- Physics
- Ready-made model
- Class 10 to 12
- Printed report included
Infrared Intruder Alarm Readymade Physics Working Investigatory Project & Model for School & College (Readymade Report Included)
Code B099QZPZR3
- Paid for and delivered by Amazon. The current price and the delivery date for your PIN code are shown there.
- Sold by Gurukul Technicals Institute, Delhi.
- Need a different topic, a custom version or a school order? Ask on WhatsApp.
In this project guide
Ready-made model
About this model
This infrared intruder alarm detects a person or object using invisible infrared light and then sounds an alarm. The listing says a readymade report is included, which helps with the written part of a school or college project.
How it works
The science behind it
The idea the model demonstrates, in words you can use in your report and when you explain it.
Infrared (IR) radiation is part of the electromagnetic spectrum, with wavelengths longer than red light, roughly from 700 nanometres up to about 1 millimetre. It is invisible to our eyes, which suits security work. In an active IR alarm, an IR LED sends out infrared and an IR receiver, such as a photodiode or an IR sensor module, detects it. There are two common arrangements. In the beam-break type, the LED and the receiver face each other, and when someone walks between them the beam is blocked and the alarm sounds. In the reflection type, they sit side by side, and the alarm sounds when an object comes close enough to reflect IR back into the receiver. The TV remote at home, automatic hand sanitiser dispensers and the sensor taps in many public washrooms use infrared in similar ways. Many phone cameras show an IR LED glowing faintly, proving that the invisible beam is there.
Make it yourself
Make an infrared intruder alarm yourself
Build your own version from scratch, or use the steps to understand how the ready-made model is put together before you present it.
What you need 10
Step by step 8 steps
Connect the IR LED in series with its 330 Ω resistor across the supply, long leg towards positive, and point it forwards through a short black tube.
Fix the photodiode beside it in its own black tube, so it cannot see the LED directly. Connect it reverse biased: cathode to positive and anode to negative through the 100 kΩ resistor. Check the legs with the multimeter's diode range.
Connect the junction of the photodiode and the 100 kΩ resistor to pin 3 of the LM358. More reflected infrared means more current and a higher voltage at this point.
Connect the preset across the supply with its middle pin to pin 2; this sets the trip level. Pin 8 goes to positive and pin 4 to negative.
Connect the LM358's output, pin 1, through the 1 kΩ resistor to the BC547's base. Put the buzzer, and the red LED with its resistor, between the positive line and the collector, and join the emitter to negative.
Look at the IR LED through a phone camera: a faint purple glow shows it is working, even though your eyes cannot see it.
With nothing in front, turn the preset until the buzzer just stops. Move your hand in front of the sensor and the buzzer should sound.
Measure the greatest distance at which a hand, a white card and a black card set it off, and mount the sensor beside a model doorway.
Read this first
Safety first
Go through these points before you build or switch anything on. Younger students should do this with an adult.
- Use the soldering iron only with an adult and rest it in its stand.
- Do not stare closely into the IR LED for long, even though you cannot see its light.
- Keep the 330 Ω resistor in series with the IR LED; without it the LED overheats and burns out quickly.
- Run the alarm from the 9 V battery only, and switch it off between demonstrations.
Troubleshooting
If something does not work
The usual problems with this model and how to fix them. Open a problem to see the fix.
The buzzer sounds all the time
The photodiode can see the LED directly, sunlight or a lamp is shining on it, or the preset is set too low. Improve the black tubes, move away from windows and turn the preset up.
Nothing sets it off
Check the IR LED glows through a phone camera (some rear cameras block infrared, so try the front camera), check that the photodiode is reverse biased, and turn the preset down.
It works indoors but goes off by itself near a window
Sunlight contains a lot of infrared. Shade the sensor, or use the alarm away from direct sunlight.
A white card is detected but a black one is not
Dark surfaces absorb most infrared and reflect little back. This is a real limitation of reflection sensors; note it in your report and compare with the beam-break type.
Exhibition day
How to present it
A running order for the exhibition table or the practical, step by step.
Move a hand or an object through the sensing area to trigger the alarm.
If your model has an IR LED, point a phone camera at it to show its faint glow, since our eyes cannot see it.
Show on a chart where infrared sits in the electromagnetic spectrum.
Compare it with a TV remote, which also uses infrared.
Practice
Viva questions
Practice questions on this model, with short answers. Try each one aloud before you open the answer.
What is infrared radiation?
Electromagnetic radiation with wavelengths longer than visible red light, which our eyes cannot see.
Why is infrared used in intruder alarms?
It is invisible, so an intruder cannot see the beam, and it is easily detected by IR sensors.
What is the difference between beam-break and reflection type IR sensors?
A beam-break sensor triggers when a beam is blocked, while a reflection sensor triggers when an object reflects IR back to it.
Name one household device that uses infrared.
A TV or AC remote control.
Project file
Project file outline
The headings of the project file, in order. Give each heading its own section and write it in your own words.
The listing includes a printed project report: use this outline to check that your own file covers every part.
Free ebook: Writing a Science Project FileContents
- Aim: to detect an intruder using invisible infrared light
- Introduction: infrared radiation in the electromagnetic spectrum
- Beam-break and reflection types of infrared sensor
- Working of the IR LED, photodiode and LM358 comparator
- Circuit diagram and construction
- Observations: detection distance for different objects and colours
- Applications: automatic doors, hand dryers, burglar alarms and TV remotes
- Limitations such as sunlight, and precautions
- Conclusion and bibliography
Buying checklist
Before you buy
What to check before you order the model, and what to do when it arrives.
1Before you order
- Check whether your teacher wants an infrared or a laser alarm, as both are common exhibition projects.
- Read the listing to see which sensor it uses and what powers it.
- Keep the box so the sensor stays pointing the right way in transport.
- Check the delivery date for your PIN code on the marketplace, and order well before the exhibition or practical.
- Practise explaining it. Judges ask what the model shows and why; knowing the science matters as much as the model. The viva questions above are a good place to start.
2When it arrives
- The listing says a readymade report is included; check it when the parcel arrives and add your own detection-distance readings.
- Test it as soon as it arrives, and again a few days before the exhibition in lighting like the hall's.
Next steps
Take it further
Ways to turn this model into a bigger investigation or a stronger exhibition entry.
Build the beam-break version too, and compare the range and false alarms of the two arrangements.
Show the IR LED's glow through a phone camera at the exhibition and explain why the camera can see what the eye cannot.
Add a 555 latch so the alarm keeps sounding after the intruder has passed, until it is reset.
Audience
Who it suits
Class 8 to 12 students and college learners making a security or sensor project.
- ClassClass 10 to 12
- SubjectPhysics
- TypeReady-made model
- Project reportPrinted report included
Free to read
Free ebooks for this topic
Free PDF ebooks from Gurukul Technicals Institute on the science, the making and the presenting of projects like this one.
- Free PDF ebook
Physics Working Models Explained
Twenty classic models, how each works and how to make it
- Free PDF ebook
Investigatory Projects for Class 11 and 12
Topics, method and report structure for physics, chemistry and biology
- Free PDF ebook
Your Science Exhibition Guide
Choose a project, build it, present it and answer the judges with confidence
- Free PDF ebook
Writing a Science Project File
How to write the report, from the cover page to the bibliography
