Fail Of The Week: How I Killed The HiPot Tester

December 29, 2016 by Jenny List 18 Comments

Have you ever wired up a piece of test equipment to a circuit or piece of equipment on your bench, only to have the dreaded magic smoke emerge when you apply power? [Steaky] did, and unfortunately for him the smoke was coming not from his circuit being tested but from a £2300 Clare H101 HiPot tester. His write-up details his search for the culprit, then looks at how the manufacturer might have protected the instrument.

[Steaky]’s employer uses the HiPot tester to check that adjacent circuits are adequately isolated from each other. A high voltage is put between the two circuits, and the leakage current between them is measured. A variety of tests are conducted on the same piece of equipment, and the task in hand was to produce a new version of a switch box with software control to swap between the different tests.

This particular instrument has a guard circuit, a pair of contacts that have to be closed before it will proceed. So the switch box incorporated a relay to close them, and wiring was made to connect to the guard socket. At first it was thought that the circuit might run at mains voltage, but when it was discovered to be only 5V the decision was made to use a 3.5mm jack on the switch box. Inadvertently this was left with its sleeve earthed, which had the effect of shorting out a DC to DC converter in the HiPot tester and releasing the smoke. Fortunately then the converter could be replaced and the machine brought back to life, but it left questions about the design of the internal circuit. What was in effect a logic level sense line was in fact connected to a low current power supply, and even the most rudimentary of protection circuitry could have saved the day.

We all stand warned to be vigilant for this kind of problem, and kudos to [Steaky] for both owning up to this particular fail and writing such a good analysis of it.

Our Fail Of The Week series has plenty to entertain the reader who is not of a nervous disposition. This isn’t the first fail to feature a suspect bit of connector wiring, not an unexpected short or even some magic smoke.

In Defense Of The Electric Chainsaw

December 28, 2016 by Jenny List 94 Comments

Here at Hackaday we are a diverse bunch, we all bring our own experience to the task of bringing you the best of the hardware scene. Our differing backgrounds were recently highlighted by a piece from my colleague [Dan] in which he covered the teardown of a cordless electric chainsaw.

It was his line “Now, we’d normally shy away from any electric chainsaw, especially a cordless saw, and doubly so a Harbor Freight special“. that caught my eye. I’m with him on cordless tools which I see as a cynical ploy from manufacturers to ensure 5-yearly replacements, and I agree that cheap tools are a false economy. But electric chainsaws? Here on this small farm, they’re the saw of choice and here’s why.

Continue reading “In Defense Of The Electric Chainsaw” →

OpenAg Is A Personal Food Computer

December 26, 2016 by Jenny List 20 Comments

When a device that calls itself a personal food computer lands in your timeline, what image springs to mind? A cloud-connected diet aid perhaps, advertised on TV infomercials by improbably fit-looking Californian ladies crediting all their health to a palm-sized unit that can be yours for only 199 dollars. Fortunately that proved not to be the case, and on further reading our timeline story was revealed to be about a computerized farming device.

The OpenAg Food Computer from the MIT Media Lab Open Agriculture Initiative bills itself as:

“a controlled-environment agriculture technology platform that uses robotic systems to control and monitor climate, energy, and plant growth inside of a specialized growing chamber”

It takes the form of a tabletop enclosure in which so-called climate recipes to replicate different conditions for plant growth can be tested. It’s probably fair to say that in this most basic form it is more of an educational device than one for full-scale food production, though they are applying the same technologies at a much greater scale. Their so-called “Food servers” are banks of OpenAg environments in freight containers, which definitely could be used to provide viable quantities of produce.

The good news is that the project is open source, and their latest story is that they have released version 2.0(alpha) of the device. If you are interested, you can read the documentation, and find all the resources you need to build one on their GitHub repository. They page linked above has a video that’s very much of the slick PR variety rather than the nuts-and-bolts, so we’ve sought out their build video for you below the break instead. Continue reading “OpenAg Is A Personal Food Computer” →

Automated Vacuum Lettuce Seed Placement

December 26, 2016 by Jenny List 7 Comments

[Jethro Tull] is a name you may well associate with a 1970s prog/folk rock band featuring a flautist, but the original [Tull] was an inventor whose work you benefit from every day. He was a British lawyer and landowner who lived over the turn of the 18th century, and who invented among other things the mechanical seed drill.

Were [Tull] alive today he would no doubt be impressed by the work of [Akash Heimlich], who has created an exquisite vacuum seed placer for his rooftop hydroponic lettuce farm. Unlike the continuous rows of seed on the Berkshire earth of [Tull]’s farm, the lettuce seed must be placed in an even grid on a foam substrate for the hydroponic equivalent. This was an extremely tedious task when done by hand, so [Akash] set about automating the process with a vacuum seeder that is a thing of beauty.

