AVR Guardian Filters Out Dogs

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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RFID Cat Feeder Helps With The Diet

[vimeo=http://vimeo.com/10896151]

When faced with having 2 cats with different dietary needs, [Landmanr] had to decide between manually stopping the cat on a diet from eating normal food, or building a dietary robot overlord. [Landmanr] chose the robot route. Using an old cd rom for the opening/closing mechanism, and RFID to distinguish between felines, [Landmanr] no longer has to stand guard while each cat eats. We particularly like the design of the antenna, so that the cat has to stick its head through it to activate the food opening. You don’t see that version in the video, but it is in the instructable.

Homemade Induction Generator

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

[Tyler LaVite] tipped us off about the generator he built. He combined a 5.5 horsepower Honda motor with a 10 horsepower electric bandsaw motor. To get an induction generator to produce alternating current you must feed electricity into the system to start the magnetic flux. [Tyler’s] solution was to include a bank of capacitors totaling 230mF which charge from the motor, then release back into the system. It’s not as green as the syngas generators we’ve seen since it still uses fossil fuel, but it reuses old parts sending less to the landfill.

A Pair Of Rube Goldberg Builds

[youtube=http://www.youtube.com/watch?v=KJfhgrNQnq4]

Here’s a couple of videos of Rube Goldberg machines that [Austin] built. The one above was completed in 2008 as a commercial contest entry for something-or-other. After the break you can see his build from 2007 which was just for fun. Both are quite nice additions to our collection of the complicated devices. We especially like the use of a sub-woofer to move a ping-pong ball and a vibrating cell phone for some wireless integration.

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Whole House Current Monitoring

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

[Debraj Deb] put together a current monitoring device that interfaces with the circuit box at his house. The system is controlled by a PIC 18F4520 and uses an LM358 Op-Amp to rectify the AC signal, as well as an MCP6S21 for range adjustments for detecting both high or low current loads. The data displayed on a character LCD includes average, RMS, and peak current. For now the data is saved to an EEPROM and can be dumped using a serial connection but [Debraj] plans to add a GSM modem so he can send energy use data to his cell phone.

[Thanks Ganesh]

Humble Homes, Simple Shacks

[Derek] puts the “hack” into the word shack.  We really enjoyed his “little yellow house” videos and shared them with you. After that, we discovered that he has published a book. No, he didn’t have it published, he published it. This guy is DIY through and through. “Humble Homes, Simple Shacks, Cozy Cottages, Ramshackle Retreats, Funky Forts (And Whatever The Heck Else We Could Squeeze In Here)” was hand produced by [Derek] himself.  It includes plans for a number of different shacks, ranging in size from too tiny for an adult to large enough to house a family. Not all of them are completely practical, but there are several that would make perfect workshops.

We got a copy of the book and have been getting lost in the seemingly endless illustrations. We highly recommend that you do so as well, if you have any interest in building from scrap, or unique structures. Even if you aren’t that interested in construction, the eclectic style and humorous rants about waste might just be enough to keep this book around.

Wireless Garage Door Indicator

[Sixerdoodle’s] garage door indicator tells him if the door is open or closed. He was inspired by the hack from last September but wanted to make it wireless. The setup uses an RF transmitter/receiver pair from Sparkfun, each controlled by an ATtiny13 microcontroller. We found his battle with RF interference from other devices to be interesting. Working out those bugs made for a great learning experience.