agent Electric rotation began cleaning / Display
Time to disconnect Time to stop motor
Instantaneous heating 5 ~ 6 seconds
High-temperature injection Xiaodaishui
Narcotics / Display
Finished washing dishes, Stop related functions, Related signs removed
Figure 3 dishwasher Software Process
?? Failure Alarm function module voltage fault in the workplace, into the valve failure, heater failure, electrical failure, cleaning agents injected into the fault and the fault Xiaodaishui temperature when used buzzer alarm, at the same time, cut-control signals, in order to ensure system security.
4 Conclusion
The control system has been successfully debugging, testing good performance can be realized by the automatic dishwasher required functions, and simple practical. But there are areas which require improvement, such as the drainage need manual intervention, man-machine interface can be considered more effective use of the characters or graphics LCD, the system needs to be raised, such as integration.