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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Waking Up With The (fake) Sun

July 9, 2010 by Mike Szczys 38 Comments

[Bogdan] has some trouble getting up in the morning. A blaring alarm will do the trick but that’s no way to start the day. To get him through the dark winter months he wanted to try a sunrise simulator. He patched into the alarm signal of his bedside clock, intercepting the command from the clock’s microprocessor and using it as an input for his own ATtiny13. From there, the tiny13 gradually brightens a 150W halogen lamp using a triac until his room is as bright as a July morning. A signal is then sent to the alarm clock’s audio amplifier to turn on the audible alarm. He’s got the system set for a 20-minute sunrise so it’s just a matter of programming his alarm 20-minutes early than the ‘I absolutely have to get out of bed now’ time.

Intruder Alarm McDonald’s Toy Hacking

April 8, 2010 by Caleb Kraft 14 Comments

[malikaii] needed to set up some kind of tripwire style alarm system for his office. His bosses kept sneaking in to find him slacking. So, like any loyal hacker, instead of just working harder he built an alarm system. After a failed attempt to recreate an IR alarm circuit he found on the web and built from old appliance parts, he found the Hack a Day article about harvesting McDonald’s toys. The end result was a fully functional IR detecting alarm for the office doorway. This is pretty simple really, the best kind of hack.

PC Fan Failure Alarm

April 6, 2010 by Caleb Kraft 29 Comments

[youtube=http://www.youtube.com/watch?v=Jznl8U9zzKM]

Need to monitor not only if a fan is running, but if it is running fast enough? Check out this PC fan failure alarm circuit. After several failed attempts using various circuits, they settled on a Schmitt trigger. They even show a couple variations including a manual reset and a relay instead of a buzzer.

[via HackedGadgets]

Time Delay Door Alarm

March 6, 2010 by Caleb Kraft 21 Comments

Ever accidentally left your front door ajar and had a pet escape? [BlackCow] came up with a simple solution to this problem. The circuit is fairly rudimentary but a great example of using the basics to get the job done. Now, instead of having an alarm that sounds as soon as the door is open, he has a 30 second delay. This helps avoid the “boy who cried wolf” effect also known as the “vista security warning” effect of being bothered too many times for a non issue. We also have to say that we like his taste in blog layouts.

[via Hacked Gadgets]

Gentle Wake Up Alarm

February 22, 2010 by Caleb Kraft 37 Comments

[Michiel], unsatisfied by his Phillips wake up light, decided just to make his own. He really wanted programmable weekend alarms as well as an easier to find snooze button. At first, his circuit was not reliable enough, losing several minutes per hour, but he gutted another alarm for the 1Hz crystal. After some carpentry, his final alarm ended up quite nice. After so many aggressive alarm clocks, it’s nice to see that not everyone needs to be assaulted out of bed.

Correction: apparently, there’s no 1Hz crystal. That was a guess on my part. -[Caleb]

[via Hacked Gadgets]