PIC Powered PicoBat Picks Up Pulsed Power

June 26, 2018 by Kerry Scharfglass 15 Comments

In 2012, [Bruno] wanted to detect some bats. Detect bats? Some varieties of bat (primarily the descriptively named “microbats”) locate themselves and their prey in space using echolocation, the same way your first robot probably did. The bat emits chirps from their adorably tiny larynx the same way a human uses its vocal cords to produce sound. The bat then listens for an echo of that sound and can make inferences about the location of its presumed prey in the volume around it. Bat detectors are devices which can detect these ultrasonic sounds and shift them into a range that humans can hear. So how would you build such a device? [Bruno]’s PicoBat probably sets the record for component count and code simplicity.

With no domain expertise the most conspicuous way to build a bat detector is probably to combine the glut of high performance microcontrollers with a similarly high performing analog to digital converter. With a little signal processing knowledge you sample the sounds at their native frequency, run them through a Fast Fourier transform, and look for energy in the ultrasonic frequency range, maybe about 20 kHz to 100 kHz, according to Wikipedia. With more knowledge about signal interference it turns out there are a surprisingly large number of ways to build such a device, including some which are purely analog. (Seriously, check out the Wikipedia page for the myriad ways this can be done.)

[Bruno] did use a microcontroller to build his bat detector, but not in the way we’d have expected. Instead of using a beastly high performance A/D and a similarly burly microcontroller, the PicoBat has a relatively tame PIC12 and a standard ultrasonic transducer, as well as a piezo buzzer for output. Along with a power rail, that’s the entire circuit. The code he’s running is similarly spartan. It configures a pair of GPIOs and toggles them, with no other logic. That’s it.

So how does this work? The ultrasonic transducer is designed mechanically to only receive sounds in the desired frequency range. Being piezoelectric, when enough sound pressure is applied the stress causes a small voltage. That voltage is fed into the PIC not as a GPIO but as a clock input. So the CPU only executes an instruction when ultrasonic sound with enough intensity hits the transducer. And the GPIO toggling routine takes four clock cycles to execute, yielding a 1:4 clock divider. And when the GPIOs toggle they flip the potential across the buzzer, causing it to make human-audible sound. Brilliant!

Check out [Bruno]’s video demo after the break to get a sense for how the device works. You might be able to do this same trick with other components, but we’re willing to be that you won’t beat the parts count.

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Putting Crimpers To The Test: How Good Are Our Crimp Tools?

June 26, 2018 by Jenny List 90 Comments

Almost every project of mine from the last quarter century, if it has contained any wiring, has featured somewhere at least one crimp connector. There are a multiplicity of different types of crimp, but in this case I am referring to the ubiquitous variety with a red, blue, or yellow coloured plastic sleeve denoting the wire size they are designed for. They provide a physically robust and electrically sound connection that is resistant to wire fatigue due to vibration, and that can carry hefty currents at high voltages without any problems.

You might expect this to now head off into the detail of crimp connection, but my colleague Dan has already detailed what makes a good or a bad crimp. Instead recently my constant searches for weird and wonderful things to review for your entertainment led me to a new crimp tool, and thence to a curiosity about the effectiveness of different styles of tool. So I’m going to evaluate the three different crimping methods available to me, namely my shiny new ratchet crimp pliers, my aged simple crimp pliers, and for comparison an ordinary pair of pliers. I’ll take a look at the physical strength of each crimping method followed by its electrical effectiveness, but first it’s worth looking at the tools themselves.

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No Caffeine, No Problem: A Hand-Soldered Chip-Scale Package

June 26, 2018 by Dan Maloney 47 Comments

It’s said that the electronic devices we use on a daily basis, particularly cell phones, could be so much smaller than they are if only the humans they’re designed for weren’t so darn big and clumsy. That’s only part of the story — battery technology has a lot to do with overall device size — but it’s true that chips can be made a whole lot smaller than they are currently, and are starting to bump into the limit of being able to handle them without mechanical assistance.

Or perhaps not, if [mitxela]’s hand-soldering of a tiny ball-grid array chip is any guide. While soldering wires directly to a chip is certainly a practical skill and an impressive one at that, this at least dips its toe into the “just showing off” category. And we heartily endorse that. The chip is an ATtiny20 in a WLCSP (wafer-level chip-scale package) that’s a mere 1.5 mm by 1.4 mm. The underside of the chip has twelve tiny solder balls in a staggered 4×6 array with 0.4 mm pitch. [mitxela] tackled the job of soldering this chip to a 2.54-mm pitch breakout board using individual strands from #30 AWG stranded wire and a regular soldering iron, with a little Kapton tape to hold the chip down. Through the microscope, the iron tip looks enormous, and while we know the drop of solder on the tip was probably minuscule we still found ourselves mentally wiping it off as he worked his way across the array. In the end, all twelve connections were brought out to the protoboard, and the chip powers up successfully.

We’re used to seeing [mitxela] work at a much larger scale, like his servo-plucked music box or a portable Jacob’s Ladder. He’s been known to get small before though, too, like with these tiny blinkenlight earrings.

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Everything You Didn’t Know You Were Missing About Bias Tees

June 26, 2018 by Dan Maloney 23 Comments

Do you need a bias tee? If you want to put a DC voltage on top of an RF signal, chances are that you do. But what exactly are bias tees, and how do they work?

