Question bout Capacitors. Polar and non-polar.

[Outlaws]

So I heard that if a schematic calls for polar, you can still use non-polar.

Now I also understand that the side with the stripe is usually the negative.  But what if it is a stripe with arrows and the leads come out of each end?  Then is the negative the side the arrows point to?

[chokeyou]

yeah, arrows point to negative

[Hevimies]

So I heard that if a schematic calls for polar, you can still use non-polar.

Is this so?

[Peter Snowberg]

So I heard that if a schematic calls for polar, you can still use non-polar.

Is this so?

Yes it is.

This is because polarization is a limitation which is accepted when you want a large value capacitor in a small space. You could use film caps everywhere, but 100uF film caps are HUGE. :shock:

[R.G.]

Yes. Here is why:

To make an aluminum electrolytic capacitor, you take two strips of thin aluminum and roll them up with a bit of paper between them. You then soak them in a liquid that conducts electricity. So far, all you have is a sloppy short circuit.

Then you impress DC across the thing. Current flows, but as it flows, the aluminum on one polarity of the DC starts oxidizing, building up a layer of aluminum oxide on one of the aluminum strips.

Aluminum oxide is an insulator, and a good one. Over time, the oxide covers one entire strip of aluminum, the DC current flow stops, and you have a capacitor.

This is a polar capacitor. If you put DC on it the direction it was formed, then no DC flows, and any decomposition of the oxide is corrected by the electricity causing new oxide in any pinhole breaks. If you put DC on it the other way, any pinhole breaks get worse with time, and it shorts.

NON-polar or bipolar aluminum capacitors have both strips of foil covered in oxide. This means that whichever direction the DC is applied, there is an oxide layer blocking the DC. So if you use it in a unipolar application, it works fine.

[Hevimies]

So I heard that if a schematic calls for polar, you can still use non-polar.

Is this so?

Yes it is.

That's cool. Thank you!