Choosing the right Programmable Logic Controller (PLC) for a conveyor system can make or break your automation project’s efficiency, scalability, and long-term reliability. Whether you’re automating a single conveyor or a complex network, here’s a refined guide to help you make the best decision based on real-world engineering principles.
Step 1: Define Your Conveyor System Goals
Begin by clearly identifying system functionality and control needs:
- How many conveyors or zones are involved?
- Are sensors, motors, solenoids, VFDs, or encoders used?
- Do you need features like timing, sorting, interlocks, or speed control?
- Is the system manual, semi-automated, or fully automatic?
Real-world Tip: For automated sortation systems, you may need advanced sequencing, buffer logic, or sensor fusion for decision-making.
Step 2: Estimate I/O Requirements with Headroom
Prepare a rough Input/Output list based on devices:
| I/O Type | Common Devices |
|---|---|
| Digital Inputs (DI) | Limit switches, photo sensors, emergency stops |
| Digital Outputs (DO) | Motor starters, relays, warning lights |
| Analog Inputs (AI) | Load cells, ultrasonic level sensors |
| Analog Outputs (AO) | VFD control signals, analog actuators |
Include a 20–30% buffer to future-proof your design.
Step 3: Match System Complexity with PLC Class
| Application Level | Recommended PLCs |
|---|---|
| Basic ON/OFF Control | Siemens LOGO!, Delta DVP-SS2 |
| Zone-level Automation + Timers | Siemens S7-1200, AB Micro850 |
| Advanced Logic, Sorting, SCADA | Siemens S7-1500, Delta AH Series |
Example: For a sorting line with dynamic speed and barcode integration, go with a mid-to-high-tier modular PLC.
Step 4: Evaluate Communication Capabilities
Ensure your PLC supports required protocols and integrations:
| Integration Need | Verify PLC Support |
|---|---|
| HMI/SCADA | Modbus TCP, Profinet, Ethernet/IP |
| Servo or VFD | RS485, CANopen, EtherCAT |
| Remote Access & Alerts | IoT/4G Modules, MQTT, VPN capabilities |
Helpful Insight: Some PLCs like the Micro850 have built-in web servers for basic diagnostics.
Step 5: Plan for Scalability and Expansion
- Choose modular I/O PLCs if system expansion is likely.
- Ensure the PLC has enough memory and CPU performance to handle additional logic later.
- Opt for add-on communication modules for flexibility.
Scenario: If adding another conveyor zone in 6 months, modular rack-based PLCs will save time and cost.
Step 6: Consider Environment and Safety
Match the PLC hardware to your installation environment:
| Factor | Recommended Feature |
|---|---|
| Dust, Vibration, Heat | IP65+ enclosure, DIN-rail industrial grade PLC |
| Panel Constraints | Compact models with side-mount I/O |
| Safety Requirements | Emergency stop logic, fail-safe relays |
Don’t forget: Safety PLCs or safety relays are mandatory in regulated environments (e.g., packaging food).
Trusted PLC Brands and Models for Conveyor Control
| Brand | Top Models for Conveyor Systems |
|---|---|
| Siemens | LOGO!, S7-1200, S7-1500 |
| Allen-Bradley | Micro820, Micro850, CompactLogix |
| Delta | DVP-SS2, DVP-ES2, AH500 Series |
| Mitsubishi | FX5U, FX3G, iQ-R Series |
| Schneider | Modicon M221, M241 |
| Omron | CP1E, CP1H, NX1P2 Series |
Final Selection Checklist
| Factor | Check |
|---|---|
| Accurate I/O count with buffer | yes |
| Protocol support for HMIs & VFDs | yes |
| Expansion capabilities | yes |
| Space and environment suitable | yes |
| Vendor support availability | yes |