Homemade 6 GHz Radar, v3

The third version of [Henrik Forstén] 6 GHz frequency-modulated continuous wave (FMCW) radar is online and looks pretty awesome. A FMCW radar is a type of radar that works by transmitting a chirp which frequency changes linearly with time. Simple continuous wave (CW) radar devices without frequency modulation cannot determine target range because they lack the timing mark necessary for accurately time the transmit and receive cycle in order to convert this information to range. Having a transmission signal modulated in frequency allows for the radar to have both a very high accuracy of range and also to measure simultaneously the target range and its relative velocity.

Like the previous versions, [Henrik] designed a four-layer pcb board and used his own reflow oven to solder all the ~350 components. This process, by itself, is a huge accomplishment. The board, much bigger than the previous versions, now include digital signal processing via FPGA.

[Henrik’s] radar odyssey actually started back in 2014, where his first version of the radar was detailed and shared in his blog. A year later he managed to solve some of the issues he had, design a new board with significant improvements and published it again. As the very impressive version three is out, we wonder what version four will look like.

In the video of [Henrik] riding a bicycle in a circle in front of the radar, we can see the static light posts and trees while he, seen as a small blob, roams around:

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A Lesson On Zener Regulators

For the longest time, Zener diode regulators have been one of those circuits that have been widely shared and highly misunderstood. First timers have tried to use it to power up their experiments and wondered why things did not go as planned. [James Lewis] has put up a worth tutorial on the subject titled, “Zener Diode makes for a Lousy Regulator”  that clarifies the misconceptions behind using the device.

[James Lewis] does an experiment with a regulator circuit with an ESP8266 after a short introduction to Zener diodes themselves. For the uninitiated, the Zener diode can operate in the reverse bias safely and can do so at a particular voltage. This allows for the voltage across the device to be a fixed value.

This, however, depends on the current flowing through the circuit which in turn relies on the load. The circuit will work as expected for loads the draw a small amount of current. This makes it suitable for generating reference voltages for microcontrollers and such.

To make a Zener into a “proper” voltage regulator, you just need to buffer the output with an amplifier of some kind. A single transistor is the bare minimum, but actually can work pretty well. You might also add a capacitor in parallel with the Zener to smooth out some of its noise.

Zener diodes are wonderful little devices and write-ups like these are indispensable for beginners and should be shared more often like the Zener and Schottky Tutorial and Diodes as a Switch.


Fix Everything and Get Your Own Flailing Arms Tube Man

The staple of used car dealerships that prompted Houston to ban all ‘attention getting devices’ is called an ‘air dancer’ and was invented in 1996. And now you can build your own, even if until now the space requirements kept you from doing so.

[dina Amin] shows how to make one from a bunch of discarded hair dryers and stuff everybody is likely to find in his or her workshop. While the build as such is rather basic — these things are really simple devices after all — [dina Amin]’s project video takes us through the interesting detours that turn a build into a project. It touches on the topics of painting plastics, hardware repairs, diagnosing and fixing DC motors, and how hair dryers actually work. As an added bonus we get a good-looking solution for fixing that enclosure with the worn out threads. All that in five minutes flat.

And while you might not know if you need one, [dina Amin]’s wacky waving inflatable arm flailing arm tube man is pretty much guaranteed to work. Unlike this one.

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Terrible Cluster of PIs

When we first saw [Ajlitt’s] Hackaday.io project Terrible Cluster we thought, perhaps, he meant terrible in the sense of the third definition:

3. exciting terror, awe, or great fear; dreadful; awful. (Dictionary.com)

After looking at the subtitle, though, we realized he just meant terrible. The subtitle, by the way, is: 5 Raspberry PI Zeros. One custom USB hub. Endless disappointment.

There are four Raspberry Pi Zero boards that actually compute and one Raspberry Pi Zero W serves as a head node and network router. The total cost is about $100 and half of that is in SD cards. There’s a custom USB backplane and even a 3D-printed case.

At first, using five tiny computers in a cluster might not seem like a big deal. Benchmarking shows the cluster (with a little coaxing) could reach 1.281 GFLOPS, with an average draw of 4.962W. That isn’t going to win any world records. However, the educational possibilities of building a $100 cluster that fits in the palm of your hand is interesting. Besides, it is simply a cute build.

We’ve seen much larger Pi clusters, of course. You might be better off with some desktop CPUs, but — honestly — not much better.

