Picture of Laser Trip Wire Security System with Combination Lock and Epic Siren!
Hi Everyone!  Welcome To My Instructable!
My laser trip-wire security system employs a programmable combination lock that acts to arm and disarm the system, as well as indicate to the microprocessor if someone has entered in a faulty code (Tampering).  There is also a really awesome and LOUD Siren with strobing indicator LEDs.  The laser trip-wire is bounced across several carefully aligned mirrors and back to the laser detection circuit.  The costs to create this project are pretty low. The only real cost is in the siren ($19) , the LS7222 ($6), and the keypad ($5).

Aligning the mirrors was the most difficult part, as I had to purchase sticky tack to stick them to the wall, and to be able to adjust the mirrors in different directions.  The sticky tack kept moving over time, which made it extremely difficult. However, patience persevered, and I was able to get a nice video demonstration. I was able to purchase the Mirrors and the sticky tack at the local dollar store!

If there was more time, I would have added an extremely sensitive laser detection circuit, and a battery backup but instead I've added these schematics and instructions into the EXTRAS section so that you can use them in your future projects.  I've posted three videos relating to this project::
1) A demonstration of my design with the mirror set-up that I have in my hallway.
2) A breakdown video of the electronics involved for those of you who don't want to have to read through the electronic block sections of this instructable.
3) A second up-close demonstration of the system with an explanation of the program algorithm.

I have worked extremely hard to offer as much detail as humanly possible regarding each aspect of the electronic hardware.  I've included copies of thoroughly commented software, and a block diagram of the program algorithm.

For the better part, I don't expect anyone to fully re-create this project, but I have detailed so much information that the viewer will be able to use many blocks and schematics, or variations of them in their own projects.  Thanks for viewing.  As always, I appreciate your comments and perhaps your votes, if you find I deserve them =)

I've designed and implemented this model into a DIY kit.  While I haven't integrated it yet, it will be available at www.engineeringshock.com and www.electroniclessons.com (Ebay Store) By mid February 2013.  It will include the circuit, a pulsing siren, and an AC adapter.  Below is the demonstration video:

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Fission Chips10 months ago

This is really cool! I made something kind of similar, only using a PIR sensor instead, because honestly a PIR works better (although you've got to admit, lasers are cooler). Check it out at: http://www.instructables.com/id/Portable-Person-Detector/

danm_daniel2 years ago
2late2 years ago
hey pat, do you mind adding just a list of materials to this page. if so thanks.
EngineeringShock (author)  2late2 years ago
When my kit is integrated (within two weeks), all components will be talked about in the assembly video. Demo:
EngineeringShock (author)  2late2 years ago
I have a kit of this coming out soon. Subscribe to my youtube channel, and you should see the kit up for sale in about 30 days =)
bdayot2 years ago
These are the things that i want to learn in my life.
Hi, I just wanted to know where u bought the LS7222 for 6 dollars and the keypad. I can only find the chip for about 32 uk pounds which I find is way too much.
i just bought LS722 here in the Philippines for just $0.43 xD
i found 9 digit pads much cheaper. try that.
DadhieMJ2 years ago
I've already purchased all of it except PIC18F1220.. im still just a student. can u give me some advice :(

what is the equivalent of PIC18F1220?

