Protect your Room with your own Laser Security System!!!

A really easy and cool electronics project and lots of fun to play with once it finished.Its basically a laser tripwire but has a large application quotient in our everyday life's! so all you teenagers and mad scientists go out there and make your rooms and labs intruder proof :D

• Breadboard / Perf-board
• Transistor- BC 109 (or any equivalent general purpose NPN transistor)
link to the datasheet of BC109 :
• Wires for connecting
• 9 volt battery
• 9 volt battery clip
• 10k ohm resistor
• LDR- mine was 8k ohm

This electronic circuit uses a transistor to detect light falling on the LDR (light dependent resistor) to activate or deactivate an alarm (or any kind of electronic component). The two resistors (the resistor and the LDR) are connected in series and the common point between them is connected to the base of the transistor, making a potential divider. It uses the property of "threshold voltage" of the transistor to trigger the alarm. This means that we can set a minimal amount of light intensity to trigger the alarm. I have set it to the intensity of sunlight as the minimal. This means that, it won't trigger indoors in ambient light but only when there is a light of high intensity (like a laser). To set your own intensity or if you don't a LDR that is working with the current specifications then just replace the resistor with a potentiometer (or other kind of variable resistor) of something like 30k ohm. Then keep changing the value until you get the desired result.
A more scientific method will be to see the reading (resistance) of the LDR in the desired light. Check the threshold voltage from the datasheet and then used the potential divider formula to calculate the required resistance of the 2nd resistor.

Note: The relay is only used for simplicity. The output can also be controlled by power transistors, to control any other device.

Please feel free to pose any questions that you might have. And make sure that you comment, rate and subscribe.
Thank you :D

Rating Rating Rating Rating Rating 
Views: 95,260
Added: 3 years
Runtime: 5:37
Comments: 56

Tags for this video:  

Find more videos in the: "Tech"
Uploaded by: Rishi Balasaria
See more videos uploaded by Rishi Balasaria

Related Videos:

Simple Laser Security System (schematic in desc.)
Rating Rating Rating Rating Rating 
Views: 47482
Just a little project I've been working on for the past few hours.. It uses 2N3904 NPN transistor, Light Dependent Resistor and potentiometer for...
How To Make A Light Sensor
Rating Rating Rating Rating Rating 
Views: 90484
This video will show you "How To Make A Light Sensor" in very easy steps The things you need are: *BC547 Transistor *270 Ohm Resistor (x2) *LDR...
laser alarm circuit made of junk components
Rating Rating Rating Rating Rating 
Views: 74349
circuit & tutorial :
homemade security alarm

Views: 188666
This is a simple homemade alarm that can be used for travel, home, auto..etc.
How To Make A Clap Switch
Rating Rating Rating Rating Rating 
Views: 89675
Watch Our Latest Video For A Better Tutorial On The Same Project: This video will show you "How To...
How to make a Laser alarm security circuit on breadboard (Step by step tutorial)
Rating Rating Rating Rating Rating 
Views: 272027
Let's make simple laser alarm security circuit. This circuit is very easy. Materials : Breadboard, Laser pointer (From laser ballpoint pen), CDS,...
Build your own Surveillance Spy Bug. FM Transmitter Bug. No special parts needed.
Rating Rating Rating Rating Rating 
Views: 681143
50% off our best selling FM Bug Transmitter at: In this video i am showing you how to make a FM transmitter Bug...
Make a Water Level Indicator at Home ( Hindi / Urdu )
Rating Rating Rating Rating Rating 
Views: 350985
New Version with Soldering: Water overflow is a common problem. So here is the solution, Make this electronic circuit...
Weekend Projects - Little Big Lamp
Rating Rating Rating Rating Rating 
Views: 446204
Complete instructions for this episode of Weekend Projects can be found at Combine your...
Circuit Skills: Electronics Enclosures
Rating Rating Rating Rating Rating 
Views: 348016
Every useful electronics project deserves a good enclosure. Providing a proper case for your circuit can protect it from accidental spills & falls...
how to build a laser security system
Rating Rating Rating Rating Rating 
Views: 22828
this one is the most simple one tht u can find eva
How To Make A Simple Relay Circuit
Rating Rating Rating Rating Rating 
Views: 250390
This Video Show You "How To Make A Simple Circuit Using A Relay" It Will Also Tell You "What Is A Relay? & What Is It Used For?" The Things You...
How to really build a Laser pointer security system
Rating Rating Rating Rating Rating 
Views: 33028
This is really quite a simple project requiring only about a half dozen electronic parts and when it's finished the security that it offers will...
Simple Touch Alarm Circuit using IC 555
Rating Rating Rating Rating Rating 
Views: 60339
How To Make Your Own Laser Security System Circuit - A Tutorial With Theory & Lab
Rating Rating Rating Rating Rating 
Views: 28065
Check us out at:
Turn a pencil into a light
Rating Rating Rating Rating Rating 
Views: 1037825
Turn a pencil into a light - como fazer uma lanterna no estilo MacGyver utilizando um lápis
Lec 1 | MIT 6.002 Circuits and Electronics, Spring 2007
Rating Rating Rating Rating Rating 
Views: 548330
Introduction and lumped abstraction View the complete course: License: Creative Commons BY-NC-SA More information at...
easy laser tripwire
Rating Rating Rating Rating Rating 
Views: 56973
laser trip wire. wanted to make a video so i threw this together schmatic can be emailed to you
Laser alarm circuit
Rating Rating Rating Rating Rating 
Views: 33293
Laser alarm circuit. 5V relay, 5V buzzer, power supply, laser pointer New circuit video (schematic included) :
How To Make a Cell Phone Jammer Out of a TV Remote
Rating Rating Rating Rating Rating
Views: 756376
This is a very easy and simple way to make a cellphone jammer.
Basic Electronic Components and their Symbols and Connections
Rating Rating Rating Rating Rating 
Views: 317970
Watch this video for electronic components and their symbols and also get idea on how to different electronic components in circuits...
automatic night light

