CN103744747A - Power failure controlling device for programmable logic controller (PLC) - Google Patents

Abstract

The invention discloses a power failure controlling g device for a programmable logic controller (PLC). The power failure controlling device comprises a microprogrammed control unit (MCU), a PLC, a power failure detection module, a permanent memory storage and a power module, when power failure of the PLC occurs, the power failure detection module transmits a power failure signal to the MCU, the data of the PLC, which are required to be stored, are stored by the MCU in the permanent memory storage, when the power failure detection module again detects that the supply voltage of the PLC reaches a certain threshold value, the power failure detection module transmits a power recover signal to the MCU, and thereby, the MCU is awakened and enabled to recover stored data. By means of the power failure controlling device for the PLC, when the power failure or instable voltage of the PLC occurs, the data of the PLC, which are required to be stored, can be stored, and when the voltage recovers, the stored data can be read so as to continue to work.

Description

A PLC power-down control device

technical field

The invention relates to a PLC power-down control device.

Background technique

Programmable controller, as a computer controller specially designed for working in industrial environment, should have high reliability and strong anti-interference ability, and can make some sudden impacts on complex and changeable industrial sites. timely response. Therefore, this requires the core control unit of the programmable controller to have a faster computing speed and a stronger real-time processing capability. However, the current programmable controller may not be able to deal with it in time when there is a sudden power failure or the voltage is not stable enough. These consequences sometimes directly affect the performance of the programmable controller.

Contents of the invention

Purpose of the invention: the purpose of the present invention is to provide a kind of control device for PLC power-down at the deficiencies in the prior art, so that PLC can save the data that PLC needs to save when power-off or voltage instability occurs. Stored data can be read after recovery to continue working.

Technical solution: In order to achieve the purpose of the present invention, the present invention discloses a PLC power-down control device, including MCU, PLC, power-down detection module, permanent memory memory and power supply module; when PLC power-off, the power-down detection module Transmit a power-down signal to the MCU, and the MCU will store the data that the PLC needs to save in the permanent memory. After the power-down detection module re-detects the PLC power supply voltage to reach a certain threshold, the power-down detection module transmits a recovery signal to the MCU. , thereby waking up the MCU and enabling the MCU to restore the above-mentioned data stored in the permanent memory that needs to be saved.

Preferably, in order to ensure the working stability of the PLC, the condition for the power-down detection module to send out the power-down signal is that the power supply voltage is lower than 4.63V.

Preferably, in order to ensure that the system works only after the voltage is stable and to improve work efficiency, the recovery electrical signal of the power-down detection module is given after a delay of 140-300 ms.

Preferably, in order to realize the low power consumption of the whole control device, the MCU adopts the Cortex-M3 processor of ARM.

As a preference, for the user program to be downloaded and updated without going through the host computer, the MCU is connected to the U disk through the USB Host interface module.

Beneficial effects: Compared with the prior art, the present invention enables the PLC to save the data that the PLC needs to save when the power is off or the voltage is unstable, and the stored data can be read to continue working after the voltage is restored.

Description of drawings

Fig. 1 is the structural diagram that the present invention is used for PLC power down control device;

Figure 2 is a sequence diagram of PLC power-down detection and recovery;

Fig. 3 is a control flow chart of the present invention for the PLC power-down control device.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention is used for PLC power-down control device and comprises MCU, and MCU comprises input and output interface, other interface, extension interface and special function module; Wherein, input and output interface comprises 16 routes of inputs, 16 routes of outputs and 2-way A/D, other interfaces include running/programming switch, power-off/power-on external interrupt and working status LED indicator, the extension part includes expansion module interface, human-computer interaction interface and external memory, and special function module includes USB- HOST, USB-DEVICE, RS-232 and JTAG.

The MCU adopts the STM32F103VET6 chip based on the ARM Cortex-M3 processor core of ultra-low power consumption, which can reach a main frequency of 72MHz and has a high operating speed; the on-chip Flash of 512KB and the on-chip SRAM of 64KB can Support large user program capacity; integrated nested vector controller, with high interrupt response efficiency; the external storage module uses ferroelectric memory as the external storage device, this type of memory has the characteristics of not being lost when power is off and can It can save the data of the soft components and the state data of the programmable controller cyclically when the power is off. The ferroelectric memory chip is FM24C128, which has a capacity of 16KB, can be erased and written up to hundreds of millions of times, and has a clock frequency of up to 400KHz, and has a high read and write speed. Therefore, it can well meet the needs of small programmable Controller job requirements. The MCU pin connected to the SCL pin of the FM24C128 chip is the I2C2_SCL pin, and the MCU pin connected to the SDA pin of the FM24C128 chip is the I2C2_SDA pin. As the control chip of PLC, MCU is equipped with a power-off detection module for system power-off and power-on state detection, and an external storage module that can be erased multiple times without losing power. When the PLC is powered off or the voltage is unstable At this time, the data that the PLC needs to save can be saved, and the stored data can be read after the voltage is restored to continue working.

As shown in FIG. 2 , in the power-off detection module, when the system is powered off, the power-off detection chip provides a power-off signal to the MCU to allow the system to store data that needs to be saved. When the system is powered on again, it wakes up the MCU and restores the backup data, so that the system can continue to operate from the state when it was powered off last time. The power-down detection chip is IMP809L, and when the system power supply Vcc is 5V, it is selected as the threshold value of the system power-down detection voltage. When the system is powered off, IMP809L will generate a falling edge to provide a power-down signal to the MCU; when the system is powered on, IMP809L will delay at least 140ms before generating a rising edge signal, which ensures that the system starts after the power supply is stable. Work. The MCU pin connected to the RESET pin of IMP809L is set as an external interrupt pin.

As shown in Figure 3, first save the user program in a USB storage device with a specific file name and connect the USB storage device to the MCU through the USB-HOST interface; after recognizing that a USB storage device is inserted, the programmable controller will Enumerate the inserted USB storage device, and then perform a series of operations such as reading files, and finally read the user program into the user program storage area of the MCU of the PLC. In this way, the user program can be downloaded and updated without going through the host computer.

This design ensures that the PLC can save the data that the PLC needs to save when the power is off or the voltage is unstable, and the stored data can be read after the voltage is restored to continue working; at the same time, the ARM Cortex-M3 processor itself has The different working states also ensure that the device can complete a series of tasks under low power consumption.

Claims (5)

1. A power-down control device for PLC, comprising MCU, PLC, power-down detection module, permanent memory memory and power supply module; When the PLC is powered off, the power-off detection module transmits a power-off signal to the MCU, and the MCU will store the data that the PLC needs to save in the permanent memory. The electrical detection module transmits a recovery electrical signal to the MCU, thereby waking up the MCU and enabling the MCU to restore the above-mentioned data stored in the permanent memory that needs to be preserved. 2. A power-down control device for PLC according to claim 1, wherein the condition for the power-down detection module to send a power-down signal is that the power supply voltage is lower than 4.63V. 3. A power-down control device for PLC according to claim 1, characterized in that, the recovery electrical signal of the power-down detection module is given after a delay of 140-300 ms. 4. A kind of control device for PLC power down as claimed in claim 1, is characterized in that, MCU adopts the Cortex-M3 processor of ARM. 5. A kind of control device for PLC power down as claimed in claim 1, is characterized in that, MCU is connected with U disk by USB Host interface module.

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