A motor that is failing announces it long before it stops, and the announcement is written into its own supply current. A broken rotor bar modulates the current at twice the slip frequency, producing sidebands either side of the supply frequency; a failing bearing produces vibration at frequencies fixed by its geometry. This project captures the stator current and the vibration of a running motor, transforms both to the frequency domain with enough resolution to separate the sidebands from the fundamental, and reports the fault indicators as trends rather than as a single pass or fail — because condition monitoring is about change over time, not about one reading.
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 1,610 to Rs 16,900 |
Spares and replacements 15 % — you will destroy something | Rs 242 to Rs 2,535 |
Consumables and hardware Wire, connectors, headers, screws, heatshrink | Rs 250 to Rs 2,028 |
Perfboard and assembly | Rs 150 to Rs 400 |
Report, printing and binding Two or three bound copies, plots and the plagiarism check | Rs 400 to Rs 1,200 |
| Total | Rs 2,652 to Rs 23,063 |
| Each, split 3 ways | Rs 884 to Rs 7,688 |
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 4.3 week figure assumes 10 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
A healthy cage rotor is symmetrical, so it draws a balanced current and the stator current spectrum is dominated by the supply frequency alone.
A broken bar makes the rotor asymmetric. The resulting backward-rotating field induces components in the stator at the supply frequency plus and minus twice the slip frequency, so sidebands appear either side of the fundamental at a spacing that depends on load.
Because those sidebands are only a few hertz from a fundamental that is tens of thousands of times larger, the capture has to be long enough to resolve them and the window function has to be chosen so the fundamental's leakage does not bury them.
The accelerometer separately measures vibration, whose characteristic frequencies for outer race, inner race, ball and cage faults are fixed by bearing geometry and shaft speed.
Every capture is reduced to a handful of indicators and stored. The diagnosis comes from the trend: a sideband that has risen ten decibels over a month means something, whereas one absolute reading means very little.
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.
f sideband = f x (1 +/- 2s)
50 x (1 - 0.06) = 47 and 50 x (1 + 0.06) = 53. Note that the sidebands close in on the fundamental as the motor is unloaded, which is why this test is done under load — an unloaded motor can hide a broken bar completely.
delta-f = 1 / T, where T is the capture length
Resolving a 3 Hz offset from a fundamental that is enormous by comparison needs far finer resolution than the offset itself. Ten seconds gives thirty bins between the sideband and the fundamental, which is enough for the window's skirt to fall away.
N = fs x T, with fs at least twice the highest frequency of interest
An anti-aliasing filter ahead of the ADC is not optional. Without it, everything above 500 Hz folds back into the band you are analysing and lands on top of the very features you are looking for.
BPFO = (n/2) x fr x (1 - (d/D) x cos(contact angle))
fr = 1450/60 = 24.2 Hz, d/D = 7.94/38.5 = 0.206, contact angle 0: BPFO = 4 x 24.2 x 0.794 = 76.8 Hz. These frequencies are not multiples of shaft speed, which is exactly how a bearing fault is told apart from imbalance or misalignment.
Sideband amplitude relative to the fundamental, in decibels
Published guide values put a healthy machine around 50 dB below the fundamental and a seriously degraded one nearer 35 dB, but the absolute figure varies with machine, load and mounting. A rise of ten decibels on the same machine is far more meaningful than any published threshold.
Usable bandwidth is half the output data rate
Enough for shaft-rate and bearing defect frequencies, but not for the high-frequency resonance that early-stage bearing damage excites. Say that plainly; a proper vibration analyser reaches tens of kilohertz and this device does not.
| Item | Qty | Unit cost |
|---|---|---|
Current transformer Split core, 20 A, with burden resistor | 1 | Rs 300 to Rs 800 |
Anti-aliasing filter Op-amp low-pass, 500 Hz corner, on a small board | 1 | Rs 80 to Rs 250 |
Accelerometer ADXL345 or ADXL355 on a breakout | 1 | Rs 250 to Rs 1,400 |
Capture platform ESP32, or a Raspberry Pi if the FFT is done on device | 1 | Rs 350 to Rs 4,500 |
External ADC ADS1115 or a 12-bit SPI ADC for the current channel | 1 | Rs 180 to Rs 550 |
Sensor mounting Magnetic base or stud mount for the accelerometer | 1 | Rs 200 to Rs 700 |
Test motor Small three-phase induction motor, plus a spare rotor to fault Ask the machines lab — many departments keep a deliberately faulted machine for exactly this experiment. | 1 | Rs 0 to Rs 6,000 |
Loading arrangement Brake drum or generator loading on the test motor Normally part of the machines lab test bed. | 1 | Rs 0 to Rs 2,000 |
Enclosure and cabling Shielded signal cable, ABS box, glands | 1 | Rs 250 to Rs 700 |
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 2,652 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 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.
Because the fault makes the rotor asymmetric, which produces a backward rotating field at slip frequency relative to the rotor. Seen from the stator, that field induces components displaced from the supply frequency by twice the slip frequency on either side. It modulates the existing supply frequency rather than adding an independent tone, which is why the signature is a pair of sidebands.
Because the sideband spacing is twice the slip frequency, and slip is nearly zero when the motor is unloaded. At no load the sidebands sit almost on top of the fundamental and cannot be resolved from it, so a genuinely faulty machine tests as healthy. Loading the machine spreads the sidebands out to where they can be measured.
The length of the captured record, and nothing else. Resolution is one divided by the capture duration, so a ten second record gives 0.1 Hz bins. Increasing the sampling rate raises the highest frequency you can see but does not improve resolution at all — that is a common misconception and it is worth stating clearly.
Because they come from the geometry of the rolling elements — the number of balls, the ball diameter, the pitch diameter and the contact angle — combined with the rolling motion, in which the cage rotates at a fraction of shaft speed. The resulting frequencies are non-integer multiples, and that is precisely what distinguishes a bearing fault from imbalance or misalignment, which appear at exact multiples of shaft speed.
Because the absolute amplitude of any indicator depends on the machine, its load, its mounting and the sensor position, so there is no universal threshold that means failure. On the same machine measured the same way, however, a steady rise over weeks is unambiguous. Condition monitoring is a rate-of-change discipline, and that is why the database matters as much as the sensor.
The current can be measured at the motor control centre, which may be a long way from the machine and in a safe, accessible location, with no sensor mounted on the machine at all. It needs no access to a running machine in a hazardous or hot area. Its limitation is that it sees electrical and rotor faults far better than it sees mechanical ones, which is why the two methods are complementary.
Normally taken as a 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.