[Blair Neal] has been working on an information database for artists and hackers – a collection of non-conventional display technologies available to us. We’ve covered this repository before, six years ago – since then, it’s moved to a more suitable platform, almost doubled in size, and currently covers over 40+ display technology types and related tricks. This database is something you should check out even if you’re not looking for a new way to display things right now, however, for its sheer educational and entertainment value alone.
[Blair] doesn’t just provide a list of links, like the “awesome-X” directories we see a lot of. Each entry is a small story that goes into detail on what makes the technology tick, its benefits and fundamental limitations, linking to illustrative videos where appropriate. It’s as if this guide is meant to give you an extensive learning course on all the ways you can visualize things on your creative journey. All of these categories have quite a few examples to draw from, highlighting individual artworks that have made use of any technology or trick in a particular way.
If you’re ever wondered about the current state of technology when it comes to flexible or transparent displays, or looked for good examples of volumetric projection done in a variety of ways, this is the place to go. It also talks about interesting experimental technologies, like drone displays, plasma combustion or scanning fiber optics. Overall, if you’re looking to spend about half an hour learning about all the ways there are to visualize something, this database is worth a read. And, if there’s a display technology the author might’ve missed and you know something about, contributions are welcome!
Someone setting out to compile information about an extensive topic is always appreciated, and helps many hackers on their path. We’ve seen that done with 3D printer resin settings and SMD part codes, to name just a few. What’s your favourite hacker-maintained database?
[Marcel] thought – what if he had more control over his house ventilation system? You could add some nifty features, such as automatically ventilating your house in the mornings when everyone’s away, only creating noise when nobody’s around to hear it. Sadly, most ventilation systems are not automation-friendly at all – he was lucky, however, as his system came with a wireless remote. [Marcel] reverse-engineered this remote, created a USB dongle speaking the same protocol, and tied it into his Home Assistant setup!
The remote in question is Orcon R15, with an Atmel MCU talking to a CC1101 chip through SPI. He sniffed the SPI communications when pressing different buttons, figured out the protocol by comparing the recordings, and built a test setup with a spare Arduino and CC1101 module. It worked, and he set out to design a separate dongle, using an ATMega32U4. The dongle looks pretty neat, and fits a Hammond enclosure – what’s not to like?
Then he set out to develop the firmware, and didn’t disappoint on that front either. His code doesn’t just imitate the original remote perfectly in terms of control, it also has user-friendly pairing flow, keeps track of the system’s current state, and still lets the original remote be used in parallel. Eagle files for the PCB are available on the project page, with the code and a PDF schematic available in the GitHub repo. This entire journey is described in the Hackaday.io page, and we would recommend you check it out for all the insights it provides!
Ventilation systems don’t tend to be designed for automation, and it’s endearing to see hackers working on conquering this frontier. Last time we’ve seen a ventilation system hack, it had the additional challenge of being landlord-friendly, and we think the hacker nailed it!
I hope last week’s introduction to bulk material handling got you all thinking up amazing hacks, and we’ll soon be reporting on DIY Cap’n Crunch Robots galore. This week we’ll look at how to measure particle sizes, separate particles, and even grind them up when you need to.
Measuring Material Properties
Last week we talked about cohesive strength. Bulk material behaves somewhere between a solid and a liquid — if you’ve done your homework, it flows down the funnel just fine. But if you haven’t, it sticks together and holds up the rest of the material. Cohesive strength is the measure of how much weight the material at the bottom of the funnel can hold up.
You can get a rough measurement by packing material in a box with a square hole at the bottom. One side of the hole should have a retractable slide. Slowly withdraw the slide, making the hole rectangular. Material will bridge over, and then at some point a larger chunk will fall out. This is about the size of the minimum opening that will not arch, and a practical measure of the material’s cohesive strength.
Many materials cohere better when wet. Dry a sample in a microwave to determine the percent moisture by weighing it before and after.
Cohesive strength is closely allied to shear strength. If you want to measure shear strength, cut two 1 cm wide rings of 5 cm diameter PVC pipe, stack them, pack with material, put a disk atop the material and load it, then drag the top ring off the bottom with a spring scale. The force per unit area is the shear strength at that pressure. If it starts packing you’ll see it in the curve.
Packing factor is another useful measurement. Gently shake material to fill a rigid container and weigh it. Now empty the container and refill, packing the material as hard as you can with a length of 1” dowel. Reweigh, and the ratio of the two weights tells you how well the material packs.
Real bulk material is almost always made up of particles of varying sizes, shapes, and compositions. Dirt is particles of different kinds of mineral and organic matter varying from outright rocks to sub micron clay particles. If you’re having problems, getting a graph of material size distribution can be helpful.
