capacitive coupling

6 Articles

High Voltage Experiment Pipes Power With Water

May 15, 2020 by 27 Comments

The idea of transferring energy with water isn’t exactly new. In fact, it’s downright ancient. Running water has been tapped to power our contrivances since folks were getting excited about that new library they were opening up over in Alexandria. But what if there was a way to deliver power with water that wasn’t kinetic, and instead relied on the electrical properties of the planet’s favorite libation?

That’s exactly what [Jay Bowles] set out to explore with his latest experiment. Since water (we know, not pure water) conducts electricity, it stands to reason that it could be used as a stand-in for traditional copper wiring. Why would you want to do such a thing? Because unlike wires, water can easily morph into whatever shape may be required, and can be moved around and controlled with nothing more complex than ball valves.

To test this concept, [Jay] put together a water distribution system out of simple acrylic tubing. A reservoir was attached to one of his high voltage generators, and copper caps were placed at the end of the tubes to serve as direct attachment points for devices.

But thanks to capacitive coupling, the fluorescent lights he uses don’t actually need to be physically connected to light up. As demonstrated in the video after the break, the lights surrounding the system can be independently controlled just by turning their respective valves on and off; all without any physical contact being made.

Of course, compared to traditional wiring there are plenty of downsides to this idea. Copper wires don’t tend to freeze in the winter and spring a leak, nor do they build up bubbles of explosive hydrogen gas. So it’s safe to say the wiring in your house probably won’t ever be replaced with a tube of charged water. But [Jay] does have some interesting ideas of how this technique could be used in non-traditional ways. For example, he describes how outdoor lighting could be powered by the energy radiating from a small stream.

Even if the practical applications of this technique are somewhat limited, there’s no question that it’s a fascinating idea. Believing that he’s the first person to ever demonstrate power transmission under these specific circumstances, he’s decided to call the concept “Bowles Transmission”. We’d love to see somebody use this principle in one of their projects, and we’re willing to bet so would [Jay].

As with his recent ozone sterilization experiments, we imagine this idea is going to be met with some debate. But that’s sort of the point. [Jay] doesn’t claim to have all the answers, and hopes these videos get people thinking and talking. As they say, nothing great was ever achieved without enthusiasm.

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Simple Acrylic Plates Make Kirlian Photography A Breeze

November 30, 2019 by 1 Comment

We know, we know – “Kirlian photography” is a term loaded with pseudoscientific baggage. Paranormal researchers have longed claimed that Kirlian photography can explore the mood or emotional state of a subject through the “aura”, an energy field said to surround and emanate from all living things. It’s straight-up nonsense, of course, but that doesn’t detract from the beauty of plasma aficionado [Jay Bowles]’ images produced by capacitive coupling and corona discharge.

Technically, what [Jay] is doing here is not quite Kirlian photography. The classic setup for “electrophotography” is a sandwich of photographic film, a glass plate, and a metal ground plate. An object with a high-voltage, high-frequency power supply attached is placed on top of the sandwich, and the resulting corona discharge exposes the film. [Jay]’s version is a thin chamber made of two pieces of solvent-welded acrylic and filled with water. A bolt between the acrylic panes conducts current from a Tesla coil – perhaps this one that we’ve featured before – into the water. When something is placed on the acrylic, a beautiful purple corona discharge streams out from the object.

It’s an eerie effect, and it’s easy to see how people can see an aura and attribute mystical properties to it. In the end, though, it’s not much different than touching a plasma globe, and just about as safe. Feeling a bit more destructive? Corona discharge is a great way to make art, both in wood and in acrylic.

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Hackaday Prize Entry: Magic Bit-Of-Wire Motion Detector Library For Arduino

September 1, 2016 by 11 Comments

We’re still not sure exactly how [connornishijima]’s motion detector works, though many readers offered plausible explanations in the comments the last time we covered it. It works well enough, though, and he’s gone and doubled down on the Arduino way and bundled it up nicely into a library.

