Sorting on a moving belt is the standard industrial automation problem, and it is harder than it looks for one reason: the part is detected in one place and acted on in another, so the controller has to remember where every part is while the belt keeps moving. This project builds that — a conveyor, a photoelectric sensor that classifies parts as they pass, a shift register in ladder logic that carries each decision along with the belt, and a pneumatic cylinder that fires exactly when the right part reaches the reject station. The interesting engineering is the tracking, not the wiring.
Not just the parts. Teams budget from a component list, then run out in week six on wire, connectors and the driver board they destroyed. These are the lines that catch them.
| Line | Cost |
|---|---|
Components and materials From the bill of materials | Rs 17,750 to Rs 58,400 |
Spares and replacements 15 % — you will destroy something | Rs 2,663 to Rs 8,760 |
Consumables and hardware Wire, connectors, headers, screws, heatshrink | Rs 2,130 to Rs 7,008 |
Report, printing and binding Two or three bound copies, plots and the plagiarism check | Rs 400 to Rs 1,200 |
| Total | Rs 22,943 to Rs 75,368 |
| Each, split 3 ways | Rs 7,648 to Rs 25,123 |
Indicative bands last checked in August 2026 — a guide, not a quotation. Prices move and vary by seller, and anything you can borrow from the lab comes straight off the total. The 3.5 week figure assumes 8 person-weeks of work shared between 3; students past 4 add coordination rather than output, so the estimate stops improving there.
The same chain in words
The belt runs continuously. As each part passes the photoelectric sensor it is classified — by height, by reflectivity, or simply as present or absent depending on the sensor chosen.
That classification is written into the first cell of a shift register. The register is shifted one position for every fixed distance of belt travel, measured by the encoder rather than by a timer, so belt slip and speed changes do not lose the part.
When a part's bit reaches the cell corresponding to the reject station, the PLC energises the solenoid valve. The cylinder extends, pushes the part into the reject bin, and retracts.
Because the cylinder takes time to extend, the valve is energised a fixed lead time before the part arrives rather than at the instant it arrives.
The emergency stop is wired as a hardware chain that drops the motor contactor and dumps air pressure directly, and is also read as an input so the program knows it happened.
This is the chapter that separates an engineering project from an assembly job. Every value below carries the formula that produced it and the assumptions it rests on — check them against your own ratings before you use them, because your motor is not this motor.
t = distance / belt speed
0.6 / 0.25 = 2.4 s. This is the delay the shift register has to bridge, and it is the whole reason the register exists.
distance per shift = belt travel per encoder pulse x pulses per shift
Shifting on belt travel rather than on a timer is what makes the tracking survive a change in belt speed. A timer-based version works perfectly on the bench and fails the first time the belt is loaded.
uncertainty = scan time x belt speed
The PLC only sees the sensor once per scan, so a part can travel a whole scan's worth of belt before the input is noticed. This sets the accuracy floor of the whole system and belongs in the design chapter.
fire the valve one extend-time before the part arrives
Measure the extend time on the actual cylinder at the actual pressure rather than taking it from the catalogue — it changes with supply pressure and with the exhaust restrictor setting.
I = P / (sqrt(3) x V x pf x efficiency)
370 / (1.732 x 415 x 0.75 x 0.75) = 0.92 A. Small motors have poor power factor and efficiency, which is why the assumed figures here are lower than a textbook's.
| Item | Qty | Unit cost |
|---|---|---|
PLC Micro PLC, 8 or more digital inputs including a high-speed counter Usually the department trainer kit — confirm access before budgeting. | 1 | Rs 4,500 to Rs 14,000 |
Conveyor Small belt conveyor, 1 m, with a gear motor The largest single cost. Many departments already have one; a fabricated belt on rollers is a cheaper option. | 1 | Rs 6,000 to Rs 18,000 |
Photoelectric sensor Diffuse or retroreflective, PNP output, 24 V DC | 2 | Rs 700 to Rs 2,200 |
Incremental encoder 500 PPR, mounted on the belt roller | 1 | Rs 1,200 to Rs 3,500 |
Pneumatic cylinder Single acting, 100 mm stroke, with flow restrictors | 1 | Rs 900 to Rs 2,600 |
Solenoid valve 5/2 way, 24 V DC coil | 1 | Rs 700 to Rs 2,000 |
Air supply Small compressor with a regulator and filter Lab compressor if there is one — otherwise this doubles the project cost. | 1 | Rs 0 to Rs 6,000 |
Contactor and overload 9 A contactor with a thermal overload relay | 1 | Rs 900 to Rs 2,400 |
Pushbuttons and E-stop 22 mm start, stop and latching emergency stop | 1 | Rs 350 to Rs 900 |
24 V power supply DIN rail SMPS, 24 V, 2 A | 1 | Rs 600 to Rs 1,600 |
Panel and wiring Enclosure, DIN rail, trunking, ferrules, terminal blocks | 1 | Rs 1,200 to Rs 3,000 |
Specifications are written as ratings rather than brands, so any equivalent part works. Where a line says to borrow from the lab, do — it is usually the largest number on the page, and the total drops to Rs 22,943 at the low end without them.
