Vacuum Chamber Gets Automation

July 30, 2023 by Bryan Cockfield 18 Comments

[Nick Poole] does a lot of custom work with vacuum tubes — so much so that he builds his own vacuum tubes of various shapes, sizes, and functions right on his own workbench. While the theory of vacuum tubes is pretty straightforward, at least to those of us who haven’t only been exposed to semiconductors, producing them requires some specialized equipment. A simple vacuum won’t get you all the way there, and the complexity of the setup that’s needed certainly calls for some automation.

The vacuum system that [Nick] uses involves three sections separated by high-vacuum valves in order to achieve the pressures required for vacuum tube construction. There’s a rough vacuum section driven by one pump, a high vacuum section driven by a second pump, and a third section called the evac port where the tube is connected. Each second must be prepared properly before the next section can be engaged or disengaged. An Arduino Pro is tasked with all of this, chosen for its large amount of ADC inputs for the instrumentation monitoring the pressures in each section, as well as the digital I/O to control the valves and switches on the system.

The control system is built into a 19-inch equipment rack with custom faceplates which outline the operation of the vacuum system. A set of addressable LEDs provide the status of the various parts of the system, and mechanical keyboard switches are used to control everything, including one which functions as an emergency stop. The automation provided by the Arduino reduces the chances for any mistakes to be caused by human error, allows the human operator to focus on other tasks like forming the glass, and can also react much faster to any potentially damaging situations such as the high-pressure pump being exposed to atmospheric pressure.

As you can probably tell, [Nick] is pretty passionate about this stuff — last year he gave a talk at the Hackaday Supercon that went over all the intricacies of building one’s own vacuum tubes.

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Magnetic Gearbox, Part 2: Axial Flux Improves Performance

July 27, 2023 by Dan Maloney 13 Comments

The number of interesting and innovative mechanisms that 3D printing has enabled always fascinates us, and it’s always a treat when one of them shows up in our feeds. This axial flux magnetic gearbox is a great example of such a mechanism, and one that really makes you think about possible applications.

The principles of [Retsetman]’s gearbox are simple for anyone who has ever played with a couple of magnets to understand, since it relies on that powerful attractive and repulsive force you feel when magnets get close to each other. Unlike his previous radial flux gearbox, which used a pair of magnet-studded cylindrical rotors nested one inside the other, this design has a pair of disc-shaped printed rotors that face each other on aligned shafts. Each rotor has slots for sixteen neodymium magnets, which are glued into the slots in specific arrangements of polarity — every other magnet for the low-speed rotor, and groups of four on the high-speed rotor. Between the two rotors is a fixed flux modulator, a stator with ten ferromagnetic inserts screwed into it.

In operation, which the video below demonstrates nicely, the magnetic flux is coupled between the rotors by the steel inserts in the stator so that when one rotor moves, the other moves at a 4:1 (or 1:4) ratio in the opposite direction. [Retsetman] got the gearbox cranked up to about 8,500 RPM briefly, but found that extended operation at as little as 4,000 RPM invited disaster not due to eddy current heating of the inserts or magnets as one might expect, but from simple frictional heating of the rotor bearings.

Torque tests of the original gearbox were unimpressive, but [Retsetman]’s experiments with both laminated stator inserts and more powerful magnets really boosted the output — up to a 250% improvement! We’d also like to see what effect a Halbach array would have on performance, although we suspect that the proper ratios between the two rotors might be difficult to achieve.

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Turning A Quartz Clock Module Into A Time Reference

July 21, 2023 by Lewin Day 11 Comments

If you’re looking for a 1-second time reference, you’d probably just grab a GPS module off the shelf and use the 1PPS output. As demonstrated by [InazumaDenki], though, an old quartz clock module can also do the job with just a little work.

The module was harvested from an old Seiko wall clock, and features the familiar 32.768 KHz crystal you’d expect. This frequency readily divides down by 2 multiple times until you get a useful 1 Hz output. The module, originally designed to run a clock movement, can be repurposed with some basic analog electronics to output a useful time reference. [InazumaDenki] explains various ways this can be done, before demonstrating his favored method by building the device and demonstrating it with a decade counter.

It has some benefits over a GPS time reference, such as running at a much lower voltage and needing no external signal inputs. However, it’s also not going to be quite as accurate. Whether that matters to you or not depends on your specific application. Video after the break.

