Product Information
Allen-Bradley is the brand name of Factory Automation Equipment manufactured by Rockwell Automation. The company manufactures programmable logic controllers, human-machine interfaces, software, safety components, and asset management services. The company was founded in 1903 as the Compression Rheostat Company by Dr. Stanton Allen and Lynda Bradley. The company was rebranded as the Allen Bradley Company in 1910. The company was one of the first to provide discrete resistors used for electronics and other products, but the company’s first patented product was a carbon disc compression-type motor controller for industrial cranes, which was demonstrated at the St. Louis World’s Fair in 1904. Rockwell International acquired Allen-Bradley in 1985 and moved its headquarters to Milwaukee in 2002. The Allen-Bradley 1756-IF 16 Analog Input Module is compatible with CompactLogix, Controllogix, MicroLogix 1500 controllers. The 1756-IF 16 controller module can provide the input component for your analog to digital conversion needs. The 1756-IF 16 controller module has a built in removable terminal block, a finger safe cover allowing the user to create a connection with I/O sensors and actuators.
The system can be changed so that the I/O wiring can be routed from underneath the primary module to the selected I/O terminal. 6 point terminals can offer onboard data alarming, scaling to engineering units, real time channel sampling, data formats in integer mode with IEEE 32 bit floating points, module keying that is electronic software configurable and RTB keying. The 1756-IF 16 Controllogix module has 16 single ended inputs with 8 differential or 4 differential for analog data. Its input range is plus or minus 10 volts. 8 point modules offer increased accuracy, repeatability, and greater stability over temperature operating ranges. The 8 point module can also offer increased precision with 24 bits of usable resolution, synchronized input sampling across all modules anywhere in a CIP Synch system, and per channel status with fault LED annunciation. Each 1756-IF 16 ControlLogix I/O module mounts in a ControlLogix chassis and requires either a removable terminal block or a 1492 interface module to connect all field side wiring. The Allen-Bradley 1756-IF 16 Analog-Input Module from Rockwell Automation comes with a significant level of documentation in the form of a full PDF with all relevant information and technical definitions with regard to current, differential, voltage, inputs, and outputs. The Allen-Bradley 1756-IF 16 also contains on board data alarming, scaling to engineering units, and real time channel sampling.The 1756-IF 16 controller also contains diagnostic features that can assist in identifying the source of problems that occur during power up or normal channel operation.
Product Identifiers
BrandAllen-Bradley
MPN1756-IF16
UPC10612598171788
Model1756-IF16
eBay Product ID (ePID)143698802
Product Key Features
Controller PlatformControlLogix
Additional Product Features
TypeAnalog Input Module
16 Point Voltage Current A/I Analog Input Module
Catalog Number: 1756-IF16
OEM Product Description: CONTROLLOGIX 16 PT A/I MODULE
Parent Company: Rockwell Automation AB A-B
Universal Product Code (UPC): 61259817178
Class: Programmable Logic Control (PLC)
EAN: 10612598171788
Product Family: PLCs and Controllers
GTIN: 00612598171781
UNSPSC: 32151705
OEM Lifecycle Status: ACTIVE
Rockwell Automation (China) Co., Ltd. is the world's largest company dedicated to industrial automation and informatization, dedicated to helping customers improve productivity and sustainable development in the world. Rockwell Automation is headquartered in Milwaukee, Wisconsin, USA, with branches in more than 80 countries around the world and currently employs approximately 22,000 people.
Rockwell Automation and 12 domestic authorized distributors, 124 approved system integrators, more than 30 Encompass strategic partners and global strategic alliances in the Asia-Pacific region, jointly provide manufacturing enterprises with a wide range of world-class products and solutions Program and service support.
Rockwell has more than 500,000 products, including: programmable controllers, power devices, sensors, operator interfaces, motion control products, communication products, software, training, customer support, application systems, quality management, technical support Services, rotating equipment (motors, mechanical power), AC inverters, DC speed regulators, enterprise asset management, process solutions. In such a huge product technology system, we have enough top talents in various related industries to guarantee.
Programmable logic controller is a kind of digital operation electronic system specially designed for application in industrial environment. It uses a programmable memory to store instructions for operations such as logic operations, sequence control, timing, counting and arithmetic operations, and control various types of mechanical equipment or production through digital or analog input and output. process.
Introduction
Programmable Logic Controller (PLC), a digital arithmetic controller with microprocessor for automatic control, can load control instructions into memory at any time for storage and execution. The programmable controller is composed of functional units such as CPU, instruction and data memory, input/output interface, power supply, and digital to analog conversion. The early programmable logic controllers had only logic control functions, so they were named programmable logic controllers. Later, with continuous development, these computer modules with simple functions at the beginning have included logic control, timing control, analog control, The name of various functions such as multi-computer communication has also been changed to Programmable Controller. However, due to the conflict between its abbreviation PC and the abbreviation of Personal Computer, and for reasons of habit, people still often use it. The term "programming logic controller" still uses the acronym PLC.
