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Hackaday Links: September 11, 2022

Good news out of Mars from the little lunchbox that could — in the seven times that MOXIE has run since it arrived in February 2021, it has reached its target production of six grams of oxygen per hour, which is in line with the output of a modest tree here on Earth. The research team which includes MOXIE engineers report that although the solid oxide electrolysis machine has shown it can produce oxygen at almost any time or day of the Martian scale, they have not shown what MOXIE can do at dawn or dusk, when the temperature changes are substantial, but they say they have ‘an ace up (their) sleeve’ that will let them do that. We can’t wait to see what they mean.

In other, somewhat funnier space news — early last Sunday morning, the ESA’s Solar Orbiter was cruising by Venus as part of a gravity-assist maneuver to get the Orbiter closer to the Sun. Two days before the Orbiter was to reach its closest point to the spacious star, it spat a coronal mass ejection in the general direction of both Venus and the Orbiter (dibs on that band name), as if to say ‘boo’. Fortunately, the spacecraft is designed to withstand such slights, but the same cannot be said for Venus — these events have their way with Venus’ atmosphere, depleting it of gasses.

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Engraving A Puzzle Box? Here’s A Collection Of Single-Line Cryptex Fonts

Here’s a neat resource from [MSRaynsford] that is worth bookmarking for anyone who gets creative with laser engravers, CNC routers, or drawing robots: SVGFonts are single-line symbol fonts that [MSRaynsford] created for his laser-cut and engraved cryptex puzzle boxes. They provide an easy way to engrave text as symbols.

Single-line fonts for engraving that include a runic-looking alphabet, a Greek-inspired set, and two symbol sets based on Flag Semaphore.

CNC engraving of letters and symbols is one of those things that seems simple, but is actually more complex than it may appear. It is often desirable to use a tool to engrave symbols with a single line, in much the same way a person would write them if using a pen. But fonts and art for letters and numbers aren’t normally a single line. Thankfully there is a solution in the form of Hershey text, an extension for which is included in Inkscape. It turns out that Hershey Fonts have their origin back in the 1960s, when the changing landscape of electronics and industry opened new opportunities and demanded new solutions.

That’s why, when [MSRaynsford] needed fonts in different styles and symbols for creating his puzzle boxes, he had to design them himself and they had to be single-line vector art, just like Hershey Text. The small collection includes English letters designed to resemble a runic alphabet, a Greek-inspired series, and two coded alphabets based on flag semaphore.

Grab ’em on GitHub, because you never know when you’ll need to make a quick cryptex.

A display in a field showing the water stress index over time

Hackaday Prize 2022: Using Infrared Thermometers To Measure Crops’ Water Stress

If you live anywhere on the Northern Hemisphere, you’re likely to have experienced one of the many heatwaves that occurred this summer. Extreme heat is dangerous for humans and animals, but plants, including important crops, also suffer. High temperatures lead to increased transpiration and evaporation, and if the water lost in this way is not replenished quickly enough, plants will stop growing and eventually wither and die.

In order to keep track of the amount of water available to crops, [Florian Ellsäßer] built the Crop Water Stress Sensor: a device that checks whether plants have enough moisture available to stay healthy. It does this by measuring the temperature of the leaves to calculate evaporation levels. If the leaves are cooler than their surroundings, this means that water is evaporating from them and the plant apparently has enough water available. If the leaves’ temperature is closer to the ambient temperature, then the plant may be running low on water.

[Florian]’s system performs this measurement using an infrared array, which is basically a low-resolution thermal camera that remotely measures the temperature of everything in its field of view. This IR array is pointed at a field, where it will see both leaves and the ground between them. The difference in temperature between these two can then be used to calculate the Crop Water Stress Index (CWSI), a standardized measure of how well-hydrated plants are. The result is shown on a display and also indicated using a convenient red-yellow-green status LED that shows if the crops in question need watering.

The system can be solar powered for completely remote operation, while its data can be read out through a WiFi interface. [Florian] is planning to update the design with a LoRa interface for greater range: the eventual goal is to build a large network of these sensors throughout agricultural areas and use the combined data to raise awareness of water shortages in certain areas. In order to make the sensors easy to build by anyone interested, all design files are available on the project page.

Keeping crops moisturized is one of the key tasks of agriculture, and we’ve seen several projects that aim to optimize and automate it, from a simple-but-effective ESP8266-based moisture sensor to complete hydroponics systems.

A Crowned Pulley Keeps Robot’s Treads On Track

[Angus] at Maker’s Muse recently created a new and tiny antweight combat robot (video, embedded below) and it has some wonderfully clever design elements we’d like to highlight. In particular: how to keep a tracked robot’s wheel belt where it belongs, and prevent it from slipping or becoming dislodged. In a way, this problem was elegantly solved during the era of the steam engine and industrial revolution. The solution? A crowned pulley.

Silicone bracelet and crowned pulley result in a self-centering belt with a minimum of parts.

A crowned pulley is a way of automatically keeping a flat belt centered by having a slight hump in the center of the pulley, which tapers off on either side. Back when steam engines ran everything, spinning axles along the ceiling transferred their power to machinery on the shop floor via flat belts on pulleys. Crowned pulleys kept those flat belts centered without any need for rims or similar additions.

The reason this worked so well for [Angus]’s robot is partly its simplicity, and partly the fact that it works fantastically with the silicone wrist bracelets he uses as treads. These bracelets are like thick rubber bands, and make excellent wheel substitutes. They have great grip, are cheap and plentiful, and work beautifully with crowned pulleys as the hubs. It’s a great solution for a tiny robot, and you can how it self-centers in the image here.

