Electrolytic capacitor: everything you need to know

electrolytic capacitor

Another new article to add a new "member" to the family of Electronic components analyzed in this blog. This time it is the turn of the electrolytic capacitor, a fairly common type of capacitor from which you will learn all the basics you need to know to start using it in your future projects.

In addition, it is interesting to know closely the technical characteristics of these capacitors, the differences from ceramic capacitors, as well as the advantages and disadvantages ...

What is a capacitor? 

Un capacitor, or capacitor, It is an essential electrical component that acts as a reservoir, storing electrical charge in the form of a potential difference in order to release it later.

La stored shit it is stored on two conductive plates that can be implemented in various ways, depending on the type and shape of the capacitor. And to insulate them electrically, there are dielectric sheets, that is, of insulating material. Thus it is achieved that these charges are stored in these conductive shields without both making contact (at least if the condenser is in perfect condition and does not pierce...).

The dielectric material that separates the plates could be air, tantalum, ceramic, plastics, paper, mica, polyester, etc., depending on the type of capacitor and quality.

The plates are charged with the same amount of charge (q), but with different signs. One will + and another -. Once charged, you can deliver cargo releasing it progressively through the same terminals that have been used to load it.

By the way, the electrical charge capacity it stores is measured in Farads. A relatively large unit for the small capacitors commonly used in conventional electronics projects. Therefore, submultiples such as microfarads (µF) or picofarad (pF) are used, sometimes also nanofarad (nF) and millifarad (mF). In fact, if in practice you wanted to reach 1 F capacity, you would need an area of ​​1011 m2 and that is outrageous ...

Despite being small capacitors, what is done to raise the surface is to use different methods in its architecture, such as rolling the layers, using multilayers, etc.

Furthermore, the body is measured in Coulombs, and if you wonder about the formula to make calculations, you should know what it is:

C = q / V

That is, the capacity of a capacitor between two conductive plates is equal to the charge in Coulombs between the voltage or potential difference (volts) between the two ends or terminals of the capacitor.

From that formula one could also clear V to get the voltage:

V = q / C

When the capacitor is charged, it is not will download instantly. As I mentioned above, it will do it little by little, just like it loads. The times will depend on the capacitance of the capacitor and the resistance in series with it. The higher the resistance, the more difficult it will be to pass current to the capacitor and the longer it will take to charge.

It is not recommended to do without the resistor, as charging could damage the capacitor.

Once the capacitor is charged, it will no longer accept charge and would behave like a open switch. That is, between the two terminals of the capacitor there would be a potential difference but no current would flow.

Once you want discharge capacitorIt will also do it progressively depending on the resistance and capacity of the capacitor, taking more or less time.

Surely you have noticed that when you turn off an electrical device that has an LED, it takes a few moments for it to turn off, that is because some capacitor was still storing charge and was delivering it to the LED even once it was turned off. Therefore, when you manipulate a power supply it is necessary to leave a few moments after turning it off or you could suffer a discharge from one of its capacitors.

Companies that formulas to determine the loading and unloading time of a capacitor are:

t = 5RC

That is, the charge / discharge time measured in seconds will be equal to five times the resistance in series (in ohms) with the capacitor and its charge. If the resistance were a potentiometer, you could even vary the time for it to discharge or charge more or less quickly ...

What is an electrolytic capacitor?

There different types of capacitors, such as variables, air, ceramic and electrolytic. But it is the electrolytic capacitor and the ceramic capacitor that have gained the most popularity and are the most used in electronics.

El electrolytic capacitor It is a type of condenser that uses a conductive ionic liquid as one of its plates. That makes it usually have more capacity per unit volume than other types of capacitors. In addition, they are widely used in circuits such as signal modulators in power supplies, oscillators, frequency generators, etc.

In this type of capacitors a dielectric which is aluminum oxide impregnated on absorbent paper. That is what will insulate the shields or conductive metal foils being charged.

As you can see in the photo, in addition to the typical capacitors radial (their terminals are in the area below), there are also the axial, which have an architecture similar to conventional resistors, that is, they will have a terminal on each side. But that does not change its characteristics or operation at all ...

Dónde comprar

Si quieres buy an electrolytic capacitor, you can easily find it in specialized electronics stores or buy them on online platforms such as Amazon. Here are some recommendations:

As you can see, they are a component quite cheap...

Differences with ceramic capacitors

ceramic capacitor vs electrolytic capacitor

There are differences These are notable between a ceramic capacitor and an electrolytic capacitor, and not only because the latter tend to have more charge and volume, but also for other reasons:

  • If we stick only to the appearance, the ceramic capacitor is usually shaped like a lentil, while the electrolytic capacitor is cylindrical.
  • The ceramic capacitor uses two metal foils at its terminals to store charge. The electrolytic capacitor only has a metal foil and an ionic liquid.
  • Most electrolytic capacitors are polarized, that is, they have a + and - terminal that you must respect. That's not the case with ceramic ones, it won't matter how you put them in the circuit.
  • This implies that ceramics can be used in AC or DC circuits, while the electrolytic capacitor is only used in DC circuits.

Advantages and disadvantages

Compared with the ceramic capacitor, the electrolytic capacitor has a series of advantages and disadvantages:

  • Being polarized, it will limit its uses in alternating current circuits. While ceramic, as it is not polarized, it will work with DC and AC indifferently.
  • Electrolytic capacitors have a higher capacity, but also a higher volume. Ceramics have lower capacity, but can be better integrated into more miniaturized devices.
  • They are immune to certain effects of mechanical vibrations. Some ceramics can pick up vibrations and transform them into unwanted electrical signal alterations, as if they were a microphone ... It is a typical effect of ceramic when compressing or vibrating it (see Xtal, piezoelectrics, ...).
  • The electrolytic capacitor uses insulating layers sensitive to high voltages, so they will not work for certain types of circuits. Ceramics are more resistant to high voltage.

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