How to make a capacitor?

An inventor lives in the soul of each of us, and therefore amateur radio is a fairly popular hobby. Self-manufacturing radio components - one of the most interesting components of this hobby. In this article we will talk about how to make a capacitor with your own hands at home.

materials

To make a capacitor, we need:

• foil,
• iron,
• papyrus paper,
• paraffin,
• lighter.

The foil does not need additional preparation, but with the help of the last three components we have to make waxed paper.

Manufacturing

So, the materials are prepared, let's get to work:

1. We heat the paraffin and carefully process the papyrus paper.
2. We fold it into an "accordion", the width of each section of which is about 30 mm. The number of harmonica layers determines the capacitance of the capacitor, each layer corresponds to approximately 100 pF.
3. In each section we put a piece of foil with an area of ​​​​30 by 45 mm.
4. We fold the accordion and iron it with a warm iron.
5. Everything, the capacitor is ready! The pieces of foil peeking out are the connecting contacts of our capacitor, through which it can be connected to the circuit.

We got the simplest household capacitor, while it is worth noting that the thicker and better the foil, the more high-voltage it will be. However, we draw your attention to the fact that it is better not to try to make a capacitor at home that can withstand more than 50 kV. "Amateur professionals" advise, if you want to get close to this value, use lamination bags as a dielectric, but you will need a laminator to heat them.

HOW TO MAKE A FIXED CAPACITOR

It is not difficult to make a capacitor of constant capacitance. This will require steel foil (tin paper), waxed paper and pieces of tin. Staniole foil can be taken from candy or chocolate wrappers, and waxed paper can be made by yourself.

To do this, take thin tissue paper and cut it into strips 50 mm wide and 200-300 mm long.

The strips are immersed for 2-3 minutes in molten paraffin (not boiling). As soon as they are taken out, the paraffin immediately hardens. After that, it must be carefully scraped off with the blunt side of the knife so as not to tear the paper. Waxed sheets are obtained.

Rice. 111. Homemade constant capacitor.

For the capacitor, waxed paper is folded with the letter “I”, as shown in Figure 111, in the intervals, on both sides of the “accordion”, sheet sheets of 45X30 mm in size are inserted.

When all the sheets are inserted, the "accordion" is folded and ironed with a heated iron. The steel ends remaining on the outside are connected to each other.

It is better to do it this way: two plates are cut out of thick cardboard, put on both sides of the "accordion" and clamped with two clips made of tin or brass. It is necessary to solder conductors to the clips, with the help of which the capacitor is soldered during installation.

With ten steel sheets, the capacitance of the capacitor will be approximately equal to 1,000 pF.

If the number of leaves is doubled, the capacitance of the capacitor will also double.

In this way, you can make capacitors with a capacity of 100 to 5 tons pf.

Large capacitors from 5 tons pf to 0.2 microfarads are made a little differently. To make them, you will need an old paper microfarad capacitor.

The paper capacitor is a roll rolled up from a tape consisting of two strips of waxed paper and two strips of steel foil laid between them.

In order to determine the length of the strip required

us for a capacitor, use the formula:

C
l = 0.014 ---
a

In this formula, C is the capacitance of the capacitor we need in pF; a is the width of the foil strip in cm; l is the length of the foil strip in cm. For example, to obtain a capacitor with a capacity of 10 tons pF with a strip width of 4 cm, the required strip length will be:

10 000
l \u003d 0.014----------- \u003d 35 cm.
4

The capacitor is made as follows; from a roll of a microfarad capacitor (Fig. 112), a tape of the length we need is unwound (all four strips). To prevent the capacitor plates from connecting to each other, at the beginning and at the end of the tape, the steel foil is cut 10 mm more than the paper.

112 Homemade high-capacity capacitor.

Before rolling the tape, from each strip

foil is terminated with a thin stranded wire or tinned copper foil. The conclusion from one lining is placed at the beginning of the tape, and from the other - at the end and in the opposite direction. Then the tape is rolled up into a tube and pasted over with thick paper on top. Paper for pasting is taken wider than the tape by 10 mm. On the protruding edges of the paper close up two rigid mounting conductors.

