Continuing his tradition of making bits of wire and scraps of wood work wonders, [HomoFaciens] is back with a unique and clever design for an electromechanical encoder.
There are lots of ways to build an encoder, and this is one we haven’t seen before. Not intended in any way to be a practical engineered solution, [HomoFaciens]’ build log and the video below document his approach. Using a rotating disc divided into segments by three, six or eight resistors, the encoder works by adding each resistor into a voltage divider as the disc is turned. An Arduino reads the output of the voltage divider and determines the direction of rotation by comparing the sequence of voltages. More resistors mean higher resolution but decreased maximum shaft speed due to the software debouncing of the wiped contacts. [HomoFaciens] has covered ground like this before with his tutorial on optical encoders, but this is a new twist – sort of a low-resolution continuous-rotation potentiometer. It’s a simple concept, a good review of voltage dividers, and a unique way to sense shaft rotation.
Is this all really basic stuff? Yep. Is it practical in any way? Probably not, although we’ll lay odds that these encoders find their way into a future [HomoFaciens] CNC build. Is it a well-executed, neat idea? Oh yeah.
Josef Prusa’s designs have always been trustworthy. He has a talent for scouring the body of work out there in the RepRap community, finding the most valuable innovations, and then blending them together along with some innovations of his own into something greater than the sum of its parts. So, it’s not hard to say, that once a feature shows up in one of his printers, it is the direction that printers are going. With the latest version of the often imitated Prusa i3 design, we can see what’s next.
Working with high voltage is like working with high pressure plumbing. You can spring a leak in your plumbing, and of course you fix it. And now that you’ve fixed that leak, you’re able to increase the pressure still more, and sometimes another leak occurs. I’ve had these same experiences but with high voltage wiring. At a high enough voltage, around 30kV or higher, the leak manifests itself as a hissing sound and a corona that appears as a bluish glow of excited ions spraying from the leak. Try to dial up the voltage and the hiss turns into a shriek.
Why do leaks occur in high voltage? I’ve found that the best way to visualize the reason is by visualizing electric fields. Electric fields exist between positive and negative charges and can be pictured as electric field lines (illustrated below on the left.) The denser the electric field lines, the stronger the electric field.
Weak and strong electric fields
Ionization in electric fields
The stronger electric fields are where ionization of the air occurs. As illustrated in the “collision” example on the right above, ionization can happen by a negatively charged electron leaving the electrically conductive surface, which can be a wire or a part of the device, and colliding with a nearby neutral atom turning it into an ion. The collision can result in the electron attaching to the atom, turning the atom into a negatively charged ion, or the collision can knock another electron from the atom, turning the atom into a positively charged ion. In the “stripping off” example illustrated above, the strong electric field can affect things more directly by stripping an electron from the neutral atom, again turning it into a positive ion. And there are other effects as well such as electron avalanches and the photoelectric effect.
In either case, we wanted to keep those electrons in the electrically conductive wires or other surfaces and their loss constitutes a leak in a very real way.
The Convention on the Rights of Persons with Disabilities is being held this week at the United Nations in New York and Hackaday will be there. Sophi Kravitz is representing us as the conference discusses assistive technology.
Sophi’s panel is Thursday mid-day, entitled: Tec Talk: Brilliant New Designs in Assistive Technology, Ease of Use & Multimedia. The Hackaday community has become a world leader in thinking about new designs, implementations, and increased availability of assistive technologies. We’re really excited to have an organization like the UN recognize this trait. Congratulations on all of you who have spent time thinking about ways to make life better for a lot of people — you are making a difference in the world.
Most notable in this category is Eyedrivomatic, the eye-controlled electric wheelechair extension project which was selected as the winner of the 2015 Hackaday Prize. Awarded second prize last year was another notable project. OpenBionics designed an open source, easily manufactured, prosthetic hand. Hand Drive, a Best Product finalist from last year, developed a device to operate a wheelchair with a rowing motion. Like we said, the list goes on and on.
But of course our biggest accomplishments lie ahead. The 2016 Hackaday Prize is currently underway and again focusing on building something that matters. The current challenge is Citizen Scientist which focuses on making scientific experimentation, equipment, and knowledge more widely available. But on August 22nd we turn our sights to the topic of Sophi’s UN Panel as the Hackaday Prize takes on Assistive Technologies. Don’t wait until then, make this the summer you change peoples’ lives. Start your design now.
According to this article in the Guardian, Premier Farnell, the electronics parts distributor who is also a UK manufacturer of the Raspberry Pi, is going to be sold to Dätwyler. Their share price immediately rose 50%, closing at just under the Swiss firm’s offer price.
Farnell itself had been on a binge, according to Wikipedia anyway, buying up electronics distributorships in Poland, India, and the US. In 2009, they bought Cadsoft, the makers of Eagle CAD software. Now they’re being sold to another distributor.
Bloomberg writes this up as being just more consolidation in an already consolidating market. What any of this will mean for the hacker on the street is anyone’s guess, but we’re putting our money on it amounting to nearly nothing. But still, now’s the time to stock up on your genuine UK-owned, made-in-UK Pis before they become Swiss-owned and made who knows where.
The handheld screw driver is a wonderful tool. We’re often tempted to reach for its beefier replacement, the power drill/driver. But the manually operated screw driver has an extremely direct feedback mechanism; the only person to blame when the screw strips or is over-torqued is you. This is a near-perfect tool and when you pull the right screwdriver from the stone you will truly be the ruler of the fastener universe.
A Bit of Screw Driver History:
The kind of fun you can have with really cheap bits.
In order to buy a good set of screw drivers, it is important to understand the pros and cons of the geometry behind it. With a bit of understanding, it’s possible to look at a screw driver and tell if it was built to turn screws or if it was built to sell cheap.
Screw heads were initially all slotted. This isn’t 100 percent historically accurate, but when it comes to understanding why the set at the big box store contains the drivers it does, it helps. (There were a lot of square headed screws back in the day, we still use them, but not as much.)
Believe it or not the “Robertson” screw came out before the Phillips. Robertson just hated money and didn’t want to license his patents. So it’s only now that they’re in common use again.
Flat head screws could be made with a slitting saw, hack saw, or file. The flat-head screw, at the time, was the cheapest to make and had pretty good torque transfer capabilities. It also needed hand alignment, a careful operator, and would almost certainly strip out and destroy itself when used with a power tool.
These shortcomings along with the arrival of the industrial age brought along many inventions from necessity, the most popular being the Phillips screw head. There were a lot of simultaneous invention going on, and it’s not clear who the first to invent was, or who stole what from who. However, the Philips screw let people on assembly lines turn a screw by hand or with a power tool and succeed most of the time. It had some huge downsides, for example, it would cam out really easily. This was not an original design intent, but the Phillips company said, “to hell with it!” and marketed it as a feature to prevent over-torquing anyway.
The traditional flathead and the Phillips won over pretty much everyone everywhere. Globally, there were some variations on the concept. For example, the Japanese use JST standard or Posidriv screws instead of Philips. These do not cam out and let the user destroy a screw if they desire. Which might show a cultural difference in thinking. That aside, it means that most of the screws intended for a user to turn with a screw driver are going to be flat-headed or Philips regardless of how awful flat headed screws or Philips screws are.
Last week was Bsides London, and [Steve Lord] was able to give a talk about the devices that could pass for either a terrible, poorly planned, ill-conceived Internet of Things Kickstarter, or something straight out of the NSA toolkit. [Steve] built the Internet of Wrongs, devices that shouldn’t exist, but thanks to all this electronic stuff, does.
