A project brief for PLC and HMI integration is the document a controls supplier uses to size the panel, choose the controller and the screen, and quote the work. When it is vague, you receive a quotation that assumes the cheapest option and an installation that stalls in commissioning. When it is complete, you compare suppliers on the same basis, and the wiring, the program and the training all follow from one description of the machine.
The checklist below is written for a buyer or plant engineer who owns the process requirements but not the controls detail. Each section states what to write down and which questions the supplier would otherwise decide for you.
Start with the machine, not the controller
Name the asset the controls will run and the cycle it has to complete. Write the sequence as an operator would describe it: load, index, process, unload, plus any interlock that must stop motion. State which steps run automatically today and which are manual, because that determines how much of the cycle the PLC supervises and what the operator confirms on screen.
If the machine already exists, attach a marked-up layout showing every axis, cylinder, valve, heater, sensor and motor the new system must drive or read. A one-page process drawing or an I/O list in a spreadsheet removes most of the guesswork before anyone quotes a part number.
Write the I/O list before choosing a PLC
Give every input and output a row: device tag, signal type, supply voltage, and where it sits on the machine. Separate digital inputs from analog inputs, and list high-speed counting or positioning axes separately, since motion changes the controller selection and the panel design. Integrators quote from the I/O count first, because it sets the module mix, the terminal count and the enclosure size.
- Device tag and a plain-language function
- Direction and signal type: digital input or output, analog, axis, or communication
- Supply voltage and whether the device sources or sinks current
- Distance from the control panel, and whether the cable is field-run or a pre-made assembly
Define what the HMI has to show, and who reads it
List the screens an operator needs at the machine: a start page showing the current state, an alarm list that says what to check rather than only the fault code, a parameter or recipe page, and a maintenance screen for manual motion. Name the languages required and who logs in, because access levels and production records are screen-programming work that costs more to add after the first draft.
Record the mounting condition too: panel cut-out size, whether the screen sits behind a cabinet door, whether it faces washdown or outdoor light, and whether operators wear gloves. These details decide screen size, brightness and enclosure rating.
List the equipment that must be reused
Integration projects fail on interfaces rather than on features. For each existing drive, scale, barcode reader, temperature controller, vision camera or third-party machine, write the make, the model and the port it exposes. Then say what the PLC must do with it: read a value, write a setpoint, or exchange cycle data. Fieldbus and protocol names belong here, along with any device that has to keep its present wiring.
State the data the plant expects afterwards
If the line reports to a plant system, a historian or a spreadsheet on a shop-floor PC, name the reader of that data and the values it needs: counts, run time, downtime reason, cycle time and alarm history. Say where the clock comes from and how records are held when the network drops. A short paragraph on this prevents a commissioning change request later and lets the integrator place the data work in the right project phase.
Give the site conditions and the rules that bind the design
Supply voltage and phases, ambient temperature, dust, moisture and any hazardous-area classification change both the components and the enclosure, so include them even when they look obvious. Add the rules your plant enforces: preferred controller brand, approved component list, panel labelling standard, cable routing method, earthing practice, and every safety function such as a light curtain, interlocked guard or emergency stop. Where the requirement depends on engineering work instead of a catalogue item, send it to a team that handles manufacturing automation and automated production line solutions , so the brief is read by people who build the panels and the lines.
Describe the handover you want
Say which documents must arrive: wiring drawings, the PLC and HMI source programs, a parameter table, a spare-parts list, and a test sheet proving each sequence. Name who attends commissioning and how long the line can be stopped, since that decides whether the work runs inside a shutdown window or alongside production. Ask for operator training in the language the crew uses, and state how many operators need it.
One-page review list before you send the brief
- Machine description and cycle sequence, including the manual steps
- Complete I/O list with signal type and voltage
- Screen list, languages and user levels for the HMI
- Existing devices with model, port and protocol
- Data to be reported and who reads it
- Site conditions, safety functions and plant standards
- Deliverables, commissioning window and training
The brief is finished when a supplier can read it without asking a question about your machine. Send it with your drawings to PowerDe and ask for the assumptions behind the quotation in writing; that one request turns a price list into an offer you can compare.
The same discipline applies on the cleaning side of the plant. State the surface, the soil and how the operator reaches it, and the equipment choice follows from your process description instead of a brochure — the starting point for any cleaning equipment enquiry.
