Wood may seem like a soft, weak material if you’re used to working with steel, but to do good work, you’ll quickly learn you need your tools sharp. Buying and maintaining a good set of tools can be expensive for the home gamer, so [shopbuilt] put together an Instructable on how to sharpen your woodworking tools on a budget.
The trick is to use sandpaper. It’s a good quality abrasive material and is readily available. You’ll want a selection of different grits – low grits to get started, higher grits when finishing. The reason this is cheaper is that you can get a selection of 5-10 different sandpapers for under $20. Getting even a couple of decent sharpening stones wouldn’t be possible at that price. In the long run, they’ll last longer but this is a budget option we’re talking about.
Obviously you can’t just sharpen something with sandpaper – [shopbuilt] suggests mounting the paper to the flattest surface you can find. The use of a tempered glass panel from a fridge shelf is, in our mind, an inspired choice here. 3D printer enthusiasts have been using similar techniques for heated beds for the best part of a decade now.
Modern quadcopter flight controllers perform a delicate dance of balancing pitch, yaw, bank, and throttle. They can do this thanks to modern MEMS gyros and accelerometers. The job is easy when the motors, propellers and speed controllers are relatively well matched. But what if they’re not? That’s the questions [SkitzoFPV] set out to answer by building Frankenquad. Frankenquad is a 250 sized FPV quadcopter with 4 different motors and 4 different propellers. The props are different sizes from different manufacturers, and even include a mix of 3 and 4 blade units. If all that wasn’t enough [SkitzoFPV] used 3 different electronic speed controller. Each speed controller has a micro running different firmware, meaning it will respond slightly differently to throttle inputs.
Keeping all this in check was [SkitzoFPV’s] branded version of the Raceflight Revolt R4 flight controller. The Revolt is powered by an STM32F4 series ARM microcontroller. Most of these controllers run variants of the cleanflight open source flight control software. The question was – would it be able to handle the unbalanced thrust and torque of 4 different power combinations?
The flight tests proved the answer was a resounding yes. The quad hovered easily. As the video shows [SkitzoFPV] went on to burn a few holes in the sky with it. Admittedly [SkitzoFPV] is a much better pilot than any of us. He did notice a bit of a bobble and a definite yaw toward the smaller propeller. Still, it’s rather amazing how easily a modern flight controller was able to turn a pile of junk-box components into a flying quadcopter. You can learn more about flight controllers right here.
When we take a new Wi-Fi router from its box, the stock antenna is a short plastic stub with a reverse SMA plug on one end. More recent and more fancy routers have more than one such antenna for clever tricks to extend their range or bandwidth, but even if the manufacturer has encased it in mean-looking plastic the antenna inside is the same. It’s a sleeve dipole, think of it as a vertical dipole antenna in which the lower radiator is hollow, and through which the feeder is routed.
These antennas do a reasonable job of covering a typical home, because a vertical sleeve dipole is omnidirectional. It radiates in all horizontal directions, or if you are a pessimist you might say it radiates equally badly in all horizontal directions. [Brian Beezley, K6STI] has an interesting modification which changes that, he’s made a simple Yagi beam antenna from copper wire and part of a plastic yoghurt container, and slotted it over the sleeve dipole to make it directional and improve its gain and throughput in that direction.
Though its construction may look rough and ready it has been carefully simulated, so it’s as good a design as it can be in the circumstances. The simulation predicts 8.6 dB of gain, though as any radio amateur will tell you, always take antenna gain figures with a pinch of salt. It does however provide a significant improvement in range, which for the investment put in you certainly can’t complain at. Give it a try, and bring connectivity back to far-flung corners of your home!
[Wisecracker] likes how the Amazon Echo Dot works, but he doesn’t like how they sound or how they resemble hockey pucks. A little 3D printing, though, and he transformed the Dot into a credible Death Star. That doesn’t sound very friendly, we guess, so he calls it Alex-Star.
What makes it work is the Death Star’s “superlaser” — the weapon operated by a console that looks suspiciously like some studio video equipment — happens to be about the size and shape of a two-inch speaker. [Wisecracker] added a slot to let the sound out of the second speaker. You can see the thing in action in the video below.
If you stuff a computer into a rack with a bunch of other machines, you’d better make it a tough machine. Server-grade means something, so using server parts in a project, like this high-wattage power supply using server voltage regulators, can take it to the next level of robustness.
But before [Andy Brown] could build this power supply, he had to reverse-engineer the modules. Based on what he learned, and armed with a data sheet for the modules, he designed a controller to take advantage of all the capabilities of them and ended up with a full-featured power supply. The modules are rated for 66 watts total dissipation at 3.3 volts and have a secondary 5-volt output. Using an ATmega328, [Andy] was able to control the module, provide a display for voltage and current, temperature sensing and fan control, and even a UART to allow data logging to a serial port. His design features mainly through-hole components to make the build accessible to everyone. A suitable case is yet to come, and we’re looking forward to seeing the finished product.
Can’t scrape together some of these modules on eBay? Or perhaps you prefer linear power supplies to switched- mode? No worries – here’s a super stable unregulated supply for you.
