Flexible circuits and wearables seem to be all the rage these days. We’ve got conductive paint, glue, and even thread. So how about conductive silicone? Well, as it turns out — it’s not that hard to make.
[Andrew Quitmeyer] has been researching flexible circuits for a while now, and recently stumbled upon an expired patent for flexible ignition cables, using carbon fibers mixed with a conductive silicone. He started playing around with it, and discovered that by dissolving pieces of carbon fiber in rubbing alcohol, letting it dry, and then mixing it into a 2-part silicone you get pretty good electrical conductivity. In fact, in the range of 40-150ohms, which is actually pretty darn impressive!
[Michael Mogenson] built Firefly Jar – a simple circuit to light up flickering LEDs inside a standard Mason Jar, to give away to friends and family for the holidays. Given it’s simplicity and through-hole design, it’s an ideal project for a “learn to solder” class or for those wanting to get started with building some really simple electronics. There’s just a handful of parts and putting it together shouldn’t take long. Given that he’s made available all of the source design files, it should be easy for others to spin off the project.
A 55mm solar cell fits on top of the 63.5mm diameter PCB, which in turn fits perfectly in a standard Mason Jar with a collar lid. When in the light, the solar cell charges two 1.2V NiMH batteries. This also switches off the P-channel MOSFET, turning the LED’s off. The LED’s are turned on only when the solar cell voltage is low and the Ni-Mh batteries are charged. A 2.1V LDO directly drives the two LEDs with built-in flickering circuits, eliminating the need for any further parts. Check out the video of the Firefly Jar below.
[gbaman] has figured out a simpler way to program the new Raspberry Pi Zero over USB without modifying the board. Why is this useful? One example which appealed to us was setting the Zero’s USB port up as a mass storage device. Imagine plugging in your Pi powered robot, dragging and dropping a Python script into the mass storage device that shows up, and pressing a button on the robot to run the new script. Pretty fancy for $5.00.
You can get the PI to emulate a whole range of devices from a USB MIDI controller to a simple USB serial interface. We’re excited to see what uses people come up with. Unfortunately the Pi Zero is still out of stock most everywhere as we wait for the next production run to finish. Though if you’ve got one, why not check out a few of our thoughts and experiences with the device!
What might you do with a few extra stereolithographic 3D printer parts? Why not make a galvo display and resurrect a couple of classic vector graphic games of yore? That’s exactly what [Matt] did. With a few extra Formlabs components and a Haskell implementation of Spacewar, [Matt] can kick back and blast his extraterrestrial foes on the surface of his Formlabs cover.
[Matt’s] source code drives the Form 2 controller board to output laser graphics on the surface of a Form 1 case. These parts might be a commodity for this Formlabs Engineer, but the output is nothing short of spectacular, given the game and USB drivers were put together from scratch. In case you want to give the Haskell source code a try, [Matt’s] kindly included an alternative software-only display using OpenGL.
Unless you’ve just upgraded from Form 1 to Form 2, odds are pretty low that you can pull this one off without breaking either your printer or your wallet. Fortunately, [Alvaro] has paved the way with a stellar galvanometer display that began as a few parts from eBay. At last! Once our Formlab printer warranties expire, we’ll know where to start looking for parts for that mosquito killer we needed.
If I asked you to find the area of a square, you would have no problem doing so. It would be the same if I asked you to find the volume of a cone or rectangle or any other regular shape. You might have to turn to Google to get the proper formula, but it would be a trivial process nonetheless. But what if I asked you to find the volume of some random vase sitting on a kitchen counter? How does one go about finding the volume of irregular shapes?
One way would be to fill the vase with much smaller objects of a known volume. Then you could add up the smaller volumes to get an estimate of the total volume of the vase. For instance, imagine we fill the vase with marbles. A marble is a sphere, and we can calculate the volume of each marble with the formula 4/3πr3. We count all of our marbles and multiply the total by the volume of a single marble and arrive at our answer. It is not perfect, however. There is a lot of empty space that exists between the marbles as they fill the vase. We are forced to conclude that our estimated volume will be lower that the actual volume.
