Raspberry Pi PoE Redux

November 9, 2018 by Jonathan Bennett 19 Comments

[Martin Rowan] was lucky enough to get his hands on the revised Power Over Ethernet (PoE) hat for the Raspberry Pi. Lucky for us, he wrote it up for our benefit, including inspection of the new hat, it’s circuit, and electrical testing to compare to the original hardware.

You may remember the original release of the PoE hat for the Raspberry Pi, as well as the subsequent recall due to over-current issues. In testing the revised board, [Martin] powered a test load off the USB ports, and pulled over an amp — The first iteration of the PoE hat would often trip the over-current protection at 300 milliamps.

This afternoon, the redesigned PoE board was officially released, and the post mortem of the problem documented in a blog post. It’s a lesson in the hidden complexity of hardware design, as well as a cautionary tale about the importance of thorough testing, even when the product is late and the pressure is on.

The PoE hat converts 48 volt power down to a 5 volt supply for the Pi using a flyback transformer. The problem was that this transformer setup doesn’t deliver clean steady 5 volt power, but instead provides power as a series of spikes. While these spikes were theoretically in spec for powering the Pi and usb devices, some Raspberry Pis were detecting those spikes as too much current pushed through the USB ports. The official solution essentially consists of better power filtering between the hat and the Pi, flattening that power draw.

We’re looking forward to getting our hands on this new and improved PoE Hat, and using it in many project to come.

The Negative Rail Explained

November 9, 2018 by Tom Nardi 45 Comments

With the high availability of modular components and incredible wealth of information and tutorials online, it’s now easier than ever for hackers and makers to assemble complex electronic projects without getting bogged down with the theory behind it all. But the downside is that the modern electronic hobbyist often doesn’t have as deep an understanding of the low-level concepts that they would have if they had to build everything from scratch. This can be a problem when they try diagnosing and repairing faults, or when they start to branch out into reverse engineering.

Which makes “Building Blocks” by [David Christensen] a very compelling series. Every week he will be demonstrating a new circuit on his blog, complete with a plain English explanation of how and why it’s used. In this first installment of the series, he’s tackling a concept most of us have seen when poking around in more complex electronic devices, but maybe never really gave much thought to: the negative rail.

What exactly is the negative rail, anyway? It’s pretty easy to understand the positive rail in a circuit and its relation to ground; even multiple positive rails, such as in devices which use both 5 V and 3.3 V, are simple enough to wrap your head around. Unfortunately when something drops below that logical 0V reference, it isn’t quite as intuitive. But as [David] explains, the negative rail in a circuit is critical for dealing with bipolar signals, such as audio, which ride above and below the 0 V center point.

[David] goes over a few methods used to create the negative rail, from the classic center-tap transformer to using a buck-boost converter. But not content with just describing how these circuits work, he walks the reader through the creation of a charge pump circuit that you can drop into your next project if you find yourself in need of the elusive voltage. After explaining and diagramming it, he builds the circuit on a scrap piece of copper clad board and puts it through some benchmarks to prove it matches the theory he laid out.

If you’re in the mood for more negative talk, check out the battle our very own [Steven Dufresne] had with voltages of varying polarity when building his BB-8 robot.

The Dual In-Line Package And How It Got That Way

November 8, 2018 by Dan Maloney 68 Comments

For most of human history, our inventions and innovations have been at a scale that’s literally easy to grasp. From the largest cathedral to the finest pocket watch, everything that went into our constructions has been something we could see with our own eyes and manipulate with our hands. But in the middle of the 20th century, we started making really, really small stuff: semiconductors. For the first time, we were able to create mechanisms too small to be seen with the naked eye, and too fine to handle with our comparatively huge hands. We needed a way to scale these devices up somewhat to make them useful parts. In short, they needed to be packaged.

We know that the first commercially important integrated circuits were packaged in the now-familiar dual in-line package (DIP), the little black plastic millipedes that would crawl across circuit boards for the next 50 years. As useful and versatile as the DIP was, and for as successful as the package became, its design was anything but obvious. Let’s take a look at the dual in-line package and how it got that way.

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Steady Hand Repurposes Cheap SSD Modules

November 8, 2018 by Tom Nardi 52 Comments

For hackers, cheap (and arguably disposable) consumer hardware makes for a ready supply of free or low-cost components. When you can walk into a big box store and pick up a new low-end laptop for $150, how many are going to spend the money to repair or upgrade the one they have now? So the old ones go to the bin, or get sold online for parts. From an ecological standpoint our disposable society is terrible, but at least we get some tech bargains out of the deal.

