This LED table really ties the room together

led-matrix-table

Along with quadrotors, and portable game consoles, one of the hacks we never get tired of seeing is an LED matrix table. [Christian Enchelmaier] wrote in to share his take on the ever popular pixelated furniture, which we think came out pretty well (Translation).

Instead of going for a full-sized coffee table, [Christian] decided to keep things on the smaller scale his first time out, opting for an ottoman/end table nstead. He constructed a 16×16 matrix using RGB LEDs, encapsulating each one in its own “pixel”, as is common with these builds. [Christian] uses an Atmega 128 to run the show, displaying the current time and date, temperature, music visualizations, games, images, along with short videos. He also outfitted the table with an IR receiver so that he can control the table’s display from afar.

As of right now, [Christian] doesn’t have any video of the table in action, but there’s plenty in the way of pictures scattered throughout his build log to keep you busy in the meantime.

Wireless door alarms protect your stuff from afar

wireless-shed-alarm

[Webby] had a friend named [Steve], and as the story goes [Steve] had a few storage sheds on his property that were prone to break-ins.

While the doors were all fitted with a lock, wooden doors are only so strong, and are easy fodder for intruders bearing crowbars and the like. [Steve] was looking for a good way to know when people were poking their heads where they don’t belong, so he rigged up a set of simple alarms that let him know when it’s time to break out the shotgun.

On each of the shed doors, he installed a small IR proximity sensor wired up to a PIC12F675 microcontroller. The PIC is is connected to the “call” button a medium range wireless radio, so that whenever the IR sensor detects that the door is ajar, the PIC triggers an alert on the base unit.

The solution is simple, which we figure also makes it pretty reliable – nice job!

UPS with dead batteries reborn as a whole-house power backup

[Woodporterhouse] must deal with regular power black outs in his area. He recently converted a rack-mount uninterruptible power supply to feed a portion of his mains wiring. This one is not to be missed, since he did such a great job on the project, and  an equally remarkable job of documenting it. It’s one of the best examples we’ve seen of how to use Imgur as a project log.

The UPS still needs to have a case, but it doesn’t need room for batteries as he’s going to use a series of high-end sealed lead-acid batteries. So he cut down the enclosure to about half of the original size. That’s it mounted just above the new batteries. For this to work you need some type of transfer switch which can automatically patch between incoming line voltage, and the battery backup. He already had one of these switches in place for use with a generator, that’s it in the upper left. The entire system powers a sub-panel responsible for his essential circuits — the electronics in the home and a few lighting circuits (we’d assume this includes utilities like the refrigerator).

One really great feature that the reused UPS brings to the project is a monitoring card with a NIC. This way he can check the server to see if the UPS is being used, and how much of the 14 battery life remains.

[Thanks Ross via Reddit]

Apartment entry morse-code lock

[Bozar88] lives in an apartment building that has a buzzer at the front security door. Guests find your name on the panel next to that door, and press a button to ring the phone just inside the entry of each apartment unit. He decided to extend the built-in capabilities by adding a morse-code entry password which unlocks the security entrance automatically (translated).

He designed a circuit and etched his own board which fits nicely inside of the wall-mounted phone. It uses an ATtiny2313 to implement the coding functions. The device attaches to the intercom line in order to detect incoming button presses from the entry panel. There’s some protection here to keep the signal at or below 5V. The output is two-fold. The microcontroller can drive the microphone line using a transistor, which gives the user audio feedback when the code is entered. To unlock the door an opt-isolated triac (all in one package) makes the connection to actuate the electronic strike on the entry door.

The video after the break is not in English, but it’s still quite easy to understand what is being demonstrated.

[Read more…]

Harvesting and graphing wireless household utility meter info

Both our electrical meter and our gas meter are located in the basement of our house (we recently had the gas meter moved outside though). When people see this they always ask if the meter readers have to come inside once a month. The answer is no, these meters broadcast usage data which is picked up once a month when a utility company vehicle drives down the street. If you have wireless meters in your house, here’s a way to harvest and graph the wireless data so that you can analyze your usage patterns.

The hardware used here is a special USB dongle. This has a 900 MHz radio which picks out the packets from a reasonably large list of meter types, and pushes them through the USB interface. In the image above you can see that an Arduino with a USB host shield is used, but there are also drivers if you want to connect this directly to your computer.

We looked around and didn’t find any specifics on the hardware used on that board. But it can’t be all that hard to make one of these at home… the populated board seems to have just two ICs and a few passive components. Anyone up to the challenge of hacking together their own packet sniffer? We wonder if the Next HOPE badge could pull down the data?

[Thanks Chris]

Auto-locking pet door ensures that your outdoor kitty obeys its curfew

auto-locking-pet-door

If you’ve got a pet that roams freely in and out of your house, you may find yourself wanting to more closely regulate how they come and go. [tareker] was looking to keep his cat indoors at night when dangerous animals might be lurking in the neighborhood, but he didn’t want it to become a hassle.

He already had locking pet door on hand, which he hacked to regulate the egress and ingress of his cat automatically. He installed a pair of reed switches to determine if the door had been opened outwards (cat leaving) or inwards (cat returning), keeping track of the state using an Arduino Nano. A servo motor attached to the door’s frame locks the door whenever it detects the cat is safely inside after nightfall.

While he also added an RGB LED to reflect the status of the door, he’s considering connecting it to the Internet so that he can control and check the door from wherever he might be at the moment.