Hurricane season is rapidly approaching those of us who live in the northern hemisphere. While that does come with a good deal of stress for any homeowners who live in the potential paths of storms it also comes with some opportunities for treasure hunting. Storms tend to wash up all kinds of things from the sea, and if you are equipped with this DIY metal detector you could be unearthing all kinds of interesting tchotchkes from the depths this year.
The metal detector comes to us from [mircemk] who is known for building simple yet effective metal detectors. Unlike his previous builds, this one uses only a single integrated circuit, the TL804 operational amplifier. It also works on the principle of beat-balance which is an amalgamation of two unique methods of detecting metal. When the wire coils detect a piece of metal in the ground, the information is fed to an earpiece through an audio jack which rounds out this straightforward build.
[mircemk] reports that this metal detector can detect small objects like coins up to 15 cm deep, and larger metal objects up to 50 cm. Of course, to build this you will also need the support components, wire, and time to tune the circuit. All things considered, though it’s a great entryway into the hobby.
Want to learn more about metal detecting? Check out this similar-looking build which works on the induction balance principle.
Continue reading “DIY Metal Detector Gives You The Mettle To Find Some Medals”
Most of us have beheld the sonic glory of an Atari Punk Console, that lo-fi synth whose classic incarnation is a pair of 555 timers set up to warble and bleep in interesting ways. Very few of us, however, have likely seen an APC built from 555s that are made from vacuum tubes.
It’s little surprise to regular readers that this one comes to us by way of [David] at Usagi Electric, who hasn’t met a circuit that couldn’t be improved by realizing it in vacuum tubes. His “hollow-state” Atari Punk Console began with the 18-tube version of the 555 that he built just for fun a while back, which proved popular enough that he’s working on a kit version, the prototype of which served as the second timer for the synth. With 32 tubes aglow amid a rats-nest of jumpers, the console managed to make the requisites sounds, but lacked a certain elegance. [David] then vastly simplified the design, reducing the BOM to just four dual-triode tubes. Housed on a CNC milled PCB in a custom wood box, the synth does a respectable job and looks good doing it. The video below shows both versions in action, as well as detailing their construction.
As cool as a vacuum tube synth may be, we realize that not everyone goes for the hot glass approach. No worries — plenty of silicon Atari Punk Consoles to choose from here. There’s one built into a joystick, a circuit sculpture version complete with mini-CRT, or even eight APCs teamed up with MIDI control.
Continue reading “The Atari Punk Console, Now With More Vacuum Tubes”
There’s a certain elite set of chips that fall into the “cold, dead hands” category, and they tend to be parts that have proven their worth over decades, not years. Chief among these is the ubiquitous 555 timer chip, which nearly 50 years after its release still finds its way into the strangest places. Add in other silicon stalwarts like the 741 op-amp and the LM386 audio amp, and you’ve got a Hall of Fame lineup for almost any project.
That’s exactly the complement of chips that powers this fun little dub siren. As [lonesoulsurfer] explains, dub sirens started out as actual sirens from police cars and the like that were used as part of musical performances. The ear-splitting versions were eventually replaced with sampled or synthesized siren effects for recording studio and DJ use, which leads us to the current project. The video below starts with a demo, and it’s hard to believe that the diversity of sounds this box produces comes from just a pair of 555s coupled by a 741 buffer. Five pots on the main PCB control the effects, while a second commercial reverb module — modified to support echo effects too — adds depth and presence. I built-in speaker and a nice-looking wood enclosure complete the build, which honestly sounds better than any 555-based synth has a right to.
Interested in more about the chips behind this build? We’ve talked about the 555 and how it came to be, taken a look inside the 741, and gotten a lesson in LM386 loyalty.
Continue reading “Classic Chip Line-Up Powers This Fun Dub Siren Synth”
I wish I could tell you that there’s some complex decision tree at play when I select a piece of hardware to take apart for this series, but ultimately it boils down two just two factors: either the gadget was something I was personally interested in, or it was cheap. An ideal candidate would check both boxes, but that’s not always the case. This time around however, I can confidently say our subject doesn’t fall into either category.
