PLC PROGRAMMING
COURSE 530: 4 DAYS
Modern PLC-based control and automation systems often have improvements and modifications made, resulting in changes needing to be made to the PLC program. This course provides the skills necessary to understand how typical modern industrial PLC programs work, how to make changes to existing programs and how to create small programs from scratch.
PARTICIPANTS
The course is designed for those who have an electrical background (for example maintenance electricians) who have successfully completed course 520 (Maintenance of PLC systems). Candidates who subsequently attend more advanced manufacturer-specific programming courses will find that their progress is enhanced by this foundation in PLC programming.
COURSE PRESENTATION
The course is presented using a wide range of industrial PLCs so that candidates learn how different manufacturers employ the programming languages involved. Allen Bradley, Siemens, Mitsubuishi and Modicon PLCs are used to control a complex training rig incorporating conveyors, solenoids, motors and industrial sensors as a 'target' system to gain the necessary programming skills. Comprehensive course notes are provided.
COURSE OBJECTIVES
On completion of the course, participants will be able to
- identify the dangers of modifying existing or creating new PLC programs
- make changes to existing programs and update 'back-up' systems
- use subroutines to structure programs
- use labels and comments to ensure that programs are easily interpreted by others
- employ logical commands (AND, OR, SET, RESET etc) using inputs, outputs and flags
- identify the timers available on PLCs, select appropriate types and program them
- identify the counters available on PLCs, select appropriate types and program them
- program mathematical operations (greater than, equal to etc)
- employ shift registers and other advanced commands
- create a PLC program to control a complex machine incorporating several motors, solenoids and sensors, using logical functions, timers and counters etc
- check that the program created is safe and free from errors.
Successful completion of the course leads to the award of the Unite / Technical Training Solutions Competence Certificate 530 - PLC Programming
What do candidates on the PLC Programming course actually do?
The PLC Programming course begins by looking at the ways in which PLCs typically work. We study the Scan Cycle used to fetch the input values, execute the program and write the outputs. Our candidates find this useful when progressing further into the course. We also look at the ways in which inputs and outputs are commonly configured in a ladder program to produce a simple outcome, and how this might relate to real-world events. We then analyse various example applications with their respective programs, checking how the suggested programs relate to the applications in question. This is a useful way of highlighting some of the subtle workings of PLCs, like for example the system flags used for initializing the PLC.
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We then look at the dangers involved when modifying PLC programs and clarify the legal situation with regard to the competence issues, the various relevant legislative documents etc. We also analyse the root causes of control system failures, using this as a way of reminding the candidates about the safety implications of PLC programming. We also mention the various relevant British Standards, Codes of Practice and typical employers' working procedures to ensure that the candidates understand this.
Candidates learn the importance of structuring programs using subroutines and labelling and commenting the program so that they are easily understood by others. We insist that our candidates take a professional approach to the creation of PLC programs and the subsequent practical exercises on the course provide practice at creating and calling their own subroutines and labelling and commenting their own programs professionally.
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Candidates are shown the ways in which logical expressions (AND, OR, SET, RESET etc) are achieved in PLCs, and how the timers and counters inside the various PLC manufacturers' PLCs typically operate.
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Practical exercises are interspersed in the theoretical part of the PLC programming course. For example, in the exercises shown in the above pictures, as well as learning about the theoretical issues the candidates are also practicing calling subroutines to implement some basic logic functions and exploring how labels and comments are added to their program. They also find out what timers and counters are available on the PLC that they are using and create some basic code to make their PLC generate timing delays and counting functions.
A series of structured exercises follow, where the candidates are given the opportunity to create their own programs to solve various control problems. These consist of getting the PLC to start and stop two conveyor motors correctly, reading several sensors to detect the presence of different targets at a sorting point on a machine and driving an electric solenoid reliably and counting components down a loading chute, using the count value to drive an electrical rotary solenoid which loads a hopper.
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The practical exercises give candidates the opportunity to try out various methods of achieving the required objectives of each of the structured exercises.
Candidates draw their solutions to the practical exercises in their course notes. The page shown here is for one of these exercises.
The structured exercises continue (in fact they consume on average 3 out of the 4 days of the course) with a PLC program required to detect if assembled components are correct and rejecting incorrectly assembled components. This can become quite involved since the assembly-checking area is some way along the conveyor from the reject position so often a series of shift registers and other complex programming techniques are required to ensure that the PLC program operates well.
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On this course we use Allen Bradley SLC500 PLCs controlled by RS Logix software, Siemens S7 214 PLCs controlled by Step 7 software, Mitsubishi FX0n PLCs controlled by FX-GP WIN software and Modicon TSX PLCs controlled by PL707 software. We expect candidates to work with at least two of these PLCs and we find that the experience of learning about a range of PLCs helps to ensure that they gain a holistic understanding of the subject so that subsequent to the course they could attempt to re-program any type of PLC.
Candidates on the PLC programming course are encouraged to explore other commands available in the PLCs that they are using and they can also try programming a range of different PLC manufacturers on the course.
The course also places them in a very strong position for attending manufacturer-specific PLC training courses where the sound foundations achieved in this course would ensure that they gained the maximum benefit from attending more advanced courses.