Leads from the capacitor plates are soldered to these conductors from the inside of the paper sleeve, as shown in the figure.

The finished condenser is filled with paraffin.

Good afternoon Today I would like to show you how to make a Leyden jar, the simplest device in which you can store an electric charge.

Static electricity is just a lack or excess of electrons on the surface of an object.

One way of education static electricity- contact between two dissimilar objects. Many still remember the experiment with an ebonite stick from school. If you rub it with wool, then part of the electrons will run over to the stick and the wool will remain positively charged, and the stick, due to an excess of electrons, will be negatively charged and will be able to attract light objects.

In everyday life, such a situation occurs, for example, when combing hair with a comb. You can even hear the crackle of electrostatic discharges. By the way, did you know that such clicks have a voltage of several thousand volts? It turns out that with the help of an ordinary comb you can get just a huge voltage. Only now the charge that a comb can hold is very, very small. The charge from the comb can be accumulated elsewhere. For example, in the Leiden Bank. The Leyden jar is essentially the simplest capacitor (two conductors separated by an insulator.

Let's start manufacturing

materials
The classic Leyden jar is usually made from glass jar, but it has too thick walls, and the charge accumulates is not very large. Therefore, we will use a plastic jar with thin walls. We will use as a guide food foil, or foil from chocolate.

Step 1
The jar needs to be covered with an even layer of foil about two-thirds in height, including the bottom itself. Avoid large wrinkles and tears.

Step 2
Now the same thing needs to be done from the inside, to the same height as the outer lining.

Step 3
In the center of the jar, attach a foil receiver, which should touch the foil inside the jar. The upper part must be taken out of the can.

If you are too lazy to bother with gluing the inside of the can, then you can simply pour saline solution there exactly to the level to which the foil is pasted on the outside. (The receiver should touch the water with one end

So, now we have where to accumulate a charge from a comb. To do this, grasp the outer cover with one hand and run the loaded comb near the receiver with the other hand.

You can discharge the jar onto yourself by holding the lining with your hand and bringing your finger to the receiver. And you can also make such a cool spark gap from a piece of foil, which will give a more even and beautiful spark.

On a note: a breakdown of 1 mm of air requires a voltage of one thousand volts. By the way, air humidity critically affects the length of the spark (the drier it is in your apartment, the longer the spark will be).

The electrical capacitance of the globe, as is known from the course of physics, is approximately 700 microfarads. An ordinary capacitor of such a capacity can be compared in weight and volume with a brick. But there are capacitors with the electrical capacity of the globe, equal in size to a grain of sand - supercapacitors.

Such devices appeared relatively recently, about twenty years ago. They are called differently: ionistors, ionixes or simply supercapacitors.

Do not think that they are available only to some high-flying aerospace firms. Today you can buy in the store a coin-sized ionistor with a capacity of one farad, which is 1500 times the capacity of the globe and close to the capacity of the largest planet in the solar system - Jupiter.

Any capacitor stores energy. To understand how large or small the energy stored in the ionistor is, it is important to compare it with something. Here is a somewhat unusual, but visual way.

The energy of an ordinary capacitor is enough for it to jump about a meter and a half. A tiny ionistor of type 58-9V, having a mass of 0.5 g, charged with a voltage of 1 V, could jump to a height of 293 m!

Sometimes it is thought that ionistors can replace any battery. Journalists depicted the world of the future with silent electric vehicles powered by supercapacitors. But so far this is far from it. An ionistor weighing one kg is capable of accumulating 3000 J of energy, and the worst lead battery - 86,400 J - 28 times more. However, when delivering high power in a short time, the battery quickly deteriorates, and it is only half discharged. The ionistor, on the other hand, repeatedly and without any harm to itself gives off any power, if only the connecting wires could withstand them. In addition, the ionistor can be charged in seconds, and the battery usually takes hours to do this.

This determines the scope of the ionistor. It is good as a power source for devices that consume high power for a short time, but quite often: electronic equipment, flashlights, car starters, electric jackhammers. The ionistor can also have military applications as a power source for electromagnetic weapons. And in combination with a small power plant, the ionistor allows you to create cars with electric wheels and fuel consumption of 1-2 liters per 100 km.