Hackaday Prize Entry: PaperBack Desktop ePaper Monitor

When we announced the Hackaday Prize with its Best Product category, [PK] polled his wife and co-workers about the idea of making a desktop monitor using 6″ 800×600 ePaper, which he has since built and calls the PaperBack. One such requirement for a monitor is to be able to connect to it using one of the usual desktop methods: VGA, DVI or HDMI. Given his previous experience making his own VGA card for the 2015 prize, he went with that. HDMI is in the works.

But it ended up being more than a desktop monitor. He first made a power and breakout board that a VGA input board would eventually connect to. To test it, he included a socket for plugging in an ESP32. With only one bodge he had the Hackaday logo displayed on the ePaper. He also now had the option of using it as a wireless internet connected display.

Moving on to VGA support, [PK] made a VGA input board using the MST9883 chip, which does the A/D conversion of the VGA RGB graphics signal and also recovers a pixel sampling clock from the HSYNC. His new VGA ePaper monitor has to identify itself to the VGA source, telling it dimensions, resolution and so on. This is called the EDID and was handled by the addition of an Atmel ATmega328 to the board. To finish it off, an LCMXO1200C FPGA does the high-speed conversions with the help of a 4 MBit SRAM framebuffer.

His very first test involved simply displaying the Hackaday logo using the ESP32, but now with the VGA input board he has it displaying Doom. Since it’s using ePaper it has only a 1-second refresh rate but it’s hard to come up with a more awesome way to proved that it works. He can also unplug it at any time and walk away with the latest screenshot intact. See it for yourself in the video below.

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Hackerspaces are Hard: Safety

Safety is one of those topics that often elicits a less-than-serious response from some tool users. For these folks, they assume their elite skills will protect them and as long as they pay attention, they never will get hurt. This explains the prevalence of the nickname “Stubby” among this population. On the opposite end of the spectrum, safety is also one of those areas where people who don’t know a lot about tools can overreact. Imagine a whole table of kids wearing goggles as one of them gingerly melts some solder. You don’t want solder in your eye, but that’s just not going to happen under normal circumstances.

And then there are freak accidents, which are a reality. On September 20th, a leaking propane tank exploded at Sector67’s new workshop, severely injuring Chris Meyer. Far from a noob, Chris is one of the most experienced people in the shop and was a co-founder of the space. He has a long road of healing ahead of him, and as seems to be the sad necessity these days, he has a GoFundMe campaign to help both with his medical expenses and to help refurbish the workshop. The Foothills Community Workshop also burned to the ground recently, although fortunately no one was injured.

All in all, hackerspaces seem to be reasonably safe, particular considering the challenges they face — or more fairly, the risks associated with the typical hackerspace’s openness. Most hackerspaces allow anyone who pay dues to be a member. There is a wide range of backgrounds, competencies, and judgments represented with, how shall I put it, some unusual viewpoints that might hinder rule-following. And once the member has a fob or key, it’s open season on any kind of tool in the place right? Not everything can have a lock on it.

Here are a few simple rules that have emerged over the years, and may help your hackerspace navigate the twin dangers of complacency and paralyzed fear while preparing for the freak accidents that may simply come to pass.

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Friday Hack Chat: The Incredible BeagleBoard

Over the last year or so, the BeagleBoard community has seen some incredible pieces of hardware. The BeagleBone on a Chip — the Octavo OSD335x — is a complete computing system with DDR3, tons of GPIOs, Gigabit Ethernet, and those all-important PRUs stuffed into a single piece of epoxy studded with solder balls. This chip made it into tiny DIY PocketBones and now the official PocketBeagle is in stock in massive quantities at the usual electronic component distributors.

For this week’s Hack Chat, we’re talking about the BeagleBoard, BeagleBone, PocketBeagle, and PocketBone. [Jason Kridner], the co-founder of BeagleBoard and beagle wrangler, will be on hand to answer all your questions about the relevance of the Beagle platform today, the direction BeagleBoard is going, and the inner workings of what is probably the best way to blink LEDs in a Linux environment.

Topics for this Hack Chat will include the direction BeagleBoard is going, the communities involved with BeagleBoard, and how to get the most out of those precious programmable real-time units. As always, we’re taking questions from the community, submit them here.

As an extra special bonus, this week we’re giving away some hardware. Digi-Key has offered up a few PocketBeagle boards. If you have an idea for a project, put it on the discussion sheet and we’ll pick the coolest project and send someone a PocketBeagle.


Our Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This Hack Chat will be going down noon, Pacific time on Friday, October 13th. Wondering why the Brits were the first to settle on a single time zone when the US had a more extensive rail network and the longitude so time zones made sense? Here’s a time zone converter! Use that to ponder the mysteries of the universe.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.