LTC3105 and LTC3109 energy harvesting chips

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[Shahriar] devoted the lastest episode of The Signal Path to looking at energy harvesting chips. These parts are designed to gather energy from non-traditional sources as efficiently as possible. The full episode, which is embedded after the break, is about one hour long. It starts with a bit of background about the nature of these parts, and a brief overview of the wide-range of chips available. Each is suited for a different type of energy source.

He moves on to test and explain the LTC3105 and the LTC3109. The former is shown above on a development board. [Shahriar] hooks it up to his bench equipment to compare its performance to the published specs. This culminates in a circuit that uses a solar cell as the source with a super capacitor used as storage. The latter is connected to a Peltier cooler and used to convert the potential energy of ice cubes to electrical energy which charges his iPhone for about thirty seconds. This might be useful in that Peltier generator we saw last week.

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Print your own 30 round AR15 magazine

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Here’s a 30 round magazine for an AR15, made just in time to add to the national conversation over things that look scary.

This magazine is the product of Defense Distributed who have previously graced the front page of Hackaday with their 3D printed scary bang bang machine. While continuing to work on their WikiWeapon – a gun printable on a home-built 3D printer – the team decided they could subvert more obtuse gun laws by making their own high-capacity magazine.

The magazine is printed on an extremely expensive commercial 3D printer, but the team is working to make it printable on more affordable models. The prototype magazine survived unloading a full 30 rounds. Video demo of that after the break.

Also on Defense Distributed’s DEFCAD is a sound moderator for paintball and air guns. While the design isn’t yet finalized for those big scary assault weapons, it should be possible to modify it for the big guns.  One of their next projects is a stock, hopefully one that includes a hinge.

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Retrotechtacular: The differential

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Any video that starts off with two minutes of motorcycle formation riding has got to be good. If the grainy black and white video didn’t tip you off that this was made in a different time the helmetless riders standing on the seats of moving motorcycles certainly would have. But there is a purpose to this exposition. A single line of motorcycles riding shoulder to shoulder as they go around a curve illustrates why a differential is necessary and soon after you’ll find out how one works.

Two wheels mounted on one axle need to turn at different speeds as a vehicle goes around a corner or one of the wheels must slip to accommodate the speed difference. The differential is necessary to allow for these different turning rates while still letting both wheels connect to the power train. We were surprised to learn from the video after the break that early automobiles got around this issues by powering only one of the four wheels.

This instructional video is a prefect compliment to the fluid coupling video we saw in the last installment of Retrotechtacular.

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Converting a weather station kit for wireless data harvesting

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Everyone loves getting something you can play with as a Christmas gift. [Thomas] was the lucky recipient of an Elektor USB weather station kit. But the fun didn’t end once he had assembled everything. He went on to hack the device for wireless data collection.

Shown above is the weather station board connected to the transmitter. The red board with a tiny antenna to the right is a Rovio RN-VX module. It is capable of transmitting serial data to its twin on the receiving end of the setup. The weather station is pretty easy to connect to the transmitter since it feeds serial data to an FTDI USB chip. [Thomas] simply connected power and ground, then added a jumper from the board’s TX pin to the Rovio’s RX pin. The receiving end uses a serial-to-USB converter — getting a signal for its RX pin from the TX pin on the Rovio receiver board.

We know from other projects that these radio modules can connect to a WiFi AP. Perhaps a future revision of [Thomas’] hack will allow the weather station to communicate with his server over the network, doing away with the need for a standalone receiver.

Coffee table arcade cabinet

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Get some Pac-Man fever while sitting on this couch thanks to the arcade rig built inside of the coffee table. The controls are a bit more sparse than more dedicated MAME rigs, but you should still be able to play most of the classics with four buttons and a joystick. After all, you need to reserve some room to put your feet up when you’re not gaming.

[Manny Flores] started the project with a Lack table from Ikea. The top is anything but solid. After tracing the outline of his LCD screen and cutting through the surface he discovered this is more of a beefed of cardboard than it is wood. The honeycomb of paperboard inside the surface of the table makes it really easy to clear out some space. In fact, when it came time to add the arcade buttons he just used a utility knife to cut the openings. Inside you’ll find a Raspberry Pi which interfaces with the buttons and joystick via an iPac USB controller board. A set of powered speakers mounted on the underside complete the design.

[via Adafruit]

Hacking grandfather clock accuracy while it’s still ticking

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[Keith] got his hands on a few grandfather clocks. Apparently the price tag is greatly reduced if you are able to get them second-hand. The mechanical timepieces require weekly winding, which is a good thing since you’ll also need to correct the time at least that often. But this drift got [Keith] thinking about improving the accuracy of these clocks. He figured out a high-tech way to adjust the timepiece while it’s ticking.

The first thing he needed was a source of super-accurate time. He could have used a temperature compensated RTC chip, but instead went the more traditional route of using the frequency of mains power as a reference. The next part of the puzzle is to figure out how to both monitor the grandfather clock and make small tweaks to its pendulum.

The answer is magnets. By adding a magnet to the bottom of the pendulum, and adjusting the proximity of a metal plate positioned below it, he can speed up or slow down the ticking. The addition of a hall effect sensor lets the Arduino measure the rate of each swing and calculate the accuracy compared to the high voltage frequency reference.

Little sister’s turn for hobby electronic party favors

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[Ian Lee, Sr.] made something special for his daughter’s birthday party. It’s pretty common for girls of this age (this was her 5th birthday) to be enthralled with stories of princesses so he made a blinky princess wand for each party guest. The motivation came when she asked what special thing he was going to do for her celebration. You may remember seeing the LED badge kits that were featured at her brother’s party earlier this year. From the look of the party guests he surely satisfied her desire for a memorable party.

The project is very inexpensive, extremely easy to assemble, and might make a perfect kit for supervised Kindergarteners. It’s basically an LED throwie with a stick and a feather added. [Ian] used CR2032 batteries along with an LED and current limiting resistor to light things up. He clipped off one leg of the LED and replaced it by soldering the LED in place. The remaining leads were then pressed to either side of the coin cell and the whole thing was shoved into a slit cut in the end of a balloon rod. The whole thing was wrapped tightly in with a rubber band before being crowned with a ping pong ball. To trim it out he hot glued a feather at the base of the ball.

The only think that has us worried is what he’s going to do next year to top these parties.