The Practical Potato Cell

October 18, 2015 by James Hobson 32 Comments

Potato batteries, lemon batteries, they’re all good fun for the classroom — but is there a way of making them better? [Marcel Varallo] decided to give it a shot — and we gotta admit, it’s a pretty cool idea!

Normally for these fruit and vegetable batteries you poke some leads into the battery, connect it to a clock, and bob’s your uncle. But what if we made them resemble batteries? [Marcel] took some copper pipe, cut it down to size, and poked it through a potato. Now he had a potato-cored, copper tube. Stick a zinc nail in the middle, and you’ve got yourself a battery cell! Or as [Marcel] likes to put it.. a Mar-Cell. Or the more scientific term.. the Solanum tuberosum based electron differencer V1.0.

Each potato cell produces approximately 0.8V, so if you throw eight in series, you’ll have the equivalent of a 6V battery, just maybe not the same mAh rating.

For another cool way to demonstrate electricity to youngsters, we love this lemon battery hack — it’s actually quite elegant.

Raspberry Pi Tablet Based On Sailfish OS

October 18, 2015 by Rud Merriam 21 Comments

There are so many hacks in this project it’s hard to know where to start. So let’s start at the SailPi tablet which is a Raspberry Pi running the Sailfish OS on an LCD touch screen powered by a cell phone battery pack. The design looks more like a high-tech sandwich with the Pi in the middle than a tablet. Despite the appearance it works, at that’s what counts. The creator, [Aleksi Suomalainen] expended a lot of effort pulling all the pieces together on this project.

The Sailfish OS project is targeted at creating a new OS for mobile devices, especially cell phones. It is open source which invites developers to contribute to the project. The touch screen user interface is designed for ease of use by gestures from one finger on the hand holding the phone.

[Aleksi] ported Sailfish to a Pi 2 during a hacking week. He’s shared the code for it on his blog. During the hack week he played with accessing the GPIO on the Pi to flash an LED. To get you up and running quickly he provided an image you can load onto an SD.

It appears the Pi is finding a niche for OS hackers in addition to the hardware hackers using the GPIO.

Don’t miss the demo after the break to see the OS running on the Pi. Continue reading “Raspberry Pi Tablet Based On Sailfish OS” →

Coke-Propane Rocket Blasts Off Without Ignition

October 18, 2015 by Mike Szczys 85 Comments

Everyone’s seen the Diet Coke and Mentos “experiment” that ends in a brown eruption. But have you seen the Coke and Propane ~~experiment~~ insanity that results in a rocket launch? As [Itay] pointed out when he sent us the tip, this doesn’t need to be lit. The simple act of turning the bottle upside down starts a powerful reaction without any ignition.

Of course it’s the how of this that tickles our brains, but let’s finish the setup. This starts with a bottle of Coke which is about 3/4 full. The head space is displaced by spraying propane into the bottle; propane is heavier than air. All that’s left is to turn the bottle upside down and pray it doesn’t smack anyone in the noggin as it takes off.

In trying to find an explanation for this phenomenon we came across a plausible answer on the Chemistry StackExchange. It points to the Mentos phenomenon combined with the temperature differential caused by the very cold propane. The answering user theorizes that tiny ice crystals form and when the bottle is turned upside down the cold propane and micro crystals rise through the warmer soda acting as a much more rapid catalyst than Mentos alone. Of course this is just a theory so please share your own ideas below.

We thought the folks who microwave stuff outside of a microwave enclosure had their fill of danger but this videos is also one of theirs. It should be no surprise that they also tried the experiment with an ignition source. That video is found after the break and should immediately convince you to never try any of this yourself.

Continue reading “Coke-Propane Rocket Blasts Off Without Ignition” →

FPGAs For The Raspberry Pi

October 18, 2015 by Brian Benchoff 101 Comments

FPGA development has advanced dramatically in the last year, and this is entirely due to an open-source toolchain for Lattice’s iCE40 FPGA. Last spring, the bitstream for this FPGA was reverse engineered and a toolchain made available for anything that can run Linux, including a Raspberry Pi. [Dave] from Xess thought it was high time for a Raspberry Pi FPGA board. With the help of this open-source toolchain, he can program this FPGA board right on the Raspberry Pi.

