1. Home
  2. Electronics Design
  3. novice: why do electrolytic capacitors...

novice: why do electrolytic capacitors...

--- The dielectric in an aluminum electrolytic capacitor is a microscopically thin layer of aluminum oxide which is maintained on one of its aluminum plates when the polarity of the voltage across the two plates, and the electrolyte between them is applied in the correct direction. If the voltage is appled in the wrong direction, the electrolyte will deplete the oxygen in the coating, reducing the oxide coating to elemental aluminum and the two plates will short-circuit through the electrolyte, destroying the capacitor.

-- John Fields

Reply to
John Fields
Loading thread data ...

Because they can only withstand the rated voltage the correct way around. They leak more with small voltages in the reverse direction as well.

Sorry, it can't be guaranteed that it won't work correctly.

Stupid metaphor of the day- consider a compressor storage tank- it can withstand internal pressure of 150psi but will crumple up on a vacuum (external pressure of 15psi).

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

They make more noise one way than the other.

--
  Keith
Reply to
keith

Why do electrolytic capacitors have to be connected the correct way around? Why does a circuit not work correctly if an electrolytic capacitor is reversed? Is it like a battery - only sinks rather than sources a charge?

Reply to
mike

Initially, current builds a very thin insulating layer on one electrode (just like anodisation of aluminium). Reversing the polarity reverses the process and so destroys the layer.

Reply to
Kryten

Search on "borax" and "rectifier" for the full story. You can think of an electrolytic capacitor as a really crappy diode that happens to have a lot of junction capacitance.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply to
Tim Wescott

To answer this - I rather like the Japanese name for an electrolytic cap. They call it a 'chemicon' - i.e a chemical capacitor ( condensor ) .

It relies on electro-chemical processes to work correctly.

As such, it effectively has an anode and cathode. This is why it has to be used the right way round.

If you want more info - google is your friend !

Graham

Reply to
Pooh Bear

I saw a guy test a power supply once, 20A at 50V unregulated, and the bloke building it had put all 4 filter capacitors in the wrong way round. Like a wedding!

Paul Burke

Reply to
Paul Burke

around? Why

reversed? Is

But probably a bit more messy... ;-) Btw. there's a "basic" group where all the "novice:" posings might be better off....

/Anders

Reply to
Anders F

Basically, yes. When reversed it acts as a very effictive current sink, but only for a fairly short time.

Reply to
Rob Gaddi

Why

Is

This is where you need to bring a supply up with a variac that has an AC current meter to monitor the current. The test procedures I wrote for linear power supplies with a bank of "Computer grade" capacitors explained the reason, and the danger of not doing it right.

--
Beware of those who suffer from delusions of adequacy!

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.