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Screenshot from the presentation, showing the datalogger product image next to the datalogger specs stated. The specs are suspiciously similar to those of a Raspberry Pi 3.

Reclaiming A Pi-Based Solar Datalogger

March 4, 2023 by 7 Comments

There’s quite a few devices on the market that contain a Raspberry Pi as their core, and after becoming a proud owner of a solar roof, [Paolo Bonzini] has found himself with an Entrade ENR-DTLA04DN datalogger which – let’s just say, it had some of the signs, and at FOSDEM 2023, he told us all about it. Installed under the promise of local-only logging, the datalogger gave away its nature with a Raspberry Pi logo-emblazoned power brick, a spec sheet identical to that of a Pi 3, and a MAC address belonging to the Raspberry Pi Foundation. That spec sheet also mentioned a MicroSD card – which eventually died, prompting [Paolo] to take the cover off. He dumped the faulty SD card, then replaced it – and put his own SSH keys on the device while at it.

At this point, Entrade no longer offered devices with local logging, only the option of cloud logging – free, but only for five years, clearly not an option if you like your home cloud-free; the local logging was not flawless either, and thus, the device was worth exploring. A quick peek at the filesystem netted him two large statically-compiled binaries, and strace gave him a way to snoop on RS485 communications between the datalogger and the solar roof-paired inverter. Next, he dug into the binaries, collecting information on how this device did its work. Previously, he found that the device provided an undocumented API over HTTP while connected to his network, and comparing the API’s workings to the data inside the binary netted him some good results – but not enough.

The main binary was identified to be Go code, and [Paolo] shows us a walkthrough on how to reverse-engineer such binaries in radare2, with a small collection of tricks to boot – for instance, grepping the output of strings for GitHub URLs in order to find out the libraries being used. In the end, having reverse-engineered the protocol, he fully rewrote the software, without the annoying bugs of the previous one, and integrated it into his home MQTT network powered by HomeAssistant. As a bonus, he also shows us the datalogger’s main PCB, which turned out to be a peculiar creation – not to spoil the surprise!

We imagine this research isn’t just useful for when you face a similar datalogger’s death, but is also quite handy for those who find themselves at the mercy of the pseudo-free cloud logging plan and would like to opt out. Solar tech seems to be an area where Raspberry Pi boards and proprietary interfaces aren’t uncommon, which is why we see hackers reverse-engineer solar power-related devices – for instance, check out this exploration of a solar inverter’s proprietary protocol to get data out of it, or reverse-engineering an end-of-life decommissioned but perfectly healthy solar inverter’s software to get the service menu password.

Cat Feeder Depends On RFID To Keep The Peace At Dinnertime

February 28, 2023 by 10 Comments

Anyone with more than one cat can tell you that the joy mischief they bring into your life is much more than twice that of a single cat. And if those felines have different dietary needs, you can end up where [Benjamin Krejci] found himself, which resulted in this fancy RFID cat feeder.

For a little backstory, [Ben]’s furry friends [Luna] and [Fermi] have vastly different eating styles, with the former being a grazer and the latter more of a “disordered eater,” to put it politely. [Fermi] tends to eat until she vomits, which is fun, and muscles her pickier sister away from the bowl if there’s anything left in it. [Ben]’s idea was to leverage [Luna]’s existing RFID chip, which he figured would be a breeze. But the vet-inserted chip is designed to be read by a high-power reader directly in contact with the cat’s skin, which made reliably reading the chip a challenge.

Several round of design iteration resulted in the current configuration, with a large antenna coil poised above and behind the food dispenser. [Luna] has no choice but to put the back of her neck and shoulder blades almost directly in contact with the coil, which makes it easier to read the 134.2-kHz chip with a long-distance RFID module. If [Luna]’s chip is found, the lid on the food bowl opens gently and quietly, so as not to spook the mild-mannered cat. The lid stays open as long as [Luna] is in place thanks to some IR sensors, but as soon as she backs out, the lid comes down to keep [Fermi] from gorging herself.