Views: 509909
This circuit is responsible for lighting a bulb, when it receives light and turns off automatically when it is dark, like street lighting lamps....
Simple LDR Circuit by Bobby
Rating Rating Rating Rating Rating 
Views: 81158
Dark Detector LED Using LDR. A small ciruit using LDR (Light dependent Resistor), where the LED light automatically turns on when the surronding...
light sensor making steps-
Rating Rating Rating Rating Rating 
Views: 185467
For more information visit us at: Find us on facebook:...
Trip-Wire laser security system - Wicked Lasers Contest Video#1
Rating Rating Rating Rating Rating 
Views: 45158
This is my laser trip-wire security system submission for the Wicked Lasers Competition. Check us out at:...


Author david shilo (2 years)
can i use transistor 9012

Author Rishi Balasaria (3 years)
thanks!!! :D actually i make this video quite long time back :P and i know
a way using logic gates, but was looking for a easier or a simpler way to
keep the alarm on, once it has been triggered. well, Glad you liked it :D

Author Lynexen03 (2 years)
Oh thank god,... i finally make it work. at the first im using a MOSFET
IRFZ44 and that when the conflict happens.... i changed the mosfet to a
transistor and it worked... anyway can i consult u if any error will appear
in future...

Author Rohan Bhojannawar (2 years)
In transistors where the notch is there is the emitter ryt ?

Author Rishi Balasaria (2 years)
I am very sorry. If you upload a video of this quality with complete void
of focus, I really wont be able to help you out. I need to see to
understand the circuit, so keep the camera still giving a focus on the
wires, connections and the breadboard will make all the difference in the
world.Please check your buzzer by directly connecting it to the battery. I
really feel that you should once just try and arrange the circuit in the
way i have shown at the start of my video. See the schematic again.

Author Rishi Balasaria (2 years)
One of the ways is to find your local electronics shop that sells
"electronics components and parts".Its crucial to search for shop offering
"electronics components" and not just electronics cause that would imply
electronics products.An easy way is to ask a electronics repair shop where
they source their parts from and anyways they would know the local shops.
Another way is to buy online on platform like ebay where you can get 20
LDRs for a dollar. Or dedicated electronics stores like digikey.

Author Rishi Balasaria (2 years)
ya, i know the way to make the system permanent :D a simpler way will be to
just use a AA battery pack. Actually given the time, i would actually
rather use a dvd burner laser diode with a laser driver (to increase my
effective range), or best use a IR laser diode and also run that with a
driver. That would make the laser absolutely invisible and wouldn't
obviously even show in dusty conditions. see the last part of the video
again, will see what i am asking :D

Author 88magar (1 year)
thanks i just made my second electronics project,is there any way of
getting the alarm to stay ringing for longer?Thanks great upload.

Author Gurcharan Singh (2 years)
Thx bro it works

Author Rishi Balasaria (1 year)
Yes, see my reply to 88magar

Author Rishi Balasaria (2 years)
It would help if you could describe your apparatus. The specifications of
your transistor, resistance of your LDR, power source (9V battery?), Have
you used a breadboard or soldered in on a perf-board, etc... Or best you
could post a video response regarding the same.

