DTMF Robot Makes Rube Goldberg Proud

May 27, 2016 by Elliot Williams 11 Comments

Sometimes you start building, and the project evolves. Layers upon layers of functionality accrue, accrete, and otherwise just pile up. Or at least we’re guessing that’s what happened with [Varun Kumar]’s sweet “Surveillance Car Controlled by DTMF“.

In case you haven’t ever dug into not-so-ancient telephony, Dual-tone, multi-frequency signalling is what made old touch-tone phones work. DTMF, as you’d guess, encodes data in audio by playing two pitches at once. Eight tones are mapped to sixteen numbers by using a matrix that looks not coincidentally like the old phone keypad (but with an extra column). One pitch corresponds to a column, and one to a row. Figure out which tones are playing, and you’ve decoded the signal.

Anyway, you can get DTMF decoder chips for pennies on eBay, and they make a great remote-control interface for a simple robot, which is presumably how [Varun] got started. And then he decided that he needed a cell phone on the robot to send back video over WiFi, and realized that he could also use the phone as a remote controller. So he downloaded a DTMF-tone-generator app to the phone, which he then controls over VNC. Details on GitHub.

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Retrotechtacular: Examining Music In 1950’s Russia

May 27, 2016 by Kristina Panos 34 Comments

If you had told 12-year-old me that one day I would be able to listen to pretty much any song I wanted to on demand and also pull up the lyrics as fast as I could type the artist’s name and part of the title into a text box, I would have a) really hoped you weren’t kidding and b) would have wanted to grow up even faster than I already did.

The availability of music today, especially in any place with first world Internet access is really kind of astounding. While the technology to make this possible has come about only recently, the freedom of music listening has been fairly wide open in the US. The closest we’ve come to governmental censorship is the parental advisory sticker, and those are just warnings. The only thing that really stands between kids’ ears and the music they want to listen to is parental awareness and/or consent.

However, the landscape of musical freedom and discovery has been quite different in other corners of the world, especially during the early years of rock ‘n roll. While American teens roller skated and sock-hopped to the new and feverish sounds of Little Richard and Elvis Presley, the kids in Soviet Russia were stuck in a kind of sonic isolation. Stalin’s government had a choke hold on the influx of culture and greatly restricted the music that went out over the airwaves. They viewed Western and other music as a threat, and considered the musicians to be enemies of the USSR.

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Hackaday Prize Entry: Open-Source Myoelectric Hand Prosthesis

May 26, 2016 by Moritz Walter 9 Comments

Hands can grab things, build things, communicate, and we control them intuitively with nothing more than a thought. To those who miss a hand, a prosthesis can be a life-changing tool for carrying out daily tasks. We are delighted to see that [Alvaro Villoslada] joined the Hackaday Prize with his contribution to advanced prosthesis technology: Dextra, the open-source myoelectric hand prosthesis.

Dextra is an advanced robotic hand, with 4 independently actuated fingers and a thumb with an additional degree of freedom. Because Dextra is designed as a self-contained unit, all actuators had to be embedded into the hand. [Alvaro] achieved the necessary level of miniaturization with five tiny winches, driven by micro gear motors. Each of them pulls a tendon that actuates the corresponding finger. Magnetic encoders on the motor shafts provide position feedback to a Teensy 3.1, which orchestrates all the fingers. The rotational axis of the thumb is actuated by a small RC servo.

In addition to the robotic hand, [Alvaro] is developing his own electromyographic (EMG) interface, the Mumai, which allows a user to control a robotic prosthesis through tiny muscle contractions in the residual limb. Just like Dextra, Mumai is open-source. It consists of a pair of skin electrodes and an acquisition board. The electrodes are attached to the muscle, and the acquisition board translates the electrical activity of the muscle into an analog voltage. This raw EMG signal is then sampled and analyzed by a microcontroller, such as the ESP8266. The microcontroller then determines the intent of the user based on pattern recognition. Eventually this control data is used to control a robotic prosthesis, such as the Dextra. The current progress of both projects is impressive. You can check out a video of Dextra below.

