You Can’t Fix What You Can’t Measure

July 10, 2021 by Elliot Williams 13 Comments

Last year, as my Corona Hobby™, I took up RC plane flying. I started out with discus-launched gliders, and honestly that’s still my main love, but there’s only so much room for hackery in planes that are designed to be absolutely minimum weight and maximum performance; these are the kind of planes that notice an extra half gram in the tail. So I’ve also built a few crude workhorse planes — the kind of things that you could slap a 60 g decade-old GoPro on and it won’t even really notice. Some have ended their lives in trees, but most have been disassembled and reincarnated — the electronics live on in the next body.

The journey has been really fun. I’ve learned about aerodynamics, gotten an excuse to put together a 4-axis hot-wire CNC styrofoam cutter, and covered everything in sight with carbon fiber tow, which is cheaper than you might think but makes the plane space-age. My current workhorse has bolted on an IMU, GPS, and a minimal Ardupilot setup, though I have yet to really put it through its paces. What’s holding me back is the video link — it just won’t work reliably further than a few hundred meters, and I certainly don’t trust it to get out of line-of-sight.

My suspicion is that the crappy antennas I have are holding me back, which of course is an encouragement to DIY, but measuring antennas in the 5.8 GHz band is tricky. I’d love to just be able to buy one of the cheap vector analyzers that we’ve covered in the past — anyone can make an antenna when they can see what they’re doing — but they top out at 2.4 GHz or lower. No dice. I’m blind in 5.8 GHz.

Of course, I do have one way in, and that’s tapping into the received signal strength indicator (RSSI) of a dedicated 5.8 GHz receiver, and just testing antennas out in practice, but that only gives a sort of loose better-worse indication. More capacitance or more inductance? Plates closer together or further apart? Try it out and see, I guess, but it’s time-consuming.

Moral of the story: don’t take measurement equipment for granted. Imagine trying to build an analog circuit without a voltmeter, or to debug something digital without a logic probe. Sometimes the most important tool is the one that lets you see the problem in the first place.

The Devil Is In The Details

July 3, 2021 by Elliot Williams 28 Comments

If you’ve taken a physics class, you’ve doubtless heard tales of mythical beasts like the massless string, the frictionless bearing, and the perfect sphere. And if you’re designing something new, it’s not always wrong to start by thinking in terms of these abstractions, just to get the basic framework laid and a first-order handle on the way things go. But once you start building, you’d better be ready to shed your illusions that a 6 mm peg will fit into a 6 mm hole.

Theory and practice are the same thing, in theory. But as soon as you step into practice, your “weekend build” can easily turn into a 500-hour project, full of hurdles, discoveries, experimentation, and eventual success. I’m not going to rehash [Scott Rumschlag]’s project here — you should really watch his detailed video — but suffice it to say that when building a sub-millimeter precision 3D measuring device, bearings do have friction and string does have non-zero mass, and it all matters.

When you start working on a project that “looked good on paper” or for whatever reason just doesn’t turn out as precisely as you’d wished, you could do worse than to follow [Scott’s] example: start off by quantifying your goals, and then identify where every error along the way accumulates to keep you from reaching them. Doing precise work isn’t easy, but it’s not impossible either if you know where all the errors are coming from. You at least have a chain of improvements that you can consider, and if you’ve set realistic goals, you also know when to stop, which is almost as important.

And if anyone out there has an infinite sheet of perfectly conductive material, I’m in the market.

How Did I Live Without A Microscope?

June 26, 2021 by Elliot Williams 48 Comments

Get yourself a decent stereo inspection microscope, preferably optical. Something that can magnify from maybe 4x to 40x is fine, anything outside this range is icing on the cake. Some people claim they’re fine with a minimum of 10x, but if you go there, you’re going to need a reducing lens eventually. Either way, get one, and you’ll thank me.

How do I know this? I finally caved in and bought one about two years ago now, and while it’s not something I use daily, it’s something that I use at least once a month and for which there is simply no substitute.

This is Hackaday, so a lot of you will be thinking “inspection scope = fine-pitch soldering” and you’re not wrong. With clearance of 10 cm or more, and a slab of sacrificial optical glass (“neutral density filter”) to protect the optics from tarry flux fumes, a stereo scope at 4x makes even the fiddliest solder joints possible. Good lighting, and sharp tweezers are also a must, of course. That’s what got me in the door.

But that’s the half of it, or less. When my scope was new to me — it hasn’t been “new” since the late 1980s — we spent a whole rainy Sunday afternoon microscoping whatever would fit under the lens. Grains of salt, blades of grass, all manner of bugs living and otherwise, shells, skin, textiles. Everything is cooler under the microscope.

