plc
2015年9月22日星期二
plc modules in several categories
programmable logic control plc because of its high reliability, simple programming, versatility, small size, compact structure, easy installation and maintenance, etc., and in industrial control has been widely used. PLC modules are generally divided into the following categories:digital output module, analog input modules, analog output modules. In industrial control especially in the field of process control analog acquisition and control needs a relatively large amount, so the PLC analog input and output modules require more, and analog input and output modules are more expensive, increasing the analog input, output modules increases the cost and reduces the cost of the entire system, limit the application of PLC. This paper presents a simulation based on the amount of communication of input and output expansion module method seeks to solve this problem.
2015年8月13日星期四
PLC input and output interfaces
The programmable controller is a digital computing operation of electronic systems, specialized applications in industrial environments. It uses memory can be programmed, used in instruction execution storage logical and sequential control, timing, counting and arithmetic operations such as operations and digital or analog input (I) and output (O) through the interface, to control various type of machine or production process.
Interface Plc modules and the electrical circuit is output through the input section (I / O) to complete. plc IO module integrates the PLC's I / O circuit, the input register reflecting the input signal, the output point to reflect the state of the output latch. Input module into the electric signal into a digital signal the PLC system, the opposite output module. I / O into the digital input (DI), switching output (DO), the analog input (AI), analog output (AO) modules.
Interface Plc modules and the electrical circuit is output through the input section (I / O) to complete. plc IO module integrates the PLC's I / O circuit, the input register reflecting the input signal, the output point to reflect the state of the output latch. Input module into the electric signal into a digital signal the PLC system, the opposite output module. I / O into the digital input (DI), switching output (DO), the analog input (AI), analog output (AO) modules.
2015年8月9日星期日
— plc input modules, a method of low-cost expansion of output module
analog output plc, a method of low-cost expansion of output module programmable controller (hereinafter referred to as PLC) because of its high reliability, simple programming, versatility, small size, compact structure, easy installation and maintenance features, in the industrial control has been widely used. PLC modules are generally divided into the following categories: digital input modules, digital output modules, analog input modules, analog output plc. In industrial control especially in the field of process control analog acquisition and control needs a relatively large amount, so the PLC analog input and output modules require more, and analog input and output modules are more expensive, increasing the analog input, output module increases the cost and reduces the cost of the entire system, limit the application of PLC. This paper presents a method based on extended analog input and output modules of communication trying to solve this problem.
2015年8月1日星期六
Programmable Logic Controller (PLC) software measures:
We have a strong self-test and protection.
① fault detection - software periodically to detect the external environment, such as a power failure, under voltage, battery voltage is too low and strong interference signals. So that timely treatment.
② Information Protection and Recovery - When sporadic fault condition occurs, does not destroy the plc industrial controller's internal information. Once the fault condition is removed, you can return to normal, continue the original program of work. Therefore, profibus module plc when the fault condition is detected, immediately put the current state stored in the memory, software with the memory is closed to the memory of any action to prevent the storage of information is obliterated.
③ Set the Watchdog WDT (Watchdog) - If the program execution time per cycle than the WDT specified time, indicating the program into an infinite loop, call the police.
④ strengthen inspection and verification procedures - once the program is wrong, call the police, and stops executing.
⑤ the program and dynamic data backup battery - after a power outage, use battery-powered back-up, and information about the status will not be lost.
PLC factory pilot project, there is an immunity test. It is required to withstand the amplitude of 1000V, the rise time 1nS, a pulse width of the pulse 1μS of interference. In general, the average time between failures of up to hundreds of thousands - tens of millions of hours; the system can be made up to 4 to 50,000 hours or longer.
① fault detection - software periodically to detect the external environment, such as a power failure, under voltage, battery voltage is too low and strong interference signals. So that timely treatment.
② Information Protection and Recovery - When sporadic fault condition occurs, does not destroy the plc industrial controller's internal information. Once the fault condition is removed, you can return to normal, continue the original program of work. Therefore, profibus module plc when the fault condition is detected, immediately put the current state stored in the memory, software with the memory is closed to the memory of any action to prevent the storage of information is obliterated.
