Passcode Protected Laser Tripwire Alarm System

March 11, 2011 by Mike Nathan 13 Comments

laser_tripwire

Sometimes security doesn’t need to be overly complex to be effective. Instructables user [1234itouch] recently built a simple laser tripwire alarm that can be mounted virtually anywhere, complete with a keypad for disarming the device.

He mounted a photo cell in a project box, along with an Arduino and a 12-button key pad. A laser pointer is aimed at the photo cell from across a gap, which results in a steady voltage being read by the Arduino. When the laser beam is broken, a drop in voltage is detected, and the alarm sounds until you enter the proper pre-configured passcode. Entering the passcode triggers a 15 second grace period during which the the alarm cannot be tripped again.

It might not be built with triple-thick steel doors and thermo-sensors, but it’s a simple device for simple needs. In its current form it could be pretty useful, and with a little reworking, there are a wide range of things it could be used for.

Continue reading to see a demo video of the tripwire alarm, and be sure to check out these other tripwire-based security systems.

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Edison Clock Uses Ammeter Plus Bulbs To Set Alarm

January 26, 2011 by Mike Szczys 8 Comments

This is the Edison clock, designed by [David Krawczyk]. It shows time in the same way as the multimeter clock, regulating power to two analog needle meters. The feature that makes this one a bit different is the alarm. You can see the series of holes on the front of the base. These have a small light bulb socked in each, and correspond to hours and 5-minute increments. Insert two bulbs to set the alarm time, and make sure that the alarm knob points to ‘on’. As you can see above, the alarm has been set to 8:15. Hidden on the last image of the article above is a PDF with just a bit more explanation. Still, much has been left out so if you replicate this clock we want to hear about it.

[via Gizmodo and Walyou]

Alarm And Wake Up Light

December 22, 2010 by Mike Szczys 18 Comments

On the shortest day of the year wouldn’t it be nice to wake up to a bright room? This alarm clock with an integrated wake-up light is one way to do just that. It has some nice features, like a wood veneer that allows the seven-segment display to shine through, but hides it when the display is turned off. There’s also a feature to adjust the color based on ambient room temperature (another way to dwell on how cold it is in your bedroom).

A CC1101 RF chip came to the party, but we can’t figure out what it’s purpose is in this circuit. If you can shed some light on its involvement please do so in the comments.

[Thanks Eric]

Alarm Clock Learns New Trick, Opening Doors

September 1, 2010 by Jakob Griffith 21 Comments

Waking up at 5:30 in the morning. [Mark Stead] didn’t like the idea either when his chickens started crying to be let out. One simple solution obviously is to eat the chickens build an automatic door opener. The mechanism starts out with an old style mechanical alarm clock, add a geared motor with some creative switch work to pull open the door, weather proof the entire thing, and done. [Mark] even modified the setup later to work with vertical doors. No MCU required for either.

Pair this with an automated feeder system, egg gathering and cooking setup, and you’re half way to having your breakfast ready for you when you wake up in the morning – around noon like the rest of us.

[Thanks MS3FGX]

Burglar Alarm In A Zippo Lighter

August 26, 2010 by Caleb Kraft 9 Comments

surprisingly awesome

[Madmanmoe64] has really done a fantastic job with this burglar alarm built into a zippo. He crammed a picaxe microcontroller, some IR LEDs, an IR sensor, a battery and various switches in there quite well. It almost closes perfectly, something we think he could remedy if it really bugged him that much.

It has several modes, all initiated by a different sequence of button presses. There is the proximity alarm, which sounds when something moves very close. The reverse proximity alarm which sounds when you remove something from its immediate vicinity. A doorbell mode, and a silent alarm mode. Check out the video after the break to see it in action.

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Modem Used In An Alarm System

August 25, 2010 by Mike Szczys 22 Comments

This alarm system senses motion and then alerts you by phone. [Oscar] had an old external modem sitting around and, with some wise hardware choices, he came up with a simple circuit to use it. First up is the PIC 16F628A chosen because it doesn’t require an external crystal. This connects with the modem via a DS275 RS232 transceiver because it requires no external parts for connection. The final portion of the puzzle is a PIR sensor that triggers a pin interrupt in the sleeping PIC, which then dials your number to alert you. It doesn’t look like anything happens other than your phone ringing, but that’s enough for a simple system. We’re just happy to see how easy it was to use that modem… time to go hunting for one in dreaded junk trunk. Don’t miss the clip after the break.

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AVR Guardian Filters Out Dogs

July 19, 2010 by Mike Szczys 29 Comments

Cats and dogs can get along quite nicely when they are raised up together. The problem with this type of arrangement tends to be keeping dogs out of the cat box and away from the cat food. [Ryan Meuth] tried out a simple electronic barrier to keep the dog away. It uses an IR transmitter and receiver to shine a beam of invisible light across the doorway to his cat room. In the demo after the break you’ll see that he took steps to make sure the cats don’t set off the alarm. The beam of light is set high enough that their bodies don’t get in the way, and the firmware measures the amount of time the beam was broken in order to avoid false positives caused by the cats’ tails. If the dog does try to get into the room it will break the beam and set off a high-pitched alarm sound.

It’s interesting that the dog doesn’t like the sound but the cat’s don’t seem to be scared of it. Also, we’ve got a less-than-ferocious feline that would love to chew on the cord that connects the two modules. Still, it’s a solution that works for [Ryan] and could be incorporated into an automatic feeder to keep the dog away from feedings while you’re out of the house.

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