Whether you’re just getting into electronics or could use a refresher on some component or phenomenon, it’s hard to beat the training films made by the U.S. military. This 1965 overview of transformers and their operations is another great example of clear and concise instruction, this time by the Air Force.
It opens to a sweeping orchestral piece reminiscent of the I Love Lucy theme. A lone instructor introduces the idea of transformers, their principles, and their applications in what seems to be a single take. We learn that transformers can increase or reduce voltage, stepping it up or down through electromagnetic induction. He moves on to describe transformer action, whereby voltages are increased or decreased depending on the ratio of turns in the primary winding to that of the secondary winding.
He explains that transformer action does not change the energy involved. Whether the turns ratio is 1:2 or 1:10, power remains the same from the primary to the secondary winding. After touching briefly on the coefficient of coupling, he discusses four types of transformers: power, audio, RF, and autotransformers.
Continue reading “Retrotechtacular: Step Up and Get Your Transformer Training”
This week, we’re taking the wayback machine to 1940 for an informative, fast-paced look at the teleprinter. At the telegram office’s counter, [Mary] recites her well-wishes to the clerk. He fills out a form, stuffs it into a small canister, and sends it whooshing through a tube down to the instrument room. Here, an operator types up the telegram on a fascinating electro-mechanical device known as a teleprinter, and [Mary]’s congratulatory offering is transmitted over wires to her friend’s local telegraph office hundreds of miles away.
We see that the teleprinter is a transceiver that mechanically converts the operator’s key presses into a 5-digit binary code. For example, ‘y’ = 10101. This code is then transmitted as electrical pulses to teleprinters at distant offices, where they are translated back into alphanumerical data. This film does a fantastic job of explaining the methods by which all of this occurs and does so with an abstracted, color-coded model of the teleprinter’s innards.
The conversion from operator input to binary output is explained first, followed by the mechanical translation back to text on the receiving end. Here, it is typed out on a skinny paper tape by the type wheel shown above. Telegraphists in the receiving offices of this era cut and pasted the tape on a blank telegram in the form of meaningful prose. Finally, it is delivered to its intended recipient by a cheeky lad on a motorbike.
Continue reading “Retrotechtacular: Teleprinter Tour, Teardown”
Whether you’ve been following Retrotechtacular for a while or have firsthand experience with the U.S. Army, you know that when they want to teach something to a someone, they’ll get the job done in spades with a side of style. The era between WWII and the Vietnam War was a golden age of clear, simple instruction that saw the Army use memorable material to teach a wide array of topics. And speaking of golden ages, the Army found success with comic book-style instructional magazines drawn chiefly by [Will Eisner] of Spirit fame.
The first of these rags was called Army Motors, which premiered in 1940. It introduced several memorable characters such as a Beetle Bailey-esque bumbling soldier named Private Joe Dope, and no-nonsense gal mechanic Connie Rodd, a sharp cookie who’s as brainy as she is buxom. Educational and entertaining in equal parts, the magazine was pretty well received.
Its successor, known simply as P.S. started its run around the beginning of the Korean War in June 1951. These magazines were intended as a postscript to the various equipment maintenance manuals that soldiers used. They offered all kinds of preventive maintenance procedures as well as protips for Army life. The eye-catching depictions of Connie Rodd demanded soldiers’ attention while the anthropomorphic equipment illustrations encouraged them to listen to what their equipment told them.
Additional artists including [Joe Kubert] and [Dan Spiegle] were brought in to produce P.S. on a monthly basis. As the years marched on, the magazine’s character base expanded to include representatives of other military branches solving specialized problems. The bumbling idiot types were 86’d pretty early on, but cheesecake was served well into the 1970s.
Did we mention that they’re still making P.S.? Here’s the February 2015 issue and a friendly PDF warning.
Thanks for the tip, [Itay]!
Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.
For their ECE 4760 final project at Cornell, [Varun, Hyun, and Madhuri] created a real-time sound spectrogram that visually outputs audio frequencies such as voice patterns and bird songs in gray-scale video to any NTSC television with no noticeable delay.