③ Set the Watchdog WDT (Watchdog) - If the program execution time per cycle than the WDT specified time, indicating the program into an infinite loop, call the police.
④ strengthen inspection and verification procedures - once the program is wrong, call the police, and stops executing.
⑤ the program and dynamic data backup battery - after a power outage, use battery-powered back-up, and information about the status will not be lost.
PLC factory pilot project, there is an immunity test. It is required to withstand the amplitude of 1000V, the rise time 1nS, a pulse width of the pulse 1μS of interference. In general, the average time between failures of up to hundreds of thousands - tens of millions of hours; the system can be made up to 4 to 50,000 hours or longer.
2015年7月28日星期二
Medium programmable control system
Medium plc industrial controller may provide the functionality and flexibility you need, do not have that kind of overhead systems, it is the perfect solution for medium-sized application projects. Select rack-based, modular package design standards and safety certification from the controller. Typical applications include complex machine control, batch processing and building automation.
2015年7月24日星期五
PLC current loop transmission
Application of the current control loop is started in the early 1900s teletype, the earliest use of the 0-60mA loops and later changed to 0-20mA loop, programmable logical controllers system is the first to use the 4-20mA loop.
4-20mA current loop has many advantages. Need to be carefully calculated in the traditional discrete component designs, and compared with the current integrated 4-20mAIC, circuit take up a lot of space.
Any current values measured are representative of certain information. Practical applications, 4-20mA current loop in 0mA to 24mA current range. But 0mA to 4mA and 20mA to 24mA current range for diagnostics and system calibration. Due to lower than 4mA and above 20mA are used for diagnostics, it is believed readings between 0mA and 4mA could indicate a broken wire in the system. Similarly, between 20mA and 24mA between readings can indicate a potential short circuit occurred in the system.
Plus 4-20mA communications Highway Addressable Remote Sensor, which is backward compatible with 4-20mA instrumentation. In HART system uses microprocessor-based intelligent integration of field devices enables two-way communication. The HART protocol capable of carrying additional digital information on the same line 4-20mA analog current signal for process control.
plc analog input output module functions can be divided into several functional groups. Many plc controller manufacturer vendors will integrate these functions as separate modules, each module with features vary with the specific application. Many modules have multiple functions, it can interface with a variety of sensors. However, for specific applications will design special modules or expansion modules, such as in most cases: resistance temperature detector (RTD), sensor, or thermocouple sensor. In general, all modules have the same core functions: analog input, analog output, distributed control (eg fieldbus), interface, digital input and output (I / O), CPU and power supply.
4-20mA current loop has many advantages. Need to be carefully calculated in the traditional discrete component designs, and compared with the current integrated 4-20mAIC, circuit take up a lot of space.
Any current values measured are representative of certain information. Practical applications, 4-20mA current loop in 0mA to 24mA current range. But 0mA to 4mA and 20mA to 24mA current range for diagnostics and system calibration. Due to lower than 4mA and above 20mA are used for diagnostics, it is believed readings between 0mA and 4mA could indicate a broken wire in the system. Similarly, between 20mA and 24mA between readings can indicate a potential short circuit occurred in the system.
Plus 4-20mA communications Highway Addressable Remote Sensor, which is backward compatible with 4-20mA instrumentation. In HART system uses microprocessor-based intelligent integration of field devices enables two-way communication. The HART protocol capable of carrying additional digital information on the same line 4-20mA analog current signal for process control.
plc analog input output module functions can be divided into several functional groups. Many plc controller manufacturer vendors will integrate these functions as separate modules, each module with features vary with the specific application. Many modules have multiple functions, it can interface with a variety of sensors. However, for specific applications will design special modules or expansion modules, such as in most cases: resistance temperature detector (RTD), sensor, or thermocouple sensor. In general, all modules have the same core functions: analog input, analog output, distributed control (eg fieldbus), interface, digital input and output (I / O), CPU and power supply.
2015年7月20日星期一
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