It would be about this time when our good friend Isaac Newton would ask the question “What if you made the marbles smaller?” Reducing the size of each marble would reduce the empty space that exists between them as they pile up in the vase, giving us a more accurate total volume. But how small? Is there a limit to how small we can make them? “Do not trouble yourself with the limit.” says [Newton]. “You will find that as you make the marbles smaller and smaller, you will begin to converge on a single number – and that number will be the exact volume of your vase.”
Reducing the size of the marble to get a more exact volume demonstrates the idea of the integral – one of the two fundamental principles of The Calculus. The other principle is known as the derivative, which we explained in our previous article by taking a very careful and tedious examination of an arrow in flight. In this article, we shall take the same approach toward the integral. By the end, you will have a fundamental understanding of what the integral is, and more importantly, how it works. Our vase example gives you a good mental image of what the integral is all about, but it is hardly a fundamental understanding of it. Just how do you make those marbles smaller? To answer this question, let us look again at one of Zeno’s moving arrows.
Since you’re going to have to be flying your “drones” indoors anyway in the USA, at least in the US Capitol region, you might as well celebrate the one freedom you still have — the freedom to re-flash the firmware!
The Eachine H8 is a typical-looking mini-quadcopter of the kind that sell for under $20. Inside, the whole show is powered by an ARM Cortex-M3 processor, with the programming pins easily visible. Who could resist? [garagedrone] takes you through a step-by-step guide to re-flashing the device with a custom firmware to enable acrobatics, or simply to tweak the throttle-to-engine-speed mapping for the quad. We had no idea folks were doing this.
Spoiler alert: re-flashing the firmware is trivial. Hook up an ARM SWD programmer (like the ST-Link V2) and you’re done. Wow. All you need is firmware.
The firmware comes from [silverxxx], and he’s written all about it on the forum at RCGroups.com. He’s even got the code up on GitHub if you’re interested in taking a peek. It looks like it’d be fun to start playing around with the control algorithms. Next step, Skynet!
Reading the forum post, it looks like you’ll have to be a little careful to get the right model quad, so look before you leap. But for the price, you can also afford to mess up once. Heck, at that price you could throw away the motors and you’d have a tricked-out ARM dev kit.
In the summer of 1929, it would probably have been hard for the average Joe to imagine the degree to which his life was about to change. In October of that year, the US stock market tumbled, which in concert with myriad economic factors kicked off the Great Depression, a worldwide economic disaster that would send ripples through history to this very day. At its heart, the Depression was about a loss of confidence, manifested in bank failures, foreclosures, unemployment, and extreme austerity. People were thrust into situations for which they were ill-prepared, and if they were going to survive, they needed to adapt and do what they could with what they had on hand. In short, they needed to hack their way out of the Depression.
Social Hacking: Welcome to the Jungle
One reaction to the change in the social contract in the 1930s was increased vagrancy. While homelessness was certainly thrust upon some people by circumstances – in the depth of the Depression in 1933, something like 25% of men were unemployed, after all – life on the road was clearly a choice for millions. A typical story was that of the bored teenage boy, facing no prospects for a job and wishing to relieve his large family of the burden of one more mouth to feed. Hitting the road with a few possessions in his “bindle,” he learned the craft of life on the road from more experienced vagrants. And thus another hobo was created.
The popular image of the hobos as unique to the Depression is a little awry. Economic upheaval certainly swelled their ranks, but in America, hobos had first appeared after the Civil War, with war-weary veterans riding the rails looking for work. By the time the Depression hit, there was an extensive hobo culture in the United States, complete with its own slang and a rough code of ethics.
Hobos were top of the heap in the vagrant hierarchy, the “knights of the road.” They were migrant workers, generally unskilled, willing to stay in one place for a paying job but unwilling to commit to settling down. When the job was done or he had made enough money, he moved on. Tramps were the next step down – wanderers who were willing to work but only when absolutely necessary. Lowest in the pecking order were the bums who stayed put and relied on the kindness of strangers for their survival. Regardless of rank, all the vagrants had one thing in common – the road. More or less constantly on the move, they had to quickly learn how to provide for themselves without the creature comforts, which before the Depression hit had begun to include many modern conveniences.
