Integrated PLC Project: Design, Wire, Program, Test, and Document a Control Circuit

Integrated PLC Project: Design, Wire, Program, Test, and Document a Control Circuit

This capstone lab brings together every skill you have built in this course. You will receive a written control narrative, then independently design, wire, program, test, and document a complete PLC-controlled circuit. No two students receive the same narrative, so every solution is yours alone. Instructors evaluate your wiring quality, program logic, documentation, and your ability to explain every decision you made.

Understanding the Control Narrative

A control narrative is a plain-language description of what a machine must do. Before writing a single rung of ladder logic, read the narrative carefully and identify every input condition and every output action. Highlight signal words such as starts, stops, times, counts, and alarms. These words map directly to PLC instructions: contacts, coils, timers, counters, and output energize instructions. If any requirement is ambiguous, ask your instructor to clarify it in writing before you proceed. Assumptions that turn out to be wrong cost far more time than a short conversation at the start.

Design Phase: Documentation First

Professional electricians do not wire first and think later. Your documentation package must be complete and approved before you touch any hardware.

I/O list and address table. List every physical device—push buttons, float switches, pilot lights, contactor coils—and assign each one a unique PLC address. Separate discrete inputs from discrete outputs and label each address clearly. Record the signal type (normally open, normally closed, sourcing, sinking) for every device.

Wiring diagram. Draw a complete schematic showing the PLC power supply connections, the I/O terminal connections, and the field device connections. Follow NFPA 79 and your trainer documentation for wire color conventions. Include terminal numbers and wire numbers so anyone picking up your drawing can trace every conductor.

Commented ladder logic printout. Plan your program on paper or in CAD before entering it into the software. Each rung must carry a comment that explains its purpose in plain English. A rung with no comment is incomplete documentation—period.

Build and Program Phase

Safety: Lockout/Tagout Every Time

Before making or breaking any wiring connection, de-energize the trainer, apply your personal lock and tag to the energy-isolating device, and verify zero energy with your digital multimeter. This is not optional and it is not a formality. An LOTO error—skipping verification, removing another student's lock, or re-energizing without checking that everyone is clear—results in an automatic fail for the entire project and requires remediation before you may re-demonstrate. Wear safety glasses whenever you are working at the trainer station.

Wiring

Work from your wiring diagram, not from memory. Route conductors neatly, use the correct gauge for the circuit, and torque terminal screws to the manufacturer's specification. Label both ends of every wire with the wire number shown on your diagram. After completing all connections and before energizing, perform a point-to-point continuity check with your multimeter to confirm that every conductor lands where your diagram says it should.

Programming

Enter your ladder logic exactly as designed. Use the address table you created—do not guess at addresses. Download the program to the PLC only after all wiring has been verified and all personnel are clear. Operate in monitor mode during initial testing so you can see rung status in real time.

Systematic Testing

Test every requirement in the control narrative individually before testing combinations. Record each test in your lab notebook: the condition you applied, the expected output, and the actual output. If the circuit does not behave as expected, troubleshoot systematically—check the program first in monitor mode, then check wiring if the program logic appears correct. Document every change you make and explain why you made it. Changes made during testing are not failures; undocumented changes are.

Demonstration and Defense

During your 30-minute demonstration you will operate the circuit live against every narrative requirement while the instructor observes. You will then answer questions about one specific rung's logic and one specific wiring decision. Prepare to explain not just what you did but why—why you chose that timer type, why you wired that device as a normally closed input, why you structured the counter reset the way you did. Submit your complete documentation package at the start of your demonstration slot.

Grading and Pass Standard

The rubric covers four areas: wiring quality, program correctness, documentation completeness, and ability to explain design decisions. The overall pass mark is 75%. Any safety violation—particularly any LOTO error—results in an automatic fail regardless of your score in other areas, and you must remediate before you may re-demonstrate. Plan your time so you are not rushing during the build phase; a circuit wired carefully and tested systematically almost always passes on the first demonstration.

Final Checklist Before Your Demonstration Slot

• All narrative requirements verified and recorded in lab notebook
• I/O list, address table, wiring diagram, and commented logic printout in order
• Every wire labeled at both ends
• No open terminals or loose conductors
• LOTO equipment returned to its proper location
• Lab notebook signed and dated for every test entry