Super Simple, Super Cheap FPV Drone Tracking

What’s more disruptive to the drone first-person view (FPV) experience than dropouts in your video feed when you’re in the middle of a race? Probably nothing, and there’s probably also not much you can do about it. Or is there? Might a simple tracker based on RSSI help keep your video signal locked in?

Honestly, we’re not sure it would, but we think it’s pretty nifty to see [FlyerFpv]’s tracker following his drone around. The idea is simple and uses the full-diversity FPV receiver he already has. Diversity receivers constantly monitor signal strength from multiple antennas to determine which one to listen to, which improves reception quality. [FlyerFpv] sends the RSSI outputs to analog inputs on an Arduino which drives a servo to keep the signals as close to each other as possible. The Arduino and the DC-DC converter needed to power it fit nicely inside the receiver case with no modifications, which is a nice touch. With a 3D-printed servo mount and some fancy directional antennas, the setup keeps pretty good track of his drone now. See it in action below.

Sure, the response could be snappier, and we’d love to see another receiver and servo added to track pitch as well as yaw. For a first pass, we think it’s great, but [FlyerFpv] should enjoy it while he can in case AI takes over our flying fun soon.

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High End PC Gets A Rustic Woodworking Piece Of Art For A Case

As [Matt] from [DIY Perks] was about to assemble a new PC, he decided to take a unique direction when it came to building a case. Despite the appearance of a woodworking piece with weird industrial radiators, there is actually a full-fledged, high-end PC hidden inside.

Those radiators are a pair of almost-the-biggest-you-can-buy heatsinks — one of which has been modified to fit the graphics card. Separating the graphics card’s stock cooling fan unit cut down significantly on noise and works with the stringent space requirements of the build. Those fans however keep other components on the card cool, so [Matt] cut pieces of copper plate to affix to these areas and joined them to the heatsink with a heat pipe, bent to shape. The elm wood case then began to take shape around the graphics card — cut into pieces to accommodate the heat pipes, and sealed with black tack to dampen the ‘coil whine’ of the GPU; it turns out the likely culprit are the MOSFETs, but close enough.

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Making Vintage Computing Easy, The Hard Way

If you want to not take for granted how easy and seamless computers have become, take up vintage computing as a hobby. If you venture down the retro path, you’ll quickly question how anyone ever got any useful work done with computers, and the farther back you go in computer history, the more difficult everything seems to become.

Case in point: how do you easily transfer files between a home-brew PC/XT and your modern desktop? Back in the day we did it with null modem cables or by sneaker-netting stacks of floppies, but [Scott M. Baker] found another way — putting a Raspberry Pi on the ISA bus as a virtual floppy drive. The heart of the ISA card is an IDT7130, a 1-kb RAM chip that allows simultaneous asynchronous access over dual ports. One port talks to the ISA bus and the other talks to the GPIO of the Pi, after level-shifting to make everything voltage compatible, of course. [Scott] wrote a driver for the card, plugged a Pi Zero W into the header pins, and threw a Python server together that makes local images available to the shared memory on the card. The upshot of this is that the retro machine thinks it has a floppy in it, but it’s actually a server. The video below has tons of detail and shows the card in action. Pretty slick.

[Scott]’s projects are always fun to check out, and he really seems to have the retro life dialed in. Whether it’s old jukebox hacks or a Unix-ish OS for Z80s, there’s plenty to learn. Although we’d like to see more about that PC/XT in the video; are those Nixies we spy along the front panel?

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A Mobile Terminal for Guerrilla Communications

We use the Internet to do everything from filing our taxes to finding good pizza, but most critically it fulfills nearly all of our communication needs. Unfortunately, this reliance can be exploited by those pulling the strings; if your government is trying to do something shady, the first step is likely to be effecting how you can communicate with the outside world. The Internet is heavily censored and monitored in China, and in North Korea the entire country is effectively running on an intranet that’s cutoff from the wider Internet. The need for decentralized information services and communication is very real.

While it might not solve all the world’s communication problems, [::vtol::] writes in to tell us about a very interesting communication device he’s been working on that he calls “Hot Ninja”. Operating on the principle that users might be searching for accessible Wi-Fi networks in a situation where the Internet has been taken down, Hot Ninja allows the user to send simple messages through Wi-Fi SSIDs.

We’ve all seen creatively named Wi-Fi networks before, and the idea here is very much the same. Hot Ninja creates a Wi-Fi network with the user’s message as the SSID in hopes that somebody on a mobile device will see it. The SSID alone could be enough depending on the situation, but Hot Ninja is also able to serve up a basic web page to devices which actually connect. In the video after the break, [::vtol::] even demonstrates some rudimentary BBS-style functionality by presenting the client devices with a text field, the contents of which are saved to a log file.