Cooking arrangements were one thing hobos excelled at, whether on the road or in one of the many hobo camps, or jungles, that sprung up at railroad crossings outside of towns. A campfire in a ring of rocks is the traditional view of outdoor cookery, but the hobos quickly learned that it’s not terribly fuel-efficient. One solution to this problem was the hobo stove, an ancestor of the rocket stove. Relying on convection to draw a huge volume of air into a combustion chamber, hobo stoves were easily fabricated from tin cans and other metal scraps that were easy to come by in a world before recycling and large municipal landfills. Most were assembled on the spot and served for a meal or two before being abandoned, but some actually had insulation between double walls and clever arrangements of the fuel shelf to feed automatically as the fuel burned away. Scraps of wood, pinecones, newspapers and cardboard – a hobo stove will eat almost anything, and burn hot enough that even damp fuel isn’t a problem.
Often finding himself with time on his hands, many a hobo kept himself busy with arts and crafts projects in camp. Making hobo nickels was a popular way to pass the time, and often resulted in a trade item far more valuable than the base value of the starting material. The Indian head figure on the US Buffalo nickels of the day were modified with tools fabricated from old nails and files; metal was pushed around the coin to create features on the figure, usually a bowler hat and facial hair. A ‘bo could trade the miniature bas-relief sculpture for a good meal; today genuine hobo nickels from the Depression era command high prices from collectors.
Radio: Razor Blades and Copper Pipe
Unless the hobo was flopping in town or at a really well-equipped jungle, chances are pretty good he wasn’t listening to the radio too much. From our 21st century outlook, it’s sometimes hard to appreciate how new and exciting radio was and the impact it had on everyday life in America during the Depression. Radio connected the nation in a way no other medium ever had. That the Depression did not kill this infant technology in its cradle is a testament to both its power as a medium – families would stop making payments on almost everything else so they could keep their radio sets – and to the tenacity of early electronics hobbyists, who learned to keep radios alive and even to fabricate them from almost nothing.
Although tube-type superheterodyne receivers were widely available all through the Depression, crystal sets were still a popular and sometimes necessary hacker project during the Depression. Relying on nothing more than a tuned circuit and a detector connected to an antenna and high-impedance headphones, a crystal set was able to pick up strong AM broadcasts and sometimes even shortwave stations. The earliest detectors were crystals of galena probed by a tiny “cat’s whisker” wire, but metal oxides could also form the necessary rectifying junction, leading to detectors built out of razor blades and safety pins. Crystal radio skills would serve many a Depression-era farm boy well during the next decade as they went off to war in Europe and the Pacific; there they created foxhole radios to listen in on broadcasts without the risk of a more sophisticated radio set, whose local oscillator could be detected by the enemy.
Receivers weren’t the only area in which Depression-era hackers made an impact. As commercial broadcasting took off, so did amateur radio, and few commercial transmitters were available to satisfy the burgeoning ham market. Depression-era hams had to home-brew almost everything and came up with some beautiful designs that modern glowbug hams recreate with loving attention to detail. A popular transmitter back in the day was based on the Hartley oscillator (PDF link). Using only a single triode tube and a tuned circuit with coils wound from 1/4″ copper tubing, Hartley transmitters could be built on a literal breadboard from scraps and widely available parts. Tuned to the 40- or 80-meter band, or even down to the 160-meter band, a Hartley or the closely related Tuned-Not-Tuned (TNT) or Tune-Plate-Tuned-Grid (TPTG) continuous-wave (CW) transmitters could put out enough power to work coast-to-coast contacts, or QSOs. Modern hams pay homage to the Depression-era pioneers of amateur radio with regular “QSO Parties” using replica Hartleys – most with bypass capacitors to keep the lethal voltages their forebears had to deal with off the coils.
The Great Depression lasted through the 1930s in America, finally dissipating just before the country mobilized for World War II. With factories suddenly working beyond capacity to supply the war effort, unemployment figures quickly plummeted, and the austere practices of the Depression were generally rolled back. Hobo culture declined and amateur radio was shut down by the federal government for the duration of the war, but neither the war effort nor full employment could kill the hobo spirit — modern hobos still ply the rails to this day. And the skills and mindsets developed by Depression-era social and electronics hackers paved the way for a lot of what was to come in the post-war years.