Junkbox Build Keeps Tesla Coils Perfectly Varnished

August 9, 2022 by Dan Maloney 21 Comments

Admittedly, not a lot of people have a regular need to varnish coils. It’s mainly something that Tesla coil builders and other high-voltage experimenters are concerned with. But since that group probably constitutes a not insignificant fraction of the Hackaday audience, and because there are probably more applications for this homebrew coil varnishing setup, we figured it would be a good idea to share it.

For [Mads Barnkob], coil maintenance isn’t something to take lightly. If you check out his Kaizer Power Electronics channel on YouTube, you’ll see that he has quite a collection of large, powerful Tesla coils, some of which are used for demos and shows, and others that seem to be reserved mainly for blowing stuff up. To prevent one of his coils from joining the latter group, keeping the coat of insulating varnish on the secondary coil windings in tip-top condition is essential.

The setup seen in the video below helps with that tedious chore. Built entirely from scraps and junk bin parts, the low-speed, low-precision lathe can be set up to accommodate coils of all sizes. In use, the lathe turns the coil very slowly, allowing [Mads] to apply an even coat of varnish over the coil surface, and to keep it from sagging while it dries.

[Mads]’ setup is probably not great for coil winding as it is, but for coil maintenance, it’s just the thing. If your needs are more along the lines of a coil winder, we’ve got a fully automated winder that might work for you.

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Hackaday Prize 2022: A Plasma Tweeter For Ultimate Clarity

August 8, 2022 by Jenny List 18 Comments

In the world of audio there are a huge variety of esoteric technologies which are rarely seen. One such is the plasma tweeter, a type of loudspeaker which generates sound by modulating a small electrical discharge. The benefit of this design comes in its delivering the closest possible to a point audio source, in effect the theoretical ideal speaker for treble frequencies. They’re a little hazardous due to the voltage but aren’t too difficult to make, as demonstrated by [Mircemk] whose version uses a recycled power pentode tube — which is how it showed up in the Hack it Back round of the Hackaday Prize.

It can be thought of as a cousin of the Tesla coil, with the same resonant oscillator but no capacity hat. Instead the top of the coil ends in a point, from which in the perfect speaker a ball of plasma replaces the Tesla’s impressive sparks. In this case the pentode is joined by a high-voltage TV line output transistor as a bias supply, which is in turn modulated with the audio through a small amplifier. It sometimes needs the plasma teasing out of it through discharge to a screwdriver, but the result is a very effective and clear plasma tweeter.

If plasma tweeters interest you, we’ve featured them before.

High Tech Pancake Tesla Coil Brings The Lightning

March 18, 2022 by Tom Nardi 4 Comments

For several years now we’ve been following [Jay Bowles] as he brings high-voltage down to Earth on his Plasma Channel YouTube channel. From spark gaps made of bits of copper pipe to automotive ignition coils driven by the stalwart 555 timer, he’s got a real knack for keeping his builds affordable and approachable. But once in a while you’ve got to step out of your comfort zone, and although the dedicated DIY’er could still replicate the solid state “pancake” Tesla coil he documents in his latest video, we’d say this one is better left for the professionals.

The story starts about nine months ago, when [Jay] was approached by fellow YouTuber [LabCoatz] to collaborate on a PCB design for a solid state Tesla coil (SSTC). Rather than a traditional spark gap, a SSTC uses insulated-gate bipolar transistors (IGBTs) triggered by an oscillator, which is not only more efficient but allows for fine control of the primary coil. The idea was to develop an AC-powered coil that was compact, easy to repair, and could be controlled with just a couple dials on the front panel. The device would also make use of an antenna feedback system that would pick up the resonant frequency of the secondary coil and automatically adjust the IGBT drive to match.

Being considerably more complex than many of the previous builds featured on Plasma Channel, it took some time to work out all the kinks. In fact, the majority of the video is [Jay] walking the viewer through the various failure modes that he ran into while developing the SSTC. Even for somebody with his experience in high-voltage, there were a number of headscratchers that had to be solved.

For example, the first version of the design used metal bolts to attach the primary and secondary coils, until he realized that was leading to capacitive coupling and replaced them with acrylic blocks instead. If his previous videos surprised you by showing how easy it could be to experiment with high-voltages, this one is a reminder that it’s not always so simple.

But in the end [Jay] does get everything sorted out, and the results are nothing short of spectacular. Even on the lower power levels it throws some impressive sparks, but when cranked up to max, it offers some of the most impressive visuals we’ve seen so far from Plasma Channel. It was a lot of work, but it certainly wasn’t wasted effort.

Fascinated by the results, but not quite ready to jump into the deep end? This affordable and easy to build high-voltage generator featured on Plasma Channel back in 2020 is a great way to get started. If you still need more inspiration, check out the fantastic presentation [Jay] gave during the 2021 Remoticon.

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A Builders Guide For The Perfect Solid-State Tesla Coil

October 31, 2021 by Dave Rowntree 13 Comments

[Zach Armstrong] presents for your viewing pleasure a simple guide to building a solid-state Tesla coil. The design is based around a self-resonant setup using the UCC2742x gate driver IC, which is used in a transformer-coupled full-wave configuration for delivering maximum power from the line input. The self-resonant bit is implemented by using a small antenna nearby the coil to pick up the EM field, and by suitably clamping and squaring it up, it is fed back into the gate driver to close the feedback loop. Such a setup within reason allows the circuit to oscillate with a wide range of Tesla coil designs, and track any small changes, minimizing the need for fiddly manual tuning that is the usual path you follow building these things.