armmony3 years ago
its a great project for me because im a student from India i want to make this project so can u please give some information about (he Program (PIC18F1220) ASM Code) and tell me how can i do this please and yes tell me what is the price of the device please .................................I'm not a engineer but i still want make this project so please give more information as u can and help me to make this u can send detail to (sutham08@hotmail.com) or u can post here.........
thank you
najito3 years ago
zixx653 years ago
Hey EngineeringShock,
I'm wondering if you can add more items to the security system like another matrix pad OR another laser... so when you have time give me a comment.
Thank you for your time!
Dakota S.
IronWill zixx653 years ago
now, I am not too sure but wouldnt adding other laser module sin series result in the same effect?
IronWill3 years ago
im impressed, nicely done.
habgroups803 years ago
its good job we are in need of these laser trip-wire security system with complete work done product in india please contact us as early as possible we are in need of bulk purchase of this product contact me at habgroups80@gmail.com or can call me at +917373195747
wouternet3 years ago
With any flashlight you can saturate the LDR sensor and just walk through the beam. The more powerful your flashlightis, the less you have to be near the LDR/circuit board. I did a quick and dirty laser detector setup like you did, but without the keypad.
With my Surefire I was able to stand 50ft away and still break the beam without setting the alarm off.
EngineeringShock (author)  wouternet3 years ago
Yes, this is true. When I published this instructable, someone else said the same thing right off the bat. It wasn't meant to be a security system, but rather an entry into a contest. After I made a laser that pulse about 1kHz, and the LDR was set up with a coupling capacitor, and amplifier, which was connected to the counter of an MCU. If enough pulses were not caught by the MCU, the alarm would go off. This countered the problem you're talking about.
Excellent solution!
karthikhs3 years ago
Is there an alternate for LS7222 & LS7220.
nof-z3 years ago
EPIC, but my mom would kill me if this went off at night...
Andrew Rose4 years ago
Your project / product is the closest thing I have found to solving a problem I'm experiencing here in Johnnasburg, that being unwanted and unwelcome people on my property. So, well done on the hard thinking, design and development. Sure there are loads of "beam type security products" out there on the shelves, but all pretty expensive and require installation teams that have to install and connect to existing alarm systems.
A project like this shows me that it is possible, with a little application, to create an inexpensive and relatively "low tech" solution.
Thanks for the sharing the ideas.
shrike44 years ago
Hello EngineeringShock,

Just wanted to say I love this project, I think it is awesome. In fact, I am trying to built your instructables just without the siren, and only using an piezo alarm. I just want to see if I can build it, and get it to work! I just hope if I run into any snags, that I could count on your expertise to help me along the way. Thank you for all the infomation you already have here. Hope to get it to work.

EngineeringShock (author)  shrike44 years ago
Hi there
Sure =) Send me a message if you get stuck. I'll do my best to help.

@engineering shock
Do you think you could send me a list or sell a DIY project for this i want it for my bedroom. i also have no experience on doing this so if you could make a video of you bulding one step by step or put it all in plain english in an instuctable i would greatly appreciate it..

i will email you my email adress if you have an email i dont want to put it out in public
willow204 years ago
could you set this system up with a LDR and Infra red light beam, as a laser would show up out side if it was foggy I think.
tinker2344 years ago
samtheking4 years ago
hi pat,
this is (sam)

its a great project for me because im a student from India i want to make this project so can u please give some information about (he Program (PIC18F1220) ASM Code) and tell me how can i do this please and yes tell me what is the price of the device please .................................I'm not a engineer but i still want make this project so please give more information as u can and help me to make this u can send detail to (sonu007adak@gmail.com) or u can post here.........
Thank You .....
EngineeringShock (author)  samtheking4 years ago
Hi Sam
I work full time and do this as a hobby, so I don't have a lot of time to spare. If you can simplify your request, I can likely help you out, but I can't go through everything with you. You'll have to just do your best to follow along with the instructable =s

Thank you for your kind comment.
Hi pat
thanks for your reply . i'm just want to know about this device where i can buy it and how its work and its really important for this project and there have not any way to complete this project ?
thanks for your timing
this is bloody epic!
gogiva4 years ago
one of a few excellent instructables, congratulations
WOW! great instructable! i've just had to make this account, just to comment on it, andim seriousley thinking of going pro, just to downloads and print all of the instructable!
I only have one question, do you have a diagram of the complete circuit on one picture? if so, could you please PM me, or email. Thanks!
EngineeringShock (author)  lukestanmore4 years ago
Hi there =)
Thanks! There is a picture in the instructable of the entire circuit. I do not have a parts list on hand, but the meat of the circuit is the LS7222, the keypad, the siren, the laser, and the light sensors. I have some of these for sale if you're interested.
Go to www.electroniclessons.com or engineeringshock.com

Thanks, I will have a look at your sites, unfortunatley, when i tried to print the diagram to a readable size, it became incredibly blury, I dont supppose you have a higher resoloution one available? Thanks
Sorry, I forgot to add; do you also have a complete parts list with everything in one place :) Thanks
Lordsauron4 years ago
Any one have a link for the sirene. i would love to get one of those.
EngineeringShock (author)  Lordsauron4 years ago
Hi there
The link for the siren in in the siren driver electronic block. They are so much louder than what you see in the video!

Spectacular. Going to try and build one myself. It may be a little more complex than it needed to be, but still an amazing idea. Much appreciated.
Thanks =)
I realize that it may be more detailed than it had to be, but I wanted to give as much info as posible. I hope that when you're done making yours, that you post it and send me the link =)

Thanks again!
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