Hats off to [Ben] for working through the problem and coming up with what looks like a fine solution. We suppose he could have tried something easier like weighing the two cats to distinguish between them, but this seems like a cleaner solution to us.

Antenna Hidden In Holiday Lights Skirts HOA Rules

February 27, 2023 by 90 Comments

For all their supposed benefits, homeowner’s associations (HOAs) have a reputation of quickly turning otherwise quaint neighborhoods into a sort of Stanford prison experiment, as those who get even the slightest amount of power often abuse it. Arbitrary rules and enforcement abound about house color, landscaping, parking, and if you’ve ever operated a radio, antennas. While the FCC (at least as far as the US is concerned) does say that HOAs aren’t permitted to restrict the use of antennas, if you don’t want to get on anyone’s bad side you’ll want to put up an antenna like this one which is disguised as a set of HOA-friendly holiday lights.

For this build, a long wire is hidden along with a strand of otherwise plain-looking lights. While this might seem straightforward at first, there are a few things that need to be changed on the lighting string in order to make both the antenna and the disguise work. First, the leads on each bulb were removed to to prevent any coupling from the antenna into the lighting string. Clipping the leads turns what is essentially a long wire that might resonate with the antenna’s frequency into many short sections of wire which won’t have this problem. This also solves the problem of accidentally illuminating any bulbs when transmitting, as the RF energy from the antenna could otherwise transfer into the lighting string and draw attention from the aforementioned HOA.

Tests of this antenna seemed to show surprising promise while it was on the ground, but when the string and antenna was attached to the roof fascia the performance dropped slightly, presumably because of either the metal drip edge or the gutters. Still, the antenna’s creator [Bob] aka [HOA Ham] had excellent success with this, making clear contacts with other ham radio operators hundreds of miles away. We’ve shared another of [Bob]’s HOA-friendly builds below as well which hides the HF antenna in the roof’s ridge vent, and if you’re looking for other interesting antenna builds take a look at this one which uses a unique transformer to get wide-band performance out of an otherwise short HF antenna.

Continue reading “Antenna Hidden In Holiday Lights Skirts HOA Rules” →

The sensor hub in all its glory, sensor itself on top, standing on 3D-printed feet, and the PCB on the bottom

Hacker-Friendly And Elegant Air Quality Sensor Hub

February 27, 2023 by 9 Comments

Ever wanted an indoor environment sensor that’s dead simple yet a complete package? That’s the anotter-sensor-hub project from [Jana Marie], designed for the Sensirion SEN05x series sensors, with a SEN055 sensor shown in the picture above. Given such a sensor, you can measure VOCs and NOCs (Volatile and Non-Volatile Organic Compounds), as well as PM1, PM2.5, PM4 and PM10 particulate matter indices, with temperature and humidity sensing thrown in for good measure. Fully open and coupled with 3D printable stand files, this alone makes for an air quality hub fit for a hacker’s desk. That’s not all, however — this board’s elegant extensibility is a good match for the sensor’s impressive capabilities!

The PCB itself might look simple, it’s simply an ESP32 and some supporting circuitry required. But you’ll notice there’s also a trove of connector footprints for different interfaces; whatever else you might want to add to your sensor hub, whether it connects through I2C, SPI or PWM, you can! As usual, the sensor itself is the most expensive part of such a project — the boards themselves are around $5 USD apiece fully assembled, but one sensor-included hub will set you back roughly $42 USD. That said, it’s a great value for the price, and the trove of sensing data you can get might just more than pay for itself in quality-of-life improvements you make. Of course, everything is open-source and comes as a complete packages for you to start using. The firmware, KiCad files, 3D holder and even Grafana dashboard files can be found on GitHub.

Such air quality sensor platforms have been getting more and more popular, and hackers have been paying attention. Having a full open-source package like this at our disposal is amazing. If you’re looking for a cheaper “baby’s first air quality sensor”, drop by your local IKEA — there’s a way less featureful but quite cheap sensor that you can equip with an ESP8266, perhaps, even on a custom PCB.

