Author: Jenny List

3466 Articles

Dragging Teletypes Into The 21st Century

May 29, 2016 by 36 Comments

If you are of a certain age you may have worked in an office in the days before the computer revolution, and the chances are that in the corner of your office there would have been a teletype machine. Like a very chunky typewriter with a phone attached, this was an electromechanical serial terminal and modem, and machines like it would have formed the backbone of international commerce in the days before fax, and then email.

Teletypes may have disappeared from the world of trade, but there are a surprising number still in private hands. Enthusiasts collect and restore them, and radio amateurs still use digital modes based on their output. The problem facing today’s teletype owner though is that they are becoming increasingly difficult to interface to a modern computer. The serial port, itself an interface with its early history in the electromechanical world, is now an increasingly rare sight.

[Eric] has a project which addresses the teletype owner’s interfacing woes, he’s created a board with all the necessary level shifters and an Atmega32u2 microcontroller to translate the teletype’s output to USB.

In his design he’s had to solve a few problems related to such an aged interface. Teletypes have a serial output, but it’s not the TTL or RS232 we may be used to. Instead it’s a high-voltage current loop designed to operate electromagnets, so his board has to incorporate an optocoupler to safely isolate the delicate computer circuitry. And once he had the teletype’s output at a safe level he then had to translate its content, teletypes speak 5-bit ITA2 code rather than our slightly newer 7-bit ASCII.

The result though is a successful interface between teletype and computer. The former sees another teletype, while the latter sees a serial terminal. If you have a teletype and wish to try it for yourself, he’s released the source code in a GitHub repository.

Teletypes have featured a few times here at Hackaday over the years. We’ve had one as an SMS client, another that monitors a Twitter feed, and while it’s not strictly a teletype, a close examination of an Olivetti mechanical serial terminal.

OzQube-1: A Tiny Australian Satellite

May 29, 2016 by 22 Comments

Over the last couple of decades we have become used to the possibility of launching a satellite into orbit no longer being the exclusive preserve of superpowers. Since the first CubeSats were launched over a decade ago a myriad others have followed, and scarcely a week passes without news of another interesting project in this area.

OzQube-1 is just such a satellite, designed for imaging of the Southern Hemisphere, and it’s the brainchild of Australian [Stuart McAndrew]. He’s posted significant details of its design: it’s a PocketQube, at 50mm cubed, an eighth the volume of a CubeSat, and its main instrument is a 2 megapixel camera with a 25mm lens. Images will be transmitted to earth as slow-scan digital video via the 70cm amateur band, the dipole antenna being made from a springy tape measure which will unfurl upon launch. Attitude control is passive, coming from a magnet aligned to ensure the camera will be pointing Earthwards as it passes over the Southern Hemisphere. The project has a little way to go yet, but working prototypes have been completed and it has a Gofundme campaign under way to help raise the money for a launch.

There are plenty of Cubesat and other small satellite builds to be found on the web, here at Hackaday we’ve covered a significant number of them. Many of them are the fruits of well-funded university departments or other entities with deep pockets, but this one comes from a lone builder from Western Australia. We like that, and we wish OzQube-1 every success!

Free Radio On My Phone

May 28, 2016 by 84 Comments

If you have owned Android phones, there’s a reasonable chance that as the kind of person who reads Hackaday you will at some time have rooted one of them, and even applied a new community ROM to it. When you booted the phone into its new environment it’s not impossible you would have been surprised to find your phone now sported an FM radio. How had the ROM seemingly delivered a hardware upgrade?

It’s something your cellphone carrier would probably prefer not to talk about, a significant number of phones have the required hardware to receive FM radio, but lack the software to enable it. The carriers would prefer you to pay for their data to stream your entertainment rather than listen to it for free through a broadcaster. If you are someone capable of upgrading a ROM you can fix that, but every other phone owner is left holding a device they own, but seemingly don’t own.