For particles above about 75 μM, you can measure the sizes with sieves. If you want to be fancy, they sell nice sets of metal sieves with wire mesh in the bottom. Screen assortments are cheaper. Below 75 μM, you have to use a hydrometer. This is messy and takes a while, but does work.
The idea is to mix the material with soapy water and then use a hydrometer from the auto parts store to measure the density. The particles fall out by Stokes law, big ones first. Stokes law is just that the drag force on a sphere is proportional to the square of the radius. Mass will go up as cube of the radius, so large particles fall faster than small ones. As they fall out, the density of the fluid decreases. This page describes how to do it, and this page has a handy calculator for interpreting the results.
Grinding
You can also change the size of particles in your mix. If particles are too large, they can be crushed or ground. You can separate by size and only grind some of the sizes or discard some of the material. There’s a whole science to grinding. The finer you grind, the harder it gets to grind. Cosmetics and pharmaceutical companies are full of grinding experts.
In general, there are three ways to make something smaller – crush it, cut it, or hit it.
Crushing is straightforward. Use rollers or jaws, a rolling pin or a rock crusher. Don’t overlook the vise. A jaw crusher only crushes particles larger than the jaw space, useful to make a certain size. Rock crushers have a complex motion (video) that should nonetheless be easily imitated by a hacker project. Amateur/hobby gold prospectors have an accessible community.
Crushing action in rollers only works until the particle is small enough that the surface of the roller deforms instead of the particle. Stones have been used to crush grain into flour for most of history.
Cutting is best for soft things, like gummy worms, and tough things (video.). Make sure the cut material has an easy path out. Think of an old fashioned kitchen meat grinder. .
If you want small particles, you need an impact grinder. A coffee mill or blender works by striking the particle with a fast moving impactor. This can be a blade – useful if the material first needs to be cut up, as in a coffee mill – or blunt. Many industrial mills use two pivoting weights on a shaft, and this unit just uses chains (video).
Another impact mill is the ball mill. Rotate a drum on it’s side with steel balls and the material. The balls travel up the side, then fall back down, striking the material.
All these work by fracturing the material. What if you’re trying to powder something that doesn’t fracture, say rubber O rings? For that, there’s cryogenic grinding.
Many rubbery materials are really glasses — materials that are a gloppy liquid at a higher temperature, often brittle at a cool temperature, and soft in-between. The glass you’re probably thinking of is a brittle, breakable material at room temperature, but at high temperature is a liquid. The transition point is the ‘glass transition temperature’.
So what about our O rings? If they’re natural rubber their transition point is about -70° C. Below that temperature they’re brittle and can be ground up. Unfortunately, grinding is going to put heat back in. So consider grinding slowly – some labs grind biological materials like skin samples with a special mortar and pestle cooled beforehand with liquid nitrogen. Just be sure everything in contact with the material has been cooled, and use a thick walled container with lots of thermal mass.
Separating Wheat From Chaff
Sometimes you have a mix and need to separate it. Your roommate dumped all the gummy bears and all those weird ginger candies into a bowl or whatever. Last week we introduced particle segregation as a bad thing. But when you want to un-mix a mixture, it can be a good thing. Any of the techniques from last week can be an aid.
Sieves and screens work to separate by size. They clog unless the material keeps moving over them. One simple way to do this is to flow the material over sieves on a slanted board, finest sieve first. Another is to mechanically shake the screen. Paper filters are just fine screens, and do clog.
A trommel is a slowly turning cylinder with walls of different sized screens along it’s length. Material is fed into the fine screen end and slowly moves towards the other.
Stokes law provides another way to separate materials as we saw above. Make an upward air draft in a vertical pipe. Deliver the material into the pipe part way up. Materials with more drag than weight will go up, larger materials will go down. You can use the air speed to control the size of particle. An industrial machine called an air classifier does this with higher velocity air blowing material into the rim of a spinning set of blades.
It could be the air (or another gas) you want to remove. There are a couple ways to do it. The first is the cyclone familiar to wood shops. The second is even simpler – inject the air/material mix into the top of a tall, slender container with a tube that extends about halfway into the container. Let the air out from an outlet pipe in the roof. The air flow expands, slows down, and the material falls out.
You can just blow the material sideways – the age old system of threshing wheat works this way. Wheat comes from the plant with a husk, you beat it with a flail to loosen the husk, giving you wheat grains and chaff mixed. Put the mix on a blanket and have four peasants toss it repeatedly. The chaff blows away in the wind.
Inertial Separation
A very sensitive separation technique is inertial separation. Here’s a mix of gummy colas and jelly beans. We separated them by tilting and gently shaking the sheet. A material moves on a sheet by staying in place until the acceleration is more than some critical value. Then it rolls or slides.
If your material is dirt or such, run a magnet through it. There’s iron ore and bits of human generated iron in a lot of soil. It can get into motors and such. If you need it out run the material past magnets. An eddy current separator uses AC magnetic effects to do the same with nonferrous metals.