In the previous article we covered [connor] demonstrating the motion detector. Something about the way the ADC circuit for the Arduino is wired up makes it work. The least likely theory so far involves life force, or more specifically, the Force… from Star Wars. The most likely theories are arguing between capacitance and electrostatic charge.

Either way, it was reliable enough a phenomenon that he put the promised time in and wrote a library. There’s even documentation on the GitHub. To initialize the library simply tell it which analog pin is hooked up, what the local AC frequency is (so its noise can be filtered out), and a final value that tells the Arduino how long to average values before reporting an event.

It seems to work well and might be fun to play with or wow the younger hackers in your life with your wizarding magics.

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Arduino Motion Detection With A Bit Of Wire

May 23, 2016 by 55 Comments

It is likely that many of us will at some time have experimented with motion detectors. Our Arduinos, Raspberry Pis, Beaglebones or whatever will have been hooked up to ultrasonic or PIR boards which will have been queried for their view of what is in front of them.

[Connornishijima] has stumbled on a different way to detect motion with an Arduino, he’s polling an ADC pin with a simple length of twisted pair hooked up to it and earth, and reliably generating readings indicating when he (or his cat) is in its vicinity. He’s calling the effect “Capacitive turbulence”, and he’s open to suggestions as to its mechanism. He can only make it work on the Arduino, other boards with ADCs don’t cut it.

Frequent Hackaday featuree [Mitxela] may have also discovered something similar, and we’ve hesitated to write about it because we didn’t understand it, but now it’s becoming unavoidable.

It’s always dangerous in these situations to confidently state your opinion as “It must be…” without experimental investigation of your own. Those of us who initially scoffed at the idea of the Raspberry Pi 2 being light sensitive and later had to eat their words have particular cause to remember this. But this is an interesting effect that bears understanding. We would guess that the Arduino’s fairly high input impedance might make it sensitive to mains hum, if you did the same thing to an audio amplifier with a phono input you might well hear significant hum in the speaker as your hand approached the wire. It would be interesting to try the experiment at an off-grid cabin in the woods, in the absence of mains hum.

If you’d like to give his experiment a try, he’s posted his sketch on Pastebin. And he’s put up the video below the break demonstrating the effect in action, complete with cats.

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Wireless Power Transfer Using Capacitive Plates

July 17, 2015 by 33 Comments

It seems like wireless power transfer is all the rage these days. There’s wireless charging mats, special battery packs, heck, even some phones have it built in! And they all use inductive coils to transfer the power — but what if there was another way? Coils of copper wire aren’t always that easy to fit inside of a product…

As an experiment, [Josh Levine] decided to try making a proof of concept for capacitive power transfer.

He first demonstrates inductive power transfer using two coils of copper wire to power up an LED. The charging coil is supplied with 15V peak-to-peak at 1MHz which is a fairly typical value for inductive charging. He then shows us two glass plates with some tinfoil taped to it. Two LEDs bridge the gap alternating polarity — since the power is oscillating, so we need a path for electrons to flow in both directions. There is no connection through the glass, but when it is set on the charging plate, the LEDs light up. The charging plate is supplied with 30V peak-to-peak at 5MHz.

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Making A Variable RF Signal Sampler

January 16, 2014 by 18 Comments

One of [Brian]’s hobbies is Amateur Ham radio, in which it is usually required to check that the transmitted signals are within specifications. As it isn’t safe to connect the radio’s output directly to measuring equipment due to the high voltages involved, [Brian] made his own dedicated RF signal sampler. It works by using capacitive coupling between the signal you wish to sample and a high impedance output. The latter can then safely be connected to an oscilloscope or spectrum analyzer for monitoring.

In the picture you see above, the air gap between the core signal conductor and the output plays the role of a capacitor. By adjusting its length you can therefore vary the output signal’s voltage range. The sampler is built using a die-cast aluminium enclosure which is 52x38x27mm. As you may have guessed, due to the case geometry the output attenuation will depend on the signal’s frequency. [Brian] tested the unit using a 30MHz signal generator and printed this frequency attenuation graph while also varying the air gap.