Complete example: Analyze a missing motor enable with Copilot

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This example shows how Copilot can help diagnose a missing motor enable in an S7 project.

Initial situation

A motor does not start although the operator command is active. The output Q 8.0 remains off.

The objective is to determine:

  • where the output is written;
  • which enable conditions are required;
  • which condition is currently missing;
  • whether the problem is caused by the program or by a live PLC value.

1. Open the relevant project context

Open the PLC project and, if known, the block containing the motor logic. If the location is not known, Copilot can search using cross-references and write locations.

Ask: 

Where is Q 8.0 written?

Copilot identifies the relevant block and network and summarizes the conditions that control the output.

2. Explain the enable logic

Open the identified network and ask: 

Explain how the enable for Q 8.0 is generated.
List all required conditions and interlocks.

The answer should identify items such as:

  • start command;
  • operating mode;
  • safety or emergency-stop chain;
  • fault acknowledgement;
  • process interlocks;
  • feedback signals;
  • reset or stop conditions.

3. Check the current state

If an online connection is available, ask Copilot to read the relevant live values: 

Read the current values required for the enable of Q 8.0.
Which condition is currently false?

Use concrete addresses where possible, for example: 

Read I 0.0, M 10.0, DB36.DBX3.1 and Q 8.0.

Copilot combines the program logic with the returned values and identifies the condition that currently prevents the output.

4. Trace the missing condition

If an intermediate enable is false, continue with a focused question: 

Where is DB36.DBX3.1 written?
Which conditions set and reset this bit?

Repeat the process until the original cause is found. This may be a missing sensor, an active interlock, a reset condition or an unexpected program path.

5. Record intermittent signals

For faults that occur only briefly, record the relevant signals: 

Record I 0.0, DB36.DBX3.1 and Q 8.0.

After reproducing the fault: 

Stop the recordings.
Show the signal sequence and explain which enable disappeared first.

6. Document the result

Ask Copilot for a short technical summary: 

Summarize the cause, the affected network, the live values and the recommended
checks. Do not propose a program change unless the cause is confirmed.

Safety note

Copilot provides diagnostic assistance only. Before changing a PLC program:

  • verify the result against the original project;
  • check all safety functions and operating modes;
  • review generated code;
  • test changes under controlled conditions;
  • follow the commissioning and approval procedures of the organization.

Further information: S5/S7 AI Copilot user guide

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