An Experiment In Shift Registers And Multiplexed LEDs

March 18, 2015 by 15 Comments

[Kratz] is working on a WiFi controlled scoreboard, but before building the full-scale version, he thought it would be wise to test out the multiplexing technique for the display. The experiment worked, but unless this scoreboard is for a foosball table, he still has a lot of work ahead of him.

The design of this prototype display is pretty simple, with just two ‘595 shift registers feeding bits to the display. Sixteen NPN transistors are being used to sink and source current to the display. It’s a relatively simple circuit, allowing [Kratz] to fit nine seven-segment displays on a small board with only six wires – ground, two V+ for the logic and LEDs, clock, data, and latch – going to the microcontroller.

There were a few snags in the design; the data is clocked in on a rising edge, but an extra falling edge was required before latching. [Kratz] can’t figure out the reason for this, and it might just be a timing issue.

Lathe Tach

Excuse Me, Sir. Do You Know How Fast Your Lathe Was Traveling Back There?

March 18, 2015 by 26 Comments

When machining metal, it is important to know how fast the cutting tool is traveling in relation to the surface of the part being machined. This amount is called the ‘Surface Speed’. There are Surface Speed standards for cutting different types of materials and it is good practice to stick with those standards in order to end up with a good surface finish as well as maximizing tool life. On a lathe, for example, having a known target Surface Speed in mind as well as a part finish diameter, it is possible to calculate the necessary spindle speed.

Hobbyist [Paul] wanted a method of measuring his lathe’s spindle speed. Since spindle speed is measured in RPM, it made complete sense to install a tachometer. After browsing eBay for a bit he found one for about $20. His purchase came with the numeric LED display, a mounting bezel and the all important hall effect sensor. The Hall effect sensor measures changes in a magnetic field and in turn varies its output voltage. [Paul] fabbed up an aluminum bracket that supports the sensor just off of the rear of the lathe spindle. A magnet was then glued to the outside diameter of the spindle below the sensor. The once per revolution signal is generated every time the magnet passes the sensor while the lathe is running. The display was mounted to the lathe near eye height by means of another aluminum bracket and case.

After a little work, [Paul] can now keep a close eye on his spindle speed with a quick glance over at his new tachometer display while he’s turning those perfect parts! If this project tickles your fancy, you may want to check out this fantastic DIY tachometer or this one that uses a soundcard.

Toggle Magnet

Switchable Magnet With A Simple Circuit

March 17, 2015 by 26 Comments

Magnets are awesome. Electromagnets are even cooler. But what if you could make a semi-permanent switchable magnet that acts like an electromagnet, but doesn’t use any energy to hold metal? You’re going to want to take a look at this Low-power Magnetic Hold and Release Mechanism.

It’s actually a very simple concept. It is basically an electromagnet attached to a permanent magnet — it’ll hold any metal object exactly as you’d expect — but if you run current through the inductor attached to it, the magnetic field created by the electricity will temporarily cancel out the field of the magnet — thus freeing your object being held. Since gravity is pretty fast acting, this impulse of current doesn’t need to be very long, only fractions of a second.

Now the real question is how big could you go? We covered another project a while ago called Open Grab which discusses the possibility of using technology like this in Quadcopters.

For a solution that uses no power at all take a look at switchable magnet clamps used for welding — they’re pretty cool — but patent protected of course.

Putting New Into The Old – A Phonograph Upgrade.

March 17, 2015 by 28 Comments

[smellsofbikes] recently came into possession of a 1970’s “stereo radio phonograph” cabinet consisting of a vinyl record player, AM and FM radio, and eight track tape player. The radio worked, the turntable didn’t sound too nice, and the tape player didn’t work at all. A new needle fixed the turntable, but the eight-track was in bad shape. So he replaced the tape player with a BeagleBoneBlack which plays streaming internet radio.

Hopefully, this fix is temporary, since he has carefully disconnected the tape player connections in the hope of fixing it soon. The swap out involved a fair bit of engineering, so he’s split his build log into several bite sized chunks. The first step was to set up the BBB, upgrade it and add in all the network and audio related stuff. Audio on the BBB is available only via the HDMI port, but [smellsofbikes] had a USB soundcard handy, so the next step was setting that up. He installed mpg321 – the command line mp3 player and set it up to play music streaming from somafm. Next up was getting some scripts and programs to run automatically during system bootup. The final part of the setup was adding a WiFi router as a repeater connected to the BBB via an ethernet cable. He could have used a tiny WiFi USB dongle, but he already had the router lying around, and he wanted to dedicate USB to audio functions alone, and use the Ethernet port for Internet.

