How To Connect to a PLC Through WiFi
In many industrial automation projects, engineers need to test and commission PLCs in the field. Imagine climbing a ladder to the top of a filling tank to check a sensor or operate a valve gate, while carrying a laptop tethered by a cable. The process is not only inconvenient but sometimes impractical—especially if the factory is not fully wired, when creating a temporary network, or when a wired connection is simply not feasible.
This is where wireless connectivity becomes essential. Connecting a PLC via Wi-Fi enables engineers to work remotely, perform diagnostics, and set up temporary or flexible networks without relying on physical cables. But how exactly can you connect a PLC to Wi-Fi? Let’s explore the possibilities.
Can I Connect to a PLC via Wi-Fi?
Yes, you can connect to a PLC via Wi-Fi. There are two main scenarios:
1. PLC with Built-in Wi-Fi Module
Some modern PLCs come with integrated Wi-Fi functionality. These typically support two modes:
AP Mode: The PLC acts as an access point. Your laptop or mobile device connects directly to the PLC’s hotspot. With proper configuration, you can program the PLC wirelessly.
Station Mode: The PLC connects to an existing Wi-Fi router or access point, and your laptop joins the same network.
This makes PLC Wi-Fi network setup much simpler. However, Wi-Fi-enabled PLCs are relatively uncommon and usually more expensive.
2. PLC without a Wi-Fi Module
Most PLCs only provide Ethernet or serial interfaces and cannot connect to Wi-Fi directly. In this case, you will need an additional device to bridge the PLC to a wireless network. Keep reading to learn more about the available options.
How to Connect to a PLC Through Wi-Fi
If a PLC does not have built-in wireless capability, the solution is to use a wireless intermediary device between the PLC and your laptop. The following methods are commonly used:
Wi-Fi Router
This is the simplest and most basic method. The PLC is connected via cable to the Wi-Fi router’s LAN port or serial port, while computers and other devices connect to the router over Wi-Fi.
If wiring the WAN Ethernet uplink is difficult in your application, you can also select a cellular WAN router, which offers reliable wireless connectivity and greater deployment flexibility.
In this setup, both the PLC and computer are on the same subnet (for example, 192.168.1.x). The computer can then access, configure, and download programs to the PLC directly using its IP address.
Wireless Client
There are two main types: Ethernet-based and serial-based.
Ethernet-to-Wi-Fi Client (Access Point):
Also known as an access point (AP). To connect a PLC, you need a model with a LAN port and routing functionality, allowing the AP to assign and manage IP addresses independently. Such devices are called “fat APs.” They can directly enable wireless networking between the PLC and other devices without additional equipment.
“Fit APs” can also be used but must connect to an existing router or switch and rely on the existing network.
This type of device is commonly referred to as a Serial-to-Wi-Fi Server or Serial-to-Wi-Fi Converter.
Choosing a model with routing capability removes the need for an additional router. For example, Come-Star’s serial-to-Wi-Fi servers support AP mode, allowing the device itself to act as a hotspot and handle up to eight connected users. If there’s an existing network that the PLC can join, routing capability becomes less critical.
Wi-Fi-Enabled Cellular Gateway
Cellular gateways generally do not include routing, DHCP, or IP management functions, so a router is usually required. However, compared with the previous options, gateways often provide additional features such as enhanced security and protocol conversion.
What to Consider When Connecting a PLC Wirelessly
PLC Interface Type
The first step is to determine whether your PLC uses an Ethernet port or a serial port.
For serial interfaces, you can use a Serial-to-Wi-Fi server or an industrial Wi-Fi router/AP/gateway with serial support.
For Ethernet-based PLCs, choose a device with at least one LAN port and wireless capability.
Come-Star offers a rich product line. Whether you need to connect a PLC via a serial port or an Ethernet port to a wireless network, we can provide the solution that best fits your needs.
Number of PLCs and Cost
Consider how many PLCs need to be connected and what type of interface they require. Select devices with enough LAN ports or serial interfaces to support them while balancing cost efficiency.
Wi-Fi Band and Technology
Determine whether 2.4 GHz, 5 GHz, or dual-band Wi-Fi is the most suitable option for your deployment.
Wi-Fi 6 technology, for example, provides higher speed, lower latency, and better performance in high-density environments.
Security Requirements
PLC programming data is critical, and secure remote access is essential to protect sensitive industrial information.
Come-Star’s industrial routers, gateways, and wireless clients include built-in security features such as access control, data encryption, authentication mechanisms, and firewall protection. These ensure your PLC wireless network remains secure, even in sensitive industrial environments.
Site Environment
Wireless PLC deployments often face challenging environments, such as:
Large-scale factories with electromagnetic interference or vibration
Outdoor temporary networks exposed to wind and rain
Electrical cabinets in extreme temperature conditions
For these scenarios, choose industrial-grade products that can withstand harsh conditions. Come-Star’s full range of industrial communication devices is purpose-built for demanding applications, featuring rugged aluminum housings, wide-temperature design, and protection against electromagnetic interference and surges.
We also offer PoE access points, which are a convenient solution for outdoor or temporary network setups where power supply may be limited.
Conclusion
Connecting a PLC to Wi-Fi is not only possible but increasingly practical in modern industrial applications. Whether using a Wi-Fi-enabled PLC, a router, an access point, or an industrial gateway, engineers can achieve flexible, cable-free access for programming, testing, and monitoring.
For reliable performance in industrial environments, Come-Star industrial Wi-Fi routers, APs, and gateways provide rugged design, secure connectivity, and advanced features to ensure your PLCs stay connected—no matter the conditions.
