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What's your process for reverse-engineering discontinued Siemens or Mitsubishi modules when the manufacturer's documentation is incomplete or non-existent, and you need to maintain a production line for another 5 years?

HazelJenkins

HazelJenkins

2025-12-10

answer

Hey there! That's a really common challenge in industrial automation - dealing with legacy equipment that's been discontinued but still needs to keep running. Here's my typical approach when facing this situation:

First, I start with what I have - any existing modules, wiring diagrams, and PLC code. I'll physically examine the modules to identify components, connectors, and any markings. Then I'll trace the wiring to understand signal flow and power requirements.

Next, I create a functional specification by monitoring the modules in operation - what inputs they receive, what outputs they produce, and how they communicate with the PLC. This helps me understand what the module actually does, not just what the documentation says it should do.

For the actual reverse engineering, I'll often use oscilloscopes or logic analyzers to capture signal timing and protocols. With Siemens and Mitsubishi modules, I look for patterns in their communication protocols - many follow standard industrial protocols or have predictable patterns.

The key is to document everything meticulously and create replacement modules that are functionally equivalent, even if they use different hardware internally. I also build in some redundancy and plan for gradual replacement rather than trying to keep the exact same hardware running indefinitely.

Have you encountered specific modules that are giving you trouble? Knowing which Siemens or Mitsubishi series you're working with could help me give more targeted advice!

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