Ionistors for a wide variety of capacities and operating voltages are on sale, but they are expensive. So if you have time and interest, you can try to make an ionistor yourself. But before giving specific advice, a little theory.

From electrochemistry it is known: when a metal is immersed in water, a so-called double electric layer is formed on its surface, consisting of opposite electric charges - ions and electrons. Between them there are forces of mutual attraction, but the charges cannot approach each other. This is hindered by the attractive forces of water and metal molecules. At its core, the electrical double layer is nothing more than a capacitor. The charges concentrated on its surface act as plates. The distance between them is very small. And, as you know, the capacitance of a capacitor increases with a decrease in the distance between its plates. Therefore, for example, the capacitance of an ordinary steel spoke immersed in water reaches several mF.

In essence, an ionistor consists of two electrodes with a very large area immersed in the electrolyte, on the surface of which, under the action of an applied voltage, a double electric layer is formed. True, using ordinary flat plates, it would be possible to obtain a capacitance of only a few tens of mF. To obtain large capacitances characteristic of ionistors, they use electrodes made of porous materials having a large pore surface at small external dimensions.

For this role, spongy metals from titanium to platinum were tried at one time. However, incomparably the best was ... ordinary activated carbon. This is charcoal, which after special treatment becomes porous. The pore surface area of ​​1 cm3 of such coal reaches a thousand square meters, and the capacitance of the electrical double layer on them is ten farads!

Self-made ionistor Figure 1 shows the design of the ionistor. It consists of two metal plates tightly pressed against the "stuffing" of activated carbon. Coal is stacked in two layers, between which a thin separating layer of a substance that does not conduct electrons is laid. All this is impregnated with electrolyte.

When the ionistor is charged in one half of it, a double electric layer is formed on the pores of the coal with electrons on the surface, in the other half - with positive ions. After charging, ions and electrons begin to flow towards each other. When they meet, neutral metal atoms are formed, and the accumulated charge decreases and may eventually disappear altogether.

To prevent this, a separating layer is introduced between the layers of activated carbon. It can be made up of various thin plastic films, paper, and even cotton.
In amateur ionistors, the electrolyte is a 25% sodium chloride solution or a 27% KOH solution. (At lower concentrations, a layer of negative ions will not form on the positive electrode.)

Copper plates with wires pre-soldered to them are used as electrodes. Their working surfaces should be cleaned of oxides. In this case, it is advisable to use a coarse-grained skin that leaves scratches. These scratches will improve the adhesion of the coal to the copper. For good adhesion, the plates must be degreased. The degreasing of the plates is carried out in two stages. First, they are washed with soap, and then rubbed with toothpowder and washed off with a stream of water. After that, you should not touch them with your fingers.

Activated charcoal, bought at a pharmacy, is ground in a mortar and mixed with electrolyte until a thick paste is obtained, which is smeared with carefully defatted plates.

During the first test, the plates with a paper gasket are placed one on top of the other, after which we will try to charge it. But there is a subtlety here. At a voltage of more than 1 V, the release of gases H2, O2 begins. They destroy carbon electrodes and do not allow our device to work in the ionistor capacitor mode.

Therefore, we must charge it from a source with a voltage of no higher than 1 V. (This is the voltage for each pair of plates that is recommended for the operation of industrial ionistors.)

Details for the curious

At a voltage of more than 1.2 V, the ionistor turns into a gas battery. This is an interesting device, also consisting of activated carbon and two electrodes. But structurally, it is made differently (see Fig. 2). Usually, two carbon rods are taken from an old galvanic cell and gauze bags of activated carbon are tied around them. KOH solution is used as electrolyte. (Salt solution should not be used, as chlorine is released when it decomposes.)