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Nanowire Batteries Never Need Replacing

May 26, 2016 by Will Sweatman 47 Comments

In this day and age we’re consistently surrounded with portable electronic devices. In order for them to be called “portable”, they must run on batteries. Most, if not all, use rechargeable batteries. These batteries have a finite lifespan, and will eventually need to be replaced. UCI chemist [Reginald Penner] and doctoral candidate [Mya Le Thai] have been hard at work on making rechargeable batteries that last forever.

Nanowires are great candidates for rechargeable battery technology because the wires, thousands of times thinner than a human hair, are great conductors of electricity. The problem is repeated charging and discharging makes them brittle, which causes them to eventually fail. Typically, the researchers at UCI could get 5000 to 7000 cycles in before they failed. After some trial and error, they found that if they coat a gold nanowire with an acrylic-like gel, they can get up to 200,000 charge/discharge cycles through it before failure.

We’ve seen rechargeable battery hacks before, but making a battery that never needs replacing is sure to get everyone excited.

Punch Cards

May 26, 2016 by Bryan Cockfield 41 Comments

Before the Commodore 64, the IBM PC, and even the Apple I, most computers took input data from a type of non-magnetic storage medium that is rarely used today: the punched card. These pieces of cardstock held programs, data, and pretty much everything used to run computers in the before-time. But with all of that paper floating around, how did a programmer or user keep up with everything? Enter the punch card sorter and [Ken Shirriff[‘s eloquent explanation of how these machines operate.

Card sorters work by reading information on the punched card and shuffling the cards into a series of stacks. As [Ken] explains, the cards can be run through the machine multiple times if they need to be sorted into more groups than the machine can manage during one run, using a radix sort algorithm.

The card reader that [Ken] examines in detail uses vacuum tubes and relays to handle the logical operation to handle memory and logic operations. This particular specimen is more than half a century old, rather robust, and a perfect piece for the Computer History Museum in Mountain View.

It’s always interesting to go back and examine (mostly) obsolete technology. There are often some things that get lost in the shuffle (so to speak). Even today, punched cards live on in the automation world, where it’s still an efficient way of programming various robots and other equipment. Another place that it lives on is in voting machines in jurisdictions where physical votes must be cast. Hanging chads, anyone?

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PhD Crystal Radio Has Pizza Capacitor

May 26, 2016 by Al Williams 35 Comments

Crystal radios are old news, but great fun. What would happen if a PhD designed a crystal set? By PhD we mean Pizza Hut Deliveryperson and [John Greenlee] (who may not actually be a PhD of either kind; we don’t know) gives us a good idea with his crystal radio in a pizza box.

Pizza boxes aren’t the only food-related material in this radio. [John] makes a tuning capacitor out of cake rounds. Coincidentally, he decorates the tuning capacitor to look like a pizza.

The schematic itself is unremarkable–just a common crystal set. But the construction of the chassis and the capacitor make it an interesting project. If you know a young person that has any interest in radio, a crystal receiver is a rite of passage you shouldn’t deny them and this one is certainly a novelty. The picture of a pizza takes it even one step further than this YouTube build, which is nonetheless a good resource.

The instructions are well done, although some of the parts may be slightly hard to find. Germanium diodes and high-Z earphones are not as plentiful as they used to be, although you can still find them if you look.

This pizza box rig could be a gateway drug to more serious crystal radios. Or you could go smaller and try building one in a match box.

Hamvention: The Flea Market

May 26, 2016 by Brian Benchoff 26 Comments

Last weekend was Hamvention, the place you want to be on the third weekend in May. It is the world’s largest gathering of amateur radio enthusiasts, and an exceedingly large flea market containing all sorts of electronica.

The booths of Hamvention include a few notable Open Hardware folk, but for the most part, you’re looking a few big booths from Yaesu, an entire section dedicated to everything ARRL, and a few pop-ups from the usual suspects. Rigol was there, showing off their test equipment and selling the DS1052E oscilloscope for far more than it’s worth. The Rigol Zed is a much better buy, anyway.

As with any gathering of hams, antennas are everywhere. The largest by far was the tower at right. With a little more equipment, this antenna could do a moon bounce. It’s a shame the moon was full this weekend, and everyone went to bed early.

Giant antennas and an amateur radio trade show notwithstanding, the biggest draw is the flea market. You’re looking at about two football fields worth of parking spaces, filled with cars, tents, and collapsible tables and the strangest electronic devices you’ve ever seen. What was that like? Read on below.

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