Most common manufacturer of plc

 Siemens - Schneider - Panasonic - Allen-Bradley - LG - Delta - Mitsubishi 
 
1- Siemens : 

-   www.siemens.com

2-Schneider :

www.schneider-electric.com

Number Systems

Any number system has a radix or base. We can use any system for counting. Every system has its own symbols. The radix of a number system determines the total number of system symbols.
Number systems are:
•    Decimal number system
•    Binary number system
•    Octal number system
•    Hexadecimal number system

PLC APPLICATIONS

PLCs perform all control tasks, from simple machines control applications to sophisticated manufacturing and process control Applications.
PLC almost in every part of industry:
1-    Steel mills (rolling mills).
                                                          rolling mills

Programming devices

We can enter program into PLC by one of  two basic types of programming devices
• Personal computers (PC).
• Mini programmers.
1- Personal computer
Due to the general-purpose architecture of personal computers, most PLC manufacturers and provide the necessary PC software to implement ladder program entry, editing, and real-time monitoring of the PLC’s program. The figure blow show PC software for PLC

Classifications of plc

We can classify plc into two categories
1-    Classification by I/O modules.
2-    Classification by application ranges.

Classification by I/O modules:
1-    DISCRETE I/O SYSTEMS.
The discrete (I/O) system provides the physical connection between the CPU and field devices that transmit and receive digital signals.

2-    ANALOG   I/O  SYSTEMS.
Analog input modules, are used in applications where the field equipment’s signal is continuous such as Pressure and Temperature.

Analog output module are used in applications which need to continuous voltage or current levels for control. An example of this type of field device is a electric motor drives.

Classification by application ranges