Build A Rhizotron: Image The World Beneath Your Feet

June 19, 2016 by Jenny List 12 Comments

The world of the subsoil is a fascinating place. Our whole ecosystem depends on its variety of fungus, bacteria and detritivore creatures that break down and decay dead matter and provide the nutrients to sustain plants that bring in the energy from the sun.

It’s easy enough to study what is happening beneath the surface, just reach for a trowel. But of course, that’s an imperfect technique, for it only gives a picture of a world you have destroyed, and then at best only a snapshot.

What if you could image underground, take pictures and video of the decay process and the creatures that are its engine? [Josh Williams] was curious how this could be achieved, so after early experiments with buried webcams proved unimpressive he created the Rhizotron. A flatbed scanner waterproofed for burial with plenty of silicone, and driven by a Raspberry Pi. The result was particularly successful, and though he has lost several scanners to water ingress he has collected some impressive imagery which he has posted on the project’s blog. Below the break we’ve included one of his videos taken with the scanner in a compost bucket, in which you can see decomposition aplenty, mating millipedes, spreading fungal hyphae and much more.

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Turn Down The Bed, Turn Down The Lights

June 19, 2016 by Bryan Cockfield 6 Comments

Home automation seems to be working its way to a computer-controlled future in which humans will be little more than an afterthought. Eventually they will take over Skynet-style, but until then, we will enjoy the relative comfort that a good home automation project provides. The latest from [Clement] certainly goes a long way towards this goal by automating his bed (Google Translate from French).

With four load cells and a microcontroller, [Clement]’s bed can tell whether or not he is sleeping. After taking a weight reading, the bed can send commands to the rest of his home automation system and tell it to turn off his stereo and turn the lights off in the house (or change them to a different color). And it doesn’t stop with just going to bed, but when he wakes up as well. The system can begin turning on lights, starting the coffee machine, and opening the blinds without any interaction from him at all.

This project goes well beyond simple home automation. With a little configuration and extrapolation, [Clement] can tell where in the bed he slept at night, what stages of sleep he was in at specific times, and the overall quality of his sleep. This could go a long way for someone who has a hard time sleeping and needs a little more information on how to correct the problem.

While we’ve seen various takes on tying a bed into one’s home automation system, this one goes above and beyond with the amount of data collected. You could even go one step further and have it turn on some Barry White if the normal weight in the bed suddenly doubles, for whatever reason. Maybe that will be a feature in Version 2.

Make Math Real With This Analog Multiplier Primer

June 19, 2016 by Dan Maloney 11 Comments

Remember learning all about functions in algebra? Neither do we. Oh sure, most of us remember linear plots and the magic of understanding y=mx+b for the first time. But a lot of us managed to slide by with only a tenuous grasp of more complex functions like exponentials and conic sections. Luckily the functionally challenged among us can bolster their understanding with this demonstration using analog multipliers and op amps.

[devttys0]’s video tutorial is a great primer on analog multipliers and their many uses. Starting with a simple example that multiplies two input voltages together, he goes on to show circuits that output both the square and the cube of an input voltage. Seeing the output waveform of the cube of a ramped input voltage was what nailed the concept for us and transported us back to those seemingly wasted hours in algebra class many years ago. Further refinements by the addition of an op amp yield a circuit that outputs the square root of an input voltage, and eventually lead to a voltage controlled resistor that can attenuate an input signal depending on its voltage. Pretty powerful stuff for just a few chips.

The chip behind [devttys0]’s primer is the Analog Devices AD633, a pretty handy chip to have around. For more on this chip, check out [Bil Herd]’s post on analog computing.

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Simple Vacuum Tube Preamp Results In A Beautiful Build

June 19, 2016 by Dan Maloney 32 Comments

We have no intention of wading into the vacuum tube versus silicon debates audiophiles seem to thrive on. But we know a quality build when we see it, and this gorgeous tube preamp certainly looks like it sounds good.

The amp is an attempt by builder [Timothy Cose] to give a little something back to the online community of vacuum tube aficionados that guided him in his journey into the world of electrons under glass. Dubbed a “Muchedumbre” – Spanish for “crowd” or “mob”; we admit we don’t get the reference – the circuit is intended as a zero-gain preamp for matching impedance between line level sources and power amplifiers. Consisting of a single 12AU7 in a cathode-follower design and an EZ81 for rectification, where the amp really shines is in build quality. The aluminum and wood chassis looks great, and the point-to-point wiring is simple and neat. We especially appreciate the neatly bent component leads and the well-dressed connections on the terminal strips and octal sockets. There’s a nice photo gallery below with shots of the build.