Antweight robots are limited to 150 grams which means every bit counts, and that constraint leads to some pretty inventive design choices. For example, [Angus]’s new robot also has a clever lifter mechanism that uses a 4-bar linkage designed to lever opponents up using only a single motor for power. Watch [Angus] explain and demonstrate everything in his usual concise and clear manner in the video, embedded below.

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Full Transparency: Stronger FDM Prints

We always look forward to [Stefan’s] CNC Kitchen videos. They are usually useful, but always carefully thought out and backed with experimental data. His latest is about creating transparent and strong FDM prints. You normally don’t associate the FDM process with clear prints even with clear filament. The problem is the filament doesn’t lay down in a particular structure, so light scatters producing a sort of white color. However, [Stefan] found a post on Printables called “How to Print Glass” which changes the structure of the part and, of course, [Stefan] wanted to see if the process also led to stronger parts.

The process is slow and the basic idea is to use no top and bottom layers. The entire part is essentially infill. You also need to set the infill to go in the same direction for each layer. As [Stefan] mentions, there have been other efforts to make transparent parts, especially in vase mode. Of course, you can also get transparent parts using resin printing, although it isn’t always as easy as you might think.

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Renewable Hydrogen Sucked From Thinish Air

Stored hydrogen is often touted as the ultimate green energy solution, provided the hydrogen is produced from genuinely green power sources. But there are technical problems to be overcome before your average house will be heated with pumped or tank-stored hydrogen. One problem is that the locations that have lots of scope for renewable energy, don’t always have access to plenty of pure water, and for electrolysis you do need both. A team from Melbourne University have come up with a interesting way to produce hydrogen by electrolysis directly from the air.

Redder areas have more water risk and renewable potential

By utilising a novel electrolysis cell with a hygroscopic electrolyte, the so-called direct air electrolysis (DAE) can operate with humidity as low as 4% relative, so perfectly fine even in the most arid areas, after all there may not be clouds but the air still holds a bit of water. This is particularly relevant to regions of the world, such as deserts, where there is simultaneously a high degree of water risk, and plenty of solar potential. Direct electrolysis of saline extracted at coastal areas is one option, but dealing with the liberated chlorine is a big problem.

The new prototype is very simple in construction, with a sponge of melamine or a sintered glass foam soaked in a compatible electrolyte. Potassium Hydroxide (alkaline) was tried as was Potassium Acetate (base) and Sulphuric Acid, but the latter degraded the host material in a short time. Who would have imagined? Anyway, with electrolysis cell design, a key problem is ensuring the separate gasses stay separate, and in this case, are also separate from the air. This was neatly ensured by arranging the electrolyte sponge fully covered both electrodes, so as the hygroscopic material extracted water from the air, the micro-channels in the structure filled up with liquid, with it touching both ends of the cell, forming the circuit and allowing the electrolysis to proceed.

Hydrogen, being very light, would rise upward through holes in the cathode, to be collected and stored. Oxygen simply passed back into the air, after passing though the liquid reservoir at the base. Super simple, and from reading the paper, quite effective too.

You can kind of imagine a future built around this now, where you’re driving your hydrogen fuel cell powered dune buggy around the Sahara one weekend, and you stop at a solar-powered hydrogen fuel station for a top up and a pasty. Ok, possibly not that last bit.

The promised hydrogen economy may be inching closer. We covered using aluminium nanoparticles to rip hydrogen out of water. But once you have the gas, you need to store and handle it. Toyota might have a plan for that. Then perhaps handling gas directly at all isn’t a great idea, and maybe the future is paste?

Thanks to [MmmDee] for the tip!

A black PCB with an ESP32 and an SBM-20 geiger counter

Flexible Radiation Monitoring System Speaks LoRa And WiFi

Radioactivity has always been a fascinating phenomenon for anyone interested in physics, and as a result we’ve featured many radioactivity-related projects on these pages over the years. More recently however, fears of nuclear disaster have prompted many hackers to look into environmental radiation monitoring. [Malte] was one of those looking to upgrade the radiation monitor on his weather station, but found the options for wireless geiger counters a bit limited.

So he decided to build himself his own Wifi and LoRa compatible environmental radiation monitor. Like most such projects it’s based on the ubiquitous Soviet-made SBM-20 GM tube, although the design also supports the Chinese J305βγ model. In either case, the tube’s operating voltage is generated by a discrete-transistor based oscillator which boosts the board’s 5 V supply to around 400 V with the help of an inductor and a voltage multiplier.

Graphs showing temperature, humidity and radiation levels
Data can be visualized in graphs, together with other data from the weather station like temperature and humidity

The tube’s output signal is converted into clean digital pulses to be counted by either an ESP32 or a Moteino R6, depending on the choice of wireless protocol. The ESP can make its data available through a web interface using its WiFi interface, while the Moteino can communicate through LoRa and sends out its data using MQTT. The resulting data is a counts-per-minute value which can be converted into an equivalent dose in Sievert using a simple conversion formula.

All design files are available on [Malte]’s website, including a PCB layout that neatly fits inside standard waterproof enclosures. Getting more radiation monitors out in the field can only be a good thing, as we found out when we tried to detect a radiation accident using community-sourced data back in 2019. Don’t like WiFi or LoRa? There’s plenty of other ways to connect your GM tubes to the internet.