Learn To Loop The Python Way: Iterators And Generators Explained

If you’ve ever written any Python at all, the chances are you’ve used iterators without even realising it. Writing your own and using them in your programs can provide significant performance improvements, particularly when handling large datasets or running in an environment with limited resources. They can also make your code more elegant and give you “Pythonic” bragging rights.

Here we’ll walk through the details and show you how to roll your own, illustrating along the way just why they’re useful.

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ARM-Based NAS Is A Low Cost, Low Power Beauty

A NAS is always a handy addition to a home network, but they can be a little pricey. [Blake Burkhart] decided to create his own, prioritising budget and low power considerations, with a secondary objective to produce some router and IoT functionality on the side.

A Banana Pi R2 was a good choice to meet these requirements, being a router-based development board that also sports dual SATA connectors and gigabit Ethernet. [Blake] had some retrospective regrets about the performance of this particular SBC, but it does just fine when functioning purely as a NAS.

The enclosure for the device is a three bay hot-swap HDD module, with one of the bays gutted and used for the Banana Pi. It’s a simple idea, elegantly executed, which looks great. To access the ports of the Banana Pi, a custom acrylic side panel was laser cut, which also allowed LEDs to shine through – obligatory for any DIY server/computer build. When mounting this panel to the existing enclosure, [Blake] was reluctant to take his chances tapping the brittle acrylic, instead opting to melt the threads into the plastic with a pre-torched screw. We find that tapping acrylic is usually okay if you take it slow, but heat-tapping does sound fun.

The 12 V fan that came built into the hot-swap enclosure was too loud and awkwardly came in a non-standard size with a non-standard connector. What’s more, a buzzer alarm was triggered any time the fan was disconnected and 0 RPM was detected. [Blake]’s solution was to rewire the power pin of the connector to a 5 V rail; he found that running the fan at 5 V led to much quieter performance whilst keeping the HDDs sufficiently cool.

We find that when it comes to DIY network gear and routers, there are two approaches. Either create your own bespoke solution that perfectly fits your needs, like this perfect home router, or work around your current gear and build some tech to automatically reboot it for you.

 

No Signal For Your Radio-Controlled Watch? Just Make Your Own Transmitter

You can win any argument about the time when you have a radio controlled watch. Or, at least, you can if there’s any signal. [Henner Zeller] lives in a place where there is no reception of the DCF77 signal that his European wristwatch expects to receive. Consequently, he decided to make his own tiny transmitter, which emulates the DCF77 signal and allows the watch to synchronise.

A Raspberry Pi Zero W is the heart of the transmitter, and [Henner] manages to coax it into generating 77500.003Hz on a GPIO pin – close enough to the 77.5kHz carrier that DCF77 uses. The signal is AM, and transmits one bit/s, repeating every minute. A second GPIO performs the required attenuation, and a few loops of wire are sufficient for an antenna which only needs to work over a few inches. The Raspberry Pi syncs with NTP Stratum 1 servers, which gives the system time an accuracy of about ±50ms. The whole thing sits in a slick 3D printed case, which provides a stand for the watch to rest on at night; this means that every morning it’s synchronised and ready to go.

[Henner] also kindly took the time to implement the protocols for WWVB (US), MSF (UK) and JJY (Japan). This might be just as well, given that we recently wrote about the possibility of WWVB being switched off. Be sure to check the rules in your area before giving this a try.

We’ve seen WWVB emulators before, like this ATtiny45 build, but we love that this solution is an easy command line tool which supports many geographical locations.

Intro to Docker: Why and How to Use Containers on Any System

If you have your ear even slightly to the ground of the software community, you’ll have heard of Docker. Having recently enjoyed a tremendous rise in popularity, it continues to attract users at a rapid pace, including many global firms whose infrastructure depends on it. Part of Docker’s rise to fame can be attributed to its users becoming instant fans with evangelical tendencies.

But what’s behind the popularity, and how does it work? Let’s go through a conceptual introduction and then explore Docker with a bit of hands-on playing around.

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A Servo Powered Robotic Arm, But Like You’ve Never Seen Before

We’ve written about a lot of DIY robotic arms. Some of them are high-performance, some are inexpensive, and some are just uniquely fun. This one certainly falls into the last category; whilst watching an episode of Black Mirror, [Gear Down For What] was struck by inspiration for a thin robotic limb. After some iterations he has a final prototype, and it’s quite something to see in action.

To make a robotic arm as slender as possible, the actuators can’t be mounted on the arm itself but must instead drive the arm remotely. There are a number of ways of doing this, and though [Gear Down For What] considered using pneumatics or hydraulics, he opted to keep it simple with RC servos which produced a nifty solution that we really like.

The arm is made out of a series of 3D printed ball joints, allowing rotation in any direction. The tricky bit is transferring the force from the servos to each joint. Initially bare fishing line was considered, but this made the remote joints difficult to control when lower joints were moving. The solution was to use the fishing line inside of tubing, similar to the way that bike brakes operate. This allows the force to be carried to the appropriate joint regardless of lower movement. Each joint needs an x and y tension to allow it to rotate in any direction, which means an army of sixteen servos is needed to operate the eight segment arm.

Robotic arms are always fun to build and we’ve seen some pretty neat uses for them, such as mapping magnetic fields in 3D, or teaching sign language.

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Hummingbirds, 3D Printing, and Deep Learning

Setting camera traps in your garden to see what local wildlife is around is quite popular. But [Chris Lam] has just one subject in mind: the hummingbird. He devised a custom setup to capture the footage he wanted using some neat tech.

To attract the hummingbirds, [Chris] used an off-the-shelf feeder — no need to re-invent the wheel there. To obtain the closeup footage required, a 4K action cam was used. This was attached to the feeder with a 3D-printed mount that [Chris] designed.

When it came to detecting the presence of a hummingbird in the video, there were various approaches that could have been considered. On the hardware side, PIR and ultrasonic distance sensors are popular for projects of this kind, but [Chris] wanted a pure software solution. The commonly used motion detection libraries for this type of project might have fallen over here, since the whole feeder was swinging in the air on a string, so [Chris] opted for machine learning.

A RESNET architecture was used to run a classification on each frame, to determine if the image contained a hummingbird or not. The initial attempt was not greatly successful, but after cropping the image to a smaller area around the feeder, classification accuracy greatly increased. After a bit of FFmpeg magic, the selected snippets were concatenated to make one video containing all the interesting parts; you can see the result in the clip after the break.

It seems that machine learning and wildlife cams are a match made in heaven. We’ve already written about a proof-of-concept project which identifies different animals in the footage when motion is detected.

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Make Your Python Prettier With Decorators

Many Pythonistas are familiar with using decorators, but far fewer understand what’s happening under the hood and can write their own. It takes a little effort to learn their subtleties but, once grasped, they’re a great tool for writing concise, elegant Python.

This post will briefly introduce the concept, start with a basic decorator implementation, then walk through a few more involved examples one by one.

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