Case Study: Using Edge Products for PLC Data Collection (Modbus/S7)

Data is the fuel of Industry 4.0, but for most factories, that fuel is trapped inside legacy PLCs that don't speak modern languages. This case study details how a manufacturing plant used edge products to solve the "data silo" problem. We explore how a single industrial edge product acts as a universal translator, simultaneously collecting data from Siemens S7-1500s via Ethernet and legacy motor drives via Modbus RTU. By deploying these smart edge computing products, the factory achieved real-time OEE monitoring and predictive maintenance without replacing a single expensive control system.

In the modern manufacturing landscape, the difference between a profitable factory and a struggling one is often data. If you know exactly how much energy your motors are using, or exactly why Line 3 stopped at 2:00 PM, you can fix it. If you don't, you are guessing.

The problem is that 90% of factories are "brownfields." They run on rock-solid but aging hardware. They have a mix of Siemens PLCs controlling the line, Modbus energy meters monitoring power, and maybe an Allen-Bradley robot arm. None of these devices were designed to talk to the cloud. They are isolated data silos.

This is the exact problem that edge products are built to solve.

A robust industrial edge product acts as the "universal translator" on the factory floor. In this case study, we’ll look at how a mid-sized packaging facility used Robustel edge products to unify their fragmented data, bridging the gap between 1990s controls and 2025 analytics.

The customer, a food packaging plant, faced a visibility crisis. Their production line was controlled by a modern Siemens S7-1500 PLC, but the conveyor belts were driven by legacy Variable Frequency Drives (VFDs) using Modbus RTU over RS485.

They had three major pain points:

1. No Unified View: To see the PLC status, they had to walk to the HMI. To see the motor currents, they had to use a multimeter on the VFDs. There was no single dashboard.
2. Reactive Maintenance: They only knew a motor was failing when it smoked and stopped the line. They had no trend data for predictive maintenance.
3. Complex Integration: Their IT team wanted data in MQTT format for an AWS dashboard. The OT team only knew ladder logic. They were stuck.

They needed a single hardware solution that could talk to everything and send it to the cloud securely. They needed professional industrial edge products.

The plant deployed a Robustel EG5120 edge computing gateway in the main control cabinet. This device was chosen because it is one of the few edge products that combines high-performance compute with the necessary physical interfaces for both modern and legacy equipment.

The VFDs communicated via a 2-wire RS485 serial chain.

• Physical: The RS485 daisy chain was wired directly into the edge product's isolated serial port.
• Protocol: Using the "Edge2Cloud" software on the edge product, the engineer configured a Modbus Master poller. They mapped the registers for "Current," "Frequency," and "Temperature" for each drive.
• Result: The edge product began polling the VFDs every second, digitizing this analog-style data instantly.

The main PLC was on PROFINET (Ethernet).

• Physical: An Ethernet cable connected the PLC to the edge product's LAN port.
• Protocol: The engineer used the native Siemens S7 driver on the edge product. In TIA Portal, they enabled "PUT/GET" access and mapped the specific Data Blocks (DBs) containing production counts and error codes.
• Result: The edge product could now read the logic state of the main controller directly over the network.

This is the magic of smart edge products. The EG5120 took the Modbus data from the serial port and the S7 data from the Ethernet port, timestamped both, and merged them into a single, standardized JSON object.

• The Output: It published this unified data stream via MQTT over a secure 4G cellular connection to the AWS cloud.

The deployment of these industrial edge products transformed the plant's operations within weeks.

• Real-Time OEE: Management now has a dashboard showing the exact speed of the line (from the PLC) vs. the energy consumption of the motors (from the VFDs). They identified that running the conveyors at 95% speed reduced energy use by 15% with zero impact on throughput.
• Predictive Alerts: By trending the Modbus data collected by the edge products, they set an alert: "If Motor Current rises by 10% without a speed increase, send an email." This alert caught a failing bearing two weeks before it would have seized, saving $10,000 in downtime.
• Scalability: Because they used RCMS to manage their edge products, they could copy this configuration to their other three factories in different cities instantly.

The customer initially considered using a Windows PC with OPC server software.

• PC Solution: Cost $2,000 (Hardware) + $1,500 (Software License) + IT Maintenance.
• Edge Product Solution: Cost ~$600 (Hardware + Software included) + Zero Maintenance.

The edge products offered a rugged, fanless, "set-and-forget" solution that survived the hot factory floor, whereas a PC would have been a dust-clogged liability.

The gap between OT and IT is not as wide as it seems. You don't need to rip and replace your old machines to get smart data. You just need the right bridge.

Modern industrial edge products are that bridge. By fluent speaking the languages of the past (Modbus) and the present (S7), while communicating in the language of the future (MQTT), these devices unlock the massive value hidden in your existing assets. Whether you are monitoring a simple pump or a complex production line, edge products are the fastest, most cost-effective path to Industry 4.0.