Power Supply Modules :
Chapter-6
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| Power Supply Module |
Some CPU modules have an integrated power supply for powering on-board circuits.
However, some PLC models or configurations require a separate system power supply for this purpose.
This system power supply converts the incoming power to filtered, regulated, low-voltage DC power.
The system power is provided to a back plane that is common to multiple modules.
Multiple system power supply types are typically available for a PLC model to match the input voltage,which may be DC or AC.
System power supplies also have a power budget that defines the amount of power available for interconnected modules.
A load power supply, also called a load current power supply, provides power to input and output devices as well as the related input and output circuits, In some cases, the load power supply also provides power to other PLC modules, including a system power supply module.
The load power supply module (PM) for a SIMATIC S7-1500 PLC mounts on the same mounting rail as other S7-1500 modules.
Siemens also offers a variety of SITOP power supplies for use with a wide range of equipment.
Signal Modules :
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| Signal Module |
PLC'S have a variety of signal module types. Each module has multiple I/O channels, and each I/O channel connects to one I/O device.
The number of I/O channels on a module varies with the module type. Some modules also have both input and output channels. Each input or output channel on a module has an LED that shows the status of that channel.
One or more additional LED'S show the status of that module. Signal modules of various types are interspersed as needed throughout a system.
Each module is configured at installation, and this configuration includes the assignment of a module address.
This address together with the module type also identifies the location of image table status bits for the connected inputs and outputs.
As a result of this configuration, a discrete input (DI) or a discrete output (DQ) is associated with a specific image table status bit, and this input and output status information is available to the user program.
Because each analog input or output must represent any value in a range of values, each analog input (AI) or analog output (AQ) is associated with a word, 16 bits, of memory.
- At one time, PLC communications primarily used networks designed by equipment manufacturers for their own equipment.
- As more control devices with built-in computers were developed, the need for common approaches for communications emerged.
- This lead to development of a variety of field bus by industry associations.
- Afield bus is an industrial network used for distributed control.
- One example of a fieldbus is PROFIBUS DP the leading fieldbus standard, which was developed by PROFIBUS & PROFINET International (Pl).
With the growth in information technology (IT), the need for control systems to communicate with IT systems increased.
IT systems often communicate via Ethernet local area networks (LAN'S), however, the original form of Ethernet was not adequate for factory communication so Industrial Ethernet was developed.
PROFINET, which was also developed by PI, is the leading Industrial Ethernet standard.
A PLC CPU often has one or more ports for a specific type of network communications. For example, S7- 1200 and S7-1500 CPU'S all have at least one PROFINET port.
When additional network ports are required or when a different type of connection is needed, communication modules are added to the configuration.
With the growth in information technology (IT), the need for control systems to communicate with IT systems increased.
IT systems often communicate via Ethernet local area networks (LAN'S), however, the original form of Ethernet was not adequate for factory communication so Industrial Ethernet was developed.
PROFINET, which was also developed by PI, is the leading Industrial Ethernet standard.
A PLC CPU often has one or more ports for a specific type of network communications. For example, S7- 1200 and S7-1500 CPU'S all have at least one PROFINET port.
When additional network ports are required or when a different type of connection is needed, communication modules are added to the configuration.
Special Purpose Modules
PLC'S are very fast and have many types of signal modules, but some tasks require special purpose modules.
Many of these modules are designed for closed-loop control applications, which involve controlling a process or machine in response to a feedback signal from a sensor.
A control loop may require a special purpose module because of the type of sensor, control device, or algorithm used.
A control algorithm is a set of rules or calculations that define the control process For example, the proportional integral- derivative (PID) control used in many applications uses a control algorithm.
PLC'S are very fast and have many types of signal modules, but some tasks require special purpose modules.
Many of these modules are designed for closed-loop control applications, which involve controlling a process or machine in response to a feedback signal from a sensor.
A control loop may require a special purpose module because of the type of sensor, control device, or algorithm used.
A control algorithm is a set of rules or calculations that define the control process For example, the proportional integral- derivative (PID) control used in many applications uses a control algorithm.
- PLC'S are very fast and have many types of signal modules, but some tasks require special purpose modules.
- Many of these modules are designed for closed-loop control applications, which involve controlling a process or machine in response to a feedback signal from a sensor.
- A control loop may require a special purpose module because of the type of sensor, control device, or algorithm used. A control algorithm is a set of rules or calculations that define the control Process.
closed-loop control
For example, the proportional- integral- derivative (PID) control used in many applications uses a control algorithm.
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| closed-loop control |
For example, the proportional- integral- derivative (PID) control used in many applications uses a control algorithm.
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