Control relays for quick and easy automation of conveyor systems

1. Application description: Modularisation using the example of a logistics application with a conveyor belt

An essential advantage of the easyE4 is the possibility of supplementing function block diagram (FBD) and ladder diagram (LD) programs with modules in structured text (ST). These function blocks can be fine-tuned to the respective application and can easily be stored for re-use in the same or similar applications. The following application example demonstrates how easy it is to implement a modular concept using the easyE4 control relay.

2. Modularisation

The creation of a program or function block begins with the definition of the functionality, the scope of performance, the performance data/features (reaction speeds, calculations, retention, etc.), the error monitoring system and the corresponding messages, as well as the design of the module or the module interface.

In the following, the procedure will be illustrated using the example of a conveyor belt application in the packaging industry.

2.1 Description of the example application

The conveyor function module “Belt_Type1” is being created in ST and will then be adapted in the ladder diagram.

The aim is to create a user function block (UF) for conveyor control, given the large number of similar conveyors in the project and the fact that similar conveyors are also envisaged as the standard solution in future projects.

Note: The software development process is based on machine building considerations. Just as complete conveyor lines are composed of various separate modules, it is now also possible to assemble entire control systems from individual modules.

The application requires that each conveyor belt can be switched on and off via a pushbutton (manual mode). At the same time, the belt features a higher-level on-and-off contact (automatic). Once the belt has started, it should stop again after a predefined time if no package or workpiece is detected by the light curtain at the entry point. A yellow warning light indicates that the motor is ready to start as soon as a package is detected (standby).

The function block should have the following inputs and outputs:

I1: Manual mode - ON/OFF

I2: Automatic start

I3: Stop - lock

I4: Light curtain at the entry point

I5: Safety system OK

IA1: Run time 1 in manual mode

IA2: Run time 2 in automatic mode

Q1: Controlling the belt drive

Q2: Indication that the drive is active – released – warning light

QA1: Run time

QA2: Current drive run time

QA3: Switching frequency of the light curtain at the entry point

In the present example, the engineers in charge will use structured text for setting up the application, while its implementation and commissioning will be carried out by trained electricians using the ladder diagram.

2.2 Settings – parameter configurations

After the functional specifications have been drawn up – which also define the input/output interface of the user function block (UF) – the parameters of the function block can be configured.

Configuring the function blocks:

• Up to 12 inputs and 12 outputs are available. The mixing of analogue (byte, WORD, double WORD) and digital inputs/outputs is possible.
• Once the UF is saved as a “user function block” under a unique name, it can then be used for the present as well as any other projects.
• It is important to maintain the consistency of the version numbers. The system comes with integrated version management.
• The password protection prevents any unauthorised changes or theft of know-how.
• Individual retentive variables and blocks can be defined for user function blocks.

As soon as the user function block (UF) has been saved and a name and version number have been assigned to it, it is ready for use and can be accessed via the “user function block” tab. After post-processing, it can also be exported to a library.

2.3 Implementing the example application in ST

The implementation takes place in ST, using four IF statements and a pick-up delay (T01).

2.4 Implementing the example application using the ladder diagram

The function block “Belt_Type1” can be implemented using either the function block diagram or structured text. The picture below shows the program in simulation mode with status display.