Logic Noise: Sweet, Sweet Oscillator Sounds

Welcome to part one of a series taking you down the rabbit hole of DIY electronic synthesizers based on (largely) CMOS logic chips. Instead of synths being commodity gear made by large corporate enterprises, we’ll be building with the cheapest available parts, using and misusing digital logic. In short, don’t expect pre-packaged smooth tones, because we’ll be making creative noise machines.

If you’re the chiptunes type, you’ll probably find something you like here. If you’re the circuit bender or electro-noise-punk type, this is gonna be right up your alley. If you just like to see CMOS chips wriggle and squirm in unintended ways, feel free to look over my shoulder. If you’re the type who insists that a screwdriver can’t be used to pry open a paint can, then maybe you’d better move along. There’s a thin line between the glitch as bug and the glitch as interesting discovery, and we’ll be dancing all over it.

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Illumination Captured in a Vacuum Jar

Experimentation with the unusual nature of things in the world is awesome… especially when the result is smokey glowing plasma. For this relatively simple project, [Peter Zotov] uses the purchase of his new vacuum pump as an excuse to build a mini vacuum chamber and demonstrate the effect his mosfet-based Gouriet-Clapp capacitive three-point oscillator has on it.

In this case, the illumination is caused due to the high-frequency electromagnetic field produced by the Gouriet-Clapp oscillator. [Peter] outlines a build for one of these, consisting of two different wound coils made from coated wire, some capacitors, a mosfet, potentiometer, and heat sink. When the oscillator is placed next to a gas discharge tube, it causes the space to emit light proportionate to the pressure conditions inside.


For his air tight and nearly air free enclosure, [Peter] uses a small glass jar with a latex glove as the fitting between it and a custom cut acrylic flange. With everything sandwiched snugly together, the vacuum hose inserted through the center of the flange should do its job in removing the air to less than 100 Pa. At this point, when the jar is placed next to the oscillator, it will work its physical magic…

[Peter] has his list of materials and schematics used for this project on his blog if you’re interested in taking a look at them yourself. Admittedly, it’d be helpful to hear a physicist chime in to explain with a bit more clarity how this trick is taking place and whether or not there are any risks involved. In any case, it’s quite the interesting experiment.

Repairing Dead USB Flash Drives

Over the last few years, [Tobias] has repaired a number of USB Flash drives. This strikes us as a little odd, given small capacity Flash drives are effectively free in the form of conference handouts and swag, but we’re guessing [Tobias] has had a few too many friends lose their thesis to a broken Flash drive.

In all his repairs, [Tobias] found one thing in common The crystal responsible for communicating with the USB controller is always broken. In a way, this makes a lot of sense; everything else on a Flash drive is silicon encased in an epoxy package, where the crystal is a somewhat fragile piece of quartz. Breaking even a small part of this crystal will drastically change the frequency it resonates at making the USB controller throw a fit.

[Tobias]’ solution for all his Flash drive repairs is to desolder and change out the crystal, bringing the drive back to life. Some of the USB Flash drives even have multiple pads for different crystal packages, making it easy to kludge together a solution should you need to repair a Flash drive five minutes ago.

Measuring tiny current with high resolution


[Paul] knew that he could get an oscilloscope that would measure the microamp signals with the kind of resolution he was after, but it would cost him a bundle. But he has some idea of how that high-end equipment does things, and so he just built this circuit to feed precision data to his own bench equipment.

He’s trying to visualize what’s going on with the current draw of a microcontroller at various points in its operation. He figures 5 mA at 2.5 mV is in the ballpark of what he’s probing. Measurements this small have problems with noise. The solution is the chip on the green breakout board. It’s not exactly priced to move, costing about $20 in single quantity. But when paired with a quality power supply it gets the job done. The AD8428 is an ultra-low-noise amplifier which has way more than the accuracy he needs and outputs a bandwidth of 3.5 MHz. Now the cost seems worth it.

