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:

Step 1: Device Features + Demonstration

Design Features:

1) A combination lock circuit that employs the versatile LS7222 combination lock IC.  The code can be re-programmed with ease using the matrix keypad.  The same code is used to arm and disarm the system.  If someone enters in an incorrect character, the tamper output pulses a warning to the microprocessor, and initiates the alarm sequence.

2) Two light sensing circuits.  One of them is aimed at the ceiling, and indicates to the microprocessor whether or not there is enough light in the room for the system to work.  After the ARM code in entered in, the system waits for the light to go out in the room before it enables the laser and starts scanning for a laser breach/tamper/or DISARM code to be entered into the keypad.  Check out the program algorithm block diagram in step#9 for more information.  The second light sensor is used to detect the laser beam.

3) The extremely loud EPIC siren with Strobing LEDs.  This siren is activated by the microprocessor via a driver circuit.  When the laser program is enabled, if someone breaks the beam that is being mirrored all over the doorway, the alarm is triggered.  As well, if someone enters in an incorrect character.... ALARM.  If the alarm goes off, the user must enter in the ARM/DISARM code to disable the program, and reset them system.

4) A 5mW red laser with a manual enable (Push button) and a software trigger/driver.  We use the manual enable to align the laser through a series of mirrors, and back to the laser detection light sensor circuit.  Once we've done that, we turn the laser off, and enable the system.  From there, the software will dictate when the laser is turned on or off.  See Step#6 (Laser electronic Block).

5) The microprocessor is a PIC18F1220 from Microchip Technologies.  It takes the signals from the light sensors and the combination locks, and outputs signals to the on-board piezo buzzer indicator, the siren, and acts to enable/disable the 5mW laser.

6) Please note that I've added in some fun extras in the EXTRAS section, such as how to employ a battery backup, and how to make an extremely sensitive laser detector.

Here is the first of three videos.  This video is the mirror demonstration.  See Step#2 for the video version of the electronic summary, and Step#9 for an up close demonstration with a program algorithm discussion.

<p>With help of the 200 in 1 electronic kit I replaced the trip wire with the cds cell and shined a laser green 50mw at it. Whenever the beam broke the alarm would sound. It keeps people out of my chemistry lab. Project the buglar alarm.</p>
<p>You see this would be a simpler version of this.</p>
<p>I am thinking of building a cds controlled 555 timer alarm with 9 volt rechargeable battery or a 3 to 24 volt buzzer. It uses a cds cell that a laser shines at. The cds cell with several 1K ohm resistors in series when it shines then causes current to loop. Then when the laser is interrupted the resistance is high so the voltage flows through the 555 timer causing a buzzer to go off. The laser is a green laser 50 mw with recharagable batteries 1.2 volts *2. </p>
<p>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: https://www.instructables.com/id/Portable-Person-Detector/</p>
<em><strong>hey pat, do you mind adding just a list of materials to this page. if so thanks.</strong></em>
HI <br>When my kit is integrated (within two weeks), all components will be talked about in the assembly video. Demo: <br>https://www.youtube.com/watch?v=Mo9Lc8TW_O0
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 =)
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 <br>
i found 9 digit pads much cheaper. try that.
I've already purchased all of it except PIC18F1220.. im still just a student. can u give me some advice :( <br> <br>what is the equivalent of PIC18F1220? <br> <br> :)
hello <br>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......... <br> thank you
Hey EngineeringShock,<br> 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.<br>Thank you for your time!<br>Dakota S.
now, I am not too sure but wouldnt adding other laser module sin series result in the same effect?
im impressed, nicely done.
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 <br>
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.<br>With my Surefire I was able to stand 50ft away and still break the beam without setting the alarm off.
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!
Is there an alternate for LS7222 &amp; LS7220.
EPIC, but my mom would kill me if this went off at night...
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 &quot;beam type security products&quot; out there on the shelves, but all pretty expensive and require installation teams that have to install and connect to existing alarm systems.<br>A project like this shows me that it is possible, with a little application, to create an inexpensive and relatively &quot;low tech&quot; solution.<br>Thanks for the sharing the ideas.
Hello EngineeringShock, <br> <br> 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.<br><br>Thanks,<br>Shrike4
Hi there <br>Sure =) Send me a message if you get stuck. I'll do my best to help. <br> <br>Sincerely, <br>Pat
@engineering shock <br>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.. <br> <br>Chandler <br>i will email you my email adress if you have an email i dont want to put it out in public
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.
hi pat,<br>this is (sam)<br><br>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......... <br> Thank You .....
Hi Sam <br>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 <br> <br>Thank you for your kind comment. <br>Pat
Hi pat<br>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 ?<br> thanks for your timing <br> Sam
this is bloody epic!
one of a few excellent instructables, congratulations<br>
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!<br> 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!
Hi there =)<br>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.<br>Go to www.electroniclessons.com or engineeringshock.com<br><br>Thanks<br>Pat
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
Any one have a link for the sirene. i would love to get one of those.
Hi there <br>The link for the siren in in the siren driver electronic block. They are so much louder than what you see in the video! <br> <br>Thanks! <br>Pat
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 =) <br>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 =) <br> <br>Thanks again! <br>Pat
you can add smoke in the background to show the laser beam in the video..!..<br><br>well can you try this with infrared beam of light.. i guess that would be a more &quot;SECURE &quot;security system..? <br> <br>nice instructable anyways!
hi i want to learn how curcuit boards and such work how did you learn this knowledge was it a class or a book and could you tell what it was called.
Hi there <br>I went to school to be an electronics technician. They gave me the tools, but if you have the passion for electronics, you have to keep building and learning as you go. There are hundreds of great websites online that could get you started. For instance, if you search &quot;breadboard explanation&quot; you'll see a ton of sites come up. A breadboard is a prototyping board that allows for you to take out and put in components, as opposed to soldering them into a PCB. Have a look around. There are TONs of great references on the internet. If you want help finding a good place to start, I am more than happy to help =) <br> <br>Sincerely <br>Pat
there is a combination lock IC !!!!<br>oh my god, i wish i had known that for when i did my electronics a level coursework (which btw was a security system like this). instead i made a switch multiplexing grid whcih connected different resistors together for each switch pressed - 3 analogue outputs (one for each row of switches) feeding into a microcontroller with 3 adc's (picaxe 18x). this would have been so much simpler, and the picaxe was really temperemental as well :(<br>really good instructable - i like how much detail you went into<br><br>(and to all the people saying this is complicated you should have seen my coursework - it took up 17 breadboards, mainly due to the ram memory i made from flipflops)
Hey! <br>I know what you mean. I created a few manual combination locks in school. One employed only HW (JK flip flops in toggle configuration, and several X-OR gates. <br> <br>I want to do what you did using the ADCs and doing comparing through programming. Thanks again for the comment. I tried to put as much detail into this as I could, and it is really nice to get comments like this. <br> <br>Thanks again! <br>Pat
your welcome - its nice to see someone put so much effort into explaining things to other people. the extra detail really helps you to get a more in depth understanding on how the system works
this is super cool... I was thinking though.. that u should modulate the laser beam with something pseudorandom, and expect to see it on the other end... so noone simply replaces your beam, or even redirects it..

About This Instructable




Bio: Hi there! My name is Patrick, and I am an electronics engineering technician who works full time as a lab tech, and part time as ... More »
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