None of these blocks you — they are learnable inside a semester. Each one you do not have costs a couple of weeks, so count them into your plan.
Anything marked required is a blocker, not a difficulty. Arrange the access before you commit to the project, not after.
Use these when your guide says the scope is too small, or when you want something in the results chapter that nobody else in your batch will have.
The structure below is what a project report is marked against, with the mistake that costs marks in each chapter. There is no template to download and there will not be one: the writing is your work, and a site that did it for you would be helping you cheat rather than helping you pass.
A diploma report is typically 40 to 60 pages. The design and results chapters carry the marks; the literature survey can be short. A mini project report runs to about 40 to 50 pages, and the literature survey is usually brief. Guides expect one clear objective, met and measured. A final year report is normally 60 to 90 pages with a substantial literature survey, and many departments expect a paper submission alongside it.
The full report guide — front matter, conventions and page countsOne paragraph covering what the problem is, what you built, and what the result was. Written last, even though it appears first.
Loses marks: Describing the problem and the method but never stating a result. If there is no number in your abstract, it is not finished.
Why the problem matters, the context it sits in, and a clear statement of the objectives your project set out to meet.
Loses marks: Objectives written so vaguely that nobody can tell at the end whether they were met. Write objectives you can tick off in the conclusion.
What has already been done, what each approach achieved, and the specific gap your work addresses.
Loses marks: A list of paper summaries with no comparison and no gap. The survey exists to justify your design choice, so end it by saying what you chose and why.
The system as a whole: the block diagram, what each block does, and the signal or power path between them.
Loses marks: A block diagram copied from a datasheet or another report. Draw yours to match what you actually built, including the parts that are inconvenient.
Every component value and rating, with the formula, the assumptions and the arithmetic that produced it. This is the chapter that distinguishes an engineering project from an assembly job.
Loses marks: Component values with no justification. If a resistor is 10 kOhm, the report must say why it is not 1 kOhm.
The circuit as built, the PCB or wiring, the flowchart, and the parts of the code that carry the actual logic.
Loses marks: Twenty pages of pasted source listing. Include the flowchart and the few functions that matter, and put the full listing in an appendix.
What you measured, in tables and graphs, compared against what you predicted in the design chapter — including where they disagreed.
Loses marks: Photographs of the working model presented as results. A photograph is evidence that it exists, not evidence that it works. Results are measurements.
Whether each objective was met, what the measured performance was, and what the honest next step would be.
Loses marks: Future scope written as a wish list of unrelated features. It should follow from a limitation you actually hit.
Every source in a consistent style, plus datasheets, full code listings and the complete bill of materials.
Loses marks: Citing a blog or a video where a datasheet or a standard exists. Cite the primary source for anything you relied on.
The demonstration is half the assessment. These are the questions this project invites, and the answers are written the way you would give them out loud.
The PLC repeatedly reads all its inputs, executes the program, then writes all its outputs; one pass is a scan. Inputs are only sampled once per scan, so an event shorter than a scan can be missed entirely, and an event is noticed up to one scan late. On a moving belt that latency becomes a distance error, which is why the scan time appears in the accuracy calculation.
Because what has to be tracked is how far the belt moved, and the belt can slip on the drive pulley. An encoder on the motor measures motor rotation, which is the same thing only when there is no slip and no gearbox backlash. Mounting it on an idler roller driven by the belt itself measures the quantity that actually matters.
A timer assumes a constant belt speed, so any change in speed or any slip puts the part in the wrong place. A shift register clocked by belt travel carries each part's decision along with the belt itself, so the tracking stays correct whatever the speed does. It also handles several parts on the belt at once, which a single timer cannot.
It is the direction of current flow at the input terminal. A sourcing sensor output, usually called PNP, supplies current into the PLC input, so the PLC input must be sinking. An NPN sensor pulls the input down to common, so the PLC input must be sourcing. Mixing them means the input either never turns on or is permanently on, and it is the most common wiring mistake with PLC sensors.
Because it has to work when the controller does not. If the program hangs, the output card fails shorted, or the CPU faults, a software stop does nothing. The emergency stop therefore breaks the contactor coil circuit directly, and dumps stored pneumatic energy, so the machine stops regardless of the state of the program. The PLC reads it as well, but only so the program knows what happened.
Because the cylinder is not instantaneous — the valve takes time to shift and the piston takes time to travel. If the valve is energised when the part is at the station, the part has already gone past by the time the piston arrives. The lead time is measured on the actual hardware at the actual air pressure and built into the tracking offset.
Normally taken as a Diploma project (C-20, 6th sem) or B.E. mini project (5th/6th sem) or B.E. final year project (7th/8th sem) project. If yours is a different course, the extensions above scope it up and the simpler half of the design scopes it down — the arithmetic does not change. Back to all projects.