The energy intensity of the gas accumulator reaches 36,000 J/kg, or 10 Wh/kg. This is 10 times more than that of an ionistor, but 2.5 times less than that of a conventional lead battery. However, a gas accumulator is not just a battery, but a very peculiar fuel cell. When it is charged, gases are released on the electrodes - oxygen and hydrogen. They "settle" on the surface of activated carbon. When a load current appears, they are connected to form water and electric current. This process, however, without a catalyst is very slow. And, as it turned out, only platinum can be a catalyst ... Therefore, unlike an ionistor, a gas accumulator cannot give high currents.

However, the Moscow inventor A.G. Presnyakov (http://chemfiles.narod.r u/hit/gas_akk.htm) successfully used a gas accumulator to start a truck engine. Its solid weight - almost three times more than usual - in this case turned out to be tolerable. But the low cost and lack of such harmful materials like acid and lead seemed extremely attractive.

gas accumulator the simplest design was prone to complete self-discharge in 4-6 hours. This put an end to the experiments. Who needs a car that can't be started after a night of parking?

But still " big equipment»I didn’t forget about gas accumulators. Powerful, light and reliable, they are on some satellites. The process in them takes place under a pressure of about 100 atm, and spongy nickel is used as a gas absorber, which under such conditions works as a catalyst. The entire device is housed in an ultra-light carbon fiber balloon. The result was batteries with an energy capacity of almost 4 times higher than that of lead batteries. An electric car could travel about 600 km on them. But, unfortunately, while they are very expensive.

Requirements to reduce the size of radio components while increasing them technical specifications led to the emergence of a large number of devices that are used everywhere today. This fully affected the capacitors. The so-called ionisters or supercapacitors are elements with a large capacity (the range of this indicator is quite wide from 0.01 to 30 farads) with a charging voltage of 3 to 30 volts. However, their size is very small. And since the subject of our conversation is a do-it-yourself ionistr, it is necessary first of all to deal with the element itself, that is, what it is.

Design features of the ionistr

In fact, this is an ordinary capacitor with a large capacitance. But ionistors have high resistance, because the element is based on an electrolyte. This is the first. The second is a small charging voltage. The thing is that in this supercapacitor, the plates are located very close to each other. This is precisely the reason for the reduced voltage, but it is for this reason that the capacitance of the capacitor increases.

Factory ionistry are made of different materials. Linings are usually made of foil, which delimits the dry substance of the separating action. For example, activated carbon (for large plates), metal oxides, polymeric substances that have high electrical conductivity.

We collect the ionistr with our own hands

Assembling an ionistr with your own hands is not the easiest thing, but you can still do it at home. There are several designs where there are different materials. We offer one of them. For this you will need:

• metal coffee jar (50 g);
• activated carbon, which is sold in pharmacies, can be replaced with crushed carbon electrodes;
• two circles of copper plate;
• cotton wool

The first step is to prepare the electrolyte. To do this, you first need to grind activated carbon into powder. Then make a saline solution, for which you need to add 25 g of salt to 100 g of water, and mix it all well. Further, activated carbon powder is gradually added to the solution. Its quantity determines the consistency of the electrolyte, it should be as dense as putty.

After that, the finished electrolyte is applied to copper circles (on one side). Please note that the thicker the electrolyte layer, the greater the capacity of the ionistr. And one more thing, the thickness of the applied electrolyte on two circles should be the same. So, the electrodes are ready, now they need to be delimited by a material that would let through electricity, but did not miss the coal powder. For this, ordinary cotton wool is used, although there are many options here. The thickness of the cotton layer determines the diameter of the metal coffee jar, that is, this entire electrode structure should fit comfortably into it. Hence, in principle, it is necessary to select the dimensions of the electrodes themselves (copper circles).

It remains only to connect the electrodes themselves to the terminals. Everything, a do-it-yourself ionistr, and even at home, is ready. This design does not have a very large capacity - no higher than 0.3 farads, and the charging voltage is only one volt, but this is a real ionistr.

Conclusion on the topic

What else can be said in addition about this element. If we compare it, for example, with a nickel-metal hydride type battery, then the ionistr can easily hold a supply of electricity up to 10% of the battery power. In addition, the voltage drop in it occurs linearly, and not abruptly. But the level of charge of the element depends on its technological purpose.