Here at Hackaday we have a bit of a preoccupation with timepieces. Maybe it’s the deeply personal connection to an object you wear on your body, or the need for ultimate reliability. Perhaps it’s just a fascination with the notion of time itself. Whatever the case, we don’t seem to be alone as there is a constant stream of time-related projects coming through our virtual doors. For this article we’ve unearthed the LED Pocketwatch 1.0 by [Dr. Pauline Pounds] from way back in 2009 (ironically via a post about a wristwatch from last year!). Fortunately for us the Internet Archive has saved this heirloom nouveau from the internet dustbin so we can appreciate the craftsmanship involved in [Dr. Pounds]’ work.
My how far we’ve come; a decade after this project was posted a hacker might choose to 3d print a case for a new wearable, but in 2009 that would have been an entire project by itself! [Dr. Pounds] chose to use the casing from an antique Elgin pocket watch. Even through the mists of a grainy demo video we can imagine how soft the well-worn casing must be from heavy use. This particular unit was chosen because it was a hefty 50mm in diameter, leaving plenty of room inside for a 44mm double sided PCBA with 133 0603 LEDs (60 seconds, 60 minutes, 12 hours), a PIC 16F946, an ERM, and a 110mAh LiPo. But what really sets the LED Pocketwatch 1.0 apart is the user interface.
The ERM is attached directly to the rear of the case in order to best conduct vibration to the outside world. For maximum authenticity it blips on the second, to give a sense that the digital watch is mechanically ticking like the original. The original pocket watch was designed with a closing lid which is released when the stem is pressed. [Dr. Pounds] integrated a button and encoder with the end of the stem (on the PCBA) so the device can be aware of this interaction; on lid open it wakes the device to display the time on the LEDs. The real pièce de résistance is that he also integrated a minuscule rotary encoder, so when the stem is pressed you can rotate it to set the time. It’s all quite elegantly integrated and imminently usable.
At this point we’d love to link to sources, detailed drawings, or CAD files, but unfortunately we haven’t found any. If this has you inspired check out some of the otherpocket watches we’ve posted about in the past. If you’re interested in a live demo of the LED Pocketwatch 1.0, check out the original video after the break.
[Eric] does, and like everything else about reloading, trickling is serious business. Getting an exact charge of powder to add to a cartridge is not a simple task, and very tedious when done manually. This smartphone-controlled auto-trickler is intended to make the job easier, safer, and more precise.
Reloading ammunition is a great way for shooters to save money and recycle the brass casings that pile up at the end of a long day at the range. It can be a fairly simple process of cleaning the casings, replacing the spent primers, adding the correct powder charge, and seating a new bullet. It’s all pretty straightforward, but the devil is in the details, especially with the powder charge. A little too much can be a big problem, so tricklers were invented to allow the reloader to sneak up on the proper charge. [Eric]’s auto-trickler interfaces to a digital powder scale and uses a standard cell phone vibration motor to gently coax single kernels of powder from a hopper until the proper charge has accumulated. It’s easier to understand by watching the video below.
The hardware behind the trickler is pretty standard — just a Raspberry Pi Zero to talk to the smartphone UI via Bluetooth, and to monitor and control the scale via USB. [Eric] has made all the code open source so that anyone can build their own auto-trickler, which we applaud; he did the same thing with his rifle-mounted accelerometer. This project might have applications far beyond reloading where precision dispensing is required.
The harp is an ancient instrument, but in its current form, it seems so unwieldy that it’s a wonder that anyone ever learns to play it. It’s one thing to tote a rented trumpet or clarinet home from school to practice, but a concert harp is a real pain to transport safely. The image below is unrelated to the laser harp project, but proves that portable harping is begging for some good hacks.
Enter this laser harp, another semester project from [Bruce Land]’s microcontroller course at Cornell. By replacing strings with lasers aimed at phototransistors, [Glenna] and [Alex] were able to create a more manageable instrument that can be played in a similar manner. The “strings” are “plucked” with the fingers, which blocks the laser light and creates the notes.
But these aren’t just any old microcontroller-generated sounds. Rather than simply generating a tone or controlling a synthesizer, the PIC32 uses the Karplus-Strong algorithm to model the vibration of a plucked string. The result is very realistic, with all the harmonics you’d expect to hear from a plucked string. [Alex] does a decent job putting the harp through its paces in the video below, and the write-up is top notch too.
When we think of physics experiments, we tend to envision cavernous rooms filled with things like optical benches, huge coils in vacuum chambers, and rack after rack of amplifiers and data acquisition hardware. But it doesn’t have to be that way – you can actually perform laser interferometry with a single component and measure sub-micron displacements and more.