Now don’t get me wrong, at first glance I found the Franz Crystal Metronome to be intriguing in its own way. With that vintage look, how could you not? But I’m about as far from a musician as one can get, so you’d hardly find a metronome on my wish list. As for the cost, a check on eBay seems to show there’s something of a following for these old school Franz models, with ones in good condition going for $50 to $80. Admittedly not breaking the bank, but still more than I’d like to pay for something that usually ends up as a pile of parts.
That being the case, why are you currently reading about it on Hackaday? Because it exploits something of a loophole in the selection process: it doesn’t work, and somebody gave it to me to try and figure out why. So without further ado let’s find out what literally makes a Franz Crystal Metronome tick, and see if we can’t get it doing so gain.
Continue reading “Teardown: Franz Crystal Metronome”
GPS technology is a marvel of the modern world. Not only can we reliably locate positions on the planet with remarkable accuracy and relatively inexpensive hardware, but plenty of non-location-based features of the technology are available for other uses as well. GPS can be used for things like time servers, since the satellites require precise timing in order to triangulate a position, and as a result they can also be used for things like this incredibly accurate frequency reference.
This project is what’s known as a GPSDO, or GPS-disciplined oscillator. Typically they use a normal oscillator, like a crystal, and improve its accuracy by pairing it with the timing signal from a GPS satellite. This one is a standalone model built by [Szabolcs Szigeti] who based the build around an STM32 board. The goal of the project was purely educational, as GPSDOs of various types are widely available, but [Szabolcs] was able to build exactly what he wanted into this one including a custom power supply, simple standalone UI, and no distribution amplifier.
The build goes into a good bit of detail on the design and operation of the device, and all of the PCB schematics and source code are available on the projects GitHub page if you want to build your own. There are plenty of other projects out there that make use of GPS-based time for its high accuracy, too, like this one which ties a GPS time standard directly to a Raspberry Pi.
We are always glad to see [Ken Shirriff] tear into something new and this month he’s looking inside a quartz oscillator module. Offhand, you’d think there’s not much to these. A slab of quartz and some sort of inverter, right? But as [Ken] mentions, “There’s more happening in the module than I expected…”
If you’ve ever wanted to decap devices, big hybrid modules like these are a good way to get started since you don’t need exotic chemicals to get at the insides. [Ken] managed to break the fragile crystal wafer on the way in. Inside was also a small CMOS IC die. Time to get out the microscope.
If you follow [Ken’s] blog, you know he’s no stranger to analyzing IC dice. The oscillator IC is a pretty standard Colpitts oscillator but it also provides a programmable divider and output drive.
The circuit uses some unusually configured capacitors. [Ken] takes the time to point out CMOS logic structures throughout. If you haven’t seen one of [Ken’s] deep dives before, before, it’s a great introduction.
You can learn more about crystal oscillator theory. We used some test equipment to characterize a crystal a few years ago.
Whatever kind of clock you’re interested in building, you’re going to need to build an oscillator of some sort. Whether it be a pendulum, a balance wheel, or the atomic transitions of cesium or rubidium, something needs to go back and forth in a predictable way to form the timebase of the clock. And while it might not make the best timepiece in the world, a tuning fork certainly fits the bill and makes for a pretty interesting clock build.
One of the nice things about this build is that [Kris Slyka] got their inspiration from a tuning fork clock that we covered a while back — we love it when someone takes a cool concept and makes it their own. While both clocks use a 440 Hz tuning fork — that’s an A above middle C for the musically inclined — [Kris] changed up the excitation method for their build. She used a pair of off-the-shelf inductors, placed near the ends of each arm and bridged by a strong neodymium magnet to both sense the 440-Hz vibrations and to provide the kick needed to keep the fork vibrating.
As for the aesthetic of the build, we think [Kris] really nailed it. Using through-hole components, old-school seven-segment displays, and a home-etched PCB, she was able to capture a retro look that really works. The RS-232 port and the bell jar enclosure complete the feel, although we’re not sure about the custom character set [Kris] designed — it’s cool and all, but makes it hard for anyone else to read without a little practice. Regardless, this is a fun build, and we’d imagine the continuous tone coming from the clock is pretty pleasing.
Continue reading “Tuning Fork Keeps This Throwback Digital Clock Ticking”