Self-regulating Water Heater


Most everyone is looking to live a little greener these days, with motivating factors typically being the preservation of the environment or financial considerations. [Fabien] fit into the latter category after realizing that about 25% of his monthly gas bill went to heating the water he and his family use each day. After a few calculations, he found that they only required hot water 68 of the 168 hours per week that the water heater was typically running. He figured the best way to save a few dollars was to rig the water heater to turn itself down when it wasn’t being used.

He connected a servo to the temperature control knob on his water heater, allowing it to be adjusted by a microcontroller. Having a rough idea as to the schedule his family keeps during an average week, he wrote an application for his Netduino that would actuate the servo when needed. A DS1307 real-time clock was wired to the Netduino for accurate timekeeping, so as to ensure [Fabien’s] wife never had to endure a cold shower.

It’s a shame that most water heaters don’t ship with some sort of programmable thermostat like you see with newer HVAC systems, but this hack is definitely a step in the right direction.

Continue reading to see his power-saving water heater in action.

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Repair Stuck IPod Nano Buttons

A system is only as strong as its weakest link and [Roberto Barrios] found that on the sixth generation iPod nano the buttons are the problem. It makes sense that the buttons would be exposed to wear since they’re movable parts. The issue isn’t one of contacts or springs wearing out, but how the buttons are assembled. Each consist of a couple of parts; the tactile piece that you see and press, the electrical switch which converts that force into an electrical signal, and a shim that bridges the gap between the two.

After two months of use the iPod [Roberto] was fixing had stopped responding to presses of the Power button. It turns out that the shims are attached with double-sided tape. Inspection of the internals revealed that the shim had slid to one side and no longer made contact with the electrical system. His solution was to remove the tape and clean off the goo, then reattach the shims using “two-part metal cement”.

With the shim back in place all is well but he made sure to execute this fix on all of the buttons before reassembly.

Force Feedback Rig

Strap yourself in, it’s going to be a bumpy ride. No really, if you don’t believe us, check out the video after the break of this bouncing and rolling game system. [Shawn McGrath] built it to compliment the gaming experience for Dyad, an indie game for which he is a developer. His wife was kind enough to demonstrate the machine, which utilizes one motor to rotate the display and cockpit, and another to add vibration to the experience. The parts for the system were mostly salvaged, with the addition of a projector for the display and a PlayStation SixAxis controller to sense the motion of the rig. The motors are powered by a 600W computer PSU and controlled by an Arduino. It helps that [Shawn’s] a developer because he was able to add feedback hooks to sync with the gameplay.

It’s not as intricate as the best flight simulators we’ve seen, but it will be fun for that next kegger.

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Gauss Weapons

This collection of gauss weapons use rare earth magnets to accelerate projectiles to damaging speeds. They work using the same concepts as a coil gun, but instead of just one projectile travelling along a length of guide track, there are many projectiles that work in a chain reaction. A series of magnets are placed at equal distances along the track. Each has a couple of large ball bearings on the muzzle side of the magnet. The first ball bearing is fired using mechanical force – like a spring mechanism – and accelerates as it approaches the magnet due to the attractive force of that magnetic field. When it impacts the magnet it sends one of the ball bearings on the opposite side down the track where it will accelerate when it nears the next magnet in the chain. The weapon above achieves a final projectile speed of about 68 miles per hour, breaking six fluorescent tubes in a row on at the right side of the apparatus.

Still prefer rail guns that use electromagnets? Check out this gauss pistol kit that is about as powerful as a BB gun.

Breaking The IClass Security

iClass is a popular format of RFID enabled access cards. These are issued to company employees to grant them access to parts of a building via a card reader at each security door. We’ve known for a long time that these access systems are rather weak when it comes to security. But now you can find out just how weak they are and how the security can be cracked. [Milosch Meriac] delved deep into the security protocol for HID iClass devices and has laid out the details in a white paper.

The most invasive part of the process was breaking the copy protection on PIC 18F family of chips in order to read out the firmware that controls card readers. This was done with a USB to serial cable and software that bit-bangs its own implementation of the ICSP protocol. After erasing and attacking several chips (one data block at a time) the original code was read off and patched together. Check out [Milosch’s] talk at 27C3 embedded after the break, and get the code for the ICSP bit banging attacks from the white paper (PDF).

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Kindle 3.1 Jailbreak


In the constant battle of manufacturers vs. jailbreakers, the turnaround time between a new software release and a new jailbreak seems to be getting shorter and shorter. [Yifan] noticed that a recent Kindle update broke a previous method of running unsigned code and started the search for a new workaround.

He eventually found a way to force the Kindle to run unsigned code based upon how the software update checked for digitally signed files. With that knowledge in hand, he discovered that he could trick the updater to run any file he wanted by exploiting the standard functionality found in the Unix ‘cat’ command.

On his site, [Yifan] provides more details, source code, and a compiled update file that performs the jailbreak for you. Much like the previous jailbreaks we have featured, it is perfectly legal to do, but you do risk voiding your warranty during the process.

[Picture via]

Building A Dead Mouse’s Switch


[Ned] had a mouse problem in a very uncomfortable place.

No, not like the back of a Volkswagen, in his ceiling. He wanted to put a mouse trap up there to take care of the critter, but knowing how nasty a tripped trap can be after a few days, he was hesitant. He recalled a project he saw online where a mouse trap was wired like a dead man’s switch and he got to work putting together a trap of his own.

He scavenged some parts from around the house and wired up the mouse trap so that a pair of LEDs were lit so long as the trap had not been sprung on an unsuspecting mouse. Once a mouse is caught in the trap, his circuit is broken, and the LEDs go off, letting [Ned] know it’s time to poke his head back up into the ceiling and clean things up.

While his trap is decidedly low-tech, we always enjoy seeing a cheap and easy solution to annoying, everyday problems.