Audio Amp Puts VFDs To Work In An Unusual Way

December 8, 2022 by Dan Maloney 14 Comments

It’s safe to say that most projects that feature a VFD emphasize the “D” aspect more than anything. Vacuum fluorescent displays are solid performers, after all, with their cool blue-green glow that’s just the right look for lots of retro and not-so-retro builds. But that doesn’t mean there aren’t applications that leverage the “V” aspect, such as this nifty audio preamp using VFDs as active components.

The inspiration behind [JGJMatt]’s build came from the Korg Nutube line of VFD-based low-voltage dual-triode vacuum tubes. Finding these particular components a little on the expensive side, [JGJMatt] turned to the old standby DM160 VFD indicator tube, which is basically just a triode, to see how it would fare as an amp. The circuit takes advantage of the low current and voltage requirements of the VFDs — the whole thing runs from a USB boost converter — by wedging them between a 2N3904 input stage and a 2N2007 MOSFET output. There’s a mix of SMD and through-hole components on the custom-etched PCB, with a separate riser card to show off the VFDs a little bit through the front panel of the 3D printed case.

All in all, we find this little amp pretty cool, and we love the way it puts a twist on the venerable VFD. We’ve seen similar VFD amps before, but this one’s fit and finish really pays off.

A Cheap 3D Printer Control Panel As A General Purpose Interface

December 1, 2022 by Jenny List 15 Comments

Browsing the usual websites for Chinese electronics, there are a plethora of electronic modules for almost every conceivable task. Some are made for the hobbyist or experimenter market, but many of them are modules originally designed for a particular product which can provide useful functionality elsewhere. One such module, a generic control panel for 3D printers, has caught the attention of [Bjonnh]. It contains an OLED display, a rotary encoder, and a few other goodies, and he set out to make use of it as a generic human interface board.

To be reverse engineered were a pair of 5-pin connectors, onto which is connected the rotary encoder and display, a push-button, a set of addressable LEDs for backlighting, a buzzer, and an SD card slot. Each function has been carefully unpicked, with example Arduino code provided. Usefully the board comes with on-board 5 V level shifting.

While we all like to build everything from scratch, if there’s such an assembly commonly available it makes sense to use it, especially if it’s cheap. We’re guessing this one will make its way into quite a few projects, and that can only be a good thing.

Taking Distance Based CAD To The Next Level

November 28, 2022 by Matthew Carlson 25 Comments

For those who model CAD models regularly, a pair of calipers is essential as it allows reasonably accurate measurements to fit a specific part. However, [Jason Harris] is taking that concept to the next level with a signed distance function-based CAD tool, SDFX.

For those who don’t know, Signed Distance Functions can tell you from a given point how close the nearest part of the model is. The model is represented as a single function that offers some exciting benefits. For instance, chamfering and fileting are often quite complex in traditional CAD programs and trivial in an SDF setting. SDFX is a golang library that allows you to write golang programs to describe the model. OpenSCAD is a favorite of Hackaday as it is a beautiful parametric code-first CAD package. But the syntax and language are somewhat cludgy, to say the best. The advantage of using golang rather than a DSL is that you can use all the niceties that a full-featured language brings. For example, you can export multiple objects, make network requests, and interface with GUI libraries to recreate something like the customizer for OpenSCAD.

Objects are rendered to STL using Marching squares. Then, they can be printed in whatever slicing software suits your fancy. It’s an excellent project with a great API and almost a hundred examples.

The code is available on GitHub under an MIT License.

A Practical Discrete 386

November 27, 2022 by Jenny List 36 Comments

There are some chips that no matter how much the industry moves away from them still remain, exerting a hold decades after the ranges they once sat alongside have left the building. Such a chip is the 386, not the 80386 microprocessor you were expecting but the LM386, a small 8-pin DIP audio amplifier that’s as old as the Ark. the ‘386 can still be found in places where a small loudspeaker needs to be powered from a battery. SolderSmoke listener [Dave] undertook an interesting exercise with the LM386, reproducing it from discrete components. It’s a handy small discrete audio amplifier if you want one, but it’s also an interesting exercise in understanding analogue circuits even if you don’t work with them every day.

A basic circuit can be found in the LM386 data sheet (PDF), but as is always the case with such things it contains some simplifications. The discrete circuit has a few differences in the biasing arrangements particularly when it comes to replacing a pair of diodes with a transistor, and to make up for not being on the same chip it requires that the biasing transistors must be thermally coupled. Circuit configurations such as this one were once commonplace but have been replaced first by linear ICs such as the LM386 and more recently by IC-based switching amplifiers. It’s thus instructive to take a look at it and gain some understanding. If you’d like to know more, it’s a chip we’ve covered in detail.

