I wanted to take control of the lights on my Christmas tree this year, so I read everything I could about interfacing an LED matrix. The idea was to have a setup where I could turn individual lights on and off, and run a little program that did something more than your typical strand of lights. All of my Googling led me to the Maxim 7219 chip, which can control up to 64 LEDs using only 3 pins on the Arduino. I used one of Paul Badger's Arduino-compatible Bare Bones Boards to run the whole show.

If you get really ambituous, you can cascade multiple 7219s and LED matrixes, so you can have a lot of lights. But I ended up getting lazy, and only built one matrix of 64 lights. I followed the diagram on page 1 of tomek ness' tutorial to build the LED matrix (be sure to read this bug report for an important update). There may be better ways to do it, but I laid out the matrix as a web of wires, using wire strippers to cut into the wire and push some insulation out of the way before I wrapped each LED's leads around the exposed wire. Then I soldered it in place, put some heatshrink wrap around the joint, and ended up with a not-too-shabby LED matrix. Once that was done, I again turned to tomek's tutorial, and hooked the Arduino up to the 7219 and the 7219 up to the matrix. tomek also has some source code available that I was able to modify for my needs. You can find my code right here.

The video above gives you an overview of the project. After the jump, you can see a high-speed video showing how I put one of the rows together (stripping, soldering, shrinking). I'll post some more on this project soon--stay tuned for details on how I got this talking to my Nokia phone over Bluetooth.

Dingolishious tipped us off to a cheap way to receive power outage notifications, as well as remotely power-cycle electronics.

Our remote wireless site keep being unplugged or having the circuit trip from some combination of cleaning devices. I took a spare UPS and asked if we could get a $200 SNMP card for it so we would know when the power was off. Boss asked me if we could do it for less.

My solution: $70 IP Power 9200 delux. The IP Delux has 4 voltage input sensors, 4 current sensors and 8 web controlled switches. There is a 5v wall wart plugged into the switched part of the UPS running to a input. When the power goes out the ups kicks in running the POE and the wall wart turns off pin 1 on the IP Delux which sends me an email.

The added bonus is that the POE is now switched so if a AP on one wireless segment locks up I can go in one of the others and power cycle the POE remotely. IP Delux even hosts WAP so I could do it from the cheapest of cell phone web browsers.

I like the idea, and it's a cheap way to monitor power status with a bottom-end UPS. Take a normal "wall wart" 5vDC adapter, plug it into an outlet, and the 5 volt output raises and lowers the input logic pin on the IP Power or your own homebrew monitoring electronics - Link.

Smart Home Hacks author Gordon Meyer has been experimenting with using Twitter for automated notifications and has hacked it to monitor his home. Check out how he gets a Twitter alert to let him know someone's at his front door.

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• Smart Home Hacks