The programmable logic controller used in the industry is now equivalent to or close to the host of a compact computer, and its advantages in scalability and reliability have made it widely used in various industrial control fields. No matter in the computer direct control system or the centralized distributed control system DCS, or the field bus control system FCS, there are always a large number of various PLC controllers used. There are many PLC manufacturers, such as Siemens, Schneider, Mitsubishi, Delta, etc., almost all manufacturers involved in the field of industrial automation will provide their PLC products.
basic structure
The programmable logic controller is essentially a computer dedicated to industrial control. Its hardware structure is basically the same as that of a microcomputer. The basic structure is described in detail as follows:
power supply
The power supply is used to convert AC power into DC power required within the PLC. At present, most PLCs use switch-mode stabilized power supplies.
Central processing unit
The central processing unit (CPU) is the control center of the PLC and the core component of the PLC. Its performance determines the performance of the PLC.
The central processing unit is composed of a controller, arithmetic unit, and registers. These circuits are all concentrated on a chip and are connected to the input/output interface circuit of the memory through an address bus and a control bus. The role of the central processing unit is to process and run user programs, perform logical and mathematical operations, and control the entire system to coordinate.
Memory
The memory is a semiconductor circuit with memory function, and its function is to store system programs, user programs, logic variables and other information. Among them, the system program is the program that controls the PLC to realize various functions. It is written by the PLC manufacturer and solidified in the read-only memory (ROM), which cannot be accessed by the user.
Input unit
The input unit is the input interface that connects the PLC to the controlled device, and is the bridge for the signal to enter the PLC. Its function is to receive the signal from the master component and the detection component. The input types include DC input, AC input, AC and DC input.
Output unit
The output unit is also the connecting part between the PLC and the controlled device. Its function is to transmit the output signal of the PLC to the controlled device, that is, convert the weak current signal sent by the central processing unit into a level signal to drive the executive element of the controlled device . The output types include relay output, transistor output, and thyristor output.
In addition to the above-mentioned parts, PLC has a variety of external devices according to different models. Its function is to help programming, realize monitoring and network communication. Commonly used external devices are programmers, printers, cassette tape recorders, computers, etc.
working principle
When the programmable logic controller is put into operation, its working process is generally divided into three stages, namely input sampling, user program execution and output refresh three stages. Completing the above three stages is called a scan cycle. During the whole operation period, the CPU of the programmable logic controller repeatedly executes the above three stages at a certain scanning speed.
Input sampling
In the input sampling stage, the programmable logic controller sequentially reads in all input states and data in a scanning manner, and stores them in the corresponding units in the I/O image area. After the input sampling is over, it goes to the user program execution and output refresh stage. In these two stages, even if the input status and data change, the status and data of the corresponding unit in the I/O map area will not change. Therefore, if the input is a pulse signal, the width of the pulse signal must be greater than one scan period to ensure that the input can be read under any circumstances.
User program execution
In the user program execution stage, the programmable logic controller always scans the user program (ladder diagram) sequentially from top to bottom. When scanning each ladder diagram, it always scans the control circuit formed by the contacts on the left side of the ladder diagram first, and performs logic operations on the control circuit formed by the contacts in the order of left and right, up and down. , And then according to the result of the logic operation, refresh the state of the corresponding bit of the logic coil in the system RAM storage area; or refresh the state of the corresponding bit of the output coil in the I/O image area; or determine whether to execute the ladder diagram The specified special function instructions.
That is, during the execution of the user program, only the state and data of the input point in the I/O image area will not change, while other output points and software devices are in the I/O image area or the system RAM storage area. The status and data may change, and the ladder diagram listed above, the program execution results will affect the ladder diagrams listed below that use these coils or data; on the contrary, the ladder diagram listed below will have The state or data of the logic coil that is refreshed can only take effect on the program above it until the next scan cycle.
If you use immediate I/O instructions during program execution, you can directly access I/O points. Even if I/O instructions are used, the value of the input process image register will not be updated. The program directly fetches the value from the I/O module, and the output process image register will be updated immediately, which is somewhat different from immediate input.
Output refresh
After scanning the user program, the programmable logic controller enters the output refresh phase. During this period, the CPU refreshes all output latch circuits according to the corresponding status and data in the I/O image area, and then drives the corresponding peripherals through the output circuit. At this time, it is the real output of the programmable logic controller.
summary
According to the description of the above process, the characteristics of the PLC working process can be summarized as follows:
① PLC adopts the working mode of centralized sampling and centralized output, which reduces the influence of external interference.
②The working process of PLC is a cycle scanning process, and the length of cycle scanning time depends on factors such as instruction execution speed and user program length.
③The influence of output on input has a hysteresis. PLC adopts the working mode of centralized sampling and centralized output. When the sampling phase is over, the input state change will not be received until the next sampling period. Therefore, the length of this lag time mainly depends on the length of the cycle period. In addition, the factors that affect the lag time include the input filter time and the lag time of the output circuit.
④ The content of the output image register depends on the result of the user program scanning execution.
⑤ The content of the output latch is determined by the data in the output image register during the last output refresh.
⑥The actual output status of the PLC is determined by the content of the output latch.
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