A milliohm meter is a very handy piece of test equipment. Most hand-held multimeters cannot measure low resistances and bench meters that can, are usually quite expensive. [barbouri] has shared details of his milliohm meter build on his blog post, and it looks pretty nice.
When using a single pair of leads to measure very low ohms, the resistance of the measuring wires and voltage drops across the various joints become substantial enough to invalidate your measurement. The solution is to use the “Kelvin method” or 4-wire measurement. This involves passing a highly stable current derived from a temperature compensated constant-current source through the unknown resistance, and then using another pair of leads to measure the voltage drop across the resistor, which then gets displayed as a resistance on a voltmeter.
The finished project not only looks good, but is able to measure up to 2Ω with a resolution of 0.0001Ω (that’s 0.1mΩ). The project is originally designed by [Louis] from [Scullcom Hobby Electronics] and [barbouri]’s second iteration adds an improved board layout to the original project.
One of the most famous lectures in the history of technology was delivered by [Douglas Engelbart] in December 1968, at a San Francisco conference. In it he described for the first time most of what we take for granted in our desktop computers and networking today, several years before even the first microprocessor made it to market. It is revered not only because it was the first airing of these ideas, but because it was the event that inspired and influenced many of those who developed them and brought them to market. You may have heard of it by its poplar name: the Mother of All Demos.
This was an exciting time to be a technologist, as it must have been obvious that we lay on the brink of an age of ubiquitous computing. [Engelbart] was by no means alone in looking to the future and trying to imagine the impact that the new developments would have in the decades to come. On the other side of the Atlantic, at the British Post Office Telephone research centre at Dollis Hill, London, his British counterparts were no less active with their crystal ball gazing. In 1969 they produced our film for today, entitled complete with misplaced apostrophe “Telecommunications Services For The 1990’s” , and for our 2017 viewpoint it provides a quaint but fascinating glimpse of what almost might have been.
You can have any phone you want, as long as it’s state-owned! A GPO 746 telephone from the early 1970s.
Until the 1980s, the vast majority of British telephone services were a tightly regulated state monopoly run as part of the Post Office. There were only a few models of telephone available in the GPO catalogue, all of which were fixed installations with none of the phone sockets we take for granted today. Accessories such as autodiallers or answering machines were eye-wateringly expensive luxuries you’d only have found in offices, and since the fax machine was unheard of the height of data transfer technology was the telex. Thus in what later generations would call consumer information technology there really was only one player, so when they made pronouncements on the future they were a good indication of what you were likely to see in your home.
The film starts with a couple having a conversation, she in her bedroom and he in a phone box. Forgotten little touches such as a queue for a phone box or the then-cutting-edge-design Trimphone she’s using evoke the era, and the conversation leaves us hanging with the promise that their conversation would be better with video. After the intro sequence we dive straight into how the GPO thought their future network would look, a co-axial backbone with local circuits as a ring.
The real future-gazing starts with an office phone call to an Australian, at which we’re introduced to their concept of video calling with a colour CRT in a plastic unit that could almost be lifted from the set of The Jetsons. The presenter then goes on to describe a mass information service which we might recognise as something like our WWW, before showing us the terminal in more detail. Alongside the screen is a mock-up of a desktop console with keypad, cassette-based answerphone recorder, and a subscriber identity card slot for billing purposes. Period touches are a brief burst of the old harsh dial tone of a Strowger exchange, and mention of a New Penny, the newly-Decimalised currency. We’re then shown the system transmitting a fax image, of which a hard copy is taken by exposing a photographic plate to the screen.
Perhaps the most interesting sequence shows their idea of how an online information system would look. Bank statements and mortgage information are retrieved, though all with the use of a numeric keypad rather than [Englebart]’s mouse. Finally we see the system being used in a home office, a situation shown as farcical because the worker is continually harassed by his children.
Scorecard
This was the cutting edge in 1980, at least for people who hadn’t seen France’s Minitel. Fair use, via Wikimedia Commons.
So nearly five decades later, what did they get right and how much did they miss? The area you might expect them to be most accurate is oddly the one in which they failed most. The BT telecommunications backbone is now fibre-optic, and for the vast majority of us the last mile or two is still the copper pair it would have been a hundred years ago. In terms of the services though we have all of the ones they show us even if not in the form they envisaged. Fax and answering machines were everyday items by the 1980s, and though it didn’t gain much traction at the time we had video calling as a feature of most offices by the 1990s. We might however have expected them to anticipate a fax machine with a printer, after all it was hardly new technology. Meanwhile the online service they show us is visibly an ancestor of Prestel, which they launched for the late 1970s and which failed to gain significant traction due to its expense.
Another area they miss is wireless. We briefly see a pager, but even though they had a VHF radio telephone service and the ancestors of our modern cellular services were on the drawing board on the other side of the Atlantic at the time, they completely miss a future involving mobile phones.
The full film is below the break. It’s a charming period production, and the wooden quality of the action shows us that while the GPO engineers might have been telephone experts, they certainly weren’t actors.
