Today I am gonna teach you about plc hardware we will start with the basic devices that
are using the plc hardware then, later on, we will jump a bit the more advanced stuff so let’s start with the basic companies of the plc hardware

1.Allen-Bradley PLC

2.GE FANUC PLC

3.Modicon PLC

4.Siemens PLC

Understanding of PLC Hardware :


  • you can see the first guy that comes in in any particular plc is a power supply but before that, I’m gonna this is the rack that we have where I will have different components of the PLC different device you can say that gonna be installed and each device like that
    for you can see power supply will use
  • That is a micro-controller based circuit. The CPU consists of following blocks :
    Arithmetic Logic Unit (ALU), Program memory, Process image memory (Internal memory of CPU), Internal timers and counters, Flags

  • CPU performs the task necessary to fulfill the PLC functions. These tasks include Scanning, I/O bus traffic control, Program execution, Peripheral and External device communication, special functions or data handling execution and self-diagnostics.
  • one slot of the PLC, so you can see that that’s this particular PLC, have 1 2 3 4 5 6 so this PLC is using 6 slots of the rack so this rack is actually where you mount these all stuff there so this is rack and the slot is one place for mounting 1 1 device in here so let’s

Start with the basic plc logic Hardware again think of light that we normally push up and light and off now let’s take out if you want to do that job by using a PLC stuff how we will accomplish it for that what we need is first is our input and that input need to be processed in a PLC and if it needs to be processed in a PLC definitely we need to have digital card for that PLC Digital Input Module

Input Module:


Input modules act as an interface between a real-time status of a process variable and the CPU.

  • Analog input module: Typical input to these modules is 4-20 mA, 0-10 V
    Ex: Pressure, Flow, Level Tx, RTD (Ohm), Thermocouple(mV)
  • Digital input module: Typical input to these modules is 24 V DC, 115 VAC, 230 VAC
    Ex. : Switches, Pushbuttons, Relays, pump valve on-off status

So if in the case you will get the signals in the digital card then you will process it this particular signal through the CPU and into the CPU whatever the logic you have implemented in there the CPU will decide something and based on the logic that you have
implement in there so then based on that you will have an output so that particular output now need to be processed to some final control if it needs to be processed in a PLC definitely we need to have digital in a card for that PLC Digital Output Module

Output Module:


Output module These modules act as a link between the CPU and the output devices in the field.
Analog output module: Typical output from these modules is 4-20 mA, 0-10 V
Ex: Control Valve, Speed, Vibration
Digital output module: Typical output from these modules is 24 V DC, 115 VAC, 230 VAC
Ex. : Solenoid Valves, lamps, Actuators, dampers, Pump
a valve on-off control

Bus System
This is a path for the transmission of the electrical signal.Bus system task to signal exchange between a processor and I/O modules

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