The system can take input from either the on-board microphone element or the 3.5mm audio jack. One ATMega1284 microcontroller is used for the audio processing and FFT stage, while a second ‘1284 converts the signal to video for NTSC output. The mic and line audio inputs are amplified individually with LM358 op-amps. Since the audio is sampled at 8KHz, a low-pass filter gets rid of frequencies above 4KHz.
After the break, you can see the team demonstrate their project by speaking and whistling bird calls into the microphone as well as feeding recorded bird calls through the line input. They built three controls into the project to freeze the video, slow it down by a factor of two, and convert between linear and logarithmic scales. There are also short clips of the recorded bird call visualization and an old-timey dial-up modem.
Continue reading “Video Voice Visualization”
There’s a lot to learn from this 1966 Army training film about the International Morse Code, but the most crucial component of good keying is rhythm. A young man named [Owens] demonstrates very clean keying, and the instructor points out that skill is the product of sending uniform and short dits, uniform and short dahs, and correct spacing between dits, dahs, letters, and words.
Throughout the film, there are title cards in a typeface that shows the stroke order of military printing. The instructor points this out after a brief interlude about the phonetic alphabet (Alpha, Bravo, Charlie, &c). Right away, we see that the Morse Code for ‘H’ is four dits that gallop with the rhythm of a horse in a hurry to get to the hotel.
Such clever and memorable pictures are painted for a few other letters. We wish he would have covered them all, but that’s not the aim of this film. The Army is more concerned with good, clean rhythm and proper spacing that marks the difference between ‘low’ planes and ‘enemy’ planes. There’s a simple, three-step plan to getting what is called a ‘good fist’, and the Army demonstrates this in the best possible way: a giant J-38 and fake hand descending from the ceiling to match. Yes, really.
The first step is to adjust the key to ensure good contact alignment, proper gap spacing, and ideal spring tension. The second step is to develop good technique by resting one’s elbow on the table and holding the key rather than slapping it. The third step is simply to practice. Learning through imitation is helpful, as is taping one’s practice sessions and playing them back. [Owens] likes to use an RD-60 code recorder, which immortalizes his signals in ink.
Continue reading “Retrotechtacular: ⋅⋅⋅⋅ ––– ⋅–– – ––– –– ––– ⋅–⋅ ⋅⋅⋅ ⋅ –⋅–⋅ ––– –⋅⋅ ⋅”
After a few years of on and off development, [Steve] from Big Mess ‘o Wires completed work on a floppy disk drive emulator for older Macs such as the Plus. The emu plugs into the DB-19 port on the Mac and acts just like a 3.5″ floppy, using an SD card to store the images. He’s been selling the floppy emus for about the last year, and assembled the first several scores of them himself. At some point, he enlisted a board house to make them, and as of November 2014, he’s had enclosures available in both clear acrylic and brown hardboard.
[Steve] recently ran out of emu stock, so it was time to call up the board house and get some more assembled. After waiting six weeks, they finally showed up. But in spite of [Steve]’s clear and correct instructions, all 100 boards are messed up. One resistor is missing altogether, and they transposed a part between the extension cable adapter board, connecting it directly to the emu main board. But get this: the boards still work electrically. They don’t fit in the housings, however, and the extension cables are useless. After explaining the situation, the board house agreed to cook up a new batch of boards, which [Steve] is waiting patiently to receive.
Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.
For centuries, human-powered flight eluded mankind. Many thought it was just an impossible dream. But several great inventions have been born from competition. Challenge man to do something extraordinary, offer him a handsome cash incentive, and he may surprise you.
In 1959, London’s Aeronautical Society established the Kremer Prize in search of human-powered flight. The rules of the Kremer Prize are simple: a human-powered plane must take off by itself and climb to an altitude of ten feet. The plane must make a complete, 180° left turn, travel to a marker one-half mile away, and execute a 180° right turn. Finally, it must clear the same ten-foot marker. While many tried to design crafts that realized this dream, man is, at his strongest, a weak engine capable of about half a horsepower on a good day.
Continue reading “Retrotechtacular: The Gossamer Condor”