You can also segregate materials by dissolving them. A mixture of table salt and white sand would seem impossible, but if you stir it into water, then decant and boil off the water, the salt and sand can be recovered separately. But we think we’re veering into chemistry now, and we should stop.
Next time we’ll finish up by looking at controlling movement: building gates and contraptions that move your bulk material without clogging up.
For anyone looking to buy a 3D printer at home, the first major decision that needs to be made is whether to get a resin printer or a filament printer. Resin has the benefits of finer detail, but filament printers are typically able to produce stronger prints. Within those two main camps are various different types and sizes to choose from, but thanks to some researchers at Switzerland’s École polytechnique fédérale de Lausanne (EPFL) there’s a new type of resin printer on the horizon that can produce prints nearly instantaneously.
The method works similarly to existing resin printers by shining a specific light pattern on the resin in order to harden it. The main difference is that the resin is initially placed in a cylinder and spun at a high speed, and the light is shined on the resin at different angles with very precise intensities and timings in order to harden the resin in specific areas. This high-speed method allows the printer to produce prints in record-breaking time. The only current downside, besides the high price for the prototype printer, is that it’s currently limited to small prints.
With the ability to scale in the future and the trend of most new technologies to come down in price after they have been on the market for some amount of time, it would be groundbreaking to be able to produce prints with this type of speed if printers like these can be scalable. Especially if they end up matching the size and scale of homemade printers like this resin printer.
Stand by the shore and watch the waves roll in, and you’ll notice that most come in at roughly the same size. There’s a little variation, but the overwhelming majority don’t stand out from the crowd. On all but the stormiest of days, they have an almost soothing regularity about them.
Every so often though, out on the high seas, a rogue wave comes along. These abnormally large waves can strike with surprise, and are dangerous to even the largest of ships. Research is ongoing as to what creates these waves, and how they might be identified and tracked ahead of time.
It’s a feature of an active language, that it will readily assimilate words from others. Pizza, karaoke, vuvuzela, parka, gateau, schadenfreude, they have all played their part in bringing a little je ne sais quoi into our everyday speech. This happens as a natural process as whatever the word is describing becomes popular, and sometimes these new words cause a backlash from those who see themselves as the language’s defenders.
Often this is a fringe activity such as the British politician who made a fool of himself in a radio interview by insisting on the now-archaic Wade-Giles “Peking” rather than the vastly more common Pinyin “Beijing”, but for some tongues it’s no laughing matter. Nowhere is this more the case than in the Francophone world, in which the Academie Francaise and the French and Quebecquois governments see themselves as very much the official guardians of French. And now it seems that the French ministry of culture have turned their eyes upon gamers.
It’s nothing new for words associated with technology to fall under this scrutiny, a quarter century ago in the CD-ROM business it was de rigeur for localized discs to talk about le logicel, l’ordinateur, and telecharger instead of program, computer, and download. The talk of the industry was that Sony refused to do this for PlayStation consoles sold in Quebec during the 1990s, and thus all their sales in the province had to be under-the-counter. But there’s a sense from reading the reports that this intervention is a little clumsy; while it’s easy to say logicel we’re not so sure that jeu video de competition or video game competition for e-sports and joueur-animateur en direct or live player-animator for streamer aren’t just too much of a mouthful for easy adoption. For the first one, we can’t help remembering that sport is also an everyday French word, so couldn’t they have come up with something less clumsy such as reseau-sports or network-sports?
Here at Hackaday more than one of us are unrepentant Francophiles, so the evolution of French words in our field is of interest to us. Habitez-vous en France ou Quebec? Donnez-nous votres idees dans les commentaires! (mais en Anglais s’il vous plait pour les Americains, excusez-nous)
Summer is rapidly approaching (at least for those of us living in the Northern Hemisphere) and if you are having to maintain a lawn at your home, now is the time to be thinking about irrigation. Plenty of people have built-in sprinkler systems to care for their turf, but this is little (if any) fun for any children that might like to play in those sprinklers. This sprinkler solves that problem, functioning as an automatic water gun turret for anyone passing by.
This project was less a specific sprinkler build and more of a way to reuse some Khadas VIM3 single-board computers that the project’s creator, [Neil], wanted to use for something other than mining crypto. The boards have a neural processing unit (NPU) in them which makes them ideal for computer vision projects like this. The camera input is fed into the NPU which then directs the turret to the correct position using yaw and pitch drivers. It’s built out of mostly aluminum extrusion and 3D printed parts, and the project’s page goes into great details about all of the parts needed if you are interested in replicating the build.
[Neil] is also actively working on improving the project, especially around the turret’s ability to identify and track objects using OpenCV. We certainly look forward to more versions of this build in the future, and in the meantime be sure to check out some other automated sprinkler builds we’ve seen which solve different problems.
