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
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.