In terms of hardware, Hot Ninja is made up of an Arduino Mega coupled to three ESP8266 boards, and a battery to keep it all running for up to eight hours so you can subvert a dictatorship while on the move. The user interface is provided by a small OLED screen and a keyboard made entirely of through-hole tactile switches, further reinforcing the trope that touch-typing will be a must have skill in the dystopian future. It might not be the most ergonomic device we’ve ever seen, but the fact it looks like something out of a Neal Stephenson novel more than makes up for it in our book.

This is not the first time we’ve seen Wi-Fi SSIDs used as a method of communication, thanks largely to how easy the ESP8266 makes it. For his part, [::vtol::] has previously experimented with using them to culturally enrich the masses.

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Hacked Fitness Trackers Aim to Improve Mental and Physical Health

We all know that the mind can affect the body in dramatic ways, but we tend to associate this with things like the placebo effect or psychosomatic illnesses. But subtle clues to the mind-body relationship can be gleaned from the way the body moves, and these hacked fitness monitors can be used to tease data from the background noise of everyday movements to help treat mental health issues.

Over the last few years, [Curt White] of the Child Mind Institute has been able to leverage an incredibly cheap but feature-packed platform, the X9 Pro Sports Bracelet, a fitness band that looks more or less like a watch. Stuffed with an ARM Cortex processor, OLED screen, accelerometer, pulse sensor, and a ton of other stuff, the $35 wearable is a hacker’s dream. And hack it he did. One version of the bracelet is called Tingle, which is used to detect and avert body-focused repetitive behaviors (BFRBs), compulsive disorders that can result in self-harm through pulling at hair or pinching. The Tingle is trained to recognize the motions associated with these behaviors and respond with haptic feedback through the vibration motor. Another hacked X9 was attached to a dental retainer and equipped with sensors to monitor respirations intraorally, in an attempt to detect overdoses. It’s fascinating stuff, and the things [Curt] has done with these cheap fitness bands is mighty impressive.

This project is yet another entry in the 2018 Hackaday Prize, which is currently in the Robot Modules phase. Got an idea for something to make robots easier to build? Start a project page on Hackaday.io and get entered. Maybe your module will even feature a hacked fitness tracker.

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Biasing That Transistor: The Common Emitter Amplifier

If you open up the perennial favourite electronics textbook The Art Of Electronics and turn to the section on transistors, you will see a little cartoon. A transistor is shown as a room in which “transistor man” stands watching a dial showing the base current, while adjusting a potentiometer that limits the collector current. If you apply a little more base current, he pushes up the collector a bit. If you wind back the base current, he drops it back. It’s a simple but effective way of explaining the basic operation of a transistor, but it stops short of some of the nuances of how a transistor works.

Of course the base-emitter junction is a diode and it is not a simple potentiometer that sits between collector and emitter. The “better” description of these aspects of the device fills the heads of first-year electronic engineering students until they never want to hear about an h-paramater or the Ebers-Moll model of transistor function again in their entire lives. Fortunately it is possible to work with transistors without such an in-depth understanding of their operation, but before selecting the components surrounding a device it is still necessary to go a little way beyond transistor man.

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Make 3D-Modeling Child’s Play with a Can of Play-Doh

You need to replicate a small part on a 3-D printer, so you start getting your tools together. Calipers, rulers, and a sketch pad at a minimum, and if you’re extra fancy, maybe you pull out a 3D-scanner to make the job really easy. But would you raid your kid’s stash of Play-Doh too?

You might, if you want to follow [Vladimir Mariano]’s lead and use Play-Doh for accurately modeling surface features in the part to be replicated. Play-Doh is a modeling compound that kids and obsolete kids alike love to play with, especially a nice fresh can before it gets all dried out or mixed in with other colors or gets dog hair stuck in it.

For [Vladimir], the soft, smooth stuff was the perfect solution to the problem of measuring the spacing of small divots in the surface of a cylinder that he was asked to replicate. Rather than measuring the features directly on the curved surface, he simply rolled it across a flattened wad of Play-Doh. The goop picked up the impressions on the divots, which were then easy to measure and transfer to Fusion 360. The video below shows the Play-Doh trick up front, but stay tuned through the whole thing to get some great tips on using the sheet metal tool to wrap and unwrap cylinders, as well as learning how to import images and recalibrate them in Fusion 360.

Run into a modeling problem that Play-Doh can’t solve? Relax, we’ve got a rundown on the basics for you.

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