Ask Hackaday: Help Me Pick A CAD Package

Of all the skills that I have picked up over the years as an engineer, there is one that has stayed with me and been a constant over the last three decades. It has helped me work on electronic projects, on furniture, on car parts, robots, and even garments, and it is likely that I will continue using it periodically for the rest of my career. You see, I am a trained PAD expert.

Don't build this, it's fundamentally flawed! Sometimes the front of an envelope is as effective as its back.
Don’t build this, it’s fundamentally flawed! Sometimes the front of an envelope is as effective as its back.

PAD, you ask? OK, it’s an acronym of my own coinage, it stands for Pencil Aided Design, and it refers to the first-year undergraduate course I sat many years ago in which I learned technical drawing to the old British standard BS308. If I’m making something then by far the quickest way for me to visualise its design is to draw it, first a freehand sketch to get a feel of how everything will sit, then a series of isometric component drawings on graph paper with careful attention to dimensions and angles. Well, maybe I lied a little there, the graph paper only comes in when I’m doing something very fancy; the back of an envelope is fine as long as the dimensions on the diagram are correct.

An Envelope Will Only Take You So Far

Working on paper is fine for the situations in which I tend to use it, running bits of wood or sheet metal through a bandsaw or pillar drill, leaning on the sheet metal folder, and filing intricate parts to shape by hand. It’s quick and simple, and the skills are intuitive and long-held. But it is of course completely useless when applied to any computer-driven manufacturing such as a 3D printer, and for that I will need a CAD package.

I’m not averse to CAD and my holding out with paper is only due to familiarity, but I have to admit that I have never found a package to which I have successfully made the jump. My need for it has been too infrequent to either take the time to scale the learning curve or for my new-found knowledge to stick. Reaching for the trusty pencil has always been the easiest option.

Hacky Racers in action
Hacky Racers in action (Mark Mellors)

All this has however recently changed, for as regular readers may have noticed I have a bit of a thing for the British Hacky Racer series. If I am to perfect my design for a slightly ridiculous contraption that will clean up on the track, it makes sense that I crowd my hackerspace with little 3D-printed scale models before breaking out the welding equipment and hacking a frame together with 25mm OD square tube. I thus need to pick a CAD package, learn it, and set to work.

So what are my needs? I’m a Linux user, so while Windows-only software is worth talking about in the comments for other people it’s less useful for me unless it’s easy to run under WINE. It’s also worth making the point that while I’m not averse to paying for good software as I did for my PCB CAD package I’m not anxious to shell out business-grade sums for something I’ll use only occasionally. This is an arena in which many of the offerings are aimed at enterprises, and I simply can’t justify spending hundreds or thousands as they can.

Round up the Usual Suspects

Given those prerequisites, there are still quite a few options. In the open source arena there are SolveSpace and BRL-CAD which I have never tried, OpenSCAD which is probably not my cup of tea (change my mind if you like), and FreeCAD which has been my tool of choice for previous attempts to dabble. I must have missed some others, what are your thoughts? If I don’t mind free-as-in-beer software there’s always TinkerCAD in my browser, is that up to a Hacky Racer chassis design in 25mm square tube? And if I’m feeling brave enough to play with WINE then perhaps I can make something of RS DesignSpark Mechanical.

My trusty pencil has given me stalwart service over many decades, but while I’ll not be hanging it up entirely it’s time to move into the 21st century for my design work. Can you help me decide upon which CAD package will suit me best? Have I even found all the choices within my criteria? As always, the comments are open.

Ask Hackaday: How Would You Detect A Marauding Drone?

The last few days have seen drone stories in the news, as London’s Gatwick airport remained closed for a couple of days amid a spate of drone reports. The police remained baffled, arrested a couple who turned out to be blameless, and finally admitted that there was a possibility the drone could not have existed at all. It emerged that a problem with the investigation lay in there being no means to detect a drone beyond the eyesight of people on the ground, and as we have explored in these pages already, eyewitness reports are not always trustworthy.

