Living Robots: Revisiting BEAM

May 29, 2021 by Elliot Williams 40 Comments

You’re hit by the global IC shortage, reduced to using stone knives and bearskins, but you still want to make something neat? It’s time to revisit BEAM robots.

Biology, electronics, aesthetics, and mechanics — Mark Tilden came up with the idea of minimalist electronic creatures that, through inter-coupled weak control systems and clever mechanical setups, could mimic living bugs. And that’s not so crazy if you think about how many nerves something like a cockroach or an earthworm have. Yet their collection of sensors, motors, and skeletons makes for some pretty interesting behavior.

My favorite BEAM bots have always been the solar-powered ones. They move slowly or infrequently, but also inexorably, under solar power. In that way, they’re the most “alive”. Part of the design trick is to make sure they stay near their food (the sun) and don’t get stuck. One of my favorite styles is the “photovore” or “photopopper”, because they provide amazing bang for the buck.

Back in the heyday of BEAM, maybe 15 years ago, solar cells were inefficient and expensive, circuits for using their small current were leaky, and small motors were tricky to come by. Nowadays, that’s all changed. Power harvesting circuits leak only nano-amps, and low-voltage MOSFETs can switch almost losslessly. Is it time to revisit the BEAM principles? I’d wager you’d put the old guard to shame, and you won’t even need any of those newfangled microcontroller thingies, which are out of stock anyway.

If you make something, show us!

Supersized Weather Station Uses Antique Analog Meters

March 10, 2021 by Bryan Cockfield 13 Comments

For most of us, getting weather information is as trivial as unlocking a smartphone or turning on a computer and pointing an app or browser at one’s weather site of choice. This is all well and good, but it lacks a certain panache that old weather stations had with their analog dials and stained wood cases. The weather station that [BuildComics] created marries both this antique aesthetic with modern weather data availability, and then dials it up a notch for this enormous analog weather station build.

The weather station uses 16 discrete dials, each modified with a different label for the specific type of data displayed. Some of them needed new glass, and others also needed coils to be modified to be driven with a lower current than they were designed as well, since each would be driven by one of two Arduinos in this project. Each are tied to a microcontroller output via a potentiometer which controls the needle’s position for the wildly different designs of meter. The microcontrollers themselves get weather information from a combination of real-world sensors outside the home of [BuildComics] and from the internet, which allows for about as up-to-date information about the weather as one could gather first-hand.

The amount of customization of these old meters is impressive, and what’s even more impressive is the project’s final weight. [BuildComics] reports that it took two people just to lift it onto the wall mount, which is not surprising given the amount of iron in some of these old analog meters. And, although not as common in the real world anymore, these old antique meters have plenty of repurposed uses beyond weather stations as well.

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An Op-Amp From The Ground Up

January 30, 2021 by Jenny List 49 Comments

If we had to pick one part to crown as the universal component in the world of analogue electronics, it would have to be the operational amplifier. The humble op-amp can be configured into so many circuit building blocks that it has become an indispensable tool for designers. It’s tempting to treat an op-amp as a triangular black box in a circuit diagram, but understanding its operation gives an insight into analogue electronics that’s worth having. [Mitsuru Yamada]’s homemade op-amp using discrete components is thus a project of interest, implementing as it does a complete simple op-amp with five transistors.

Looking at the circuit diagram it follows the classic op-amp with a long-tailed pair of NPN transistors driving a PNP gain stage and finally a complimentary emitter follower as an output buffer. It incorporates the feedback capacitor that would have been an external component on early op-amp chips, and it has a couple of variable resistors to adjust the bias. Keen eyed readers will notice its flaws such as inevitably mismatched transistors and the lack of a current mirror in the long-tailed pair, but using those to find fault in a circuit built for learning is beside the point. He demonstrated it in use, and even goes as far as to show it running an audio power amplifier driving a small speaker.

For the dedicated student of op-amps, may we suggest further reading as we examine the first integrated circuit op-amp?

Homebrew Slide Rule Gets Back To Mathematical Basics

November 11, 2020 by Dan Maloney 49 Comments

In the grand scheme of things, it really wasn’t all that long ago that a slide rule was part of an engineer’s every day equipment. Long before electronic calculators came along, a couple of sticks of wood inscribed with accurate scales was all it took to do everything from simple multiplication to logarithms and trig functions.

