test

31 Articles

Designing Electronics That Work

November 15, 2021 by 36 Comments

[Hunter Scott] who has graced these pages a fair few times, has been working on electronics startups for the past ten years or so, and has picked up a fair bit of experience with designing and building hardware. Those of us in this business seem to learn the same lessons, quite often the hard way; we call it experience. Wouldn’t it be nice to get up that learning curve a little quicker, get our hardware out there working sooner with less pain, due to not falling into the same old traps those before us already know about? The problem with the less experienced engineer is not their lack of talent, how quickly they can learn, nor how much work they can get done in a day, but simply that they don’t know what they don’t know. There’s no shame in that, it’s just a fact of life. [Hunter] presents for us, the Guide to Designing Electronics that Work.

The book starts at the beginning. The beginning of the engineering process that is; requirements capturing, specifications, test planning and schedule prediction. This part is hard to do right, and this is where the real experience shows. The next section moves onto component selection and prototyping advice, with some great practical advice to sidestep some annoying production issues. Next there’s the obvious section on schematic and layout with plenty of handy tips to help you to that all important final layout. Do not underestimate how hard this latter part is, there is plenty of difficulty in getting a good performing, minimal sized layout, especially if RF applications are involved.

The last few sections cover costing, fabrication and testing. These are difficult topics to learn, if up till now all you’ve done is build prototypes and one-offs. These are the areas where many a kickstarter engineer has fallen flat.

Designing Electronics That Work doesn’t profess to be totally complete, nor have the answer to everything, but as the basis for deeper learning and getting the young engineer on their way to a manufacturable product, it is a very good starting point in our opinion.

The book has been around a little while, and the latest version is available for download right now, on a pay what-you-want basis, so give it a read and you might learn a thing or two, we’re pretty confident it won’t be time wasted!

Testing Hardware With ASCII Waveforms

June 6, 2020 by 14 Comments

Testing software is — sometimes — easier than testing hardware. After all, you can always create test files and even fake user input before monitoring outputs using common tools. Hardware though, is a bit different. Sometimes it is hard to visualize exactly what’s happening. [Andrew Ray’s] answer? Produce simulated waveforms using ASCII text.

The process uses some custom tools written in OCaml, but the code is available for you on GitHub. The tool, called Hardcaml, allows you to write test benches for hardware — not a new idea for FPGA developers. The output, however, is an ASCII text waveform and common software development tools can check that waveform against the expected output.

Continue reading “Testing Hardware With ASCII Waveforms” →

Continuous Integration: What It Is And Why You Need It

January 6, 2020 by 35 Comments

If you write software, chances are you’ve come across Continuous Integration, or CI. You might never have heard of it – but you wonder what all the ticks, badges and mysterious status icons are on open-source repositories you find online. You might hear friends waxing lyrical about the merits of CI, or grumbling about how their pipeline has broken again.

Want to know what all the fuss is about? This article will explain the basic concepts of CI, but will focus on an example, since that’s the best way to understand it. Let’s dive in. Continue reading “Continuous Integration: What It Is And Why You Need It” →

Are You Getting Your Money’s Worth From Threaded Inserts?

December 12, 2019 by 14 Comments

Have you ever wondered whether it’s worth the time and expense to install threaded inserts into your 3D-printed projects? [Stefan] from CNC Kitchen did, and decided to answer the question once and for all, with science.

If this sounds familiar, it’s with good reason: we covered [Stefan]’s last stab at assessing threaded inserts back in March. Then, he was primarily interested in determining if threaded inserts are better than threads cut or printed directly into parts. The current work is concerned with the relative value of different designs of threaded inserts. He looked at three different styles of press-in inserts, ranging in price from pennies apiece to a princely 25 cents. The complexity of the outside knurling seems not to be correlated with the price; the inserts with opposed helical knurls seem like they’d be harder to manufacture than the ones with simple barbs on the outside of the barrel, but cost less. And in fact, the mid-price insert outperformed the expensive one in pull-out tests. Surprisingly, the cheapest inserts were actually far worse at pull-out resistance than printing undersized holes and threading an M3 screw directly into the plastic.