A dark grey couch with a white pegboard on a drawer slide protruding from its arm. The pegboard has a magazine holder, pen holder, and several other miscellaneous bins holding odds and ends on it.

Sofa Armrest Is A Nifty Storage Spot

February 26, 2023 by 7 Comments

If you’re like us, you’re always in need of a little more space to store things. [Javier Guerrero] realized his sofa wasn’t living up to its full storage potential and designed this sofa armrest storage.

[Guerrero]’s sofa arms were hiding 80 liters of space, so he really wanted to do something with it. After disassembling them, he found his original plan of just cutting them up wouldn’t work due to the minimal structure inside. Not to be discouraged, he drew up some plans and built replicas from 15 mm plywood.

For one armrest, he made a single giant box that opens from the top where he can store a couple of folding chairs. On the other side, he made a shorter top-opening bin for charging phones and storing the remote. Underneath that is a large pull out drawer with a pegboard for organizational bliss.

The arms were upholstered using the fabric from the original arms plus a little extra from another slip cover. Separate arm modules and easily obtainable matching fabric aren’t a given for every couch, but we expect that almost any sofa with arms could benefit from this hack given a little ingenuity.

If you’re looking for more storage hacks, checkout this Modular Storage from Old Filament Spools, the Last Component Storage System You’d Ever Need, or the ever popular Gridfinity.

Pi Pico Calculates Water Usage

February 25, 2023 by 18 Comments

Modern WiFi-enabled microcontrollers have made it affordable and easy to monitor everything from local weather information to electricity usage with typically no more than a few dollars worth of hardware and a little bit of programming knowledge. Monitoring one’s own utility data can be a little bit more difficult without interfering with the metering equipment, but we have seen some clever ways of doing this over the years. The latest is this water meter monitoring device based on a Raspberry Pi Pico.

The clever thing here isn’t so much that it’s based on the tiniest of Raspberry Pis, but how it keeps track of the somewhat obscured water flow information coming from the meter. Using a magnetometer placed close to the meter, the device can sense the magnetic field created as water flows through the meter’s internal sensors. The magnetic field changes in a non-obvious way as water flows through it, so the program has to watch for specific peaks in the magnetic field. Each of these specific waveforms the magnetometer detects counts to 0.0657 liters of water, which is accurate for most purposes.

For interfacing with a utility meter, this is one of the more efficient and elegant hacks we’ve seen in a while. There have, of course, been other attempts to literally read the meter using web cams and computer vision software, but the configuration for these builds is much more complex than something like this. You can interface with plenty of utility meters other than water meters, too, regardless of age.

Automating The Most Analog Of HVAC Equipment

February 20, 2023 by 35 Comments

Burning wood, while not a perfect heating solution, has a number of advantages over more modern heating appliances. It’s a renewable resource, doesn’t add carbon to the atmosphere over geologic time scales like fossil fuels do, can be harvested locally using simple tools, and it doesn’t require any modern infrastructure to support it. That being said, wood stoves aren’t something that are very high-tech and don’t lend themselves particularly well to automation as a result, at least with the exception of this wood stove from [jotulf45v2].

While this doesn’t automate the loading or direct control of a modern pellet stove, it does help [jotulf45v2] know when the best times are for loading more wood into the stove and helps keep the stove in the right temperature range to avoid the dangerous formation of creosote on the inside of his chimney caused by low temperature burns. Two temperature sensors, one on the stovetop and the other on the stove pipe, monitor the stove exhaust temperature. They feed data to a Node-RED system running on a Raspberry Pi which automatically notifies the user by text message when certain stove temperatures are reached.

For anyone heating with wood, tools like this are indispensable to help avoid spending an otherwise unnecessary amount of time getting a fire up to temperature quickly without over-firing the stove. Modern pellet stoves have some more modern conveniences like this built in, but many of the perks of using cord wood are lost with these devices. There are plenty of other ways to heat with wood too; take a look at this custom wood boiler which serves as a hot water heater.