Across North America there is a group campaigning to do something about this situation. Free Radio On My Phone and their Canadian sister organization are lobbying the phone companies and manufacturers to make the FM radio available, and in the USA at least they have scored some successes.

We have covered numerous attempts to use the DMCA to restrict people’s access to the hardware they own, but this story is a little different. There is no question of intellectual property being involved here, it is simply that the carriers would rather their customers didn’t even know that they had bought an FM radio along with their phone. If this bothers you, thanks to Free Radio On My Phone you can now join with others and find a voice on the matter.

It’s interesting to note that many FM radio chips also support a wider bandwidth than the North American and European 88 to 108MHz or thereabouts. In parts of Asia the broadcast band extends significantly lower than this, and the chipset manufacturers make products to support these frequencies. This opens up the interesting possibility that given a suitable app a cellphone could be used to receive other services on these frequencies. Probably more of a bonus for European radio amateurs with their 70MHz allocation than for North American residents.

Via CBC News. Cellphone image: By Rob Brown [Public domain], via Wikimedia Commons.

Flame Triodes Don’t Need Any Vacuum

May 26, 2016 by 37 Comments

There is a rich history surrounding the improvisation of electronic components. From cats-whisker foxhole radio detectors using razor blades through radio amateurs trying antique quartz lenses as crystal resonators and 1950s experimenters making their own point-contact transistors, whenever desirable components have been unavailable the ingenuity of hackers and makers has always sought to provide.

In an age when any component you might wish for is only a web browser and a courier package away, you might think there would be no need for such experiments. But it is in our curious nature to push the boundaries of what can be made without a factory at our disposal, so there are still plenty of ingenious home-made components under construction.

One such experiment came our way recently. It’s a few years old, but it’s a good one. [Nyle Steiner, K7NS] made a working triode without any form of vacuum, instead its medium is a flame. He’s demonstrated it as a rectifier, amplifier, and oscillator, and while it might not be the best triode ever it’s certainly one of the simplest.

In a traditional vacuum triode the current flows as electrons released from a hot cathode and are able to cross the space because there are no gas molecules for them to collide with. The flame triode has an abundance of gas, but the gasses within it and its immediate surroundings are also strongly ionized, and thus electrically conductive. Flame ionization detectors have exploited this phenomenon in scientific instruments for a very long time.

A roaring flame might not be the most practical thing to keep in your electronic equipment, but [Nyle]’s experiment is nonetheless an impressive one. He’s posted a video showing it in action, which you can see below the break.

Continue reading “Flame Triodes Don’t Need Any Vacuum” →

Arduino Motion Detection With A Bit Of Wire

May 23, 2016 by 55 Comments

It is likely that many of us will at some time have experimented with motion detectors. Our Arduinos, Raspberry Pis, Beaglebones or whatever will have been hooked up to ultrasonic or PIR boards which will have been queried for their view of what is in front of them.

[Connornishijima] has stumbled on a different way to detect motion with an Arduino, he’s polling an ADC pin with a simple length of twisted pair hooked up to it and earth, and reliably generating readings indicating when he (or his cat) is in its vicinity. He’s calling the effect “Capacitive turbulence”, and he’s open to suggestions as to its mechanism. He can only make it work on the Arduino, other boards with ADCs don’t cut it.

Frequent Hackaday featuree [Mitxela] may have also discovered something similar, and we’ve hesitated to write about it because we didn’t understand it, but now it’s becoming unavoidable.

It’s always dangerous in these situations to confidently state your opinion as “It must be…” without experimental investigation of your own. Those of us who initially scoffed at the idea of the Raspberry Pi 2 being light sensitive and later had to eat their words have particular cause to remember this. But this is an interesting effect that bears understanding. We would guess that the Arduino’s fairly high input impedance might make it sensitive to mains hum, if you did the same thing to an audio amplifier with a phono input you might well hear significant hum in the speaker as your hand approached the wire. It would be interesting to try the experiment at an off-grid cabin in the woods, in the absence of mains hum.

