Antenna Analyzer is a Lab in a Box

There was a time when the measure of a transmitting radio antenna was having it light an incandescent bulb. A step up was a classic SWR/Power meter that showed you forward and reflected power. Over the years, a few other instruments have tried to provide a deeper look into antenna performance. However, the modern champion is the antenna analyzer which is a way of measuring vector impedance.

[Captain Science] did a review of an inexpensive N1201SA analyzer. This device is well under $200 from the usual Chinese sellers. The only thing a bit odd is the frequency range which is 140 MHz to 2700 MHz. For some extra money (about $80 or $100 more) you can drop the low-end frequency to just under 35 MHz.

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Powering A Laptop With Supercapacitors

What do you do when you find a small horde of supercapacitors? The correct answer is a spectrum of dangerous devices ranging from gauss guns to quarter shrinkers. [Rinoa] had a less destructive idea: she’s replaced the battery in a laptop with a bank of supercapacitors.

The supercaps in question are 2.7 Volt, 500 Farad caps arranged in banks six for a total of about 3 watt-hours in each bank. The laptop used for this experiment is an IBM Thinkpad from around 1998. The stock battery in this laptop is sufficiently less advanced than today’s laptop batteries. Instead of using a microcontroller and SMBus in the battery, the only connections between the battery and laptop are power, ground, and connections for a thermocouple. This is standard for laptops of the mid-90s, and common in low-end laptops of the early 2000s. It also makes hacking these batteries very easy as there’s no associated microprocessors to futz around with.

With all the capacitor banks charged, the laptop works. It should – there isn’t a lot of intelligence in this battery. With one bank of six supercaps, [Rinoa] is getting a few minutes of power on her laptop. With a stack of supercaps that take up about the same volume as this already think Thickpad, [Rinoa] can play a few turns of her favorite late-90s turn-based strategy game. It’s not much, but it does work.

Check out [Rinoa]’s video below.

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How Good Is Your Aim First Thing In The Morning?

For the less than highly-driven individuals out there — and even some that are — sometimes, waking up is hard to do, and the temptation to smash the snooze button is difficult to resist. If you want to force your mind to immediately focus on waking up, this Nerf target alarm clock might get you up on time.

Not content to make a simple target, [Christopher Guichet] built an entire clock for the project. The crux of the sensor is a piezoelectric crystal which registers the dart impacts, and [Guichet]’s informative style explains how the sensor works with the help of an oscilloscope. A ring of 60 LEDs with the piezoelectric sensor form the clock face, all housed in a 3D printed enclosure. A rotary encoder is used to control the clock via an Arduino Uno, though a forthcoming video will delve into the code side of things; [Guichet] has hinted that he’ll share the files once the code has been tidied up a bit.

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Using Backscatter Radio for a Soil Sensor Network

With almost 8 billion souls to feed and a changing climate to deal with, there’s never been a better time to field a meaningful “Internet of Agriculture.” But the expansive fields that make industrial-scale agriculture feasible work against the deployment of sensors and actuators because of a lack of infrastructure to power and connect everything. So a low-power radio network for soil moisture sensors is certainly a welcome development.

We can think of a lot of ways that sensors could be powered in the field. Solar comes to mind, since good exposure to the sun is usually a prerequisite for any cropland. But in practice, solar has issues, the prime one being that the plants need the sun more, and will quickly shade out low-profile soil-based sensors.

That’s why [Spyros Daskalakis] eschewed PV for his capacitive soil moisture sensors in favor of a backscatter technique very similar to that used in both the Great Seal Bug and mundane RFID tags alike. The soil sensor switches half of an etched PCB bowtie antenna in and out of a circuit at a frequency proportional to soil moisture. A carrier signal from a separate transmitter is reflected off the alternately loaded and unloaded antenna, picking up subcarriers with a frequency proportional to soil moisture. [Spyros] explains more about the sensor design and his technique for handling multiple sensors in his paper.

We really like the principles [Spyros] leveraged here, and the simplicity of the system. We can’t help but wonder what sort of synergies there are between this project and the 2015 Hackaday Prize-winning Vinduino project.

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Making Laser Cutter Designs Work in a 3D Printer

The main mechanical tools in a hacker’s shop used to be a drill press and a lathe. Maybe a CNC mill, if you were lucky. Laser cutters are still a rare tool to find in a personal shop, but today’s hackers increasingly have access to 3D printers. What happens when you have a design for a laser cutter (2D parts) but only have access to a 3D printer? You punt.

[DIY3DTECH] has a two-part video on taking a 2D design (in an SVG file) and bringing it into TinkerCad. At that point, he assembles the part in software and creates a printable object. You can see the videos below.

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Record Players Explained for the Streaming Generation

How do you consume your music, these days? Aside from on the radio, that is. Do you play MP3 or other files on your phone and computer, or perhaps do you stream from an online service? If you’re really at the cutting edge though you’ll do none of those things, because you’ll be playing it on vinyl.

The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Dydric [CC BY-SA 2.5)], via Wikimedia Commons.
The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Photo by Dydric CC-BY-SA 2.5
A few years ago reporting on a resurgence of sales of vinyl records was something you would never have expected to see, but consumer tastes are unpredictable. Our red-trousered and extravagantly bearded hipster friends have rediscovered the glories of the format, and as a result it’s popping up everywhere. For those of us who are old enough to have genuinely been into the format before it was cool again, the sight of Sergeant Pepper and Led Zeppelin II on 12″ at outrageous prices on a stand at the local supermarket is a source of amusement. It’s good to see your first love back in vogue again, but is it really the £20($25) per album kind of good?

With the turntable having disappeared as an integral part of the typical hi-fi setup the new vinyl enthusiast is faced with a poor choice of equipment. Often the best available without spending serious money at an audiophile store is a USB device with the cheapest possible manufacture, from which the playback will be mediocre at best. We’ve lost the body of collective knowledge about what makes a good turntable to almost thirty years of CDs and MP3s, so perhaps it’s time for a quick primer.

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Amazon S3: Out Like a Light; On Like a Bathtub

You no doubt heard about the Amazon S3 outage that happened earlier this week. It was reported far and wide by media outlets who normally don’t delve into details of the technology supporting our connected world. It is an interesting thing to think that most people have heard about The Cloud but never AWS and certainly not S3.

We didn’t report on the outage, but we ate up the details of the aftermath. It’s an excellent look under the hood. We say kudos to Amazon for adding to the growing trend of companies sharing the gory details surrounding events like this so that we can all understand what caused this and how they plan to avoid it in the future.

Turns out the S3 team was working on a problem with some part of the billing system and to do so, needed to take a few servers down. An incorrect command used when taking those machines down ended up affecting a larger block than expected. So they went out like a light switch — but turning that switch back on wasn’t nearly as easy.

The servers that went down run various commands in the S3 API. With the explosive growth of the Simple Storage Service, this “reboot” hadn’t been tried in several years and took far longer than expected. Compounding this was a backlog of tasks that built up while they were bringing the API servers back online. Working through that backlog took time as well. The process was like waiting for a bathtub to fill up with water. It must have been an agonizing process for those involved, but certainly not as bad as the folks who had to restore GitLab service a few weeks back.

[via /r/programming]