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# Deliberately Capacitative Cable

Embrace the complexity!
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If my experience with biological science has taught me anything* it's that you must embrace complexity. Conversely, my brushes with the world of electronics demonstrate that they have quite enough complexity thankyouverymuch and if they wanted ambiguity then they'd have done an arts degree.

Nowhere is this more apparent than in circuit designs. There's a symbol for each type of component, and usually, a value or two attached to that symbol. The symbol is what, the value is how much. -/\/\- 100k. A resistor that does 100 kOhm worth of resisting. Lovely, simple, logical organized. Circuit layouts are 2D with lots of straight lines, you can trace where everything goes and easily represent it on paper or a screen. It all has a calming sense of order. Components have a purity of purpose and the engineer can simply arrange them to achieve the desired result. It works very well, but it's wrong.

A peek under the petticoats of electronics reveals sordid secrets. Complexity and messiness that the greybeard engineers talk about in hushed tones. Those 2D circuit designs aren't very good, the components would be more efficiently arranged in 3D space. At the small scale, it gets worse. A diode in a microchip is a really crap diode. Resistors resist, but they're not 100 kOhm when manufactured, they're a distribution around 100 kOhm. Even the simple wire isn't. Represented by a line, it's pure, a conductor. In reality, it's a conductor, and a resistor, and a capacitor and an inductor. It's amazing anything works at all.

So, instead of fighting the futile fight, we can embrace the opportunities. I've recently been dabbling with an electronic motor controller. It is sensitive to voltage drops when the battery can't keep up with demand. To solve this, a bank of capacitors sits at the controller end of the battery connection to act as a short term power supply buffer. This is a feature universal to almost anything with a DC power supply and fluctuating DC demand, which is a lot of things. Instead of using wire/cables optimized for low capacitance and then adding capacitors at the end, how about optimizing the cable FOR capacitance.

A capacitor can be made by taking two thin foil-like conductors separated by the thinnest insulator possible and then rolling them up together. To make a capacitative cable, you can simply extend this idea lengthwise and have terminals at both ends. Cable capacitance will be proportional to length. The cable can be cut to length and then the two conductors teased apart and soldered appropriately, a little like a coaxial cable.

Now, if you have power-hungry components, like a MOSFET, or a sub-component like an HDD in a computer, the supply will be inherently smoothed.

*Graphs are made from grant money via salty water.

 — bs0u0155, Feb 14 2019

Similar thought but compressed slices. FLUED_20wire
Designing the perfect electron path for use. [wjt, Feb 16 2019]

Stripline filter https://en.wikipedi...low-pass_form_2.svg
A circuit made from a single wire. [Wrongfellow, Feb 17 2019]

 Before the invention of coaxial cable, and before impedance matching was understood, there were a few attempts at building a maximally capacitive (and minimally inductive) cable. They didn't catch on.

Practically speaking, most of the time adding capacitance to the input side of a circuit is balanced against inrush current, especially in the world of plug-and-play devices, and often the inductance of the cable before the caps is advantageous.
 — mitxela, Feb 14 2019

 Nifty. I once thought about how, "Even the simple wire isn't. Represented by a line, it's pure, a conductor. In reality, it's a conductor, and a resistor, and a capacitor and an inductor." and if it is bare, possibly a semiconductive oxide layer.

 I wondered if you could build a circuit with a resistor and an inductor from one wire, perhaps with a Y shape at one end doing capacitance, and make a pulsed waveform from just a length of screen-door-spring looking wire with a Y on the end or at branches.

It is different than capacitive wire, but somewhere on here there might be an idea I had about making circuit board traces out of [] hollow square wires that function like waveguides with the idea of reducing EM interference at corners or through-holes. I have no idea if it would have worked.
 — beanangel, Feb 15 2019

 ""It works very well, but it's wrong.""

[marked-for-tagline]
 — 2 fries shy of a happy meal, Feb 15 2019

Won't the layers buckle if you bend it with any reasonable radius?
 — notexactly, Feb 16 2019

 //I wondered if you could build a circuit with a resistor and an inductor from one wire, perhaps with a Y shape at one end doing capacitance, and make a pulsed waveform from just a length of screen-door-spring looking wire with a Y on the end or at branches.//

This is actually quite common. [link]
 — Wrongfellow, Feb 17 2019

 //Won't the layers buckle if you bend it with any reasonable radius?//

You could make it like ribbon cable, you could make sub- conductors, like a fine stranded wire with a core and an outside insulated from one another. There are a few ways, all very doable.
 — bs0u0155, Feb 21 2019

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