jason9

modified 4 years ago

Bipolar cap from two polarized capacitors

157

01:43:31

A polarized capacitor is destroyed from negative voltage because it has a built in diode that can flow current with negative voltage and when that happen it heats up and eventually explodes. This arrangement of two polarized capacitors takes advantage of the built in diode to create a bipolar capacitor.

Please note that the diodes here are part of the capacitors and need not be included in real life. I am only including them because EC doesn’t simulate them as part of the polarized capacitor.

published 4 years ago

Robert_Kidd

4 years ago

@jason9, you’ve kind of confused me here. Are you seriously saying real life caps have a diode?

jason9

4 years ago

Polarized capacitors have a diode. Connecting the cap in reverse often flows significant current through the diode heating it up which damages the cap and can cause it to explode or catch fire. Apparently a diode is formed because the insulator in an electrolytic cap can flow electrons but not ions and when forward biased only ions are present but when reverse biased electrons are pushed through.

fatcat2

4 years ago

What's the point of simulating a bipolar cap in EC? If we were to make a practical design involving electrolytic caps, we could check the voltage across each caps, although it'd be tedious that way.

jason9

4 years ago

It demonstrates how a bipolar cap can be created from two polarized capacitors and shows how this arrangement functions. This arrangement of the polarized capacitors is for cases when a large capacitor is needed and there’s no easy way to avoid negative polarity.

badassfromaus

4 years ago

A polarized electrolytic capacitor is like a battery it doesn't have a diode in it and if you try to charge a battery with the wires in reverse it will have the same result. As I said all EC capacitors are bipolar so we don't have polarized capacitors in EC to try.

jason9

4 years ago

Well, one way or another current flows when reverse voltage is applied and that clearly doesn’t happen with forward voltage (except for leakage current) and that sounds like a diode to me.

Robert_Kidd

4 years ago

Look up manufacturing methods for capacitors. You’ll find no mention of a diode.

stanislav_maslovski

4 years ago

Well, of course there is no real semiconductor diode in a polar electrolytic capacitor, but that is true that some electrolytic capacitors conduct current when reverse voltage is applied. The trick of connecting two polar caps in series in mutually reverse polarity to obtain a non-polar cap is well known.

stanislav_maslovski

4 years ago

Moreover, there was such a thing as electrolytic rectifier. You can easily make one yourself from aluminum foil and a graphite electrode placed into a water solution of baking soda.

jason9

4 years ago

Yeah, what stanislav_maslovski said. Also, I didn’t know about the electrolytic rectifier. I’ve gotta try that myself.

badassfromaus

4 years ago

I'm sorry I didn't notice that we now have Polarized capacitors in the google chrome version but not in the android app. In saying that they still don't have a diode

Robert_Kidd

4 years ago

@stanislav_maslovski, just so.

jason9

4 years ago

@badassfromaus well, it depends on what you consider to be a diode. If it’s anything that has diode-like behavior (lets current through one way but not the other) then electrolytic capacitors have diodes in the form of an electrolytic rectifier. If you require the rectification behavior to be from a semiconductor in order to consider it a diode, then electrolytic capacitors do not have diodes, but can behave similar to them (although they get damaged when conducting current).

Robert_Kidd

4 years ago

Well, look at that, the polarised capacitor has now been added to the mobile app!

jason9

4 years ago

Yep, two days later for you than me. I wonder why people get updates at different times.

Robert_Kidd

4 years ago

:-)

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