PLCs - Programmable Logic Controllers

A PLC (programmable logic controller) is an industrial digital computer designed for the control and automation of manufacturing processes or robotic devices. Programmable Logic Controllers are used where reliability control, simple programming and fault diagnosis is necessary. They were originally built to replace electromechanical relay systems in industrial automation.

A CPU (central processing unit) forms part of the PLC system. PLC CPUs are a microprocessor-based control system and act as the electronic circuitry within an industrial computer. They are usually built-in carry out instructions from the computer program via programming languages, performing basic mathematical, logical, control, input and output operations.

PLC Applications

PLC controllers are incredibly useful and have many applications across several industries such as manufacturing, food & beverage, and building control. PLC's control the automation process in the machinery used for:

  • Production plants
  • Traffic light controls
  • Packaging machines
  • Lifts and escalators
  • Medical applications
  • Automatic gate systems
  • Heating control systems

How do PLC's work?

PLC Controller's respond to inputs from programming software and give a desired output. Programmable Logic Controllers can also include human-machine interfaces.

Different models use varying PLC Programs based on the programming languages used in the software. Programming languages that are used in PLC programming include:

  • ST: Structured Text (text-based)
  • FBD: Function Block Diagram (graphic-based)
  • LAD: Ladder logic (graphic-based)
  • STL: Statement List (text-based)
  • SCL: Structured Control Language (graphic-based)

PLC programming can be quite complex but there are simpler, image-based options available such as Ladder Logic that has user-friendly Ladder diagrams to understand and improve processes. Laptop and software are usually used for Ladder Logic and Ladder Diagrams, however, some older models use handheld controllers.

Types of PLC's

Programmable Logic Controllers can be categorised in multiple ways, each with different functions, features and capabilities. For example, Soft PLC's are software based and use their own operating system but do not have their own CPU. Whereas, Hard PLC's are hardware based and typically only include the essential control functions. The full range of programmable controllers include:

  • Hard PLC's
  • Soft PLC's
  • Compact PLC's
  • Slot PLC's
  • Unitary PLC's
  • Modular PLC's

Programmable Controllers can also be made more efficient by using equipment such as, HMI displays, DIN Rails, and Communication modules (such as MODBUS) which can be enhanced into a highly functional automated control system with PLC accessories. More information can be found our complete PLCs guide


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Beskrivning Pris For Use With Manufacturer Series Number of Inputs Number of Digital Inputs Output Type Input Type Number of Analogue Inputs Voltage Category Number of Digital Outputs Supply Voltage Number of Analogue Outputs Interface Kit Included Number of Outputs
RS-artikelnummer 917-6370
VarumärkeRS PRO
1 160,88 kr
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- - 8 - Digital, Relay Analogue, Digital - - - 12 → 24 V dc - - - 4
RS-artikelnummer 917-6392
VarumärkeRS PRO
447,25 kr
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RS PRO Logic Modules - 1 - RS485 Protocol (D-), RS485 Protocol (D+), RS485 Protocol (Two Wires) TTL Level - - - 12 → 24 V dc - - - 1
RS-artikelnummer 917-6373
VarumärkeRS PRO
986,42 kr
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- - 8 - Digital, Relay Digital - - - 110 → 240 V ac - - - 4
RS-artikelnummer 917-6399
VarumärkeRS PRO
165,83 kr
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RS PRO Logic Modules - - - - - - - - - - - - -
RS-artikelnummer 917-6377
VarumärkeRS PRO
985,14 kr
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- - 8 - Digital, Relay Analogue, Digital - - - 12 → 24 V dc - - - 4
RS-artikelnummer 917-6389
VarumärkeRS PRO
605,40 kr
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RS PRO Logic Modules - 8 - Digital, Relay Digital - - - 12 → 24 V dc - - - 4
RS-artikelnummer 917-6361
VarumärkeRS PRO
1 152,99 kr
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- - 8 - Digital, Relay Digital - - - 110 → 240 V ac - - - 4
RS-artikelnummer 917-6386
VarumärkeRS PRO
553,04 kr
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RS PRO Logic Modules - 8 - Digital, Relay Digital - - - 110 → 240 V ac - - - 4
RS-artikelnummer 917-6383
VarumärkeRS PRO
414,83 kr
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RS PRO Logic Modules - 1 - RS485 Protocol (D-), RS485 Protocol (D+), RS485 Protocol (Two Wires) TTL Level - - - 110 → 240 V ac - - - 1
RS-artikelnummer 864-4538
Tillv. art.nr0850-0600
VarumärkeBARTH
1 602,17 kr
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STG-600 lococube mini-PLC 10 - PWM, Solid State Analogue, Digital - - - 7 → 32 V dc - - - 9
RS-artikelnummer 442-0795
Tillv. art.nrAL2-24MR-A
VarumärkeMitsubishi
2 420,73 kr
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- Alpha 2 15 - Relay Digital - - - 100 → 240 V ac - - - 9
RS-artikelnummer 763-1002
Tillv. art.nr1SAP186200R0004 TA574-D-T-ETH
VarumärkeABB
7 127,82 kr
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AC500-eCo Series AC500-eC0 8 8 Digital Digital - 24 V dc 6 - - - Yes 6
RS-artikelnummer 442-0789
Tillv. art.nrAL2-14MR-D
VarumärkeMitsubishi
1 642,26 kr
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- Alpha 2 8 - Relay Analogue - - - 24 V dc - - - 6
RS-artikelnummer 862-4487
Tillv. art.nr6ES7215-1AG40-0XB0
VarumärkeSiemens
6 824,96 kr
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SIMATIC S7-1200 Series S7-1200 14 (Digital Input, 2 switch as Analogue Input) 14 Digital, Transistor Analogue, Digital - 24 V dc 10 20.4 → 28.8 V - - - 10 (Digital Output, Transistor Output)
RS-artikelnummer 825-1685
Tillv. art.nr6ED1055-1NB10-0BA2
VarumärkeSiemens
1 322,34 kr
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LOGO! 8, LOGO! 8.2 LOGO! 8 8 Relay Digital - - 8 24 V dc - - - 8
RS-artikelnummer 760-9229
Tillv. art.nrZEN-10C2AR-A-V2
VarumärkeOmron
2 646,00 kr
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- ZEN 6 - Relay Analogue - - - 85 → 264 V ac - - - 4
RS-artikelnummer 536-9001
Tillv. art.nr88970161
VarumärkeCrouzet
2 985,49 kr
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- Millenium 3 16 - Relay Analogue, Digital - - - 24 V dc - - - 10
RS-artikelnummer 442-0802
Tillv. art.nrAL2-24MR-D
VarumärkeMitsubishi
2 420,73 kr
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- Alpha 2 15 - Relay Digital - - - 24 V dc - - - 9
RS-artikelnummer 885-0904
Tillv. art.nr0850-0100
VarumärkeBARTH
2 490,66 kr
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STG-100 lococube mini-PLC 8 - Analogue Analogue, Digital - - - 7 → 32 V dc - - - 12
RS-artikelnummer 704-8333
Tillv. art.nr88974161
VarumärkeCrouzet
3 563,70 kr
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XD26 Series XD26 16 - Relay Analogue, Digital - - - 24 V dc - - - 10