With the advent of low-cost software defined radio (SDR), anyone who’s interested can surf the airwaves from the FM band all the way up to the gigahertz frequencies used by geosynchronous satellites for about $20 USD. It’s difficult to overstate the impact this has had on the world of radio hacking. It used to be only the Wizened Ham Graybeards could command the airwaves from the front panels of their $1K+ radios, but now even those who identify as software hackers can get their foot in the door for a little more than the cost of a pizza.
But as many new SDR explorers find out, having a receiver is only half the battle: you need an antenna as well. A length of wire stuck in the antenna jack of your SDR will let you pick up some low hanging fruit, but if you’re looking to extend your range or get into the higher frequencies, your antenna needs to be carefully designed and constructed. But as [Akos Czermann] shows on his blog, that doesn’t mean it has to be expensive. He shows how you can construct a very capable ADS-B antenna out of little more than an empty soda can and a bit of wire.
He makes it clear that the idea of using an old soda can as an antenna is not new, another radio hacker who goes by the handle [abcd567] popularized their own version of the “cantenna” some time ago. But [Akos] has made some tweaks to the design to drive the bar even lower, which he has dubbed the “coketenna”.
The primary advantages of his design is that you no longer need to solder anything or even use any special connectors. In fact, you can assemble this antenna with nothing more than a pocket knife.
You start by cutting the can down to around 68 mm in length, and cutting an “X” into the bottom. Then strip a piece of coax, and push it through the X. The plastic-coated center conductor of the coax should emerge through the bottom of the can, while the braided copper insulation will bunch up on the other side. If you want to make it really fancy, [Akos] suggests cutting a plastic drink bottle in half and using that as a cover to keep water out of the “coketenna”.
How well does it work? He reports performance being very similar to his commercial ADS-B antenna which set him back $45 USD. Not bad for some parts of out the trash.
We’ve covered the math of creating an ADS-B antenna in the past if you’d like to know more about the science of how it all works. But if you just want an easy way of picking up some signals, this “coketenna” and an RTL-SDR dongle will get you started in no time.
Performing high-energy physics experiments can get very expensive, a fact that attracts debate on public funding for scientific research. But the reality is that scientists often work very hard to stretch their funding as far as they can. This is why we need informative and entertaining stories like Gizmodo’s How Physicists Recycled WWII Ships and Artillery to Unlock the Mysteries of the Universe.
The military have specific demands on components for their equipment. Hackers are well aware MIL-SPEC parts typically command higher prices. That quality is useful beyond their military service, which lead to how CERN obtained large quantities of a specific type of brass from obsolete Russian naval ordnance.
The remainder of the article shared many anecdotes around Fermilab’s use of armor plate from decommissioned US Navy warships. They obtained a mind-boggling amount – thousands of tons – just for the cost of transport. Dropping the cost of high quality steel to “only” $53 per ton (1975 dollars, ~$250 today) and far more economical than buying new. Not all of the steel acquired by Fermilab went to science experiments, though. They also put a little bit towards sculptures on the Fermilab campus. (One of the few contexts where 21 tons of steel can be considered “a little bit”.)
Continue reading “Military Surplus Repurposed for High Energy Physics”
[Mathieu] wrote in with his laser target practice game. It’s not the most amazing hack in the history of hackery, but it’s an excellent example of the type of simple and fun things you can do with just a little bit of microcontrollering.
First off, the gun is a broken toy gun that used to shoot something other than red collimated light beams. The Arduino knockoff inside reacts to a trigger pull and fires the laser for around 200 milliseconds. The gun also has a “gas gauge” that fills up with repeated shots and cools down over time. And therein lies the game — a simple race to ten, where each player only has a fixed number of shots over time.
The targets are simply a light sensor, scorekeeping LED display, and a buzzer that builds tension by beeping at you as the countdown timer ticks down. The bodies are made out of 3D-printed corners that connect some of [Mathieu]’s excess wooden goat-cheese lids.
All the code is up on GitHub so you can make your own with stuff that you’ve got lying around the house. The “gun” can be anything that you can embed a laser in that makes it aimable. Good clean fun!
[Sven337]’s rebuild of a cheap and terrible baby monitor isn’t super visual, but it has so much more going on than it first seems. It’s also a how-to for streaming audio via UDP over WiFi with a pair of ESP8266 units, and includes a frank sharing of things that went wrong in the process and how they were addressed. [Sven337] even experimented with a couple of different methods for real-time compression of the transmitted audio data, for no other reason than the sake of doing things as well as they can reasonably be done without adding parts or spending extra money.
The original baby monitor had audio and video but was utterly useless for a number of reasons (French). The range and quality were terrible, and the audio was full of static and interference that was just as loud as anything the microphone actually picked up from the room. The user is left with two choices: either have white noise constantly coming through the receiver, or be unable to hear your child because you turned the volume down to get rid of the constant static. Our favorite part is the VOX “feature”: if the baby is quiet, it turns off the receiver’s screen; it has no effect whatsoever on the audio! As icing on the cake, the analog 2.4GHz transmitter interferes with the household WiFi when it transmits – which is all the time, because it’s always-on.
