Exploring Basement Humidity With A Raspberry Pi

July 1, 2019 by Dan Maloney 16 Comments

Sometimes a hack isn’t about building something cool. Sometimes it’s more tactical, where the right stuff is cobbled together to gather the information needed to make decisions, or just to document some interesting phenomenon.

Take this impromptu but thorough exploration of basement humidity undertaken by [Matthias Wandel]. Like most people with finished basements in their homes, [Matthias] finds the humidity objectionable enough to warrant removal. But he’s not one to just throw a dehumidifier down there and forget about it. Seeking data on how well the appliance works, [Matthias] wired a DHT22 temperature/humidity sensor to a spare Raspberry Pi to monitor room conditions, and plugged the dehumidifier into a Kill-A-Watt with a Pi camera trained on the display to capture data on electrical usage.

His results were interesting. The appliance does drop the room’s humidity while raising its temperature, a not unexpected result given the way dehumidifiers work. But there was a curious cyclical spike in humidity, corresponding to the appliance’s regular defrost cycle driving moisture back into the room. And when the dehumidifier was turned off, room humidity gradually increased, suggesting an unknown source of water. The likely culprit: moisture seeping up through the concrete slab, or at least it appeared so after a few more experiments. [Matthias] also compared three different dehumidifiers to find the best one. The video below has all the details.

We always appreciate [Matthias]’ meticulous approach to problems like these, and his field expedient instrumentation. He seems to like his creature comforts, too – remember the target-tracking space heater from a few months back?

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Building A DIY Desktop-Sized Arcade Machine

June 29, 2019 by Lewin Day 10 Comments

Full-sized arcade cabinets are undeniably cool, but take up a lot of space and can be somewhat of a handful. [PleaseNoFisticuffs] desired something a little more fun-sized, and so built a desktop arcade machine that has some serious style.

It’s a build that’s remarkably accessible for even the inexperienced builder. Paper templates are used to cut out the plywood parts for the cabinet, and the electronic components are all off-the-shelf items. Assembly is readily achievable with high-school level woodworking and soldering skills. Like most similar builds, it relies on the Raspberry Pi running RetroPie, meaning you’ll never run out of games to play.

Where this project really shines, however, is the graphics. Cribbed from Mortal Kombat II and looking resplendent in purple, they’re key to making this cabinet a truly stunning piece. The attention to detail is excellent, too, with the marquee and screen getting acrylic overlays for that classic shine, as well as proper T-moulding being used to finish the edges.

We’d love to have something like this on our desk, though we’d likely get far less work done in such an event. For another take on an arcade build, check out this impressive Undertale pinball cabinet.

Accurate Time On Your Pi, The Extreme Way

June 26, 2019 by Jenny List 27 Comments

The Raspberry Pi is an extremely versatile little computer, but even its most ardent fans would acknowledge that there are some areas in which its hardware is slightly lacking. One of these is in the field of timing, the little board has no real-time clock. Users must rely on the on-board crystal oscillator, which is good enough as a microprocessor clock but subject to the vagaries of temperature as it is, not so much as a long-term timepiece.

[Manawyrm] has tackled this problem in a rather unusual way, by dispensing entirely with the crystal oscillator on an older Pi model and instead using a clock derived from a GPS source. The source she’s used is a Leo Bodnar mini precision GPS reference clock, which includes a low-jitter synthesiser that can be set to the Pi’s 19.2 MHz required clock. Unexpectedly this also required a simple LC low-pass filter which was made on a sheet of PCB material, because the Pi at first appeared to be picking up a harmonic frequency. The Pi now has a clock that’s sufficiently stable for tasks such as WSPR transmission without constant referral to NTP or other timing sources to keep it on-track.

It’s a short write-up, but it brings with it a further link to a discussion of different time synchronisation techniques on a Pi including using a kernel module to synchronise with the more common GPS-derived 1PPS signal. We’ve not seen anyone else do this particular mod to a Pi before, but conversely we’ve seen a Pi provide an RF time reference to something else.

The Cheese Grater In Fusion 360

June 25, 2019 by Jenny List 34 Comments

By now you will all have heard so much about the grille on Apple’s new “Cheese grater” Mac Pro that you might think there was nothing more to say. Before we move on though there’s one final piece of work to bring to your attention, and it comes from [Andy Pugh]. He’s replicated the design in Fusion 360, and used it to produce rather an attractive Raspberry Pi case.