The event that triggered this article wasn’t my son’s school project this week to photograph dandelion seeds. Nope, today my wife found a bug in the basement; to the microscope! And with a very quick and unfortunately very positive identification, we now know that we have to strain all of our flour for bread beetles and pitch whichever bags they came in with. Hooray!

The inspection scope was intended for the soldering bench, but has found general use as an irreplaceable household tool. While I admittedly also intended to use it to lure my son into science, the real fight over scope time has been with my wife. And that’s why you want an optical scope instead of one that’s tethered to a monitor — as a general-purpose tool, portability is paramount. No menu diving, no power source, and anyone can just grab it and go.

Convinced? Ready to pull out your wallet? Microscopes are like cars. You can spend as much as you’d like on one, the cheapest will cause you nothing but pain and suffering, and the difference between the mid-range and high-end is full of diminishing returns. Buying used, especially if you can kick the metaphorical tires, can be a great bargain, and a high-end used scope will hold its value a lot better than a new budget model. Just around $200 is a sweet spot new and $300-$400 will get you the top of the line from yesteryear if you shop around. That’s not cheap, but if you’re the microscope type, it’s easily worth it. Trust me.

Growing Up With Computers

June 19, 2021 by Elliot Williams 78 Comments

My son is growing up with computers. He’s in first grade, and had to list all of the things that he knows how to do with them. The list included things like mousing around, drawing ghosts with the paint program, and — sign of the times — muting and unmuting the microphone when he’s in teleconferences. Oh yeah, and typing emojis. He loves emojis.

When I was just about his age, I was also getting into computers. But home computers back then were in their early years as well. And if I look back, I’ve been getting more sophisticated about computers at just about the same pace that they’ve been getting more sophisticated themselves. I was grade school during the prime of the BASIC computers — the age of the Apple II and the C64. I was in high school for the dawn of the first Macs and the Amiga. By college, the Pentiums’ insane computational abilities just started to match my needs for them to solve numerical differential equations. And in grad school, the rise of the overclockable multi-cores and GPUs powered me right on through a simulation-heavy dissertation.

When I was a kid, they were playthings, and as a grownup, they’re powerful tools. Because of this, computers have never been intimidating. I grew up with computers.

But back to my son. I don’t know if it’s desirable, or even possible, to pretend that computers aren’t immensely complex for the sake of a first grader — he’d see right through the lie anyway. But when is the right age to teach kids about voice recognition and artificial neural networks? It’s a given that we’ll have to teach him some kind of “social media competence” but that’s not really about computers any more than learning how to use Word was about computers back in my day. Consuming versus creating, tweeting versus hacking. Y’know?

Of course every generation has its own path. Hackers older than me were already in high-school or college when it became possible to build your own computer, and they did. Younger hackers grew up with the Internet, which obviously has its advantages. Those older than me made the computers, and those younger have always lived in a world where the computer is mature and taken for granted. But folks about my age, we grew up with computers.

What Every Geek Must Know

June 12, 2021 by Elliot Williams 176 Comments

How is it possible that there’s a geek culture? I mean, it’s one thing to assume that all folks of a nerdy enough bent will know a little Ohm’s law, can fake their way through enough quantum mechanics to at least be interesting at a cocktail party, and might even have a favorite mnemonic for the resistor colors or the angles involved in sine, cosine, and tangents. But how is it that we all know the answer to life, the universe, and everything?

Mike and I were podcasting a couple of weeks back, and it came out that he’d never played Starcraft. I was aghast! Especially since he’s into video games in general, to have not played the seminal 3-way-without-being-rock-scissors-paper game! My mind boggled. But then again, there was a time in my life when I hadn’t actually read all of Dune or Cryptonomicon, which would have left Mike’s jaw on the floor.

Whether you prefer Star Trek or Star Wars, the Matrix or the Hobbit, it’s even more surprising that we have so much in common! And thinking about it, I’m pretty sure that exactly our interchange is the reason — it’s a word of mouth culture thing. Some folks at the hackerspace are talking about Cthulu, and chances are you’re going to be reading some Lovecraft. An argument about the plausibility of the hacks in The Martian has sent at least a couple of geeks to the cinema or the library. And so it goes.

So do your part! Share your geek-culture recommendations with us all in the comments. If you were stranded on a desert island, with a decent bookshelf and maybe even a streaming video service, what’s on your top-10 list? What do you still need to see, read, or hear?

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!