Small wonder [Sven337] decided to go the DIY route. Instead of getting dumped in the trash, the unit got rebuilt almost from the ground-up.
Continue reading “Baby Monitor Rebuild is also ESP8266 Audio Streaming How-To”
Hackers can be a diverse bunch. My old hackerspace had folks ranging from NSA employees (ahem, independent security contractors) to space-probe pilots to anarchist vegan punks. And we all got along because we shared a common love for what we’re doing. One summer night we were out late in Adams Morgan and my vegan-punk friend reaches into the trash can and pulls out a discarded pepperoni Jumbo Slice.
“Wait a minute! Vegans don’t eat pepperoni pizza with cheese.” But my friend was a “freegan” — a vegan who, for ethical reasons, won’t buy meat or milk but who also won’t turn it down if it’s visibly going to waste. It’s actually quite a practical and principled moral proposal if you think about it: he’s not contributing to the use of animals that he opposes, but he gets to have a slice of pizza just the same. And fishing a slice of pizza, in a cardboard container, off the top of the trashcan isn’t as gross as you’d imagine, although it pays to be picky.
A Fracker is Born
That was the night that we realized we all had something deeper in common: we were all “frackers”. If you’ve been around hackers long enough, you’ll have noticed this tendency, but maybe you’ve never put a name to it. Tearing something apart, even if you might break it in the process, isn’t a problem if you fished it out of the e-waste stream to begin with. If you’re able to turn it into something, so much the better. It’s all upside. Need practice de-soldering tricky ICs? Looking for a cheap target to learn reverse engineering on? Off to the trashcan! No hack is too dirty, no method too barbaric. It’s already junk, and you’re a fracker.
Do you have a junk shelf where you keep old heatsinks in case you need to cut some up and use it? Have you used a heat gun more frequently for harvesting parts than for stripping paint? Do you know that certain satisfaction that you get from pulling some old tech out of the junk pile and either fixing it up again or, better yet, making it do something else? You might just be a fracker too.
Continue reading “Frackers: Inside the Mind of the Junk Hacker”
Over here at Hackaday, we love stuff made from other (unrelated) stuff. Maybe it’s the ingenuity behind the build or the recycling of parts… or it could be both. Either way, it’s cool and a side benefit of re-using parts from the junk drawer is that it keeps the project cost down, maybe enough that the project wouldn’t even be feasible without the re-use of parts.
That brings us to the topic of this post, a Delta-style 3D Printer made from recycled parts not typically seen in such a machine. It was built by DIYer [hesamh] and is almost unrecognizable visually. The usual extruded aluminum or precision shaft frame has been replaced with 5 pieces of MDF, finger-jointed together at the seams. Attached to the 3 vertical MDF frame pieces are rail and carriage assemblies scavenged from Epson dot matrix prints saved from the scrap yard. The best part is that these rail/carriage assemblies already had stepper motors and belts installed!
The end effector is also unique among delta-style printers. This one is made from aluminum plate and provides a mount for the extruder. There is no need for a bowden tube setup when the extruder is mounted on the end effector, although the increase in mass may reduce the printer’s top speed. That’s fine by us as we’d rather have a good-looking slow print than a fast ball of spaghetti. Another scavenged stepper motor is used for the extruder. The accompanying belt pulley acts as a direct drive feed gear.
The print bed is a re-purposed flatbed scanner. The guts were removed and a heating element was placed under the glass. The bed heater is controlled separately by way of a household thermostat. An Arduino Leonardo and 4 stepper drivers replace the normally used Mega/RAMPS/Pololu combo. Overall, this is a cool build that shows what is possible with a little thought and resourcefulness. The only part used in this build that was actually made for use in a 3D Printer is the hotend!
[BenN] was at his local hackerspace one day when a friend stopped by and offered him a used 5AH lead acid battery. As any good tinkerer would, he jumped on the opportunity and immediately started looking around for a project to use the battery in. One of [BenN’s] recent other projects involved 12volt landscaping lights, the same voltage as the battery he was just given. At this point it was clear that he had a good start to making a lantern. This lantern project also supports [BenN’s]
obsession with hobby of preparing for the zombie apocalypse.
A lantern needs an enclosure. Over on the hackerspace’s spare-parts rack was an old ATX power supply. All of the internal electrical components were removed to make room for the battery which fit inside nicely. The landscaping light just happened to be slightly larger than the power supply’s fan cut outs. Once the grill was removed from the metal power supply enclosure, the lamp fit in nicely and was secured using silicone glue which can tolerate any temperature the bulb can produce.
The feature that separates a lantern from a flashlight is the top-mounted carrying handle and this lantern will receive one made from the wiring removed from the ATX power supply. The electrical wiring is fairly straight forward. The battery is connected to the landscaping light by way of the original ATX on/off switch. The two terminals of the battery were also wired to the power supply’s AC input connector. This allows [BenN] to connect a DC battery charger to two of the three pins in order to charge the battery. Although this is a creative way to re-use the AC connector, it leaves quite a bit of potential to accidently plug in a 120v AC cord!