PLC Selection Guide for Industrial Automation in Bangladesh
PLC Selection Guide for Industrial Automation in Bangladesh
Programmable Logic Controllers, commonly known as PLCs, are widely used in industrial automation systems.
They control machinery, monitor input signals, process logic, and operate connected equipment according to programmed instructions.
PLCs are used in manufacturing plants, packaging machines, material handling systems, water treatment plants, and many other industrial applications.
Choosing the correct PLC is important because the controller must support the required inputs, outputs, communication interfaces, operating environment, and future system requirements.
This guide explains the major factors to consider when selecting a PLC for industrial applications.
What Is a PLC?
A PLC is an industrial controller designed to monitor signals from field devices and execute programmed logic.
Based on the program and received input signals, the PLC can control motors, valves, indicators, alarms, relays, and other equipment through appropriate interfaces.
A typical PLC-based system may include:
- PLC CPU
- Digital input modules
- Digital output modules
- Analog input modules
- Analog output modules
- Communication modules
- Power supply
- Programming software
- Field sensors and actuators
- HMI or SCADA system
The exact configuration depends on the application.
Common PLC Applications
PLCs are used for:
- Conveyor control
- Packaging and filling machines
- Motor and pump control
- Production line automation
- Process monitoring
- Machine sequencing
- Material handling
- Utility system monitoring
- Automated equipment control
The required PLC specification varies according to the complexity of the process.
Seven Factors to Consider When Selecting a PLC
1. Number of Inputs and Outputs
Calculate the required number of digital and analog inputs and outputs.
Digital inputs may receive signals from proximity sensors, push buttons, limit switches, and other switching devices.
Digital outputs may control relays, contactors, indicator lamps, and compatible actuators.
Analog inputs may receive signals from transmitters and measurement instruments.
Analog outputs may be used for compatible control signals, such as references to variable frequency drives or control valves.
Allow for reasonable future expansion when selecting the PLC configuration.
2. CPU Performance
The required CPU performance depends on the number of I/O points, program complexity, communication requirements, and process speed.
Simple machine control may require fewer resources than a complex production line involving multiple communication networks and extensive data processing.
3. Communication Protocols
Industrial systems may use communication protocols such as Modbus, PROFINET, EtherNet/IP, or other interfaces, depending on the equipment.
Before selecting a PLC, confirm compatibility with existing drives, HMIs, remote I/O, instruments, and supervisory systems.
Do not assume that every PLC supports every protocol in the same way.
4. Expansion Capability
Some applications may require additional I/O modules, communication interfaces, or specialised modules in the future.
Review the controller’s expansion limitations and module compatibility before purchasing.
5. Programming Software
Check the manufacturer’s supported programming environment, licensing requirements, software versions, and engineering tools.
For replacement projects, compatibility with the existing program and hardware platform may be particularly important.
6. Operating Environment
Industrial controllers are often installed inside electrical panels.
Review the manufacturer’s requirements for operating temperature, humidity, vibration, mounting, electrical noise, and power supply.
Suitable panel design and installation practices are also important.
7. Spare Parts and Long-Term Support
For critical industrial systems, consider product lifecycle information, availability of compatible modules, documentation, and maintenance requirements.
Before replacing an existing PLC, evaluate the impact on software, communication, wiring, and connected equipment.
PLC Replacement: What Should Be Checked?
Replacing a PLC is more complicated than selecting a controller with a similar number of I/O points.
Before ordering a replacement, check:
- Existing PLC manufacturer and model
- CPU and module configuration
- Digital and analog I/O requirements
- Communication protocols
- Program compatibility
- Power supply specifications
- Expansion requirements
- HMI and SCADA interfaces
- Installation dimensions
- Required engineering software
Depending on the system, replacing a PLC may require program conversion, wiring modifications, testing, and commissioning.
How to Prepare an Accurate PLC Requirement
When requesting a quotation, provide the existing PLC model, required configuration, quantity, project description, and any relevant technical documents.
If the project involves replacing an existing controller, photographs of the installed PLC and module labels may also help with initial identification.
Industrial Automation Products from Voltec Engineering Limited
Voltec Engineering Limited provides industrial engineering and automation-related product solutions.
To discuss your automation requirements, review our product catalogue and contact our team.
Conclusion
Selecting a PLC requires careful consideration of I/O capacity, CPU performance, communication protocols, expansion capability, programming software, and long-term maintenance requirements.
A clear technical specification helps reduce compatibility issues and supports better purchasing decisions.
For assistance with PLC and industrial automation product requirements, contact Voltec Engineering Limited with your project details.