A Hacker Walks Into A Trade Show: Electronica 2022

November 22, 2022 by Elliot Williams 24 Comments

Last week, the world’s largest electronics trade fair took place in Munich, so I had to attend. Electronica is so big that it happens only once every two years and fills up 14 airplane hangars. As the fairly generic name suggests, it covers anything and everything having to do with electronics. From the producers of your favorite MLCC capacitors to the firms that deliver them to your doorstep, from suppliers of ASIC test equipment to the little shop that’ll custom wind toroids for you, that’s a pretty wide scope. Walking around, I saw tomorrow’s technology today from the big players, but I also picked up some ideas that would be useful for the home gamer.

When I first walked in, for instance, I ran into the Elantas booth. They’re a company that makes flexible insulation and specialty industrial coatings. But what caught my eye was a thermoformed plastic sheet with circuit traces on it. To manufacture them, they cut out copper foil, glue it to a flat plastic sheet with a glue that has a little give, and then put it all together into a vacuum former. The result is a 3D circuit and organically formed substrate in one shot. Very cool, and none of the tech for doing that is outside of the reach of the determined hacker.

The Cool Stuff

All of the stands, big or small, try to lure you in with some gimmick. The big fish, firms with deep pockets, put up huge signs and open bars, and are staffed by no shortage of salespeople in suits. The little fish, on the other hand, have to resort to showing you the cool stuff that they do, and it’s more often the application engineers sitting there, ready to talk tech. You can guess which I found more interesting.

For instance when I walked up to an obviously DIY popcorn popper that was also showing 5000 FPS footage of kernels in mid-pop, I had to ask. The company in question was a small UK outfit that made custom programmable power supplies and digital acquisition gear that interfaced with it. You could plug in their box to some temperature probes, fire off the high-speed video camera, and control the heating and cooling profile without writing any code. Very sweet. Continue reading “A Hacker Walks Into A Trade Show: Electronica 2022” →

An Open Source Modular Flexure Construction Set

November 22, 2022 by Dave Rowntree 14 Comments

Flexures are one of those innocent-looking mechanisms that one finds inside practically any kind of consumer device. Providing constrained movements with small displacements, complete with controlled tension, they can be rather tricky to design. GrabCAD designer [Vyacheslav Popov] hails from Ukraine, and due to the current situation there, plans to sell a collection of flexure building blocks became difficult. In the end, [Vyacheslav] decided to generously release his work open source, for all to enjoy. This collection is quite extensive, looking like it could solve a huge variety of flexure design problems. (Links to the first three sets: Set00, Set01, Set02 but check the author’s collection page for many others)

It’s not just those super-cheap mechanisms in throw-away gadgets that leverage flexures, it’s much more. The Mars rovers use flexure-based suspension, scientific instruments (interferometers and the like) make use of them for small motions where specific axis constraints are needed, and finally, MEMS accelerometers and gyroscopes are based entirely upon them. We’re not even going to try to name examples of flexures in the natural world. They’re everywhere. And, now we’ve got some more design examples to use, so why not flex your flexure muscles and send one to the 3D printer and have a play?

We see flexures here quite a bit, like this nice demonstration of achievable accuracy. Flexures can make some delicious mechanisms, and neat 3D printable input devices.

Thanks to [Addison] for the tip!

New Part Day: The Smallest Batteries You Have Ever Seen

November 15, 2022 by Jenny List 17 Comments

We’re used to some pretty small batteries in miniaturized electronics, thanks to the manufacture of lithium-polymer pouch cells. But they’re still pretty big, and they’re hardly the most stable power storage solution. The French company ITEN may have an answer for designers of micro-power devices though, in the form of a range of tiny surface-mount solid-state rechargeable lithium batteries. These come in a range of capacities from 0.1 mAh to 0.5 mAh, and in a 3.2 by 2.5 mm package look very much like any other slightly larger SMD chip component.

These devices are most likely to be found in applications such as remote wireless sensors, where they can store the energy from a small solar cell or similar to produce the burst of power required to transmit a packet of data as well as the tiny current required to keep things ticking over. The solid state chemistry should provide a long life and lack of leaks. For now they have some evaluation kits on offer, and unless we missed something, no full data sheet. We’d be particularly interested to learn about their temperature sensitivity when it comes to soldering, as we’ve taken to heart the warnings about soldering to more traditional lithium cells.

Via CNX Software.