An FPGA And A Few Components Can Make A Radio

April 18, 2020 by Jenny List 18 Comments

There was a time when making a radio receiver involved significant work, much winding of coils, and tricky alignment of circuitry. The advent of Software Defined Radio (SDR) has moved a lot of this into the domain of software, but there is of course another field in which a radio can be created via code. [Alberto Garlassi] has created a radio receiver for the AM and HF bands with a Lattice MachXO2 FPGA and minimal external components.

He describes it as an SDR, which given that it’s created from Verilog, is a term that could be applied to it. But instead of using an SDR topology of ADC and digital signal processing, it implements a surprisingly traditional direct conversion receiver.

It has a quadrature AM demodulator which has a passing similarity to an SDR with I and Q phased signals, but that’s where the similarity ends. Frequency selection is via an oscillator controlled from a serial port, and there is even a PWM amplifier on board that can drive a speaker. The result can be seen in the video below, and as you can hear the direct conversion with quadrature demodulator approach makes for a very effective AM receiver.

If this is a little much but you still fancy a radio with minimal components, you should have a look at the Silicon Labs range of receiver chips.

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3D Printed Speakers With Many Lessons Learned

April 18, 2020 by Danie Conradie 24 Comments

Although we all wish that our projects would turn out perfect with no hiccups, the lessons learned from a frustrating project can sometimes be more valuable than the project itself. [Thomas Sanladerer] found this to be the case while trying to build the five satellite speakers for a 5.1 surround sound system, and fortunately shared the entire process with us in all its messy glory.

[Thomas] wanted something a little more attractive than simple rectangular boxes, so he settled on a very nice curved design with few flat faces and no sharp corners, 3D printed in PLA. Inside each is an affordable broadband speaker driver and tweeter, with a crossover circuit to improve the sound quality and protect the drivers. The manufacturer of the drivers, Visatron, provides very nice speaker simulation software to select the appropriate drivers and design the crossover circuit. The front of each speaker consisted of a 3D printed frame, covered with material from a cut-up T-shirt. These covers attach to the main body using magnets and really look the part.

After printing, [Thomas] soaked all the parts in water to clean of the PVA support structures but discovered too late that the outer surfaces are not watertight and a lot of water had seeped into the parts. In an attempt to dry them he left them in the sun for a while which ended up warping some parts, so he had to reprint them anyway. The main bodies were printed in two parts and then glued together. This required a lot of sanding to smooth out the glue joints, and many cycles of paint and sanding to get rid of the layer lines. When assembling the different pieces, he found that many parts did not fit together, which he suspects was caused by incorrect calibration on the delta-bot printer he was using.

In the end, the build took almost two years, as [Thomas] needed breaks between all the frustration, and eventually only used one of the speakers. We’re glad he shared the messy parts of the project, which will hopefully spare someone else a bit of trouble in a project.

Listening to a high-quality audio setup is always a pleasure, and we’ve covered several projects from audiophiles, including affordable DML speakers, and 3D printed speaker drivers.

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Fixing An Agilent Oscilloscope Power Supply

April 18, 2020 by Jenny List 22 Comments

We should all be so lucky as [Salvaged circuitry], who scored a cheap Agilent oscilloscope from an online auction. Of course, its low price had a reason behind it, the ‘scope didn’t work. At fault was its power supply, the repair of which was documented in the video below.

These ‘scopes have relatively straightforward 12 V power supplies, extremely similar to off-the-shelf parts. The video is an interesting primer in switch-mode power supply repair, as the obvious failure of the filter capacitor and a MOSFET is traced further to the PSU controller chip. We see a new capacitor mounted proud of the board to reduce the risk of heat damage, and then some careful solder rework to save some lifted pads.

The result, a working oscilloscope. Maybe we’d have hacked in another 12 V supply, but given that this is a piece of test equipment perhaps it’s best to stay as close to the original spec as possible. As a parting shot he shows us an equivalent power supply, and promises us a side-by-side test in a future video.

These ‘scopes aren’t as popular in our circles as the cheaper Rigol range, but it’s worth remembering that they also have a budget model.

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The Game That Launched 1,000 Hackers

April 18, 2020 by Elliot Williams 6 Comments

John Conway passed away this week. Even if you don’t know much about mathematics, you will probably know nearly everyone’s favorite cellular automata ruleset: Conway’s “Game of Life”. It’s so much a part of our cultural history, that proto-hacker Eric Scott Raymond suggested using the glider as the hacker emblem.

The idea that a very simple set of rules, applied equally and everywhere, could result in “life” was influential in my growth as a young hacker, and judging from the comments on our article about Conway, I’m not alone. But I won’t lie: I was a kid and thought that it could do much more than make pretty patterns on the screen. I was both right and wrong.

Although amazingly complex machines can be built in Conway’s Life, just check out this video for proof, in the end no grand unifying theory of cellular automata has emerged. As a research topic Conway’s chosen field of mathematics, cellular automata is a backwater. It didn’t really go anywhere. Or did it?

