Laser Tripwire Alarm System Uses Mirrors To Increase Coverage


Instructables user [EngineeringShock] has been hard at work building a laser trip wire security system, complete with a combination lock. The security system works just like you see in the movies, employing an array of mirrors to bounce the laser across an opening several times in order to secure the space.

A PIC18F1220 micro controller sits at the center of the alarm and handles the majority of its functions. It takes input from the laser detection circuit, triggers the buzzer, as well as arms and disarms the entire alarm system. An LS7222 digital lock handles the passcode verification side of things, taking input from a 16-button matrix keypad, and telling the PIC when the proper code has been entered.

As you can see in the video below, the alarm system works and the buzzer is quite loud. There is one small problem however – the alarm only arms itself after the proper code has been entered and the lights have been turned off. The light sensing circuit he uses is too sensitive and can only operate in darkness, though he discusses the ability to add a more accurate sensing solution.

If you are interested in reading more about laser tripwire security systems, check out this similar passcode-based system, this alarm system built into a toy, and this Arduino-based alarm system.

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Laser Camera Sees Around Corners

After reading over the proceedings of the 2005 SIGGRAPH, [Dan] realized he could reproduce one of the projects with $50 worth of equipment and some extreme cleverness.

[Dan]’s dual scanning laser camera operates by scanning a laser across an object. The light reflected from the object illuminates a flat surface, and this light is measured by a photocell. After measuring the resistance of the photocell, an image can be reconstructed from the light reflected off the flat surface. The result is quite ingenious, and we’re very grateful [Dan] gave us a great walkthrough with the code and theory of operation.

The project was covered in this Slashdot story a from a few years ago, and we’re surprise no one has bothered to cobble this project together. It’s a very simple build – two servos to control the x and y axes of the laser scanner, a photocell, and an ATMega board. Dan says the microcontroller isn’t even necessary, and this ‘remote imaging’ could be done with an ADC hooked up to a parallel port.

[Dan] was kind enough to to give us a video of his contraption in action. A very nice build from a very accomplished guy.

Nixie Tube Conference Badge


Maker [Jeffrey Gough] was recently asked to construct a set of badges for the TROOPERS11 IT security conference held in Heidelberg last month. The badges were to reflect the overall theme of this year’s conference – personal progression, education, and striving to become better IT security professionals. To do this, he designed a badge that tracked a conference attendee’s participation in various activities.

The badge sports a center-mounted nixie tube that is used to show the attendee’s score. It is worn around the neck using a Cat-5 cable that acts as a LANyard as well serves as a power switch for the badge. The badge can be plugged in to a special programmer used by conference organizers, which updates the attendee’s score after completing each activity.

[Jeffrey] made sure to add all sorts of extra goodies to the badge, including a capacitive touch button that displays a secret message via the nixie, as well as plenty of hole and SMT pads so that hackers could get their game on.

Overall, the reception of the badge was extremely positive. All of the conference attendees had lots of fun exploiting the badges as well as adding components such as LEDs and speakers.

Continue reading to check out a quick demonstration video [Jeffrey] put together, highlighting the badge’s features.

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Xerox Phaser Drum Unit Hacked, Lives To Print Another Day

Faced with a printer that would stop printing for no apparent reason, Finnish pirate and hacker [Janne] decided he had had enough. After doing a bit of research, he disassembled the drum assembly and replaced some components. The end result? Supposedly ‘broken’ printers started working again.

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Open Hacker Conference Badge Project Needs Your Help!

[Aestetix] writes in to tell us that the OpenAMD (Attendee Meta-Data) project is working on a new revision of their hardware, to be debuted at CCC Camp this fall.

For the uninitiated, OpenAMD combines an Active RFID tracking system with social networking, and is completely open-source. You walk into the conference, put on the OpenAMD badge, and suddenly you can see yourself as a dot moving around on a map. Or you can log into the social networking site, create a profile, and watch as your personal information is pulled into the mesh, which then tells you talks you might like, people you might like, where those people are, and more. There’s even an open API where you can create your own ‘killer’ apps, which may include games or other interesting aggregates of the attendee information.

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Auxiliary Battery Pack For Field Operations


Ham operator [Ken – wa4mnt] wrote us to share a small project that he uses nearly every time he goes out in the field. His portable sealed lead acid battery pack (PDF) always ensures that he has a 12v power source at his fingertips, both for fun as well as in emergency situations.

The battery pack is pretty simple, and includes a 12v, 17ah battery strapped into a light aluminum chassis which he fabricated. The battery is secured with zip ties, so it can easily be swapped out or replaced without much fuss. The frame also sports a tiltable 4w, 17.5v solar panel that keeps the battery topped off and ready to go at all times. He stuck a voltmeter to the top of the battery to keep an eye on things, and he employs a 10A fuse to make sure he doesn’t fry any sensitive radio components should something go wrong.

The battery pack is pretty compact when you think about it, and we imagine it would be great to have on hand for a wide array of outdoor activities. Even if you’re not into Ham field operations, it’s hard to argue with its usefulness during power outages.

[Ken] doesn’t appear to have any published plans for the chassis or the electronic portion of the pack, but we’re pretty sure he would share if asked.

Mechanical Twitter Feed For Offline Reading


Twitter can be a great tool for keeping up to date with your favorite person/company/band/etc. You can find a Twitter client for just about anything that plugs in these days, but sometimes we find that we simply need a break from our computers and smart phones – even if just for a few minutes. What happens when you want to unplug, but still need to know what everyone is up to?

[Patrick Dinnen] asked himself the same thing, and decided that the solution was a mechanical Twitter feed display. The display consists of a static user list strung up against the wall, with a mobile speech bubble mounted next to it. The bubble moves to the user who has most recently updated their status (presumably using a pair of servos), and uses a projector to display their messages. The effect is pretty neat, and it still allows you to get your Twitter fix without staring blankly at your computer screen or smart phone.

We think it would be even cooler if it used a projector on both sides, enabling it to dynamically shuffle through users and status messages at the same time. [Patrick] says that for right now it is merely a proof of concept, so there is no telling how he’ll tweak it going forward.

Continue reading to see his mechanical Twitter feed in action.

[via Adafruit]

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