If you’d like to give his experiment a try, he’s posted his sketch on Pastebin. And he’s put up the video below the break demonstrating the effect in action, complete with cats.

Continue reading “Arduino Motion Detection With A Bit Of Wire” →

A Minitel Terminal As A USB Linux Terminal

May 22, 2016 by 20 Comments

If you paid a visit to France in the 1980s the chances are you’d have been surprised to see a little brown screen and keyboard sitting next to the telephones wherever you went. At the time, it was another reason apart from the food, wine, and super-fast trains to envy our Gallic cousins. This was Minitel, their take on the cutting-edge of online data services of the day.

Minitel stood apart from similar services of the day in most other countries, because of its business model. Unlike the UK’s Prestel or West Germany’s BTX for which you had to spend significant money on a terminal, the French Minitel terminals were free. Thus in the early 1980s everybody in France was busy using videotext while most of the rest of Europe was still excited by chipping bits of flint into arrow heads. Or at least, that’s how it seemed at the time to those of us who didn’t have Minitel.

The Minitel service was finally shuttered in 2012, but the terminals can still be found. [Tony Pigram] bought one, an Alcatel Minitel 1, and made it into something useful by turning it into a USB serial terminal for his Raspberry Pi. Surprisingly the physical interface between the Minitel and the USB port is a relatively simple level shifter, but the configuration of both the Minitel and the Pi was anything but.

The problem was that Minitel terminals were meant to work with Minitel, and [Tony]’s difficulties were increased by his machine being an earlier model without the handy function key to access settings found on later terminals. A lot of research paid dividends though, and he now has what must be one of the most compact and stylish CRT serial terminals available. We can’t help noticing it has a QWERTY keyboard and English menus, it would be interesting to know which non-French market it was made for.

We’ve featured an RS-232 integration into a Minitel terminal before here at Hackaday, but if you are really interested in Gallic retro-tech take a look at our discussion of their 8-bit scene.

PTC Heaters For Reflow Soldering

May 21, 2016 by 12 Comments

Reflow soldering – setting components on a PCB in blobs of solder paste and heating the whole assembly at once to melt all joints simultaneously – has been the subject of many ingenious hacks. Once it was the sole preserve of industrial users with specialist microprocessor-controlled ovens, now there are a myriad Arduino-controlled toaster ovens, hot air blowers, and hotplates that allow hackers and makers to get in on the reflow act too.

This morning a fresh idea in the reflow soldering arena has come our way. It’s not the most earth-shattering, but it does have some advantages so is worth a second look. [Analog Two] has successfully used a PTC heating element as a reflow soldering hotplate.

PTC heating elements are thermistors with a positive temperature coefficient. As their temperature rises, so does their electrical resistance. By careful selection of materials they can be manufactured with a sharp increase in resistance at a particular temperature. Thus when an electrical current is passed through them they heat up until they reach that temperature, then the current decreases as the resistance goes up, and they do not heat beyond that point. Thus as heaters they are intrinsically self-regulating. From our point of view they have another advantage, they are also cheap. Fitted as they are to thousands of domestic heating products they are readily available, indeed [Analog Two] found his on Amazon.

The heater chosen was a 200W 110V model with a temperature of 230 Celcius to match the solder he was using. They are also available for other mains voltages, and even at 12 and 24V for automotive applications. He reports that the time to reflow was about 90 seconds.

We’ve mentioned the advantages of this heater as its price and regulated temperature. Looking at the pictures though a disadvantage is its size. This is a reflow plate for small boards. There are larger PTC heater elements available though, it would be interesting to hear people’s experiences reflowing with them.

Hotplates for reflow soldering have featured before a few times here at Hackaday. We recently had this tiny plate, but we’ve also had a PID-controlled plate, and an Arduino-controlled domestic hotplate. We’re sure this is an avenue with further to go.