Implementing Conway’s Life in BASIC on a Tandy Color Computer was one of the first things that launched me on my geeky path. It ranks with MENACE: the matchbox-based machine learning algorithm from the 1960’s and an introduction to Markov Chains in the form of a random text generator in my young algorithmic life, all of which I incidentally read about in Martin Gardner’s column in “Scientific American”. Conway’s Life, along with some dumb horse-race game, also taught me about bad random-number generators: the screen would populate the same “randomly” every time on the old CoCo.

So maybe Conway didn’t want to be remembered just for his “Life” because it was a bit of a mathematical dead-end. But in terms of its impact on the world, an entire generation of hackers, and my own personal life, it was able to fill up significantly more than a screen full of pixels. Here’s to Conway, his “Life”, and everyone else who is inspiring the next. You’re not just gliders, you’re glider guns!

[Game of Life example shown in this article is John Conway’s Game of Life – 1.0 written in Python by Nick Jarvis and Nick Wayne]

Get Back Out There, Robotically

April 18, 2020 by Bryan Cockfield 8 Comments

When interacting with reality at a distance is the best course of action, we turn to robots. Whether that’s exploring the surface of Venus, the depths of the ocean, or (for the time being) society at large, it’s often better to put a robot out there than an actual human being. We can’t all send robots to other planets, but we can easily get them in various other places with telepresence robots.

This tiny telepresence robot comes to us from [Ross] at [Crafty Robot] who is using their small Smartibot platform as a basis for this tiny robot. The smartibot drives an easily-created cardboard platform, complete with wheels, and trucks around a smartphone of some sort which handles the video and network capabilities. The robot can be viewed and controlled from any other computer using a suite of web applications that can be found on the project page.

The Smartibot platform is an inexpensive platform that we’ve seen do other things like drive an airship, and the creators are hoping that as many people as possible can get some use out of this quick-and-easy telepresence robot if they really need something like this right now. The kit seems like it would be useful for a lot of other fun projects as well.

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Mathematical Proof The Eagle In The USPS Logo Is FAST!

April 18, 2020 by Daniel Bogdanoff 33 Comments

The logo for the United States Postal Service is a mean-looking eagle. But a true fluid dynamics geek might look at it and realize that eagle is moving so fast it’s causing a shock wave. But just how fast is it moving? [Andrew Higgins] asked and answered this question, posting his analysis of the logo’s supersonic travel. He claims it’s Mach 4.9, but, how do we know? Science!

It turns out if something is going fast enough, you can tell just how fast with a simple picture! We’ve all seen pictures of jets breaking the sound barrier, this gives us information about the jet’s speed.

How does it work?

Think about it like this: sound moves at roughly 330 m/s on Earth at sea level. If an object moves through air at that velocity, the air disturbances are transmitted as sound waves. If it’s moving faster than sound, those waves get distributed downstream, behind the moving object. The distance of these waves behind the moving object is dependent on the object’s speed.

This creates a line of these interactions known as a “Mach line.” Find the angle difference of the Mach line and the direction of travel and you have the “Mach angle” (denoted by α or µ).

There is a simple formula for determining the speed of an object using the Mach angle, the speed of sound (a), and an object’s velocity (v): sin(µ) = a / v. The ratio of v to a is known as the Mach number, (M). If an object is going exactly the speed of sound, it’s going Mach 1 (because v = a).

Since Mach number (M) is v / a, we can plug it into the formula from above as 1 / M and use [Andrew]’s calculation shown in the image at the top of the article for a Mach angle (µ) of ~11.7°:

$\bf \sin ( \mu ) = \frac{1}{M} \\ \\ M = \frac{1}{\sin(\mu)} \\ \\ M = \frac{1}{\sin(11.7)} \\ \\ M = \frac{1}{0.202787295357} \\ \\ M = 4.9312753949380048$

The real question is, did the USPS chose Mach 4.93 as a hint to some secret government postal project? Or, was it simply a 1993 logo designer’s attempt to “capture the ethos of a modern era which continues today”?

Model Rocket Launcher Is So Serious, It Has A Briefcase

April 17, 2020 by Kristina Panos 24 Comments

What could be more thrilling than launching a complex rocket that you built yourself? For starters, launching it with literally anything better than the stock ignition system would be a step in the right direction. How about a briefcase full of fantastically fun overkill?

[FastEddy59] is in the middle of building a model rocket complete with a Thrust Vector Control (TVC) system to help with stabilization. Much to our delight, he’s designed an equally ambitious controller to spice up the launch sequence with security codes and a physical key. And what’s a launch controller without a giant emergency stop button to shut down everything? Incomplete, if you ask us.

Under the carbon fiber-wrapped acrylic hood, there’s an Arduino MEGA engine and an NRF24 LoRa module for transmission to the rocket. There’s even a DHT11 temperature sensor to verify that launch conditions are ideal. It’s still a work in progress with plenty of features to come, like fancier labels and plenty of launch-appropriate sound files for the hidden speaker. There’s a lot to this case, and [FastEddy59]’s video brief is ready and waiting on the pad after the break.

[FastEddy59] plans to hold the first launch in a few months, and we sincerely hope he outfits the rocket with a camera.

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