Keep Scraps Around

August 21, 2021 by Elliot Williams 30 Comments

When I’m building something, I like to have a decent-sized scrap pile on hand. Because when I’ve got to test something out — does this glue adhere to this fabric, how much force will this hold if I tap it and put a screw in, will it snap if reinforced with carbon fiber and epoxy — it’s nice to have some of the material in question on hand just for experimentation. So I pull a chunk out of the scrap pile!

But scrap piles can’t expand forever, and we all know that “too much of a good thing” is a thing, right? Scrap piles require constant pruning. You don’t really need more than a few aluminum extrusion cutoffs, so when you start building up excess inventory, it’s time to scrap it. I mean, throw it away.

A corollary of this, that I’ve only recently started to appreciate, is that if I limit the number of materials that I’m working with, it’s a lot more manageable to keep the scrap pile(s) under control. It’s simple math. If I’m working with twenty different materials, that’s twenty different heaps of scrap. But if I can get by with one weight of fiberglass for everything, that one pile of scraps can do double or triple duty. There is also the added benefit that I already know how the material works, and maybe even have old test samples on hand.

Indeed, I’m such a scrapaholic that it’s almost painful to start working with a new material and not have a scrap pile built up yet. I’m always loathe to cut into a nice square piece of stock just to test something out. But this too is part of the Great Circle of Life. By not testing things out beforehand, I’m almost guaranteed to screw up and create scrap out of what I had hoped was going to be a finished piece. See? No problem! Next version.

What do you think? Are scrap, offcuts, and their close cousins — test pieces and samples — worth keeping around in your shop? Do you have a disciplined approach, or do you just throw them in the corner? Purge per project, or only when the mountain of XPS foam gets as high as your head?

Goals And Goalposts

August 14, 2021 by Elliot Williams 14 Comments

In the winter, I hatched a vague plan to learn some of the modern unmanned aerial vehicle tech. Everybody needs an autonomous vehicle, and we’ve got some good flying fields within walking distance, so it seemed like it could work. Being me, that meant buying the cheapest gear that could possibly work, building up the plane by myself, and generally figuring out as much as possible along the way. I learn more by making my own mistakes anyway. Sounds like a good summer project.

Fast-forward to August, and the plane is built, controller installed, and I’ve spent most of the last month trying to make them work well together. (The firmware expects a plane with ailerons, and mine doesn’t have them, but apparently I’d rather tweak PID values than simply add a couple wing servos.) But it’s working well enough that it’s launching, flying autonomous waypoint missions, and coming home without any intervention. So, mission accomplished, right?

Nope. When I’m enjoying a project, I have a way of moving the goalposts on myself. I mean, I don’t really want to be done anyway. When a friend asked me a couple weeks ago what I was planning to do with the plane, I said “take nice aerial videos of that farm over there.” Now I see flight opportunities everywhere, and need to work on my skills. The plane needed an OLED display. It probably still needs Bluetooth for local configuration as well. Maybe a better long-range data link…

This is creeping featurism and moving-the-goalposts in the best of ways. And if this were a project with a deadline, or one that I weren’t simply enjoying, it would be a problem. Instead, having relatively low-key goals, meeting them, and letting them inspire me to set the next ones has been a blast. It makes me think of Donald Papp’s great article on creating hacking “win” projects. There he suggests creating simple goals to keep yourself inspired. I don’t think I could have planned out an “optimal” set of goals to begin with — I’ve learned too much along the way that the next goal isn’t obvious until I know what new capabilities I have. Creeping is the only way.

What about you? Do you plan your hobby projects completely in advance? Not at all? Or do you have some kind of hybrid, moving-the-goalposts sort of strategy?

Hearing The Unhearable

August 7, 2021 by Elliot Williams 51 Comments

My wife was watching a crime drama, and one of the plot twists involved a witness’ hearing aid malfunctioning so that he could hear electromagnetic waves around him. It’s not so implausible, if you think about it. Many hearing aids have a t-coil, which is essentially an inductor that’s designed to couple with the speaker in a telephone. If that went haywire, maybe you could hear all the changing magnetic fields around you, and if you could escape the constant hum of the mains power line, it might even be interesting.

So of course, she turns to me and says “we need to make one!” It shouldn’t be hard at all — a big inductor and an amplifier should do the trick. In fact, it’ll probably be easy enough that it’ll make a good introduction-to-electronics project for my son. But there are also enough unknowns here that it’ll be interesting. How big a coil? How close? How sensitive? What about that mains frequency bit? Ferrite core or not?

None of this is rocket science, for sure, but it will probably be full of kludges, discoveries, and straight-up exploration. In short, the perfect weekend project. And in the end, it’ll expose something that’s normally invisible, and that’s where the fun lies.

This must be the same urge that drove Faraday and Marconi, Volta and Maxwell. There’s something amazing about directly sensing, seeing, hearing, and understanding some of the stuff that’s outside of our limited hearing and eyesight, and yet is all around us. I can write down the equations that describe it — I learned them in school after all — but there’s no substitute for poking around in your own home. Who knows, maybe in a few more weekends we’ll build ourselves an all-band receiver.

What’s your favorite super power?

The Man-Machine

July 31, 2021 by Elliot Williams 4 Comments

This week we saw a couple DIY tools for small-run manufacturing at home that help make your life easier if you’re climbing out of the happy bucket and into the pit of despair — when you’re making enough of the item that it’s not fun any more, but you still don’t have the volume to leave the manufacturing to someone else.

