A small remote I/O application can take up more panel space than expected. Once you add a bus coupler, I/O cards, separate relays, and all the wiring between them, a simple control need can quickly become a more complex and costly design.
In comes the Phoenix Contact PLC-INTERFACE Ethernet gateway. It offers a more compact way to handle relay-heavy applications by bringing network communication, configurable I/O, and pluggable relays into one modular system. This article looks at the common ways these applications are built today, where those approaches can fall short, and how PLC Logic may offer a simpler option.
Key Takeaways- Combines a network gateway, configurable I/O, and coupling relays - Supports common industrial Ethernet protocols - Handles standard digital, analog, relay, and temperature signals - Expands to up to 56 inputs and outputs - Allows relays to be replaced one channel at a time - Provides a simpler option when a full remote I/O system is more than the application needs |
The Problem | Common Workarounds for Remote Relays | The Solution | What Does the PLC-INTERFACE Ethernet Gateway Do? | Which Network Protocols Does PLC Logic Support? | How Many I/O's Can it Support? | Where Does PLC Logic Fit Best? | When is a Full Remote I/O System Still the Better Choice? | Logic or Remote I/O? | More Focused Option for Relay-Heavy Applications | Explore PLC Logic Availability | Additional Resources
Sensors, valves, contactors, drives, and other devices are not always located near the main control panel. The PLC still needs to collect their signals, send commands, and communicate with them over the machine network.
A traditional design may require:
- A network bus coupler
- Separate input and output cards
- Coupling relays
- Terminal blocks
- Wiring between each layer
- A larger enclosure to hold everything
That approach makes sense when the machine needs advanced signal types, high-speed control, safety I/O, or a large number of channels. But many applications mainly need standard digital or analog signals and relay outputs. In those cases, a full remote I/O system may add cost and complexity that the application does not need
Before choosing a new design, engineers usually compare a few common approaches.
A traditional remote I/O system offers broad functionality and many module choices. It may be the right fit when the application requires safety signals, high-speed counting, motion or encoder signals, specialized communication, or a large number of I/O points. The tradeoff is that you may need a bus coupler, I/O cards, relays, and more setup than a smaller application requires.
Another option is to keep the I/O and relays in the main enclosure and run individual cables back from each device.
This avoids a remote station, but it can add:
- Longer wire runs
- More installation labor
- More crowded wireways
- Longer troubleshooting paths
- Less flexibility when the machine changes
Relay boards and PLC output cards can reduce some wiring, but they may have other limits. When one relay fails, maintenance may need to replace a larger board or complete output card. The cost per relay channel may also be higher than using individually replaceable relay modules.
Phoenix Contact identifies relay boards, relay output cards, and cost-sensitive remote I/O applications as key areas where the PLC-INTERFACE Ethernet gateway may fit.
Phoenix Contact PLC Logic already combined basic control with pluggable PLC-INTERFACE relays. The new Ethernet gateway adds network communication, turning the system into a compact option for remote relay and I/O applications.
As the graphic shows, a traditional setup may require a separate gateway, I/O modules, wiring, and relay layer. The PLC-INTERFACE Ethernet gateway brings these functions together in one modular system.
The system combines:
- Industrial Ethernet communication
- Configurable digital and analog signals
- Pluggable PLC-INTERFACE relay modules
For the right application, this can mean fewer separate components, less wiring, and a more compact panel design. The system is best viewed as a network-connected remote-relay solution for standard signals. It is not intended to replace every full-featured remote I/O platform.
The base module provides eight configurable signal positions. Inputs and outputs can be assigned based on the needs of the application.
Depending on the modules selected, the system can support:
- Digital inputs
- Relay inputs
- Relay outputs
- Analog inputs
- Analog outputs
- PT100 temperature inputs
Available analog functions include 4–20 mA, 0–20 mA, 0–10 V, and 2–10 V signals.
This allows one station to collect sensor data and control field devices such as valves, contactors, pumps, fans, lights, and drives.