Since the primary is driven with IGBTs, bigger is better. If the coil is too small, the resonant frequency would surpass the recommended 400 kHz, which could damage the IGBTs since they can’t switch much faster with the relatively large currents needed. An important part of designing Tesla coil driver circuits is matching the primary coil to the driver. You could do worse than checkout JavaTC to help with the calculations, as this is an area of the design where mistakes often result in destructive failure. The secondary coil design is simpler, where a little experimentation is needed to get the appropriate degree of coil coupling. Too much coupling is unhelpful, as you’ll just get breakdown between the two sides. Too little coupling and efficiency is compromised. This is why you often see a Tesla coil with a sizeable gap between the primary and secondary coils. There is a science to this magic!

A 555 timer wired to produce adjustable pulses feeds into the driver enable to allow easily changing the discharge properties. This enables it to produce discharges that look a bit like a Van De Graaff discharge at one extreme, and produce some lovely plasma ‘fire’ at the other.

We’ve covered Tesla coils from many angles over the years, recently this plasma tweeter made sweet sounds, and somehow we missed an insanely dangerous Tesla build by [StyroPyro] just checkout that rotary spark gap – from a distance.

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Is It A Plasma Tweeter Or A Singing Tesla Coil?

June 19, 2021 by Jenny List 6 Comments

When our ears resolve spatial information, we do so at the higher treble frequencies rather than the bass. Thus when setting up your home cinema you can put the subwoofer almost anywhere, but the main speakers have to project a good image. The theoretical perfect tweeter for spatial audio is a zero mass point source, something that a traditional speaker doesn’t quite achieve, but to which audio engineers have come much closer with the plasma tweeter. This produces sound by modulating a small ball of plasma produced through high-voltage discharge, and it’s this effect that [mircemk] has recreated with his HF plasma tweeter.

A look at the circuit diagram and construction will probably elicit the response from most of you that it looks a lot like a Tesla coil, and in fact that’s exactly what it is without the usual large capacitor “hat” on top. This arrangement has been used for commercial plasma tweeters using both tubes and semiconductors, and differs somewhat from the singing Tesla coils you may have seen giving live performances in that it’s designed to maintain a consistent small volume of discharge rather than a spectacular lightning show to thrill an audience.

You can see it in operation in the video below the break, and it’s obvious that this is more of a benchtop demonstration than a final product with RF shielding, It’s not the most efficient of devices either, but given that audiophiles will stop at nothing in their pursuit of listening quality, we’d guess that’s a small price to pay. Efficiency can be improved with a flyback design, but for the ultimate in showing off how about a ring magnet to create the illusion of a plasma sheet?

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Physics Of Lightning Hack Chat

March 29, 2021 by Dan Maloney 2 Comments

Join us on Wednesday, March 31 at noon Pacific for the Physics of Lightning Hack Chat with Greg Leyh!

Of all the things that were around to terrify our ancestors, lightning must have been right up there on the list. Sure, the savannahs were teeming with things that wanted to make lunch out of you, but to see a streak of searing blue-white light emerge from a cloud to smite a tree out of existence must have been a source of dread to everyone. Even now, knowing much more about how lightning happens and how to protect ourselves from it, it’s still pretty scary stuff to be around.

But for as much as we know about lightning, there are plenty of unanswered questions about its nature. To get to the bottom of this, Greg Leyh wants to build a lightning machine of gargantuan proportions: a pair of 120 foot (36 m) tall Tesla towers. Each 10-story tower will generate 8.8 million volts and recreate the conditions inside storm clouds. It’s an ambitious goal, but Greg and his team at Lightning on Demand have already built and demonstrated a 1/3-scale prototype Tesla tower, which is impressively powerful in its own right.

As you can imagine, there are a ton of engineering details that have to be addressed to make a Tesla tower work, not to mention the fascinating physics going on inside a machine like this. Greg will stop by the Hack Chat to answer our questions about the physics of lightning, as well as the engineering needed to harness these forces and call the lightning down from the sky.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, March 31 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.
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Electric Candle Replaces Flame With Plasma

February 1, 2021 by Dan Maloney 32 Comments

Ah, the charm of candlelight! Nothing says “romance” — or “extended power outage” — like the warm, soft glow of a real candle. But if you’re not a fan of burning wax for whatever reason, this electric plasma candle may be just the thing to build for your next dinner for two.

This re-imagining of the humble candle comes to us by way of plasma super-fan [Jay Bowles], who has a lot of experience with plasmas and the high-voltage circuits that often go along with them. Even so, he had to enlist help with the circuit, with is essentially a 10-MHz Class-E oscillator, from [Leon] at the Teslaundmehr channel on YouTube. The most prominent feature of the build is the big resonator coil, surrounded by the shorter primary coil and sitting atop the heatsink for the MOSFET driver. [Jay]’s usual acrylic-rich style is well represented here, and the resulting build is quite lovely.

The tuning process, though, sounds like it was pure torture. It took a lot of tweaking — and a lot of MOSFETs — to get the candle to produce a stable flame. But once it did, the results were striking. The plasma coming off the breakout point on the resonator coil is pretty much the same size, shape, and — occasionally — the color as a candle flame. It’s also hot enough to do some damage, so do be careful if you build this. We’ve included both [Jay]’s and [Leon]’s videos below; [Leon]’s has great step-by-step build instructions.

We’ve been following [Jay]’s journey through the plasmaverse for a while now, from his cheap and simple Tesla coils to using corona discharge to clean his hands. He even hosted a Hack Chat on the subject last year.

Note: [Jay] reached out to us after publication about mitigating RF noise. He does his experiments inside a steel-reinforced concrete building with grounded metal screens over the windows. An RF-wizard friend has checked across the spectrum and detected no leaks to the outside. Sounds like the business to us.

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