As much as we appreciate the miracles that can be accomplished with silicon, there’s still magic aplenty with vacuum tubes. For more thermionic goodness, check out these minimalist homebrew vacuum tubes or these artisanal vacuum tubes.

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Hackaday Prize Entry: Microscopy With Blu-ray

June 18, 2016 by Brian Benchoff 5 Comments

Confocal microscopy is an imaging technique that provides higher resolution micrographs than that of traditional optical microscopy. Confocal microscopes attain this higher resolution from an image sensor behind a pinhole. By eliminating out of focus light, and by scanning the specimen back and forth under the microscope, a very high resolution image may be produced. This technique has applications ranging from life sciences to semiconductor work. For this year’s Hackaday Prize, [andreas.betz] is building a confocal microscope using little more than a Blu-ray drive read head.

[andreas]’ build uses a standard Playstation 3 Blu-ray drive mechanism. The read head for this mechanism is well documented, but [andreas] still has to drive the laser and the voice coils for this machine to do anything. With the Blu-ray drive working, only the optics remained.

Just this last week, [andreas] imaged the die of a transistor with a resolution of about 680nm. An inductor was also imaged, showing a track separation of about 10um. This is approaching the limits of optical microscopy, and the apparatus is simple enough for anyone to replicate.

As a feat of technical ingenuity, this is a great project. It’s one of the best we’ve seen for the Citizen Science portion of the Hackaday Prize, and can’t wait to see what other images [andreas] can make with this machine.

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Very Clever 555 Bassline Synth/Sequencer

June 18, 2016 by Elliot Williams 13 Comments

If we had a dime for every 555-based noisemaker circuit we see… But this one’s got a twist.

[Tristan] does two things that elevate his sawtooth-wave noisemaker above the norm. First, he gets a clean sawtooth wave out of it so that it sounds about right. Then he manages to make it more or less playable. It’s a refined version of a classic hack.

The first trick is a matter of putting a constant current supply upstream of the timing capacitor. The usual 555-timer circuit just charges the capacitor up from the power rails through a resistor. This is fine if all you care about is timing. But because the current is proportional to the constantly dropping voltage difference, the voltage on the capacitor is an exponential function over time.

A simple transistor current source linearizes the waveform in no time. Raw sawtooth waves are “rich in harmonics” which is synth-geek code for “a bit grating”, but it will surely do well with a little filtering. The Javascript suggests that he’s already thinking in that direction, but we’re going to need video proof!

The second cool trick up [Tristan]’s sleeve is the light-dependent resistor (LDR) that determines the pitch. Yeah, we’ve all made those before — the light-dependent “Theremin”. But [Tristan] took the extra step and wrote up a Javascript application that makes his monitor brighter and darker, enabling him to get musical pitches out of the gizmo.

We’ve always wanted to implement LED-to-LDR control while writing the Logic Noise series, but never found a reliable way to make it work. It’s cool to see [Tristan]’s efforts. Maybe we’ll pull a 555 out of the junk box in his honor.

Solvespace: A Parametric CAD Tool

June 18, 2016 by Elliot Williams 31 Comments

3D printing seems like it takes forever when you’re waiting for a part to come out. But if you’re like us, the real time spent in making something new is in modelling and refining the piece. There are tons of CAD programs out there, and finding one that meets your needs is part functionality and part personal preference. Reader [Leibowitz] pointed us to Solvespace, and it looks like it fills the gap between something like OpenSCAD and something more feature-full (and complicated) like FreeCAD.

We’re wondering why we hadn’t heard of Solvespace before. It looks great. It has a lot of what we like about OpenSCAD — the ability to quickly and easily specify two 5 mm holes exactly 21 mm from each other, center-to-center and then change that distance easily. But it also has other features like constraint solvers for mechanisms and linkages. It looks like a great way to design your next Strandbeest. The tutorials seem like a good way to get started quickly.

As we said above, choosing a 3D modeller is partly based on your requirements, but also partly on your feelings. If you’re feeling limited by OpenSCAD, there’s also ImplicitCAD. Or try out Autodesk’s free (but not open) Fusion 360. And now there’s Solvespace. It’s great to have options.