Hackaday Prize 2021 entrant [Philip Ian Haasnoot] has been building a well-polished power bank. But this is no ordinary little power bank the like you would throw in your rucksack for a day out. No, this 2.5 kW luggable power bank is neatly encased in a tough, waterproof Pelican 1550 case, and is suitably decked out with all the power sockets you could possibly need for a long weekend of wilderness camping and photography.
Boy, that’s a lot of tab welding
This box sports USB-C and USB 3.0 connectors for gadget charging, as well as 12 VDC cigarette lighter and XT-60 ports for high-drag devices. Also it provides a pair of 120 VAC sockets via an integrated inverter, which at 1.5 kW could run a small heater if you were really desperate, but more likely useful to keep your laptop going for a while. Now if only you could get Wi-Fi out in the desert!
[Philip] doesn’t actually talk much about the solar panels themselves, but we know the box contains a 600 W MPPT boost converter to take solar power in, and feed the LiPo battery pack in the correct manner.
The battery pack is custom-made from salvaged and tested 18650 cells, as you would expect, which we reckon took an absolute age to make by hand. The whole project is nicely finished, and looks like something we’d be happy to throw in the back of the car before heading out into our local wilderness.
As [Philip] says in the project description, it’s a tough job to carry enough power and keep all his drones, cameras and lighting equipment charged, not mention helping prevent the campsite occupants from freezing overnight during the chilly Arizona nights.
Many power bank designs have graced these fair pages over the years, like this rather polished build, and long may they continue to do so.
Come on now, admit it. You’ve done it. We’ve done it. You know — you were really sure that sheet of plastic stock you found lying around the hackerspace was acrylic right? You dialled in the settings, loaded the design, set the focus and pushed the little green ‘start’ button. Lots of black smoke, fire, and general badness ensued as you lunged for the red ‘stop’ button, before lifting the lid to work out how you’re going to clean this one up.
The technique makes use of so-called ‘speckle imaging’ where a material illuminated by a laser will produce a unique pattern of reflected spots, or speckles into a camera. By training a deep neural model with a large set of samples, it was found possible to detect up to 30 types of material with 98% accuracy.
The pre-baked model runs on a Raspberry PI zero with an off-the-shelf camera all powered from a power bank. This allows the whole assembly to simply drop onto an existing laser cutter head, with no wiring needed.
Even if you’re a seasoned laser cutter user, with a well-controlled stock pile, the peace-of-mind this could give would definitely be worth the effort. A more detailed description and more videos may be found by reading the full paper. Here’s hoping they release the system as open source, one day in the not-to-distant future. If not, then, you know what to do :)
The majority of non-SLA resin 3D printers, certainly at the hacker end of the market, are most certainly LCD based. The SLA kind, where a ultraviolet laser is scanner via galvanometers over the build surface, we shall consider no further in this article.
What we’re talking about are the machines that shine a bright ultraviolet light source directly through a (hopefully monochrome) LCD panel with a 2, 4 or even 8k pixel count. The LCD pixels mask off the areas of the resin that do not need to be polymerised, thus forming the layer being processed. This technique is cheap and repeatable, hence its proliferance at this end of the market.
They do suffer from a few drawbacks however. Firstly, optical convergence in the panel causes a degree of smearing at the resin interface, which reduces effective resolution somewhat. The second issue is one of thermal control – the LCD will transmit less than 5% of the incident light, so for a given exposure at the resin, the input light intensity needs to be quite high, and this loss in the LCD results in significant internal heating and a need for active cooling. Finally, the heating in the LCD combined with intense UV radiation degrades the LCD over time, making the LCD itself a consumable item.
Those of us old enough may remember the heyday of the text adventure game genre from the first time around. London-based Magnetic Scrolls was an early pioneering company producing titles for the first Amiga and Atari ST platforms. Fast-forward to 2017 and [Hugh Steers], the original co-founder and core developer for Magnetic Scrolls has formed an initiative to revive and re-release the original games on modern platforms. Since the 1980s-era DEC MicroVAX used originally for development is not particularly rare in retro computing circles, and media containing source code was found in someone’s loft space, reviving the games was not a tall order.
First, he needed to recover a copy of the original source code from the backup tapes. But there was a problem, it turns out that the decaying tapes used a unstable polyurethane-based binder to stick the oxide material (which is what stores the data) to the backing tape, and this binder can absorb water over the years.
Not much happens until you try to read the tape, then you trip over the so-called sticky-shed syndrome. Secondly you may find that a small amount of the oxide layer sheds from the tape, coating the read head, rollers and guides inside the complicated tape mechanism. This quickly results in it gumming up, and jamming, potentially chewing up the tape and destroying it permanently.
This was further exacerbated by the behaviour of the DEC TK50Z tape drive, which needed to shuttle the whole length of the tape as part of its normal operation.
A temporary solution was to bake the tape in an oven to drive out the moisture and reduce the stickiness enough to run it through the drive safely. Then only the oxide-shedding problem remained. The TK50Z drive was swapped for a TZ30 which shuttles the tape less, but also critically with a simple hack, would allow the heads to be cleaned with IPA between read passes. This was enough to keep the gumming up at bay and allow enough data to be read from the tapes to recover several games worth of code, ready for the re-releasing process.