[Stefan] also looked at torque resistance, and found no substantial difference between the three insert types. Indeed, none of the inserts proved to be the weak point, as the failure mode of all the torque tests was the M3 bolt itself. This didn’t hold with the bolt threaded directly into the plastic, of course; any insert is better than none for torque resistance.

We enjoyed seeing [Stefan]’s tests, and appreciate the data that can help us be informed consumers. [John] over at Project Farm does similar head-to-head tests, like this test of different epoxy adhesives.

Continue reading “Are You Getting Your Money’s Worth From Threaded Inserts?” →

Student-Built Rocket Engine Packs A Punch

October 24, 2019 by 30 Comments

A group of students at Boston University recently made a successful test of a powerful rocket engine intended for 100km suborbital flights. Known as the Iron Lotus (although made out of mild steel rather than iron), this test allowed them to perfect the timing and perfect their engine design (also posted to Reddit) which they hope will eventually make them the first collegiate group to send a rocket to space.

Unlike solid rocket fuel designs, this engine is powered by liquid fuel which comes with a ton of challenges to overcome. It is a pressure-fed engine design which involves a pressurized unreactive gas forcing the propellants, in this case isopropanol and N2O, into the combustion chamber. The team used this design to produce 2,553 lb*ft of thrust during this test, which seems to be enough to make this a class P rocket motor. For scale, the highest class in use by amateurs is class S. Their test used mild steel rather than stainless to keep the costs down, but they plan to use a more durable material in the final product.

The Boston University Rocket Propulsion Group is an interesting student organization to keep an eye on. By any stretch of the imagination they are well on their way to getting their rocket design to fly into space. Be sure to check out their other projects as well, and if you’re into amateur rocketry in general there are a lot of interesting things you can do even with class A motors.

Continue reading “Student-Built Rocket Engine Packs A Punch” →

Test PCBs On A Bed Of Nails

February 9, 2019 by 35 Comments

While it might be tempting to start soldering a circuit together once the design looks good on paper, experience tells us that it’s still good to test it out on a breadboard first to make sure everything works properly. That might be where the process ends for one-off projects, but for large production runs you’re going to need to test all the PCBs after they’re built, too. While you would use a breadboard for prototyping, the platform you’re going to need for quality control is called a “bed of nails“.

This project comes to us by way of [Thom] who has been doing a large production run of circuits meant to drive nixie tubes. After the each board is completed, they are laid on top of a number of pins arranged to mate to various points on the PCB. Without needing to use alligator clamps or anything else labor-intensive to test, this simple jig with all the test points built-in means that each board can be laid on the bed and tested to ensure it works properly. The test bed looks like a bed of nails as well, hence the name.

There are other ways of testing PCBs after production, too, but if your board doesn’t involve any type of processing they might be hard to implement. Nixie tubes are mostly in the “analog” realm so this test setup works well for [Thom]’s needs.

Flash Memory: Caveat Emptor

May 13, 2018 by 29 Comments

We all love new tech. Some of us love getting the bleeding edge, barely-on-the-market devices and some enjoy getting tech thirty years after the fact to revel in nostalgia. The similarity is that we assume we know what we’re buying and only the latter category expects used parts. But, what if the prior category is getting used parts in a new case? The University of Alabama in Huntsville has a tool for protecting us from unscrupulous manufacturers installing old flash memory.

Flash memory usually lasts longer than the devices where it is installed, so there is a market for used chips which are still “good enough” to pass for new. Of course, this is highly unethical. You would not expect to find a used transmission in your brand new car so why should your brand new tablet contain someone’s discarded memory?

The principles of flash memory are well explained by comparing them to an ordinary transistor, of which we are happy to educate you. Wear-and-tear on flash memory starts right away and the erase time gets longer and longer. By measuring how long it takes to erase, it is possible to accurately determine the age of chip in question.

Pushing the limits of flash memory’s life-span can tell a lot about how to avoid operation disruption or you can build a flash drive from parts you know are used.