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Connecting the Bridge to PLCs (Siemens, Allen-Bradley)

Estimated reading time: 10 min

Pulling data without touching the program

The iGromi Bridge reads production variables (tags) straight from PLC memory without stopping the machine or modifying the original ladder code.

Option A: Ethernet (Profinet / EtherNet/IP)

If your PLC has a spare Ethernet port (e.g. Siemens S7-1200/1500 or Allen-Bradley CompactLogix):

  1. Connect the iGromi Bridge to the same industrial switch as the PLC.
  2. Give the Bridge a static IP on the same network segment as the PLC (e.g. if the PLC is on 192.168.0.10, use 192.168.0.50).
  3. In the iGromi portal, add the data source and enter the memory addresses: DB1,X0.0 (for machine state) or DB2,D4 (for a piece counter).

Option B: Serial (Modbus RTU / RS485)

For legacy PLCs or temperature controllers:

  1. Use shielded twisted-pair cable (Belden 3105A or equivalent).
  2. Wire A(+) and B(-) from the PLC's RS485 port to the matching terminals on the iGromi Bridge.
  3. Ground the cable shield at one end only, to avoid ground loops.
  4. In the iGromi portal, select Modbus RTU. Match the exact baud rate, parity and stop bits configured on the master PLC.

The Bridge starts polling the variables at 10Hz and packages them into MQTT Sparkplug B messages.

Where to go next

Edge Hardware

Installing Production Sensors

How to wire 24V photoelectric, inductive or limit-switch sensors to the iGromi Bridge digital inputs to count production cycles and compute OEE automatically.

Computer Vision

Deploying iGromi Cam (AI Vision)

Mounting, focal distance and lighting for iGromi Cam to detect defects, colors or overlapping products on a conveyor with YOLO/OpenCV inference at the Edge.

Edge Hardware

Basic iGromi Bridge Installation

Installing the iGromi Bridge in a cabinet: 35 mm DIN rail, 24V DC supply, WiFi or Ethernet link and pairing the gateway with your iGromi OS account.

Reference

Supported Industrial Protocols

List of the 40+ industrial protocols natively supported by iGromi OS and its Edge nodes: OPC-UA, Modbus TCP, S7, EtherNet/IP, Profinet, MQTT and more.

Is this for your plant?

This documentation describes how it is done. If you want to know what your particular installation would need, which equipment can be read today and which cannot, the conversation is shorter than reading the whole wiki.

Talk to an engineer Manuals and integration sheets
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