The system combines a bus coupler, I/O functions, and coupling relays in one assembly.
Fewer separate components can mean:
- Less panel space
- Fewer connections
- A shorter bill of materials
- Less time spent selecting matching components
The plug-in design reduces the wiring normally required between I/O cards and external relays.
This can make the panel easier to assemble and may also make it easier to trace signals during troubleshooting.
PLC-INTERFACE relays can be exchanged one channel at a time.
When a relay reaches the end of its service life, maintenance can replace that relay rather than changing an entire multi-channel output card. Phoenix Contact also lists a lower channel price compared with relay output cards as one of the system’s main cost benefits.
The gateway can be installed closer to sensors and controlled devices instead of routing every signal back to the main panel.
Shorter field wiring may help reduce installation work and make future machine changes easier to manage.
The PLC-INTERFACE Ethernet gateway is designed to connect with common automation platforms through open industrial Ethernet protocols.
The documentation lists EtherNet/IP, PROFINET, and Modbus/TCP.
It also shows integration with:
- Phoenix Contact PLCnext Engineer
- Siemens TIA Portal
- Rockwell Automation Studio 5000
- Beckhoff TwinCAT
This gives engineers more freedom to use the gateway with the PLC platform already specified for the machine.
The base module can be expanded with as many as three extension modules.
Each extension module provides 16 additional I/O points. With all available extension modules installed, the system can support:
- Up to 56 total inputs and outputs
- Up to 32 configurable PLC-INTERFACE modules
- Up to 24 digital inputs through extension-module terminal blocks
Additional analog inputs may also be added through the extension-module connections.
This lets you begin with a smaller station and add capacity as the machine or application grows.
The PLC-INTERFACE Ethernet gateway may be a good fit when your application:
- Uses many relay outputs
- Works with standard digital or analog signals
- Needs I/O located away from the main panel
- Has limited enclosure space
- Would benefit from individually replaceable relays
- Needs EtherNet/IP, PROFINET, or Modbus/TCP
- Does not require advanced or safety-related I/O
Common applications may include the control or monitoring of:
- Solenoid valves
- Contactors
- Pumps
- Fans
- Indicator lights
- Standard sensors
- Analog process devices
- Drive control signals
PLC Logic is not intended to replace a complete remote I/O platform in every application.
According to Phoenix Contact, the Ethernet gateway is not designed for safety signals, frequency signals, dynamic or incremental signals, or advanced real-time control applications.
Its main purpose is to handle standard relay, digital, analog, and temperature signals in a compact remote system.
A full remote I/O system may still be the better choice when the machine requires high-speed functions, safety communication, specialized signal modules, or more than 56 I/O points.
The right choice depends on the application.
|
Consider PLC Logic when… |
Consider full remote I/O when… |
|
✅ Most outputs use relays |
❌ The system uses many specialized signal types |
|
✅ The application uses standard digital or analog signals |
❌ Safety I/O is required |
|
✅ You need 56 or fewer I/O points |
❌ The application needs more than 56 I/O points |
|
✅ Lower complexity is important |
❌ Advanced control functions are required |
|
✅ Individual relay replacement is useful |
❌ High-speed or real-time signals are required |
Phoenix Contact’s product-positioning chart places the PLC-INTERFACE Ethernet gateway below its Axioline remote I/O platforms in both price and functional complexity. It fills the space between individual relay wiring and a larger remote I/O system.
The PLC-INTERFACE Ethernet gateway gives engineers another way to build remote relay and I/O stations without automatically moving to a full remote I/O platform.
By combining network communication, configurable signals, and pluggable relays, the system may help reduce panel space, wiring, part count, setup time, and replacement costs.
The best fit is a smaller or mid-sized application that relies on standard signals and uses a high number of relay channels.
Airline offers Phoenix Contact PLC Logic components, including the PLC-INTERFACE Ethernet gateway, relay modules, and extension options.
Browse available products online to compare current pricing and availability. Airline can also help identify the base module, relay types, and extension modules required for your system.
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