The video after the break shows [Rob Jarratt] working through the process of the data recovery.
It appears they can. [Ian Charnas] wanted his very own Thor Hammer. He wasn’t happy to settle on the usual cosplay methods of spray painting over foam and similar flimsy materials. He presents a method for nickel plating onto a 3D printed model, using conductive nickel paint to prepare the plastic surface for plating. In order to reduce the use of hazardous chemistry, he simplifies things to use materials more likely to be found in the kitchen.
As the video after the break shows, [Ian] went through quite a lot of experimentation in order to get to a process that would be acceptable to him. As he says, “after all, if something is worth doing, it’s worth over-doing” which is definitely a good ethos to follow. Its fairly hard to plate metals and get a good finish, and 3D printed objects are by their nature, not terribly smooth. But, the effort was well rewarded, and the results look pretty good to us.
But what about the 400 kV I hear you ask? Well, it wouldn’t be Thor’s hammer, without an ungodly amount of lightning flying around, and since [Ian] is part of a tesla coil orchestra group, which well, it just kinda fell into place. After donning protective chainmail to cover his skin, he walks straight into the firing line of a large pair of musical tesla coils and survives for another day. Kind of makes his earlier escapade with jet-powered roller skates look mundane by comparison.
[Petteri Aimonen] presents for us a modular differential probe, as his entry into the 2021 Hackaday Prize.
This project shows a simple and well polished implementation of a differential-to-single-ended preamplifier, which allows a differential signal to be probed and fed to an oscilloscope via a BNC cable.
PCB Spark gap for primary ESD protection
It implements a classic instrumentation amplifier, where we have two amplifier stages. The first gives us the options for a gain of either 1 or 10, if we need it, with the second stage having a gain of 2.
The remaining circuit is a power supply to generate the necessary dual-rail supplies to feed the opamps. There is a lot of filtering on those output rails as well as on the USB power input side to try keep all that switched-mode power supply noise out of the signal path.
There are a couple of interesting design choices including the use of PCB material for the long removable probe arms, that integrate PCB spark gaps to offer a first defence against ESD reaching the more delicate parts of the system.
Why This Is Useful
There are two main classes of signals we electronics engineers care about: single-ended and differential-mode.
With the first kind, the signal is carried on a single wire, which is defined as being referenced to the common system ground. Current flows along the wire and returns to its source along the path of least resistance, at least at low frequencies. At higher frequencies, the path of least inductance is more relevant. This is all well and good, so long as you design the PCB correctly.
Coupling from adjacent wires due to mutual capacitance and inductance, as well as noise in the reference ground all conspire to mangle the signal we want to pass down the wire.
As the frequencies increase, and especially if you’re dealing with sharp edges, with all that extra odd-harmonic power, things start to get bad real fast. The way we deal with this is by utilising differential-mode signalling. This is where instead of a single wire, referenced to some notion of ground, we send the signal down a pair of wires, where the voltage difference between the wires forms the signal. Any external noise that leaks into the pair, will (hopefully!) affect both wires equally, forming what we call a common-mode component. When you look at the difference, this common mode noise disappears. (Our own [Bil Herd] covered this some time ago.)
When probing a circuit, it pays to have the right kind of probe as well as an understanding of the effect the probe will have on the circuit in operation. If you have a single-ended signal and you want to view it on your scope, your choice is either a passive or active probe. Usually some kind of passive probe will be most available. These commonly come in 50 Ω and 1 MΩ versions, and you need to be careful to use the correct probe type for your application.
For probing differential signals, it is possible to use a pair of probes, one for each signal wire, and then utilise the scope’s math difference function to show the signal. This is quite often a desperate measure, and what you really want is a differential front-end in hardware. You need a differential active probe.
The circuit may be simple, but don’t underestimate how much tweaking it needs to have good performance – a little slip with the PCB layout, as the author describes, caused some annoying resonances which can be hard to track down.
The project is still under active development, with the author showing the process as the project progresses, but its looking pretty good already, if you ask us.
Sources can found on his GitHib, which uses all Open Source tools, so its pretty accessible too.
Monowheels are nothing new, first being patented in the middle of the 19th century, but never really went mainstream due to, well, quite a lot of obvious issues. We’ve got problems with forward visibility, stability, steering, especially at speed, and the hilariously-named ‘gerbiling’ where the rider can spin around inside the wheel akin to a gerbil in a wheel. Fun times! But obviously that didn’t stop [The Q] from adding to the monowheel corpus by building one out of wood.
Sometimes people take on these projects simply for a laugh, like this bright orange one we covered a while back. Sometimes they’re powered by a motor, be it electric or internal combustion. Some are hand-cranked, some are pedal-powered, its all been tried.
[The Q] is no stranger to interesting wooden builds, and this video from a year ago shows him building a very simple direct-pedal-drive monowheel. The vast majority of the structure is wood, glued and screwed the old-fashioned way, with a bit of metalwork where necessary. We particularly like the simple counterweight solution which doubles up as a parking brake. It may look a little ungainly, but we can’t think of a simpler solution that would make much sense.
The build video after the break is six and half minutes of well executed videography for your viewing pleasure.
