Mini Laser Security Alarm System Using BC547

by | Mar 14, 2022 | Physics, Science

Home » DIY » Mini Laser Security Alarm System Using BC547


In this tutorial, we will show you how to make a mini laser security alarm system using BC547.

There is a circuit that will help you to make the model easily.


We need some tools and materials to make this mini laser security alarm system with transistor using simple circuit:


  • Hot glue gun
  • Soldering iron


  • BC547 transistor
  • Buzzer
  • 10k resistor
  • LDR
  • 3v coin cell and holder
  • Wire
  • Laser diode
  • Holder

Steps To Make Mini Laser Security Alarm System Using BC547

Just follow these steps to make this DIY security alarm system:

Step 1: Attach the transistor to the buzzer.

Step 2: Now, connect the legs of the transistor with the buzzer ( as shown in the picture).

Step 3: Now, connect LDR in the middle leg and 3rd  leg, and transistor with middle leg and buzzer using a soldering iron.

Step 4: Attach the whole circuit to the holder.

Step 5: Connect the wire with it and the coin cell.

Step 6: Now, take another holder and connect the laser diode with the coin cell.

Step 7: When you turn on the laser diode, and the buzzer will come in contact with the laser, it’ll start a sound.


This tutorial will help students understand the working and principle concept of a security alarm and how we can make it at home for your science project.

Things To Remember

  • Use the leftover material from previous crafts.
  • Be careful while using soldering iron.
  • Take the help of an adult while making models.



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