The inspiration for [Dave]’s board came from the XuLA and StickIt! boards that give the Raspberry Pi an FPGA hat. These boards had a problem; the Xilinx bitstreams had to be compiled on a ‘real’ PC and brought over to the Raspberry Pi world. The new project – the CAT Board – brings an entire FPGA dev kit over to the Raspberry Pi.

The hardware for the CAT Board is a Lattice iCE-HX8K, 32 MBytes of SDRAM, a serial configuration flash, LEDs, buttons, DIP switches, grove connectors, and SATA connectors (although [Dave] is just using these for differential signals; he doesn’t know if he can get SATA hard drives to work with this board).

Despite some problems with his board house, [Dave] eventually got his FPGA working, or at least the bitstream configuration part, and he can blink a pair of LEDs with a Raspberry Pi and programmable logic. The Hello World for this project is done, and now the only limit is how many gates are on this FPGA.

Continue reading “FPGAs For The Raspberry Pi” →

Guinea Pig Methane Power!

October 18, 2015 by James Hobson 44 Comments

Half-way around the world, a couple in Peru is harnessing the power of guinea pig poop, to generate methane for their farm. We couldn’t make that up if we tried.

The couple are a pair of retired plant physiology professors who have taken to running a sustainable agriculture program in their very own villa called Casa Blanca. It’s a beautiful set of gardens complete with a lab for research. But the most curious thing is the thousand guinea pigs they raise. They have a special shed for them with small compartments separated by brickwork. The guinea pigs eat specialized plant waste, and in turn, produce an astonishing 3 tonnes of fecal matter per month.

They use around 200kg of the excrement to power their very own bio-digester which in turn produces 3 cubic meters of methane per day which they use for powering their villa. The rest of it is used for fertilizer that they sell to local farms.

Continue reading “Guinea Pig Methane Power!” →

C++ Turns 30 – Looking Forward To The Future

October 17, 2015 by Rud Merriam 37 Comments

[Bjarne Stroustrup] introduced C++ to the world on Monday 14th October 1985 at the ACM annual conference on “The Range of Computing”. On its 30th anniversary [Bjarne] reviewed the history, his experience, and his thoughts on the future of the language in an interview. Also on that day the first edition of his book, “The C++ Programming Language” was released. It’s now available in a 4th edition. The title differed only in the “++” from the classic C book by [Kernighan] and [Ritchie] that graced the desktops of a multitude of C programmers.

The first versions of C++ were compiled with CFront, a compiler that generated C code which was then compiled as normal. Around the 1990s, it’s unclear when, numerous native compilers became available, notably for PCs, which lead to explosive growth from 400,000 users to an estimated 4.4 million today.

One of the frustrations [Stroustrup] expresses is how C++ is viewed by developers,

… a problem that has plagued C++ forever: Poor teaching and poor understanding of C++ even among its practitioners. There has always been a tendency to describe C++ as some odd variant of something else.

Soon the standards committee is meeting to discuss C++17 in Hawaii. Fair winds and bright skies look to be in the future of C++.

LED Pendulum Pulses Out Clock Face

October 17, 2015 by Rud Merriam 31 Comments

You have to admit [Dylan Rush’s] clock is a real swinger. Literally. You’ve seen the desk novelties where an arm with leds mounted on it sweeps out a message? [Dylan] did the same thing to make a clock but instead of drawing numbers, he actually draws an analog clock face. Y’know one of those round things with arms?

Behind the clock is an Arduino driving a MAX7219 LED controller. Using the MAX7219 was a challenge because it expects a grid of LEDs while the clock needs a linear array. [Dylan] used a line of individual LEDs wired to match what the controller wanted. A rotary encoder tells the processor the position of the arm so the Arduino sketch can determine which LEDs should be lit to show the time and clock face.