It seems that for Fusion 360 users the problem lies in that package’s method of placing spheres which differs from that of some other CAD software. Using the page linked in our previous coverage of the grille he’s taken its geometry information and produced a video detailing every step in recreating it for Fusion 360. This is where following someone who really knows your CAD package pays dividends, because we suspect it would take us days to figure out some of the tricks he shows us.

The result is the Raspberry Pi case, which is for the Pi 3 and others like it. Sadly we couldn’t break our embargo and tell him about the Pi 4 and its different connector layout, but we’re guessing a halfway competent CAD operator could put together a Pi 4 case. Andy’s files can be found on Thingiverse, so you can all make one for yourselves.

Andy’s appeared here before a few times, not least for his Ner-A-Car motorcycle, and for designing a Robot Wars robot.

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Raspberry Pi 4 Just Released: Faster CPU, More Memory, Dual HDMI Ports

June 23, 2019 by Brian Benchoff 260 Comments

The Raspberry Pi 4 was just released. This is the newest version of the Raspberry Pi and offers a better CPU and more memory than the Raspberry Pi 3, dual HDMI outputs, better USB and Ethernet performance, and will remain in production until January, 2026.

There are three varieties of the Raspberry Pi 4 — one with 1GB of RAM, one with 2GB, and one with 4GB of RAM — available for $35, $45, and $55, respectively. There’s a video for this Raspberry Pi launch, and all of the details are on the Raspberry Pi 4 website.

A Better CPU, Better Graphics, and More Memory

The CPU on the new and improved Raspberry Pi 4 is a significant upgrade. While the Raspberry Pi 3 featured a Broadcom BCM2837 SoC (4× ARM Cortex-A53 running at 1.2GHz) the new board has a Broadcom BCM2711 SoC (a quad-core Cortex-A72 running at 1.5GHz). The press literature says this provides desktop performance comparable to entry-level x86 systems.

Of note, the new Raspberry Pi 4 features not one but two HDMI ports, albeit in a micro HDMI format. This allows for dual-display support at up to 4k60p. Graphics power includes H.265 4k60 decode, H.264 1080p60 decode, 1080p30 encode, with support for OpenGL ES, 3.0 graphics. As with all Raspberry Pis, there’s a ~~component~~ composite video port as well tucked inside the audio port. The 2-lane MIPI DSI display port and 2-lane MIPI CSI camera port remain from the Raspberry Pi 3.

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DIY Raspberry Pi Multi FX Stomp Box

June 17, 2019 by Rich Hawkes 3 Comments

From building your own analog effects pedal to processing audio through micro controllers, a lot of musicians love building their own boxes of sound modification. In his entry for the 2019 Hackaday Prize, [Craig Hissett] has a project to build an all-in-one multi-effects stomp box.

At the center of the box is a Raspberry Pi with an AudioInjector stereo sound card. The card takes care of stereo in and out, and passing the signal to the Pi. The software is Modep, an open source audio processor that allows the setup of a chain of digital effects plugins to be run on the Pi. After finding some foot switches, [Craig] connected them to an Arduino Pro Micro which he set up as a MIDI device that sends MIDI messages to the Modep software running on the Pi.

There are still a few steps to go, but [Craig] has the basic layout covered. Next up is wiring it up and building a proper case for it, as well as working on latency. A few years ago, another multi-effects stomp box was featured in the Hackaday Prize, and last year, this multi-effects controller was featured.

Shorting Pins On A Raspberry Pi Is A Bad Idea; PMIC Failures Under Investigation

June 12, 2019 by Jonathan Bennett 153 Comments

You may have noticed, we’re fans of the Raspberry Pi here at Hackaday. Hardly a day goes by that we don’t feature a hack that uses a Pi somewhere in the build. As useful as the Pis are, they aren’t entirely without fault. We’ve talked about the problems with the PoE hat, and multiple articles about keeping SD cards alive. But a new failure mode has popped that is sometimes, but not always, caused by shorting the two power rails on the board.

The Pi 3 B+ has a new PMIC (Power Management Integrated Circuit) made by MaxLinear. This chip, the MxL7704, is a big part of how the Raspberry Pi foundation managed to make the upgrades to the Pi 3 without raising the price over $35.

A quick look at the Raspberry Pi forum shows that some users have been experiencing a specific problem with their new Raspberry Pi 3 B+ units, where the power LED will illuminate but the unit will not boot. The giveaway is zero voltage on the 3v3 pin. It’s a common enough problem that it’s even mentioned in the official boot problems thread.

Make sure the probe you are measuring with does not slip, and simultaneously touches any of the other GPIO pins, as that might instantly destroy your PI, especially shorting the 3V3 pin to the 5V pin will prove to be fatal.

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