The astute viewer of [Ben Krasnow]’s video below will note that in order to use the one component, a laser diode, as an interferometer, he needed a whole bunch of support gear, like power supplies, a signal generator, and a really, really nice mixed-signal oscilloscope. But the principle of the experiment is the important bit, which uses a laser diode with a built-in monitoring photodiode. Brought out to a third lead, older laser diodes often used these photodiodes to control the light emitted by the laser junction. But they also respond to light reflected back into the laser diode, and thanks to constructive and destructive interference, can actually generate a signal that corresponds to very slight displacements of a reflector. [Ben] used it to measure the vibrations of a small speaker, the rotation of a motor shaft, and with a slight change in setup, to measure the range to a fixed target with sub-micron precision. It’s fascinating stuff, and the fact you can extract so much information from a single component is pretty cool.
We really like [Ben]’s style of presentation, and the interesting little nooks and crannies of physics that he finds a way to explore. He recently looked at how helium can kill a MEMS sensor, an equally fascinating topic.
We’ve reduced printed circuit board design to practice so much that we hardly give a thought to the details anymore. It’s so easy to bang out a design, send it to a fab house, and have ten boards in your hands in no time at all. All the design complexities are largely hidden from us, abstracted down to a few checkboxes on the vendor’s website.
There’s no doubt that making professional PCB design tools available to the hobbyist has been a net benefit, but there a downside. Not every PCB design can be boiled down to the “one from column A, one from column B” approach. There are plenty of applications where stock materials and manufacturing techniques just won’t cut it. PCBs designed to operate in space is one such application, and while few of us will ever be lucky enough to have a widget blasted to infinity and beyond, learning what’s behind space-rated PCBs is pretty interesting.
No matter how excited you are to dive headfirst into the “Internet of Things”, you’ve got to admit that the effort and expense of going full-on Jetsons is a bit off-putting. To smarten up your home you’ve generally got to buy all new products (and hope they’re all compatible) or stick janky after-market sensors on the gear you’ve already got (and still hope they’re all compatible). But what if there was a cheap and easy way to keep tabs on all your existing stuff? The answer may lie in Cold War era surveillance technology.
As if the IoT wasn’t already Orwellian enough, Vibrosight is a project that leverages a classic KGB spy trick to keep tabs on what’s going on inside your home. Developed by [Yang Zhang], [Gierad Laput] and [Chris Harrison], the project uses retro-reflective stickers and a scanning laser to detect vibrations over a wide area. With this optical “stethoscope”, the system can glean all kinds of information; from how long you’ve been cooking something in the microwave to whether or not you washed your hands.
The project takes its inspiration from the optical eavesdropping system developed by Léon Theremin in the late 1940’s. By bouncing a beam of light off of a window, Theremin’s gadget was able to detect what people inside the room were saying from a distance. The same idea is applied here, except now it uses an automated laser scanner and machine learning to turn detected vibrations into useful information that can be plugged into a home automation system.
For Vibrosight to “listen” to objects, the user needs to place retro-reflective tags on whatever they want to include in the system. The laser will periodically scan around the room looking for these tags. Once the laser finds a new tag, will add it to a running list of targets to keeps an eye on. From there Vibrosight is able to take careful vibration measurements which can provide all sorts of information. In the video after the break, Vibrosight is shown differentiating between walking, jogging, and running on a treadmill and determining what kind of hand tools are being used on a workbench. The team even envisions a future where Vibrosight-ready devices would “hum” their IP address or other identifying information to make device setup easier.
Vibration is a fact of life in almost every machining operation. Whether you’re milling, drilling, turning, or grinding, vibration can result in chatter that can ruin a part. Fighting chatter has generally been a matter of adding more mass to the machine, but if you’re clever about things, chatter reduction can be accomplished electronically, too. (YouTube, embedded below.)
When you know a little something about resonance, machine vibration and chatter start to make sense. [AvE] spends quite a bit of time explaining and demonstrating resonance in the video — fair warning about his usual salty shop language. His goal with the demo is to show that chatter comes from continued excitation of a flexible beam, which in this case is a piece of stock in the lathe chuck with no tailstock support. The idea is that by rapidly varying the speed of the lathe slightly, the system never spends very long at the resonant frequency. His method relies on a variable-frequency drive (VFD) with programmable IO pins. A simple 555 timer board drives a relay to toggle the IO pins on and off, cycling the VFD up and down by a couple of hertz. The resulting 100 RPM change in spindle speed as the timer cycles reduces the amount of time spent at the resonant frequency. The results don’t look too bad — not perfect, but a definite improvement.
It’s an interesting technique to keep in mind, and a big step up from the usual technique of more mass.