Case in point, the dirt cheap 32 GB eMMC SSDs [Jason Gin] recently scored. Used by Hewlett Packard on their line of budget laptops, he was able to snap up some of these custom drives for only $12 each. Only problem was, since they were designed for a very specific market and use case, they aren’t exactly the kind of thing you can just slap in your computer’s drive bay. He had to do some reverse engineering to figure out how to talk to them, and then some impressive fine-pitch soldering to get them plugged in, but in the end he got some very handy drives for an exceptionally low price.

[Jason] starts by figuring out the drive’s pinout using the cornerstone of the hacker’s electronic toolkit: the multimeter. By putting one lead on an obvious ground point such as the PCB’s screw holes, you can work through the pins on the connector and make some educated guesses as to what’s what. Ground pins will read as a short, but the meter should read power and data pins as a forward-biased diode. With a rough idea of the pin’s identities and some luck, he was able to figure out that it was basically a standard SATA connection in a different form factor.

To actually hook it up to his computer, he pulled the PCB off of a dead SATA hard drive, cut it down to size, and was able to use fine magnet wire to attach the conductors in the drive’s ribbon cable to the appropriate pads. He sealed everything up with a healthy dose of hot glue to make sure it didn’t pull loose, and then ran some drive diagnostics on his cobbled together SSD to make sure it was behaving properly. [Jason] reports the drive isn’t exactly a speed demon, but given the low cost and decent performance he still thinks it’s worth the work to use them for testing out different operating systems and the like.

[Jason] seems to have something of an obsession with eMMC hacking. Last time we heard from him, he was bringing a cheap Windows tablet back from the dead by replacing its shot eMMC chip.

Teardown Of A (Relatively) Cheap Thermal Camera

November 7, 2018 by Tom Nardi 32 Comments

The cost of tools and test equipment has largely been on the downward trend for years, making it now more affordable than ever to get into the hacking and making scene. This is particularly visible with something like the venerable oscilloscope: a piece of equipment that was near unobtainium for the home hacker a decade ago, you can now get digital pocket scope for as little as $20 USD. But there are still pieces of gear which haven’t quite hit the sort of prices we’d like to see.

A perfect example are thermal imaging cameras. The cheap ones are usually so low resolution they might as well just be thermometers, but the higher resolution ones can cost thousands. [Rob Scott] recently wrote in to tell us about a very promising middle ground, the HTI HT-A1. But he didn’t just point it out to us, he also tore it down and laid its internal’s bare for our entertainment. Now that’s our kind of introduction.

[Rob] walks us through the disassembly of the device, which is made unnecessarily difficult due to the fact that half the screws are hidden under a glued on screen bezel. That means a heat gun, a thin tool, and patience are in order if you want to get inside the device. It’s bad enough they use these kinds of construction techniques on modern smartphones, but at least they’re so thin that we can understand the reasoning. Why this chunky thing needs to resort to such measures is beyond us.

Eventually he cracks the HT-A1 open and is greeted with a single double-sided PCB. The top side is pretty much bare except for the buttons and the LCD display, and the flip side is largely just a breakout for a quad-core Allwinner A33 daughterboard. [Rob] theorizes this is to keep costs down by allowing reuse of the modular A33 board on other devices. Given the A33’s use in so many cheap tablets, it’s also possible HTI simply purchased these daughterboards as a drop-in component and designed their own board around it.

There’s not much else inside the HT-A1 beyond the rechargeable battery pack and thermal camera, both attached to the device’s rear panel. [Rob] noticed that the date on the thermal camera PCB is a full two years older than the date on the main PCB, leading one to wonder if HTI might have gotten a good deal on a bunch of these slightly outdated sensors and spun up a whole device around them.

The HT-A1 is high enough resolution that you can actually pick out individual components on a PCB, and at $400 USD is approaching a reasonable price point for the individual hacker. Which is not to say it’s cheap, but at least you get a useful tool for your money. We wouldn’t suggest you buy this device on a whim, but if you do a lot of diagnostic work, it might pay for itself after a couple repairs.

If that’s still a little too rich for your blood, we’ve covered a handful of DIY options which might better fit your budget.