Not much use against a small and mostly plastic multirotor. Sixflashphoto [CC BY-SA 4.0]
Not much use against a small and mostly plastic multirotor. Sixflashphoto [CC BY-SA 4.0]

Radar Can’t See Them

It seems odd at first sight, that a 21st century airport lacks the ability to spot a drone in the air above it, but a few calls to friends of Hackaday in the business made it clear that drones are extremely difficult to spot using the radar systems on a typical airport. A system designed to track huge metal airliners at significant altitude is not suitable for watching tiny mostly-plastic machines viewed side-on at the low altitudes. We’re told at best an intermittent trace appears, but for the majority of drones there is simply no trace on a radar screen.

We’re sure that some large players in the world of defence radar are queueing up to offer multi-million-dollar systems to airports worldwide, panicked into big spending by the Gatwick story, but idle hackerspace chat on the matter makes us ask the question: Just how difficult would it be to detect a drone in flight over an airport? A quick Google search reveals multiple products purporting to be drone detectors, but wouldn’t airports such as Gatwick already be using them if they were any good? The Hackaday readership never fail to impress us with their ingenuity, so how would you do it?

Can You Hear What You Can’t See?

It’s easy to pose that question as a Hackaday scribe, so to get the ball rolling here’s my first thought on how I’d do it. I always hear a multirotor and look up to see it, so I’d take the approach of listening for the distinctive sound of multirotor propellers. Could the auditory signature of high-RPM brushless motors be detected amidst the roar of sound near airports?

I’m imagining a network of Rasberry Pi boards each with a microphone attached, doing some real-time audio spectrum analysis to spot the likely frequency signature of the drone. Of course it’s easy to just say that as a hardware person with a background in the publishing business, so would a software specialist take that tack too? Or would you go for a radar approach, or perhaps even an infra-red one? Could you sense the heat signature of a multirotor, as their parts become quite hot in flight?

Whatever you think might work as a drone detection system, give it a spin in the comments. We’d suggest that people have the confidence to build something, and maybe even enter it in the Hackaday Prize when the time comes around. Come on, what have you got to lose!

Ask Hackaday: What are Your Less Extreme Brain Hacks?

Kahn — perhaps Star Trek’s best-hated villain — said: “Improve a mechanical device and you may double productivity, but improve man and you gain a thousandfold.” In fact, a lot of hacking effort goes into doing just that. Your phone has become an extension of your memory, for example. We use glasses, cameras, and hearing aids to shore up failing senses or even give us better senses than normal. But hacking your body — or someone else’s — has always been controversial. While putting an RFID chip in your finger is one thing, would you consider having a part of your brain removed? That sounds crazy, but apparently, there is a growing interest in having your amygdala removed.

To be clear: we think this is a terrible idea. The science is shaky, at best, and we certainly wouldn’t want to be among the first to try something so radical. But why is anyone even talking about it?

The amygdala is part of your brain that causes at least some of your fear and anxiety. Get rid of your amygdala, get rid of anxiety? What’s even stranger is this the procedure — an amygdalectomy — has been going on since the 1960s! Injections of oil and wax destroy the tissue and this treatment is used for some forms of epilepsy and to manage certain aggressive behavior problems in mentally ill patients. In modern times, the procedure is not very common although it appears that it does still occur in some places. But the technology to do it does exist. There have also been documented cases where people lose their amygdala from natural causes that gives us some clues of what life would be like without one.

However, it is hard to say if these people lost fear. Most of the surgical patients were already suffering from a variety of problems. There is some evidence that the naturally occurring amygdalaless patients experienced less fear in some situations, but may experience more fear in others. They also may have other problems such as difficulty understanding social cues or making eye contact. We’re not 100% sure what the amygdala does, even disregarding potential side effects.

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Ask Hackaday: Why Aren’t We Hacking Cellphones?

When a project has outgrown using a small microcontroller, almost everyone reaches for a single-board computer — with the Raspberry Pi being the poster child. But doing so leaves you stuck with essentially a headless Linux server: a brain in a jar when what you want is a Swiss Army knife.

It would be a lot more fun if it had a screen attached, and of course the market is filled with options on that front. Then there’s the issue of designing a human interface: touch screens are all the rage these days, so why not buy a screen with a touch interface too? Audio in and out would be great, as would other random peripherals like accelerometers, WiFi, and maybe even a cellular radio when out of WiFi range. Maybe Bluetooth? Oh heck, let’s throw in a video camera and high-powered LED just for fun. Sounds like a Raspberry Pi killer!