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Practical Inductors In LTSpice

July 18, 2023 by Al Williams 8 Comments

LTSpice and the underlying Spice engine does a great job of simulating ideal components. But it is also capable — if you know how — of handling models of real-world devices. Inductors, for example, are one of the most imperfect components. Their constituent wire has resistance, and there is parasitic capacitance between the windings. If there is a core, it also will have many imperfections and losses. [Sam Ben-Yaakov] has a lecture about modeling real inductors in LTSpice, and he covers how you can capture some of these imperfections in the video below.

There is a bit of math in the presentation, but we liked that it relates back to datasheets for actual components. Being able to understand what the parameters on a datasheet mean is crucial, and if you ever wondered what some of these entries mean, you’ll get a lot from this video.

The main feature of the model is the flux equation. The tanh (hyperbolic tangent) function is similar to the curve you want for the flux equation, so it plays a major part. Of course, there are other parts of the inductor you may have to model, too, but this is one of the most difficult parts.

You can also model transformers using LTSpice. You can also create custom components.

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These Fake Nixie Tubes Have A Bootup Screen

July 15, 2023 by Donald Papp 34 Comments

[IMSAI Guy] bought a fake Nixie clock, and luckily for all of us has filmed a very close look and demonstration. Using OLED displays as the fake Nixie elements might seem like cheating to some, the effect is really very well done.

Clock digits with bootup screens is something we didn’t know we liked until we saw it.

When it comes to Nixie elements, it’s hard to say which gets more attention and project time from hardware folks: original Nixie tube technology, or fake Nixie elements. Either way, their appeal is certainly undeniable.

Original Nixie tubes have shown up in modern remakes of alarm clocks, and modern semiconductors make satisfying a Nixie tube’s power requirements much easier with clever and compact Nixie drivers costing under $3 USD. This is also a good time to remind people that Nixie tubes don’t have to be digits. This audio spectrum visualizer, for example, uses IN-13 tubes which serve as elements of a bar graph.

Authentic Nixie elements require high voltages and are labor-intensive to manufacture to say the least, and as far as fake Nixie elements go, this one looks pretty good once it lights up. You can see it in action in the video, embedded below.

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No Acid: Open ICs With A Tesla Coil

July 12, 2023 by Al Williams 21 Comments

We’ve taken ICs apart before, but if they are in an epoxy package, it requires some lab gear and a lot of safety. Typically, you’ll heat the part and use fuming nitric acid (nasty stuff) in a cavity milled into the part to remove the epoxy over the die. While [100dollarhacker] doesn’t provide much detail, he appears to have used a Tesla coil to do it — no hot acid required.

Initial results were promising but took a long time to work. In addition, the coil gets very hot, and there is a chance of flames. The next attempt used a 3D printed cone with a fan to push the plasma over the chip. The first attempt shorted something out, and so far, each attempt eventually burns out the MOSFET driver.

We are always interested in the practical uses of Tesla coils and what’s inside ICs, so this project naturally appealed to us. We hope to see more success reported on the Hackaday.io page soon. Meanwhile, if you have a coil and an old IC lying around, try it. Maybe you’ll figure out how to make it work well and if you do, let us know.

The easiest chips to open are ceramic packages with a gold lid. Just use a hobby knife. There are less noxious chemicals you can use. If you want to use fuming nitric, be sure you know what you are doing and maybe make some yourself.

Proper Decoupling Capacitors

July 12, 2023 by Al Williams 37 Comments

If you’ve been building circuits for any length of time, you probably know you need decoupling capacitors to keep your circuits stable. But even though it’s a favorite technique of ours, just scattering some around your PCB and hoping for the best isn’t necessarily the best approach. If you want to dig deeper into the why and how of decoupling, check out [Stephen Fleeman’s] post on the topic.

It is easy to think of capacitors as open circuits at DC and short circuits at high frequencies, shunting noise to ground. But the truth is more complex than that. Stray resistance and inductance mean that your simple decoupling capacitor will have a resonant frequency. This limits the high frequency protection so you often see multiple values used in parallel to respond to different frequencies.

Because the stray resistance and inductance plays a part, you may want to use fatter traces — less resistance — and shorter runs for less inductance. Of course, you can also use power and ground planes on the PCB as a form of decoupling. At the end of the post, [Stephen] talks a little about the importance of digital and analog ground that interact in a specific way.

If you want to do some empirical testing, you can build a test rig and do the work. Or check with [Bil Herd] about PCB inductance.