Author Rohan Bhojannawar (2 years)
what is Power ratings of the LDR used in ? is it specific ? reply ASAP gta
complete ma project....:P :)

Author halone het (2 years)
hello bro i want to ask two question 1) can i use 9v light instead of
buzzer 2)can use ldr of 12m and which laser i hv to use how much watt.

Author Rishi Balasaria (2 years)
Well, that's exactly what suppose to happen, the buzzer needs to stop when
the laser is falling on it and go off when there is no laser on it (to
indicate an external disturbance). its a "Dark-activated circuit".So will
only start the alarm/buzzer when there is darkness (or in our case when the
laser is obstructed). What do you want the circuit to do? if you could
explain me your goal, you would enable me to assist you better.

Author rishabh uppal (2 years)
hyy bro u doing engineering??? whch help me??? eva i wannna do same like
these thing whch is related 2 dezzz.!!! cool gadgets..?? help me.??

Author Rishi Balasaria (2 years)
Ya sure! Would love to be of any help regarding the project. Please share a
little more about this project. I would need to know your objective, are
you protecting a room? a precious item? what is it? Also what you wish to
achieve by the end of the project? is there a specific understanding that
the project needs to convey/showcase?

Author Chirag Patel (2 years)
buddy use an not gate ic so that wen any one cut offs the laser 1 goes to o
and den use

Author Lynexen03 (2 years)
Can you help me with my project.. (BURGLAR alarm..) if ok.. here is my fb
( i really need help its requirements for me.. i need
to pass please..

Author Rishi Balasaria (2 years)
Ya, of course because of the simplicity of the circuit we can just directly
connect the components together. Using a pair of pliers (or bare hands) by
twisting them together. Or a more permanent solution will be to just solder
all the points (that need to be connected) together.

Author Abdul Rehman (2 years)
okay.... :) thank you..

Author Gurcharan Singh (2 years)
hey bro, i have made the security system but its not working properly.when
i put the laser light on LDR the buzzer go off and when i remove light form
LDR the buzzer is stop....plz help me to fix this problem

Author kannam shashank (2 years)
i'm having 5v buzzer then which transistor and resistor are to be used.

Author Ghazanfar Uruj (2 years)
hey man where can i get LDR

Author Rishi Balasaria (1 year)
Not yet. I am yet to finish my schooling. I actually did this long back in
the 10th standard If i remember right. But sure, happy to help regarding
any electronics projects...

Author MrKillswich112 (1 year)
Okay, so I changed the schematic to allow the buzzer or relay to latch on,
reply back so I can post a video and schematic.

Author Rishi Balasaria (2 years)
Sure you can use a 9volt bulb. The problem is that bubs use a lot of energy
and will drain your battery rather quickly. So if you do decide to use a
bulb add a 9v power regulated supply so you don't need to worry about the
battery running out. "ldr of 12m"? what's 12m? 12mega ohms? Any low powered
laser will do. I used a simple laser pointer.

Author Rishi Balasaria (2 years)
Its really hard to believe you! Most electronic appliances (except mobiles)
use an adapter run on 9v. A popular example being Computer speakers, the
auxiliary input speakers, run with a 9v adapter. Anyways answering your
question, use the same transistor. Try with same resistor if it doesn't
work replace it with a variable resistor (potentiometer) and set/tune it to
the resistance it works at. Or else see the threshold voltage of the
transistor and calculate the value of the resistor.

Author Adnan Khan (2 years)
i have a doubt that how do u use this breadboard

Author Rishi Balasaria (2 years)
Yes, true. If you are in doubt you should all ways look up the datasheet
for the component. It will greatly help you get your connections right. The
link to the datasheet for the BC109 has been added in the description.

Author Rishi Balasaria (1 year)
Well the solution is pretty straight forward... just exchange the positions
of the LDR and the resistor. It should work just fine.

Author Rishi Balasaria (1 year)
Yes there are many ways to get the alarm to stay on longer. You may use a
microcontroller like an Arduino, PIC, BASIC stamp, atmel, AVR... or an set
of logic gates to set of the alarm and then control it with a switch to
turn it off. However the simplest and most practical would be to just use a
555 timer. You can even control how long you would want for it to be on.
Hope this Helps

Author halone het (2 years)
hi my friend sorry i cant find any 9v output so i can find only 12v output
so please tell me which transistor and resistor to use please help me,

Author Rohan Bhojannawar (2 years)
I sumhow m nt gettin the output.......!!! The buzzer aint goin off when
laser is put on LDR Kindly HELP.........!!!!

