Nondestructive misuse of capacitors competition

[RoGeorge]

Anybody in the mood for a competition?

The rule is to post your project in the https://www.eevblog.com/forum/projects/ then link to it here.
Get creative, because anything goes.  The prize will be as many Internet points as you can carry.

Open until first day of 2025.  What do you say?

[I wanted a rude username]

What are the rules? Any non-traditional use of a capacitor, as long as it doesn't lose its ability to capacitate?

[The Soulman]

We'd need a better definition of "misuse" would that include using it (without damage):

*Beyond maximum ratings
*As a mechanical device
*In a clever but unconventional way

?

[RoGeorge]

Anything goes, don't want to exclude or limit the fun in any way.  Though, a capacitor that is filtering the mains ripple after a bridge, or separating the AC from DC between two stages, most probably won't win a competition about capacitors misuse.  But what do I know?

If it gets particularly interesting, or if it comes with a twist, even the most common way of using a capacitors may win.

[temperance]

Capacitors can be used as spacers.

Edit: of course they also provided decoupling.

[RoGeorge]

+1 

[Zoli]

Capacitors can be used to decorate ceilings.

[ebastler]

Use a large electrolytic cap as mechanical mounting point to support your ferrite antenna. 

[temperance]

Class II capacitors with their DC bias dependent capacitance to replace a "varicap diode". Y5V capacitors will provide the largest tuning range.

[Infraviolet]

Just making a guess, but might someone be able to come up with a circuit exploiting the polarised nature of electrolytic caps. It is my understanding (I generally stick to ceramics to avoid having to worry about the exact details of this, so don't consider what I'm about to say as being in any way certain...) that reverse voltages on an electrolytic should not harm it provided they are very small and that the maximum possible backward current is kept very limited by large series resistors.

[DavidJRobertson]

We'd need a better definition of "misuse" would that include using it (without damage):

*Beyond maximum ratings
*As a mechanical device
*In a clever but unconventional way

?

One of the products I've worked on uses some unconnected SMD electrolytic caps as spacers in a board stack. The part was already used elsewhere in the design and cheaper than 'proper' mechanical standoffs.

[amyk]

I have used the piezoelectric effect of SMD ceramic caps as a simple diagnostic code generator, in a relatively niche product that I won't name for various reasons; but I wonder how many users have taken it apart and wondered where the sounds come from with no obvious speaker on the board.

Here is a slightly related but amusingly worded article: https://industrial.panasonic.com/ww/faq/faq0032

Also, this: https://hackaday.com/2015/08/20/using-a-capacitor-as-an-actuator/

[TimFox]

Before retirement, we built high-resolution x-ray CT scanners for industrial imaging.
Among other test objects, we used film-foil polypropylene capacitors (Sprague 715P) and monolithic porcelain capacitors from ATC (roughly 0.1" cubes).

[Kim Christensen]

I think you need to be more specific... 

[Whales]

Just making a guess, but might someone be able to come up with a circuit exploiting the polarised nature of electrolytic caps. It is my understanding (I generally stick to ceramics to avoid having to worry about the exact details of this, so don't consider what I'm about to say as being in any way certain...) that reverse voltages on an electrolytic should not harm it provided they are very small and that the maximum possible backward current is kept very limited by large series resistors.

I used a chemistry similar to backward electrolytic capacitors as chemical diodes.  If you pass current one direction: they charge up and block.  Pass current the other direction: current flows continuously (and unwanted chemical reactions are forced).  These unwanted reactions _might_ be reversible to a certain degree, but under long term DC conditions I expect things won't work as well.

https://halestrom.net/darksleep/blog/026_diode_array/
https://halestrom.net/darksleep/blog/043_diodes4/

[Zero999]

Class II capacitors with their DC bias dependent capacitance to replace a "varicap diode". Y5V capacitors will provide the largest tuning range.

I've seen that before. The advantage of using a capacitor over a varicap diode is, it has a much larger capacitance, so can be used at much lower frequencies.

[Njk]

Recalled that in the primary school it was one time popular among the boys to solder a short wires (like a bull horns) to a big capacitor, charge it from the wall socket and bite the others by electricity or intimidate with a loud spark. Electrolytic caps worked better because of larger capacity, and in that case, there were three horns, one of them is a diode