While finding a slide rule these days isn’t impossible, it’s still not exactly easy, and buying one off the shelf isn’t as fun or as instructive as building one yourself. [JavierL90]’s slide rule build started, ironically enough, on the computer, with a Python program designed to graphically plot the various scales needed for the fixed sections of the slide rules (the “stators”) and the moving bit (the “slide”). His first throught was to laser-engrave the scales, but the route of printing them onto self-adhesive vinyl stock proved to be easier.

With the scale squared away, work turned to the mechanism itself. He chose walnut for the wood, aluminum for the brackets, and a 3D-printed frame holding a thin acrylic window for the sliding cursor. The woodworking is simple but well-done, as is the metalwork. We especially like the method used to create the cursor line — a simple line scored into the acrylic with a razor, which was then filled with red inks. The assembled slide rule is a thing of beauty, looking for all the world like a commercial model, especially when decked out with its custom faux leather carry case.

We have to admit that the use of a slide rule is a life skill that passed us by, but seeing this puts us in the mood for another try. We might have to start really, really simple and work up from there.

Eye-Catching And Crumb-Suspending

September 10, 2020 by Brian McEvoy 5 Comments

Printed circuit boards used to be green or tan, and invariably hidden. Now, they can be artful, structural, and like electronic convention badges, they are the entire project. In this vein, we find Open LEV, a horseshoe-shaped desktop bauble bristling with analog circuitry supporting an acoustic levitator. [John Loefler] is a mechanical engineer manager at a college 3D printing lab in Florida, so of course, he needs to have the nerdiest stuff on his workspace. Instead of resorting to a microcontroller, he filled out a parts list with analog components. We have to assume that the rest of his time went into making his PCB show-room ready. Parts of the silkscreen layer are functional too. If you look closely at where the ultrasonic transducers (silver cylinders) connect, there are depth gauges to aid positioning. Now that’s clever.

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An Analog IC Design Book Draft

August 31, 2020 by Al Williams 21 Comments

[Jean-Francois Debroux] spent 35 years designing analog ASICs. He’s started a book and while it isn’t finished — indeed he says it may never be — the 180 pages he posted on LinkedIn are a pretty good read.

The 46 sections are well organized, although some are placeholders. There are sections on design flow and the technical aspects of design. Examples range from a square root circuit to a sigma-delta modulator, although some of them are not complete yet. There are also sections on math, physics, common electronics, materials, and tools.

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Analog Noise Generator, Fighter Of Other Noises

July 6, 2020 by Donald Papp 11 Comments

A chaotic drone of meaningless sound to lull the human brain out of its usual drive to latch on to patterns can at times be a welcome thing. A nonsense background din — like an old television tuned to a dead channel — can help drown out distractions and other invading sounds when earplugs aren’t enough. As [mitxela] explains, this can be done with an MP3 file of white noise, and that is a solution that works perfectly well for most practical purposes. However he found himself wanting a more refined hardware noise generator with analog controls to fine tune the output, and so the Rumbler was born.

The Rumbler isn’t just a white noise generator. White noise has a flat spectrum, but the noise from the Rumbler is closer to Red or Brownian Noise. The different colors of noise have specific definitions, but the Rumbler’s output is really just white noise that has been put through some low pass filters to create an output closer to a nice background rumble that sounds pleasant, whereas white noise is more like flat static.

Why bother with doing this? Mainly because building things is fun, but there is also the idea that this is better at blocking out nuisance sounds from neighboring human activities. By the time distant music (or television, or talking, or shouting) has trickled through walls and into one’s eardrums, the higher frequencies have been much more strongly attenuated than the lower frequencies. This is why one can easily hear the bass from a nearby party’s music, but the lyrics don’t survive the trip through walls and windows nearly as well. The noise from the Rumbler is simply a better fit to those more durable lower frequencies.

[Mitxela]’s writeup has quite a few useful tips on analog design and prototyping, so give it a read even if you’re not planning to make your own analog noise box. Want to hear the Rumbler for yourself? There’s an embedded audio sample near the bottom of the page, so go check it out.

For a truly modern application of white noise, check out the cone of silence for snooping smart speakers.