Continue reading “Teardown Of A (Relatively) Cheap Thermal Camera” →

Arduino Nitrox Analyzer For The Submarine Hacker

November 3, 2018 by Tom Nardi 51 Comments

For Hackaday readers who don’t spend their free time underwater, nitrox is a blend of nitrogen and oxygen that’s popular with scuba divers. Compared to atmospheric air, nitrox has a higher concentration of oxygen; which not only allows divers to spend more time underwater but also reduces the risk of decompression sickness. Of course when fiddling with the ratio of gases you breathe there’s a not inconsequential risk of dying, so nitrox diving requires special training and equipment to make sure the gas mixture is correct.

Divers can verify the ratio of oxygen to nitrogen in their nitrox tanks with a portable analyzer, though as you might expect, they aren’t exactly cheap. But if you’re confident in your own hacking skills, [Eunjae Im] might have the solution for divers looking to save some cash. He’s come up with an Arduino based nitrox analyzer that can be built for considerably less than the cost of a commercial unit.

Now before you get the torches lit up, we should be clear: ultimately the accuracy, and therefore safety, of this device depends on the quality of the oxygen sensor used. [Eunjae] isn’t suggesting you get a bottom of the barrel sensor for this build, and in fact links to a replacement sensor that’s intended for commercial nitrox analyzers as a way to verify the unit is up to the task. The downside is that the sensor alone runs $80. If you want to go with something cheaper, you do so at your own risk.

With a suitable sensor in hand, the project really boils down to building up an interface and enclosure for it. [Eunjae] is using an Arduino Nano, a 128×64 OLED screen, and a battery inside of a rugged waterproof case. He also added an ADS1115 16 Bit DAC between the oxygen sensor and the Arduino for fast and accurate readings over I2C. With the hardware assembled, calibrating the device is as simple as taking it outside and making sure you get an oxygen reading of 20.9% (the atmospheric normal).

While [Eunjae] is happy with his analyzer on the whole, he does see a few areas which could be improved in future revisions. The case is bulky and rather unattractive, something that could be addressed with a custom 3D printed case (though waterproofing it might be an issue). He also says the only reason he used a 9V alkaline battery was because he had it on hand, a small rechargeable battery pack would be a much more elegant solution.

We’ll go out on a limb and say that most Hackaday readers aren’t avid scuba divers. For better or for worse, we’re the sort of folks who stay in the shallow end of the pool. But when one of our ilk does dip below the waves, they really seem to go all out.

Continue reading “Arduino Nitrox Analyzer For The Submarine Hacker” →

Corporate Badgelife: Oracle’s Code Card

October 31, 2018 by Tom Nardi 30 Comments

We tend to think of elaborate electronic conference badges as something limited to the hacker scene, but it looks like the badgelife movement is starting to hit the big time. Now even the “big boys” are getting into the act, and pretty soon you won’t be able to go to a stuffy professional conference without seeing a sea of RGB LEDs firing off. We’ll let the good readers of Hackaday determine if this means it’s officially post-cool or not.

[Noel Portugal] writes in to tell us about how he created the “Code Card” during his tenure with the Oracle Groundbreakers Team. Featuring an ESP8266 and an e-ink screen, the Code Card serves not only as swanky way of identifying yourself, but as a real-world demonstration of physical devices pulling content from Oracle’s Cloud. Gotta keep those corporate overlords happy.

The Code Card is a fairly simple piece of hardware as far as badges go these days, but then the goal was never to be flashy. It does feature dual four-pin Grove System connectors on the backside though, so you can plug in additional sensors and gadgets for the customary badge hacking sessions.

To maximize runtime on the rechargeable coin cell battery, the Code Card only turns on the ESP after the user has pressed one of the buttons on the front. Once the ESP has finished performing whatever task the user requested, its powered back off completely rather than put into standby. Combined with the e-ink screen, power consumption while the device isn’t actively updating the display or pulling down new content is negligible.

[Noel] really went all-out on the software side, going as far as developing a web application which let conference attendees configure their Code Cards from their smartphones. Different functions could be assigned to short and long presses on the badge’s two buttons, and users could even select icons for the various functions from a list of images included in the firmware. A feature where attendees could upload their own images didn’t make the cut, but that surely won’t stop people from hacking around in the published Arduino source code and figuring out how to do it manually.

If you think the Code Card looks a bit familiar, it’s perhaps because it was designed in conjunction with Squarofumi, creators of the Badgy. So even if you aren’t hitting up any of Oracle’s upcoming conferences, you’re not completely out of luck if you want an e-ink badge to play with.