Biomedical Engineering + Health Technology
Build a heart-rate monitor with a light sensor
Detect your pulse from light passing through a fingertip and display beats per minute.
- DifficultyIntermediate
- Estimated time1–2 weeks
- Budget₹500–₹1,000
- ClassClass 10 to college
- TeamSolo or up to 3
- You needArduino required
Prerequisites: Arduino basics
Original · by TechnifyedArduino ProjectHardware ProjectHardwareWell documentedTwo subjects
Overview
Each heartbeat changes how much blood is in the fingertip, which changes how much light passes through. A pulse sensor or an LED and photodiode picks this up; filtering and peak detection turn the signal into a heart rate.
Why build this?
It shows how a common medical measurement works and teaches signal processing on a signal you can feel.
What you will learn
- How light-based pulse sensing works
- How to filter a noisy signal
- How to detect peaks and compute a rate
- Why this is a learning device, not a medical one
Skills you will use
Safety and ethics
- Use only batteries or a low-voltage supply (12 V or less). Never connect a project to a wall socket.
- This project involves people. Explain what you are doing and get their consent (a parent's or teacher's for children), let anyone stop at any time, collect only what you need, and remove names before you share results.
Materials and tools
- Arduino
- Pulse sensor module or an LED and photodiode
- Display (optional)
- Computer for plotting
Tools and software
Step-by-step roadmap
Start
You will finish with: a working monitor, plots of the signal and a comparison table.
- 1
Prerequisites
Know this first: arduino basics. Then collect the 4 items in the materials list.
- 2
Learn
- How light-based pulse sensing works
- How to filter a noisy signal
- How to detect peaks and compute a rate
- Why this is a learning device, not a medical one
- 3
Plan
Sketch the design, list every part with its price and decide how you will know it works.
- 4
Build
- Read the sensor and plot the raw signal on the computer.
- Smooth it with a moving average.
- Detect each peak above a moving threshold.
- Measure the time between peaks and compute beats per minute.
- Average over ten beats and display the result.
- Compare with a manual pulse count for five people.
- 5
Test
Your reading should agree with a manual count within about five beats per minute at rest.
- 6
Document
Photograph each build stage, keep the circuit or drawing, and note what failed and how you fixed it. Report structure
- 7
Present
Demonstrate it working first, then explain how it works and what you would improve. Presentation structure · Viva questions
- 8
Publish
Share a short video, the parts list and the drawing or code so someone else can build it.
Expected outcome
A working monitor, plots of the signal and a comparison table.
Other versions of this project
Beginner version
Only plot the raw waveform and count beats by eye.
Advanced version
Measure heart-rate variability and compare rest with after exercise.
Research version
Test how skin tone, finger pressure and ambient light affect accuracy, with consenting volunteers.
Make this project better
- BasicOnly plot the raw waveform and count beats by eye.
- This projectBuild a heart-rate monitor with a light sensor
- AdvancedMeasure heart-rate variability and compare rest with after exercise.
- ResearchTest how skin tone, finger pressure and ambient light affect accuracy, with consenting volunteers.
Ways to do this project
Text marked "You write this" is a prompt for your own work; everything else is specific to this project.
- Research question
- You write thisOne question you can answer with data, narrow enough to finish in the time you have.
- Hypothesis
- You write thisWhat you expect to find, and why.
- Variables
- You write thisWhat you change or compare, what you measure, and what you hold constant.
- Methodology
- Test how skin tone, finger pressure and ambient light affect accuracy, with consenting volunteers.
- Data collection
- You write thisSay what you will record, how many times, and how you will keep the records safe.
- Analysis
- You write thisChoose the table, chart or test that answers the question; report averages with their spread.
- Limitations
- You write thisList what could have affected the result: small sample, instrument limits, things you could not control.
Literature review
Find five to eight sources (your textbook, review articles, reports) and note what each says about your question. Group them by idea, not one after another, and end with what is still not known.
References
List every source you used in one style throughout (author, year, title, where it was published, link and the date you opened it).
- Problem
- Each heartbeat changes how much blood is in the fingertip, which changes how much light passes through.
- Target user
- You write thisOne specific person: who they are and when they would use this.
- Solution
- Detect your pulse from light passing through a fingertip and display beats per minute.
- First version (MVP)
- Only plot the raw waveform and count beats by eye.
- Tech stack
- Arduino
- Architecture
- You write thisA quick sketch of the parts and how they connect.
- Demo
- Your reading should agree with a manual count within about five beats per minute at rest.
- Stretch goals
- Measure heart-rate variability and compare rest with after exercise.
Team roles
Plan by length
24-hour
- Hours 0–2: agree the problem, the user and the one thing the demo must show
- Hours 2–16: build only the first version
- Hours 16–20: test the demo path end to end and fix what breaks
- Hours 20–24: slides, a 2-minute demo script and a backup recording
48-hour
- Evening 1: problem, user, sketch and task split
- Day 1: first version working end to end
- Day 2 morning: one stretch goal and testing
- Day 2 afternoon: polish, slides and demo practice
1-week
- Day 1: research the problem and talk to two possible users
- Days 2–4: first version
- Day 5: stretch goals
- Day 6: testing and write-up
- Day 7: demo video and presentation
Working as a team
Solo or up to 3. Suggested roles:
Report and presentation
Report structure
- Title and aim
- The problem it solves
- How it works (principle)
- Parts list with cost
- Design: drawing, circuit or block diagram
- Build steps
- Testing and results
- Problems faced and fixes
- Limitations
- Future improvements
- References
Presentation structure
- The problem
- The idea
- How it works (one diagram)
- Parts and cost
- The build (photos)
- Live demo or video
- Test results
- What did not work
- Next version
Viva questions
Try answering before you open each one.
Why does the signal pulse?
Blood volume in the fingertip rises with each heartbeat and absorbs more light.
Why filter the signal?
To remove noise from movement and ambient light.
Is this a medical device?
No, it is not calibrated or certified and must not be used for diagnosis.
How do you compute beats per minute?
Sixty divided by the average time between peaks in seconds.
Resources
Source and attribution
Original
Written by Technifyed. Free to use for your own school or college project; write the report in your own words. Added 1 Oct 2026.
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