Floppy disks are rapidly aging, and archivists are working hard to preserve what data is left. This has led to the development of advanced floppy controllers capable of capturing the raw flux data from disks. [bzotto] was experimenting with the Applesauce archival hardware, and had some fun with the tools.
The result is a highly esoteric Easter egg. [bzotto]’s Picturedsk tool takes a bitmap image as input, and imprints that image into the magnetic flux of the disk. Thus, when viewing a dump of the disk’s magnetic flux on an archival program, the hidden image will be revealed. As an extra treat, it also writes a 1-bit version of the image to track 0, along with a barebones Apple ][ program to display the image and implore the user to investigate further.
Building antennas is a time-honored ham radio tradition. Shortwave antennas tend to be bulky but at VHF frequencies the antenna sizes are pretty manageable. [Fjkaan’s] 2 meter quadrifilar helicoidal antenna is a good example and the structure for it can be created with 3D printing combined with electrical conduit.
Many people, including [G4ILO] use PVC pipe for the structure, and that design inspired [Fjkaan]. Despite being a bit less substantial, the conduit seems to work well and it is easy to cut. The helical design is common for satellite work owing to its circular polarization and omnidirectional pattern.
Mouser and Digi-Key are great for servicing most needs, and the range of parts they offer is frankly bewildering. But given the breadth of the hardware hacking community’s interests, few companies could afford to be the answer to everyone’s needs.
That’s especially true for the esoteric parts needed when one’s hobby involves high voltages and homemade lasers, like [Les Wright]. He recently came up with a DIY doorknob capacitor design that makes the hard-to-source high-voltage caps much easier to obtain. We’ve seen [Les] use these caps in his transversely excited atmospheric (TEA) lasers, a simple design that uses high-voltage discharge across a long, narrow channel filled with either room air or nitrogen. The big ceramic caps are needed for the HV supply, and while [Les] has a bunch, they’re hard to come by online. He tried a follow-up using plain radial-lead ceramic capacitors, and while the laser worked, he did get some flashover between the capacitor leads.
[Les]’s solution was to dunk the chunky caps in acetone for a week or so to remove their epoxy covering. Once denuded, the leads were bent into a more axial configuration and soldered to brass machine screws. The dielectric slug is then put in a small section of plastic tubing and potted in epoxy resin with the bolts protruding from each end. The result is hard to distinguish from a genuine doorknob cap; the video below shows the build process as well as some testing.
Hats off to [Les] for taking pity on those of us who want to replicate his work but find ourselves without these essentials. It’s nice to know there’s a way to make unobtanium parts when you need them.
[Kevin]’s build manages 12-note polyphony, an impressive feat for the ATmega328 at the heart of the Arduino Uno. It’s done by running an interrupt on a timer at a steady rate, and implementing 12 counters, one per note. When a counter overflows, a digital IO pin is flipped. This outputs a square wave at a certain pitch on the IO pin, producing the given note. The outputs of 12 digital IO pins are mixed together with a simple resistor arrangement, producing a basic square wave synth. Tuning isn’t perfect, but [Kevin] notes a few ways it could be improved down the line.
If you want to move a pen (or a CNC tool, or a 3D printing hot end) in the X and Y plane, your choices are typically pretty simple. Many machines use a simple cartesian XY motion using two motors and some sort of linear drive. There’s also the core-XY arrangement where two motors move belts that cause the head to travel in two directions. Delta printers use yet another arrangement, but one of the stranger methods we’ve seen is the dual disk polar printer which — as its name implies — uses two rotating disks.
The unique mechanism uses one motor to rotate a disk and another motor to rotate the entire assembly. The print head — in this case a pencil — stays stationary. as you can see in the video below.
Measuring temperature turns out to be a fundamental function for a huge number of devices. You furnace’s programmable thermostat and digital clocks are obvious examples. If you just needed to know if a certain temperature is exceeded, you could use a bimetalic coil and a microswitch (or a mercury switch as was the method with old thermostats). But these days we want precision over a range of readings, so there are thermocouples that generate a small voltage, RTDs that change resistance with temperature, thermistors that also change resistance with temperature, infrared sensors, and vibrating wire sensors. The bandgap voltage of a semiconductor junction varies with temperature and that’s predictable and measurable, too. There are probably other methods too, some of which are probably pretty creative.
You can often think of creative ways to do any measurement. There’s an old joke about the smart-alec student in physics class. The question was how do you find the height of a building using a barometer. One answer was to drop the barometer from the top of the building and time how long it takes to hit the ground. Another answer — doubtlessly an engineering student — wanted to find the building engineer and offer to give them the barometer in exchange for the height of the building. By the same token, you could find the temperature by monitoring a standard thermometer with a camera or even a level sensor which is a topic for another post.
The point is, there are plenty of ways to measure anything, but in every case, you are converting what you want to know (temperature) into something you know how to measure like voltage, current, or physical position. Let’s take a look at how some of the most interesting temperature sensors accomplish this.
Hackaday editors Elliot Williams and Mike Szczys recount the coolest hacks from the past week. Most clocks keep time with a quartz crystal, but we discuss one that uses a tuning fork… like the kind you use to tune a piano. Ghidra is a powerful reverse engineering tool developed by the NSA that was recently put to good use changing an embedded thermometer display from Celsius to Fahrenheit. We talk turkey on the Texas power grid problems and Tesla’s eMMC failures. And of course there’s some room for nostalgia as we walk down memory lane with the BASIC programming language.
Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!