If that’s your question, [W2AEW] has an answer for you with this informative video on the basics of bias tees. A bias tee allows a DC bias to be laid over an RF signal, and while that sounds like a simple job, theory and practice often deviate in the RF world. The simplest bias tee would have a capacitor in series with the RF input and output to pass AC but block DC from getting out the input, and a DC input with a series inductance to prevent RF from getting into the DC circuit. Practical circuits are slightly more complicated, and [W2AEW] covers all you need to know about how real-world bias tees are engineered. He also gives some use cases for bias tees, from sending DC signals up a feed line to control an antenna tuner or rotator to adding a DC bias to a high-speed serial line.

It’s an interesting circuit, and we learned a lot, which is par for the course with [W2AEW]’s videos. Check out some of his other offerings, like a practical guide to the mysteries of Smith charts, or his visualization of how standing waves work.

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The Hills Are Alive With The Sound Of Train Whistles

June 25, 2018 by Adam Fabio 19 Comments

In Northern England, the hills used to be home to steam trains. The trains have long faded into history, but the sound of their whistle is making a brief return. Artist [Steve Messam] has created “Whistle” as part of The Great Exhibition of the North. [Steve] doesn’t cover the installation on his website yet, but there have been a few great articles about it in the local press.

Whistle consists of 16 steam engine whistles around Newcastle. From June 22 to September 9, you can hear the whistles at 1pm. First one whistle sounds, then another, then another after that. In all, 16 whistles are included in the art installation, all controlled by Raspberry Pi computers. The Pi’s were programmed by Nebula Labs. Tech details are slim on this one, but we’re guessing each Pi has a Cellular radio built-in.

The whistles used in this installation aren’t old train whistles. They are brand new cast brass whistles based upon the original steam train sounders. The compressed air available today doesn’t sound exactly like steam though, so the brass whistles were modified to sound more authentic. [Steve’s] idea is to get the whistle as perfect as possible, which will trigger the memories of those who are old enough to have heard the originals.

Want to know more about steam engines? Check out this Retrotechtacular about repairing steam locomotives!

Conquering The Earth With Cron

June 25, 2018 by Tom Nardi 15 Comments

The GOES-R series of Earth observation satellites are the latest and greatest NASA has to offer. As you might expect, part of the GOES-R job description is imaging Earth at high-resolution, but they also feature real-time lighting monitoring as well as enhanced solar flare and space weather capabilities. Four of these brand new birds will be helping us keep an eye on our planet’s condition into the 2030s. Not a bad way to spend around 11 billion bucks.

To encourage innovation, NASA is making the images collected by the GOES-R satellites available to the public through a collaboration with Google Cloud Platform. [Ben Nitkin] decided to play around with this data, and came up with an interactive website that let’s you visualize the Earth from the perspective of GOES-R. But don’t let those slick visuals fool you, the site is powered by a couple cron jobs and some static HTML. Just as Sir Tim Berners-Lee intended it.

But it’s not quite as easy as scheduling a wget command; the images GOES-R collects are separated into different wavelengths and need to be combined to create a false-color image. A cron job fires off every five minutes which downloads and merges the raw GOES-R images, and then another cron job starts a Python script that creates WebM time-lapse videos out of the images using ffmpeg. All of the Python scripts and the crontab file are available on GitHub.

Finally, with the images merged and the videos created, the static HTML website is served out to the world courtesy of a quick and dirty Python web server. The site could be served via something more conventional, but [Ben] likes to keep overhead as low as possible.

If you want to take the more direct route, we’ve covered plenty of projects focused on pulling down images from weather satellites; from using old-school “rabbit ears” to decoding the latest Russian Meteor-M N2 downlink.

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Makerbot Printer Reborn As PCB Engraver

June 25, 2018 by Steven Dufresne 14 Comments

Makerbot 3D printers were among the first to hit the market, so it makes sense that old and broken ones now litter the shelves of hackerspaces and home workshops alike. Rather than throw his one out, [Foaly] saw an opportunity to convert it to some sort of CNC machine. Given its lack of inherent rigidity and relatively weak motors, he opted to make a low-impact circuit board engraver which he appropriately calls the MakerbotCNC. We like the thought he put into this project, and it was clearly backed by plenty of experience.

Fortunately, his Makerbot Replicator 2 stemmed from a time when MakerBot was more open, meaning he could control the machine using a simple, open library. A little more open software handled his conversion of Gerber files to G-code. First tests drawing with a pen were successful, so he moved on to the carving head. He opted for an inrunner brushless motor to minimize dust getting into the motor but since these motors have a tendency to heat up he had to add fans to cool it. That still didn’t stop the heat from melting and bending his attempt at a 3D printed PLA carriage, so he switched it to a laser-cut MDF board to fix it. Finding the right collet proved tricky but eventually, he found the perfect fit was a collet clutch normally used to couple flex shafts to RC boat motors.

The result, as you can see was worth it. Using shallow passes, he can even cut carbon fiber parts.

While [Foaly] didn’t opt to replace more parts and go for a more powerful CNC, check out this 3D printer to CNC conversion which can cut wood, acrylic, and even aluminum.