And this development platform should be cheap, or better yet, free. Free like any one of the old cell phones that sit piled up in my “hack me” box in the closet, instead of getting put to work in projects. While I cobble together projects out of Pi Zeros and lame TFT LCD screens, the advanced functionality of these phones sits gathering dust. And I’m not alone.

Why is this? Why don’t we see a lot more projects based around the use of old cellphones? They’re abundant, cheap, feature-rich, and powerful. For me, there’s two giant hurdles to overcome: the hardware and the software. I’m going to run down what I see as the problems with using cell phones as hacker tools, but I’d love to be proven wrong. Hence the “Ask Hackaday”: why don’t we see more projects that re-use smartphones?

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Ask Hackaday Answered: The Tale of the Top-Octave Generator

We got a question from [DC Darsen], who apparently has a broken electronic organ from the mid-70s that needs a new top-octave generator. A top-octave generator is essentially an IC with twelve or thirteen logic counters or dividers on-board that produces an octave’s worth of notes for the cheesy organ in question, and then a string of divide-by-two logic counters divide these down to cover the rest of the keyboard. With the sound board making every pitch all the time, the keyboard is just a simple set of switches that let the sound through or not. Easy-peasy, as long as you have a working TOG.

I bravely, and/or naïvely, said that I could whip one up on an AVR-based Arduino, tried, and failed. The timing requirements were just too tight for the obvious approach, so I turned it over to the Hackaday community because I had this nagging feeling that surely someone could rise to the challenge.

The community delivered! Or, particularly, [Ag Primatic]. With a clever approach to the problem, some assembly language programming, and an optional Arduino crystalectomy, [AP]’s solution is rock-solid and glitch-free, and you could build one right now if you wanted to. We expect a proliferation of cheesy synth sounds will result. This is some tight code. Hat tip!

Squeezing Cycles Out of a Microcontroller

Let’s take a look at [AP]’s code. The approach that [AP] used is tremendously useful whenever you have a microcontroller that has to do many things at once, on a rigid schedule, and there’s not enough CPU time between the smallest time increments to do much. Maybe you’d like to control twelve servo motors with no glitching? Or drive many LEDs with binary code modulation instead of primitive pulse-width modulation? Then you’re going to want to read on.

There are two additional tricks that [AP] uses: one to fake cycles with a non-integer number of counts, and one to make the AVR’s ISR timing absolutely jitter-free. Finally, [Ag] ended up writing everything in AVR assembly language to make the timing work out, but was nice enough to also include a C listing. So if you’d like to get your feet wet with assembly, this is a good start.

In short, if you’re doing anything with hard timing requirements on limited microcontroller resources, especially an AVR, read on!

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Ask Hackaday: Is There a Common Mechanical Parts Library?

Like many stories, this one started on the roof. This particular roof is located in Michigan and keeps the rain and snow off of the i3Detroit hackerspace. Being an old industrial building, things up on the roof can start getting creaky, and when an almighty screech started coming from one of the rooftop vents as it swiveled in the wind, Nate, one of the group’s coordinators, knew it was time to do something about it.

Previous attempts to silence the banshee with the usual libations had failed, so Nate climbed up to effect a proper repair with real bearings. He dug into the unit, measured for the bearing, and came down to order the correct items. That’s when it struck him: How many should I order? After all, bearings are useful devices, not just to repair a wonky vent but especially handy in a hackerspace, where they can be put to all sorts of uses. Would extra bearings be put to good use, or would they just sit on a shelf gathering dust?

That’s when Nate dropped us a line and asked a question that raises some interesting possibilities, and one which we couldn’t answer offhand: Is there a readily accessible online library of common mechanical parts?

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Ask Hackaday: What Color Are Your PCBs?

A decade ago, buying a custom-printed circuit board meant paying a fortune and possibly even using a board house’s proprietary software to design the PCB. Now, we all have powerful, independent tools to design circuit boards, and there are a hundred factories in China that will take your Gerbers and send you ten copies of your board for pennies per square inch. We are living in a golden age of printed circuit boards, and they come in a rainbow of colors. This raises the question: which color soldermask is most popular, which is most desirable, and why? Seeed Studio, a Chinese PCB house, recently ran a poll on the most popular colors of soldermask. This was compared to their actual sales data. Which PCB color is the most popular? It depends on who you ask, and how you ask it.
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