Retrotechtacular: Singing bird automata


Our cats were both sleeping near the computer and these videos were driving them nuts. To our ears these birdsongs sound pretty good. They didn’t trick the cats into stalking mode, but they did spark an audible complaint. So the predators aren’t drooling but the mechanical engineers reading this should be. These automata combine the precision of a mechanical clock with a bellows and specialized whistle to recreate birdsong.

You’ve got to hear it for yourself to appreciate the variety produced by the mechanisms. The first video shows off the device seen on the left. This particular model is from the 1890′s and the demo gives a good look at the arms that open and block a passageway to alter the sound. After seeing that link — which was sent in by [Stefan] — we started searching around for more info on the devices. The one pictured to the right turned up. It’s from YouTube user [Singing Bird Boxes] who has many videos showcasing these types of devices. We picked this one because he tried to explain how each part of the mechanism works. These are still being made today, but there’s something magical about seeing one built during the steam age.

We’d like to make Retrotechtacular a weekly feature every Tuesday. Help us out by sending in links to projects that highlight old technology, instructional videos of yore, tours of museums or similar relics.

[Read more...]

Leap motion controls hexapod with hand signals


Moving your hand makes this hexapod dance like a stringless marionette. Okay, so there’s obviously one string which is actually a wire but you know what we mean. The device on the floor is a Leap Motion sensor which is monitoring [Queron Williams'] hand gestures. This is done using a Processing library which leverages the Leap Motion API.

Right now the hand signals only affect pitch, roll, and yaw of the hexapod’s body. But [Queron] does plan to add support for monitoring both hands to add more control. We look at the demo after the break and think this is getting pretty close to the manipulations shown by [Tom Cruise] in Minority Report. Add Google Glass for a Heads Up Display and you could have auxiliary controls rendered on the periphery.

While you’re looking at [Queron's] project post click on his ‘hexapod’ tag to catch a glimpse the build process for the robot.

[Read more...]

Avalanche pulse generator design


This avalanche pulse generator is a great way to test your mettle as an Electronics Engineer. The challenge is to truly understand how each part of the design works. We certainly got a failing grade when first studying the schematics more than a week ago. But we’re slowly beginning to understand what’s going on under the hood.

The concept of an avalanche transistor is some wicked voodoo from the analog side of the street which leverages a transistor’s breakdown voltage to achieve a predictable result. In laymen’s terms it (mis)uses a transistor to produce a really fast pulse. The write-up linked above references several previous avalanche pulse generator designs, but this one is a bit different in how it produces about 50V from a pair of AAA batteries using a multivibrator circuit.

Even if you have no idea what’s going on here you may be interested in the last few paragraphs where the circuit is measured using a cutting-edge Teledyne LeCroy Wavemaster 820Zi-A. That’s a 20 GHz scope with a 15.3″ screen which you’ll never ever own.

Replacing knurled thumb screws


[Pete] bought himself an old South Bend lathe, but unfortunately some of the thumb screws were missing from this fine old machine. Originally, the lathe had knurled thumbscrews, and with a thumbscrew from Ace hardware the lathe itself was functional, but by no means looking its best. With a lathe you can make just about anything, so [Pete] decided he would make his own knurled thumbscrews and bring this lathe back to life.

Knurling is a diamond or linear pattern of indentations usually found on fancy metal knobs, flashlights, and other equipment that needs a good grip. While there are knurling tools for lathes, [Pete] decided to use his knurlmaster – a handheld device that looks like a pipe cutter – to cut a few knurls into a steel bar.

As for making this knurled bar into a proper thumbscrew, [Pete] shows us two methods: the first is tapping the knurled steel, putting in the right screw for the job, and securing the parts with Loctite. The second method involves cutting the threads on the lathe, an excellent example of how a lathe can make just about anything, even parts for itself.

Bench equipment tip: Screenshot of old oscilloscopes


Here’s a quick tip on capturing the output of oscilloscopes that don’t have that native feature. [Paulo Renato] used a cookie tin as a camera cowl for capturing CRT oscilloscope screenshots.

We figure if you’ve got any kind of functioning oscilloscope you’re lucky. And although it’s nice to pull down the measurements to your PC on the newer models, the results [Paul] gets with this rig are still satisfactory. The plastic cookie box he used blocks out ambient light while holding the camera at a consistent focal length. He used some flat black spray paint to make sure the obnoxious yellow plastic didn’t interfere with the image, then drilled a hole which fits tightly around his camera lens.

You’ll need to monkey with the exposure settings to get the best image. But once you’ve got it dialed in it should be the same every time you want to take a picture of the screen.

Making Digi-Key much, much prettier


We all love Digikey, but of all the major component retailers out there, their web interface really isn’t that great. A lot of online sources for parts are much, much prettier, but nothing a good Greasemonkey script can’t fix. This is all the work of [Ben], and adds a ton of really, really useful features to the Digikey web interface.

First up is a whole bunch of pictures right at the top of the search results. If you’re looking for pin headers or weird connectors, this is an astonishing useful feature that will help you select the right part faster. After that is a ‘helper’ button for voltages. As you know, selecting a part with a 5V input requires clicking multiple options including 3.3-5V, 2.3-6V, and 5-40V. Clicking on the helper button and entering 5 V will select all the entries in the filter that contain a 5V part.

[Ben]‘s project has been tested with Firefox and Chrome with Greasemonkey extensions. Head on over to his project page for a much better demo of all the features for this really great tool.