The first was an automatic through-hole soldering machine made from a 3D printer. This actually makes sense even if you’re getting boards assembled for you, because through-hole pads are a lot more expensive than SMT parts, and they usually charge per pin. Put a 2×20 pin header on your project, and it can end up costing a lot. Or you can robotificate the solution.

This week’s second solution really caught my eye. PnPassist is machine that turns your PCB around, locates a laser crosshair over the next SMT piece that you need to place, and even has an OLED screen that tells you what to put there. There are many great mechanical design choices here, but what really drew my attention is how well this machine fills a gap between manual and fully automatic pick-and-place.

I know you hate looking back and forth between the board and the schematic or parts list, trying to find just where Q23 is on the darn board, or looking up resistor values. With PnPassist, you still have to do the placing, but with machine guidance. If you don’t have the money or the space for a fully automatic PnP, this is an obvious win, but also for short runs when loading up the reels takes more time than populating the board, this could be a huge win.

I love this kind of human-capability-enhancing machine, and I’m always happy to see a design like this. It reminds me of the very clever Shaper Origin, or even just this handy automatic XY table for drilling many precise holes. In all these cases, there’s some part of the problem that would be hard to solve, require extremely bulky or expensive machinery, or can just be more simply accomplished by a meatbag. But combining machine precision with the human element produces something more than the sum of the parts.

What’s your favorite human-enhancing tool?

Learning To Desolder Gracefully

July 24, 2021 by Elliot Williams 45 Comments

When you’re just learning to sketch, you use graphite. Why? It’s cheap, great at training you to recognize different shades, and most of all, it’s erasable. When you’re learning, you’re going to make mistakes, and un-making them is an important part of the game. Same goes for electronics, of course, so when you’re teaching someone to solder, don’t neglect teaching them to desolder.

We could argue all day about the best ways of pressing the molten-metal undo button, but the truth is that it’s horses for courses. I’ve had really good luck with solder braid and maybe a little heat gun to pull up reluctant SOIC surface-mount chips, but nothing beats a solder sucker for clearing out a few through-holes. (I haven’t tried the questionable, but time-tested practice of blasting the joint with compressed air.)

For bulk part removal, all you really have to do is heat the board up, and there’s plenty of ways to do that, ranging from fancy to foolish. Low-temperature alloys help out in really tough cases. And for removing rows of pinheaders, it can help to add more solder along the row until it’s one molten blob, and then tap the PCB and watch the part — and hot liquid metal! — just drop out.

But the bigger point is that an important step in learning a new technique is learning to undo your mistakes. It makes it all a lot less intimidating when you know that you can just pull out the solder braid and call “do-over”. And don’t forget the flux.

Open Source Is Choice

July 17, 2021 by Elliot Williams 79 Comments

If you haven’t been following along with the licensing kerfuffle surrounding the open-source Audacity audio editing software, take a sec to read Tom Nardi’s piece and get up to speed. The short version is that a for-profit company has bought the trademark and the software, has announced plans to introduce telemetry where there was none, made ominous changes to the privacy policy that preclude people under the age of consent from using the software, and requested that all previous developers acquiesce to a change in the open-source license under which it is published. All the while, the company, Muse, says that it will keep the software open, and has walked back and forth on the telemetry issue.

What will happen to “Audacity”? Who knows. But also, who cares? At least one fork of the codebase has been made, with the telemetry removed and the old open licenses in place. The nicest thing about open source is that I don’t care one bit if my software is named Audacity or Tenacity, and this is software I use every week for production of our podcast. But because I haven’t paid any license fees, it costs me absolutely nothing to download the same software, minus some anti-features, under a different name. If the development community moves over to Tenacity, it’ll all be fine.

Tom thinks that the Audacity brand is too big to fail, and that Muse will have a hit on their hands. Especially if they start implementing new, must-have features, they could justify whatever plans they have in store, even if they’re only available as a “freemium” Audacity Pro, with telemetry, under a more restrictive license. When that does happen, I’ll have to make the choice between those features and the costs, but I won’t be left out in the cold as long as the Tenacity fork gets enough eyes on it. So that’s just more choice for the end-user, right? That’s cool.

Compare this with closed source software. There, when the owner makes an unpopular decision, you simply have to take it or make the leap to an entirely different software package. This can be costly if you’ve gotten good at using that software, and between licenses and learning, there’s a lot of disincentive to switching. Not so in this case. If I don’t want to be tracked while editing audio offline, I don’t have to be. Woot.

The elephant in the room is of course the development and debugging community, and it’s way too early to be making predictions there. However, the same rules apply for devs and users: switching between two virtually identical codebases is as easy as git remote add origin or apt get install tenacity. (Unpaid) developers are free to choose among forks because they like the terms and conditions, because one group of people is more pleasant to work with, or because they like the color of one logo more than the other. Users are just as free to choose.

Time will tell if Audacity ends up like the zombie OpenOffice, which is downloaded in spite of the much superior LibreOffice just because of the former’s name recognition. I know this split riles some people up, especially in the LibreOffice development community, and it does seem unfair that the better software somehow enjoys less reputation. But for those of us in the know, it’s just more choice. And that’s good, right?

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.