Скачать или смотреть laser security system experiment

Here’s a simple and safe Laser Security System experiment you can easily make for a school physics / electronics demo 🔴🔔
(It matches your usual DC + LED + sensor style experiments.)
🔐 Experiment: Laser Security Alarm System
🎯 Aim
To design a security system that detects interruption of a laser beam and triggers an alarm.
🔧 Materials Required
Laser pointer (red laser)
LDR (Light Dependent Resistor)
Buzzer 🔔 (3–12 V)
BC547 / BC548 transistor
Resistor: 10 kΩ
Variable resistor (potentiometer) 100 kΩ (optional but recommended)
LED + 220 Ω resistor (indicator)
Battery (9 V or 5–12 V supply)
Breadboard / wires
Cardboard or stand to align laser
🔌 Circuit Connections
LDR + 10 kΩ resistor → make a voltage divider
Junction of LDR & resistor → base of transistor
Emitter → Ground
Collector → Buzzer + LED (with 220 Ω) → Battery +
Laser beam continuously focused on LDR
⚙️ Working Principle
When laser light falls on LDR, its resistance is low
Transistor stays OFF
Buzzer OFF
🚨 When someone cuts the laser beam:
LDR resistance becomes high
Transistor turns ON
Buzzer sounds + LED glows
This shows light → electrical signal → alarm activation
🧪 Demonstration Tips
Do experiment in low light room
Align laser exactly on LDR
Use potentiometer to adjust sensitivity
Show “laser ON = safe, laser OFF = alarm”
📘 Physics Concept Used
Photo-resistive effect
Transistor as a switch
Opto-electronics
Security & automation systems
🧠 Extensions (Advanced Ideas)
Add relay to control a door lock
Use Arduino for timer & reset
Replace buzzer with DC motor siren
Use mirror reflection path for long range
⚠️ Safety
❌ Do NOT point laser into eyes
✅ Use low-power laser pointer only
If you want, I can also give:
Circuit diagram (hand-drawn style)
Arduino version
Explanation for viva / exam
Low-cost ₹ experiment version
Just tell me 👍