The oscilloscope screenshot in [Paul’s] post is really impressive. Using two 1 Ohm resistors in parallel on the microcontroller’s power line he’s able to monitor the chip in slow startup mode. It begins at 120 microamps and the graph captures the point at which the oscillator starts running and when the system clock is connected to it.

Build your own metal detector

[Dzl] and his rather serious looking son are metal detector enthusiasts. But when they couldn’t find their store-bought metal detector earlier this summer they just went ahead and built their own. [Dzl] starts his write up with an explanation of how most oscillator based metal detectors work. This one differs by using an Arduino to read from the metal detecting coil.

The circuit starts with an oscillator that produces a signal of about 160 kHz which is constantly measured by the Arduino. When metal enters the coil it alters the frequency, which is immediately picked up the Arduino. Instead of that characteristic rising tone this rig uses a Piezo buzzer, issuing the type of clicks you’d normally associate with a Geiger counter.

The last part of the build was to find the best coil orientation. They settled on thirty turns around a metal bucket. An old Ikea lamp is the perfect form factor to host their hardware which seems to work like a charm.

Hackaday Links: March 25, 2013

Illegal, yet impressive


Want a soda? Just grab a robot, shove it in a vending machine, and grab yourself one. This video is incredibly French, but it looks like we’ve got a custom-built robot made out of old printers and other miscellaneous motors and gears here. It’s actually pretty impressive when you consider 16 ounce cans weigh a pound.



Okay, we got a lot of emails on our tip line for this one. It’s a group buy for a programmable oscillator over on Tindie. Why is this cool? Well, this chip (an SI570) is used in a lot of software defined radio designs. Also, it’s incredibly hard to come by if you’re not ordering thousands of these at a time. Here’s a datasheet, now show us some builds with this oscillator.

Chiptune/keygen music anywhere


[Huan] has a co-loco’d Raspi and wanted a media server that is available anywhere, on any device. What he came up with is a service that streams chiptune music from your favorite keygens. You can access it with Chrome (no, we’re not linking directly to a Raspberry Pi), and it’s extremely efficient – his RAM usage didn’t increase a bit.

Take it on an airplane. Or mail it.


[Alex]’s hackerspace just had a series of lightning talks, where people with 45-minute long presentations try to condense their talk into 10 minutes. Of course the hackerspace needed some way to keep everything on schedule. A simple countdown timer was too boring, so they went with a fake, Hollywood-style bomb. No, it doesn’t explode, but it still looks really, really fake. That’s a good thing.

Printers have speakers now?


[ddrboxman] thought his reprap needed a nice ‘print finished’ notification. After adding a piezo to his electronics board, he whipped up a firmware hack that plays those old Nokia ringtones. The ringtones play over Gcode, so it’s possible to have audible warnings and notifications. Now if it could only play Snake.

[Jeri] uses light bulbs in an oscillator

Way back when [Ms Ellsworth] was a kid, she kept seeing the same circuit over and over again in her various op-amp books. It was a Wien bridge oscillator, a small circuit that outputs a sine wave with the help of a light bulb. Now that [Jeri] is much wiser, she decided to play around with this strange oscillator and found it’s actually pretty impressive for, you know, a light bulb.

The interesting portion of the Wien bridge is the gain portion of the circuit. It’s just a simple resistor divider, with a light bulb thrown in on one of its legs. When the current increases, this causes the light bulb to warm up (not enough to glow, though). When the temperature increases, the resistance in the light bulb increases, making the oscillator reach an equilibrium.

It’s a clever setup, but what about swapping out a resistor in place of the light bulb? In the video, [Jeri] tries just that, and it’s a mess. Where the light bulb circuit is amazingly stable with very, very low distortion, the resistor circuit looks like a disaster on the scope with harmonics everywhere.

A very cool build that would be perfect for an audio synth, but as [Jeri] says in her YouTube comments, “This doesn’t have enough distortion for indie bands.”

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