This paper introduces a method of simulating PLC control with Atmel89S51 single-chip microcomputer, designing a controller suitable for rigid clutch punching machine, introducing the basic structure and working principle of photoelectric isolation input and output circuit, focusing on the design idea of ​​internal keyboard display circuit. At the same time, the electrical schematic of the punch control is given.
The system hardware configuration is based on the AT89S51 microcontroller. The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4Kb ISP (In-system programmable) flash-ready program memory that can be erased 1000 times. The device uses ATMEL's high-density, non-volatile Manufactured in memory technology, compatible with standard MCS-51 command system and 80C51 pin structure, built-in watchdog (WDT) circuit.
The powerful AT89S51 provides a cost-effective solution for many embedded control applications. The punch controller designed by the single chip has the following characteristics:
â— The controller adopts the concept of PLC design, with high reliability and strong anti-interference ability.
â— The 6-digit seven-segment LED display on the panel can be used to adjust parameters and display the count value during operation.
â— Modular design, small size and easy to install.
â— With the AT89S51 with ISP function, you can download the program in the field to realize the function of the programmable controller.
hardware designThe hardware structure of the controller is shown in Figure 1. It mainly consists of a keyboard display circuit, an EEPROM circuit, a power failure detection, a program download interface, and an opto-isolated input and output module. The power module is a switching power supply with +24V and +5V output designed with TOP220Y. When the system is powered off, the power failure detection circuit sends a signal to the AT89S51, and the system immediately stores the parameters and the count value into the EEPROM circuit.
The keyboard display circuit is shown in Figure 2. In order to save the I/O line, the lower 3 bits of the P0 port are reused here. The following describes the working principle of the circuit: when displaying, first set P3.3, P0.0~P0.5 is high level, and then output the code corresponding to the display content to the shift register 74HC164 which is serially connected to the output. Common cathode digital tube, then set the bit to be displayed low, delay 1ms, and then set the displayed bit high. As long as the frequency of such dynamic scanning is sufficiently high, the controller adopts 80 Hz, and the display function can be realized due to the visual persistence characteristic of the human eye, and there is no flicker phenomenon. When scanning the keyboard, set P3.3 low, then the output of the 74HC164 is low, which prevents interference display when scanning the keyboard. When no key is pressed, the read P0.0~P0.2 are low level. When the keyboard is pressed, the corresponding input will be read as high level, and then the delay debounce method can be judged. Which function is pressed and then goes to the function of the corresponding key. The display scan, keyboard scan, and debounce of the controller are all done in the timer interrupt.
The photoelectric isolation input circuit is shown in Figure 3. The input terminal and the COM terminal are connected by a voltage-free contact or an NPN open collector transistor. For the sake of reliability, the input current is 7 mA, and the input is ON. The input is OFF when the input current is less than 1.5mA. The output circuit uses an opto-isolated relay output to electrically isolate the internal circuitry of the controller from external circuitry to prevent external interference.
applicationThe punch control wiring is shown in Figure 4. When working, the 6-digit digital tube on the panel displays the count value. When the parameter needs to be set, press the function for 5 seconds to set the duration of the single action and the lubrication. Parameters such as number of operations, duration of lubrication, etc.
Rotate the selector switch to the single stroke position. When the slider is in the top dead center range, the left and right hand buttons are pressed simultaneously, the double valve is energized, the slider reciprocates once, and when the cam is turned to the braking position, the controller De-energize the double valve and stop the slider at the top dead center.
When the selector switch is placed in the inching position, press the left and right hand buttons at the same time, the controller makes the double valve energized, the slider can be actuated, the button is released, the controller de-energizes the double valve, and the slider stops. .
to sum upThe punch controller designed with AT89S51 single chip described in this paper has been tested and operated. The controller has reliable operation and strong anti-interference ability. It cooperates with software algorithm design and photoelectric protection to prevent the punching of the punch and ensure the operation. The safety of personnel. In addition, the AT89S51 single-chip microcomputer has a unique advantage of its command system, such as rich, compact, low-cost, flexible and easy to expand. In the designed punch controller, the cost performance of the whole system can be greatly improved.
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