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PHT Introduction Unit

1.0 Introduction to Hardware & Software

As a name Downtime Reduction stands for, all courses offered by Academy are geared towards the purpose of those courses — is to get a knowledge of the Downtime Reduction Methodology and its implementation. Knowledge is the only awarding when it’s properly applied and capable of creating benefits to those who are struggling with downtime losses.

The following video will provide a view to the Downtime Reduction Methodology, the process of its implementation, benefits and its usefulness. Then we will provide the insight to PLC Hardware & Software — the first course towards to Become PLC/HMI/SCADA Technician — 6-in-1 certified course.

1.1 PLC Makes, Types and Specs

PLC is Programmable Logic Controller is also known as Industrial Computer. It is the major component in the industrial automation industry. Due to its robust construction, exceptional functional features like PID controllers, sequential control, timers and counters, ease of programming, reliable controlling capabilities and ease of hardware usage – this PLC is more than a special-purpose digital computer in industries as well as in other control-system areas. Different types of PLCs from vast number of manufacturers are available in today’s market.  Let us study about PLCs and their types.

The table below shows the most popular PLC manufacturers in the World. By making a click on any underscored text you will be able to see PLC products of every PLC manufacturer listed below:

As a rule, every PLC manufacturer produce PLCs, HMI and SCADA hardware and software.

Please understand that programming methods used are completely identical for any PLC around the world. Those methods are the international standard initially developed by IEC — International Electrotechnical Commission in Geneva Switzerland back in 60s. More about Programming Methods see below.

PLC Specs Part 1

PLC Hardware Architecture

The basic architecture of a PLC consists of main components-the processor module, the power supply, and the I/O modules. The processor module consists of the central processing unit (CPU) and memory. In addition to a microprocessor, the CPU also contains at least an interface to a programming device and may contain interfaces to remote I/O and other communication networks. The power supply is usually a separate module, and the I/O modules are separate from the processor. The types of I/O modules include discrete (on/off), analog (continuous variable), and special modules like motion control or high-speed counters. The field devices are connected to the I/O modules.

Hardware Components of a PLC System
Central Processor unit (CPU), Memory, Input/Output, Power Supply unit, Programming Hand-held unit, discrete and analogue input/output cards, network unit, simulator unit, etc.

Central Processing Unit (CPU)
CPU – Microprocessor based, provides arithmetic operations, logic operators, block memory moves, computer interface, local area network, functions, etc.

System Busses
The internal paths along which the digital signals flow within the PLC are called busses.
The system has four busses:

    • The CPU uses the data bus for sending data between the different elements
    • The address bus to send the addresses of locations for accessing stored data
    • The control bus for signals relating to internal control actions
    • The system bus is used for communications between the I/O ports and the I/O unit.

Memory
Read Only Memory (ROM) gives permanent storage for the operating system and the fixed data used by the CPU.
Random Access Memory RAM is used for data storage and manipulation. This is where information is stored on the status of input and output devices and the values of timers and counters and other internal devices. EPROM or Erasable Programmable Read-Only Memory is a type of a chip that retains its data when its power supply is switched off.

I/O Sections
Inputs monitor field devices, such as pushbuttons, switches, and sensors.
Outputs control other devices, such as motors, pumps, solenoid valves, and indicating lights.

Power Supply
Most PLC controllers work either at 24 VDC or 120 VAC. Some PLC controllers have electrical supply as a separate module, while small and medium series already contain the supply module.

Programming Device
The programming device is used to enter the required program into the memory of the processor.
The program is developed in the programming device and then transferred to the  memory unit of the PLC.

PLC Specs Part 2

When you consider buying or replacing PLC, you should be aware of PLC specifications that might be mostly suitable to your production application, your PLC and plant networking, and many other aspects, such as:

  • Total Number of Points (inputs or outputs)
  • Number of Instructions
  • Network
  • PLC Power Supply
  • Inputs
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  • Scan Time
  • Data Memory
  • Computer Interface
  • PLC Mounting
  • Outputs
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1.2  AB, Siemens, Schneider, GE, Omron, etc.

For introduction purpose we will show you only those few, which are the most popular in all industries. for any other PLC manufacturer please refer to the Part 1.1 above. The table below shows families of PLC and HMI products produced by these 4 companies:

Allen-Bradley

Siemens Automation

Omron

GE Fanuc

You should be able to recognize PLC make by looking at it.

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