It uses a simple yet effective mechanism involving a row of pipettes connected to a vacuum line, that are rotated over a vibrating hopper of seeds from which each one collects a single seed, before being rotated back over the foam where the seeds are dropped in a neat row through 3D-printed funnels. The foam is advanced, and the process is repeated until there is a neat grid of seeds. In only four minutes it can deliver 150 seeds, reducing several hours work into under half an hour.

The whole machine is controlled by an Arduino, with a couple of stepper motors to move foam and pipettes alongside the vibrator motor. You can see its operation in the video below the break.

Continue reading “Automated Vacuum Lettuce Seed Placement” →

Hackspace U

December 26, 2016 by Jenny List 58 Comments

No Timmy, we're not preparing you for a life of mindless drudgery! PD, via Wikimedia Commons. — No Timmy, we’re not preparing you for a life of mindless drudgery! PD, via Wikimedia Commons.

It’s funny, how obsessed we are with qualifications these days. Kids go to school and are immediately thrust into a relentless machine of tests, league tables, and exams. They are ruthlessly judged on grades, yet both the knowledge and qualifications those grades represent so often boil down to relatively useless pieces of paper. It doesn’t even end for the poor youngsters when they leave school, for we are now in an age in which when on moving on from school a greater number of them than ever before are expected to go to university. They emerge three years later carrying a student debt and a freshly-printed degree certificate, only to find that all this education hasn’t really taught them the stuff they really need to do whatever job they land.

A gold standard of education is revealed as an expensive piece of paper with a networking opportunity if you are lucky. You need it to get the job, but in most cases the job overestimates the requirement for it. When a prospective employer ignores twenty years of industry experience to ask you what class of degree you got twenty years ago you begin to see the farcical nature of the situation.

In our hackspaces, we see plenty of people engaged in this educational treadmill. From high schoolers desperately seeking to learn something other than simply how to regurgitate the textbook, through university students seeking an environment closer to an industrial lab or workshop, to perhaps most interestingly those young people who have eschewed university and gone straight from school into their own startups.

Continue reading “Hackspace U” →

The First Bug On Mars

December 25, 2016 by Jenny List 18 Comments

Interplanetary probes were a constant in the tech news bulletins of the 1960s and 1970s. The Space Race was at its height, and alongside their manned flights the two superpowers sent unmanned missions throughout the Solar System. By the 1980s and early 1990s the Space Race had cooled down, the bean counters moved in, and aside from the spectacular images of the planets periodically arriving from the Voyager series of craft there were scant pickings for the deep space enthusiast.

The launch in late 1996 of the Mars Pathfinder mission with its Sojourner rover then was exciting news indeed. Before Spirit, the exceptionally long-lived Opportunity, and the relatively huge Curiosity rover (get a sense of scale from our recent tour of JPL), the little Sojourner operated on the surface of the planet for 85 days, and proved the technology for the rovers that followed.

In these days of constant online information we’d see every nuance of the operation as it happened, but those of us watching with interest in 1997 missed one of the mission’s dramas. Pathfinder’s lander suffered what is being written up today as the first bug on Mars. When the lander collected Martian weather data, its computer would crash.

Like many other spacecraft, the lander’s computer system ran the real-time OS VxWorks. Of the threads running on the craft, the weather thread was a low priority, while the more important task of servicing its information bus was a high priority one. The weather task would hog the resources, causing the operating system equivalent of an unholy row in our Martian outpost. A priority inversion bug, and one that had been spotted before launch but assigned a low priority.

You can’t walk up to a computer on another planet and swap out a few disks, so the Pathfinder team had to investigate the problem on their Earthbound replica of the lander. The fix involved executing some C code on an interpreter prompt on the spacecraft itself, something that would give most engineers an extremely anxious moment.

The write-up is an interesting read, it’s a translation from a Russian original that is linked within it. If the work of the JPL scientists and engineers interests you, this talk from the recent Hackaday superconference might be of interest.

[via Hacker News]

Track Wi-Fi Devices In Your Home

December 25, 2016 by Jenny List 31 Comments

How do you audit your home Wi-Fi network? Perhaps you log into your router and have a look at the connected devices. Sometimes you’ll find an unexpected guest, but a bit of detective work will usually lead you to the younger nephew’s game console or that forgotten ESP8266 on your bench.

Wouldn’t it be useful if your router could tell you where all the devices connected to it are? If you are [Zack Scholl], you can do all this and more, for his FIND-LF system logs Wi-Fi probe requests from all Wi-Fi devices within its range even if they are not connected, and triangulates their position from their relative signal strengths across several sniffing receivers. These receivers are a network of Raspberry Pis with their own FIND-LF server, and any probe requests they pick up are forwarded to [Zack]’s FIND server (another of his projects) which does the work of collating the locations of devices.

It’s an impressive piece of work, though with a Raspberry Pi at each receiver it could get a little pricey. [Zack] has done other work in this field aside from the two projects mentioned here, his other work includes an implementation of the [Harry Potter] Marauder’s Map.

This is by no means the only indoor location system we’ve seen over the years. One that uses ESP8266 modules for example, or this commercial product that is similar to the project shown here.