Author Ardhendu Chakraborty (1 year)
hey...umm...I've completed my device based on your circuit... it actually
works...but the other way... if m focusing a laser light on it...the buzzer
goes off... and when i'm placing an obstacle between the laser and the
device....the buzzer doesn't make a noise... I checked all my connections
and they are just the perfect... not able to understand the cause of this
problem... some-one please help..!!

Author Abdul Rehman (2 years)

Author Rishi Balasaria (3 years)
Thank you :D tell me, what do you wanna know specifically? it a normal red
laser pointer. they come in all ranges of power and quality (the china ones
start at like 0.8$). For this kind of an experiment you don't need a
powerful fancy laser, cause even the normal lasers have a range of a
mile.However if you wish to made a real security system, (or something more
permanent) then getting a powerful, good quality one is the right way to go

Author Rishi Balasaria (2 years)
I used a laser as it offers more range between the receiver and the emitter
than any led will. For the system to be effective there should be a
significant difference in light intensity of the source and ambient light.
Ultimately the choice of your light source really depends on your
application. If your only looking at the width of a door then yes a
infrared led should work. You do get LED's that are high powered and LED's
with in build lens for focus.

Author Abdul Rehman (2 years)
I made the exact circuit as you made... and thanks to you it works
properly..... I made the circuit as a project for my sister who is in
twelfth grade....!! She just was asking if you could explain a little more
in detail about the working of this circuit and the components used so as
to help her write the project report.....

Author Anshul Aggarwal (3 years)
Sweet!!!! put for question in the form of an application! So right now this
tutorial can help you build a model for some application! Which is that
application that you are struggling with!! am sure your friends will come
up with ideas:) good going rishi!!!

Author Rishi Balasaria (2 years)
the LDR i used was 8k ohms (as mentioned in the description). No there isnt
any rower rating on it. You will have use just use common sense to figure
where it will and will not work (so probably the maximum power circuit you
could safely use it with would be around 12-18volts and 2A max). As long as
you are using a battery you are good to go. a 1.5v AA, 9v, high power 4.5v
lithium ion/polymer battery's,etc... if You could explain your project and
your power source, that would be helpful :D

Author Abhishek Thakur (2 years)
Thanks budy really nice one

Author Noras Lalruatfela Chinzah (2 years)
Pliz can u tel me where to conecu the relay part to used in light system

Author Rishi Balasaria (2 years)
Well, where you went wrong was the connections. Just interchange the
positions of the buzzer and the resistor and you should be good to go :D
When ever you face a problem in electronics especially when you dealing
with experiments like such at grass root level just go through the
schematic again. You will get rid of your problem. Hope this helps :)

Author Nigel Menezes (2 years)
can i use an infra red led ?? n how do i focus it on the ldr??

Author AakashMJ Sachdeva (2 years)
laser:Take the laser diode out of the laser light toy through a screw
driver which you have got..the mouth portion is the positive terminal and
the spring one is the negative terminal..connect both with a 9V battery
along with two 10k ohm resistors as the your laser light works on
connect this system with a switch..and stick this light in front of the
LDR..and you can also connect the buzzer with a switch..hope it was
helpful.. :-)

Author Rohan Bhojannawar (2 years)
Sorry I gt the Exact O/P as expected...! i too designed xactly lyk u on a
LASER... its working..but i styl gta build it on PCB....SOldering OMG.

Author Rishi Balasaria (2 years)
Nah, i that will not work as the 9012 is a PNP type transistor and the
BC109 is a NPN type transistor

Author Rishi Balasaria (2 years)
Yep, soldering can be quite a challenge to get started at.There are a lot
of soldering tutorial on YouTube, you should find them very helpful. You
might also consider using a prototyping board (Perf board) rather than a
printed circuit board. They are very cheap allow for rapid prototyping.
Perf boards come in different orientations, some are in the same
orientation as the bread board, so you can directly fabricate the circuit
in the same orientation. Making the project a lot easier.

Author armel mongane (3 years)
very helpfull!!but i need more detail about the LASER POINTER!!!!HELP

Author Rishi Balasaria (2 years)
Ya, relays can at times really get a little difficult to figure out (as
there are 5 points).An effective method to find out which point does what
is by simply searching for the datasheet online (just google the part no).
The datasheet will tell you which 2 points are the load (which you will
connect in series with the mains and light) and which 2 are the coil points
(you will in this case need to connect by a normally open configuration,
implying the light will only be on when the coil is high)

Embed Video:


Search Video

Top Videos

Top 100 >>>


Analyse website