He then worked on identifying the wires that go from the tape player to the amplifier, spliced them, and hooked them up to the audio sound card on the BBB. With this done, the upgrade was more or less complete – the system played streaming music and stations could be switched remotely (via SSH to BBB). [smellsofbikes] reckoned it would be nice to use the existing controls in the phonograph cabinet to control the internet streaming music, instead of controlling it via a remote computer. The cabinet had 4 indicator lamps that indicated which track was being played and a button to switch between tracks. He removed the old indicator panel and put in a fresh PCB, designed in KiCad and cut on his LPKF circuit board plotter. An aluminum knob machined out of hex bar-stock works as the new track change button. At this point, he called it a wrap. The BBB and Asus router go inside the cabinet, and the old (non-functional) tape player is put in place. Quite an interesting build, and we look forward to when he actually gets the tape player working. [Alan Martin], aka “The Most Interesting Engineer In The World” has told him that “it is a moral imperative that you repair the eight-track and get it working”. [Alan] has promised to send [smellsofbikes] a suitcase full of brand new, still in their plastic wrappers, eight-track tapes when he gets it working.

SXSW Create: ATX Hackerspace Area

March 17, 2015 by 9 Comments

We had a wonderful time over the weekend at the 2015 SXSW Create. I was really excited to see that there was a very large area set aside for the Hackerspaces of the Austin area and they took full advantage of that. Most notably, ATX Hackerspace who had multiple tables and was drawing a huge crowd.

sxsw-atx-thereminThis table is a good example of the demonstrations on hand. Primarily It’s a collection of ultrasonic theremin. The classic theremin uses oscillator-based sound production (we’ve been running a series on that concept) with a set of antennas that uses your body’s proximity to tweak that signal. This version mimics the user interface but greatly simplifies the skillset needed to produce the instrument by swapping the antenna for an ultrasonic rangefinder and generating the audio digitally. The more astute viewer will have noticed the instrument being held. I neglected to ask about this but it sure looks like a Holophonor which is another great seed idea for your next project. Update: it’s a Hulusi.

sxsw-atx-solderingI do think it’s worth noting that ATX also set aside a lot of table-space for their members to actually work on building projects at the event. We’re big advocates of this rather than simply exhibiting finished projects. It doesn’t really matter what you’re working on; seeing a table covered with interesting parts and tools, being worked on by fun people obviously enjoy each other’s company is the core message of a Hackerspace… right?

I talk with [Gardner] about ATX in the video after the break, and make a quick loop around the display tables.

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DIY Hololens

DIY Hololens Uses Pepper’s Ghost In A Box!

March 17, 2015 by 20 Comments

Entirely too excited about Microsoft’s Hololens, the DIY community has leaped on the challenge to make some hardware before the real deal comes out. [Sean Hall] has an excellent 3D printed prototype that makes use of the Pepper’s Ghost illusion to create a “hologram” for this pair of unique VR goggles.

Similar to other DIY virtual reality goggles we’ve seen, [Sean] has 3D printed the enclosure — but instead of slapping the smart phone right in front of your eyes, it’s mounted above the goggles, reflecting off of a mirror and then a piece of transparent plexi-glass, which produces a hologram like effect thanks to the concept of Pepper’s Ghost illusion.

The problem with any of these reflection-based-holograms is they aren’t always that easy to see, so [Sean] is planning to try out some 1-way reflective car tint to get a more visible reflection while still being able to see through the image. He also plans to add gaze tracking with some open-source software called Project Haytham. It’s a depth sensor using a Kinect, head tracking using a Playstation Move and maybe even a leap motion controller for virtual object manipulation.

Check out the current state of this hack in the clip after the break.

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Retrotechtacular: On The Wings Of Goodyear

March 17, 2015 by 34 Comments

At the opposite end of the spectrum from the various blimp and rigid-hull airships Goodyear has created over the years stands the Goodyear Inflatoplane, the company’s foray into experimental inflatable aircraft. Goodyear had recently created a rubberized nylon material they called Airmat, the faces of which were connected internally by nylon threads. This material was originally developed during research into the viability of emergency airplane wings.

The United States military became interested in the Inflatoplane after Goodyear had performed successful testing of demonstration model GA-33. They believed that the Inflatoplane could be dropped from the air in a rigid container to facilitate an emergency rescue, or trucked around with the rest of the cargo as a last resort for just exactly the right situation. It seems like a good idea on paper. The Inflatoplane could stay packed into a fairly small container until it was needed. The GA-468 one-seater model could go almost 400 miles on 20 gallons of fuel, and required less pressure to inflate than the average car tire.

This episode of the Discovery Channel series WINGS includes a real-time demonstration of taking an Inflatoplane from crate to air set to late ’80s montage music. It takes the pilot a full five minutes to unfurl and  the plane, and he does it on a nice and level grassy spot by a lake that looks more like a cozy picnic spot than threatening enemy territory. While it’s better than not having an inflatable emergency aircraft, it just isn’t that practical.

Goodyear had all kinds of plans for future improvements, such as a vertical takeoff model and a rocket-powered version. But the Inflatoplane military initiative was grounded around the time that someone speaking for the Army deadpanned that they “could not find a valid military use for an aircraft that could be taken down by a well-aimed bow and arrow.”

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