Basic: Capacitors

Capacitors: Capacitors are passive electronic components widely used in electronic circuits, they are used in the source filter circuit, noise, signal ac circuit, oscillator circuit. etc. ...

1. The construction of a capacitor.

The construction of a capacitor consists of two parallel plates, in the middle of an insulating layer called a dielectric.
People often use paper, ceramic, mica paper impregnated with chemicals to dielectrics and capacitors are also classified with the names of the dielectric as paper, ceramic capacitors, autobiographical.

Structure composed of ceramic capacitors

2. Actual shape of the capacitor.

The shape of the ceramic capacitors.

The shape of the convergence of

3. Capacitance units and symbols of the capacitor.

* Capacity: A measure of the ability to speak on two charged plates of the capacitor, the capacitance of the capacitor depends on the polar area, quality materials dielectric and distance to keep the two plates by the formula

C = ξ. S / d

• In which C is the capacitance capacitors, the FARA unit (F)
• ξ: A dielectric constant of the insulating layer.
• d: the thickness of the insulating layer.
• S: is the area of ​​the capacitor plates.

* The unit capacitance of the capacitor : The unit is Fara (F), 1Fara are great in practice so often use smaller units like MicroFara (μF), NanoFara (nF), PicoFara (pF).

• Fara Fara μ 1 = 1,000,000 = 1,000,000,000 = 1,000,000,000,000 p F n F
• 1 μ = 1000 n Fara Fara
• 1 n = 1,000 p Fara Fara

* Symbol : Capacitor symbol is C (Capacitor)

Symbol of the capacitor on sprinciple there.

4 . The charging of the capacitor discharge.

An important property of the capacitor is charging the capacitor discharge characteristics, by the nature of this convergence is likely to lead AC.

Illustrating the nature of the load capacitor discharge.

* Capacitor recharge: As the picture above we see that, when the switch K1 is closed, current from passing through the bulb U to load capacitor, the load makes bulbs flashing, when the load capacitor is fully charged down equal to 0 so that the lamp is off.

* Capacitor discharge: When the capacitor has fully charged, if the switch K1 open, closing switch K2, the current from the anode (+) of the capacitor discharge through the lamp on the negative (-) as flashing lights, the convergence electric discharge lamps all off.

=> If the larger the capacitance capacitors flashing lights for as long or longer time to load release.

5. How to read the capacitance value of capacitor.

* As of: The value of the capacitance of the capacitor is recorded directly on the relative convergence

=> Gathering of the capacitors are polarized (-) (+) and always cylindrical.

Capacitor of capacitance is 185 μF note / 320 V

* The paper capacitors, ceramic capacitors: capacitor paper and ceramic capacitors have values ​​recorded by the symbol

Ceramic capacitor values ​​recorded by the symbol.

• Reading: For the first two digits multiplied by 10 ^{(number 3 caps)}
• For example, ceramic capacitors on the recorded image on the right 474K mean value = 47 x 10 ⁴ = 470 000p (in units of pico Get Fara) = 470 n = 0.47 μF Fara
  
  
• K or J at the end is just wrong of 5% or 10% of the capacitor.

* Do read the value of the capacitor.

How to read together washer and value ceramic capacitors. Note: The letter K is the error of convergence. 50V is the maximum voltage that capacitor tolerance.

* Paper and ceramic capacitors also have a number of other records are recorded in decimal, and take the unit is MicroFara

A record number of convergence of paper and ceramic capacitors.

6. The idea of ​​the value stated in the body voltage capacitor:

• We see that no matter how well written the capacitor voltage value after the capacitance value, this is the maximum value that the capacitor voltage withstand, the voltage of this capacitor will explode.
• When inserted into a circuit capacitor voltage is U, then it is never mounted capacitor voltage value of about 1.4 times higher than Max.
• For example, to mount capacitor circuit 12V 16V, 24V circuit 35V capacitor must be inserted. etc. ..

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7 - Classification of capacitor

7.1) of paper, ceramic capacitors, mica capacitors. (Capacitors are not polarized)
The convergence of this kind regardless of Yin and Yang and often have small capacitance 0.47 μF or less, the capacitors are often used in high frequency circuits or circuit noise.

Ceramic capacitor - the capacitor is not polarized.

7.2) of capacitors (capacitors are polarized)
capacitor is a capacitor with polarity of yin and yang, convergence of a greater value and values ​​from 0.47 μF to 4,700 μF capacitors chemical commonly used in the circuit has a frequency low number of sources or to filter, convergence of the cylinder always ..

Capacitor goods - is a yin-yang polarity.

7.3) Capacitor rotation.
Capacitor capacitor can rotate the wheel to change the capacitance value, capacitor is usually installed in the radio to the resonant frequency changes when we tune.

Rotating capacitors used in the Radio

8 - Method of test capacitors

8.1) Measure test paper capacitors and ceramic capacitors.

Paper capacitors and ceramic capacitors are often corrupted in the form of leak or short, to detect the leak or short focus, one observes the following image.

Measure the test capacitor or ceramic capacitor paper .

• In the image on the test measurements ceramic capacitors, there are three capacitors C1, C2 and C3 have equal capacitance, where C1 is a good convergence, the capacitor C2 and C3 detectors as convergence has been short.
• When measuring the capacitor C1 (Capacitor better) launched a little metal and then return to previous position. (Note the small focus too <1nF load, the needle will not release)
• When measuring capacitor C2 (Capacitor detector) shows up halfway up the scale needle and stopped to return to previous position.
• When measuring capacitor C3 (been short-Capacitor) = 0 we see the needle on Ω and not return.
• Note: When measuring the test capacitor or ceramic capacitor paper we have to clock in or x10KΩ x1KΩ scale, and to the island clockwise several times after that.

8.2) Measurement test of convergence

Convergence of detectors or rarely been short as capacitor paper, but they or damage in the form of dry (dry chemical inside the dielectric layer) to the capacitance of the capacitor is reduced, to test the convergence of, we compare magnification of the load capacitor with a good convergence with the same capacitance, the image below illustrates the convergence of these tests.

Measurement test of convergence

• To check the convergence of C2 has a value of 100μF capacitance is reduced or not, we use a new capacitor C1 also has the same capacitance and measurement comparisons.
• To clock in scale from x1Ω to x100Ω (the larger the capacitance to the lower scale)
• Measure the two together and compare the load release, when we reverse the probe measured several times.
• If two equal load capacitor discharge is also good to check capacitors, capacitor C2 at the launch loads seen less so in the capacitor C2 has been dry.
• Where the needle back up without the capacitor detector.

Note: If you check the capacitors directly on the circuit, we need to draw from an empty vessel in a leg together, then tested as above.

9 - The type of problems and applications

9.1. Capacitors connected in series.

• The capacitor in series with the equivalent capacitance C TD is calculated by the formula : 1 / C td = (1 / C1) + (1 / C2) + (1 / C3)
• Where only two capacitors connected in series, then C = Total C1.C2 / (C1 + C2)
• When connected in series, the withstand voltage of the capacitor voltage equal to the sum of the capacitors together . TD U = U1 + U2 + U3
• When the capacitor connected in series, if the focus of our attention should be paid dimensions of the capacitor, the negative before the positive capacitor must be connected to the following:

Capacitors connected in series parallel capacitor

9.2 - parallel capacitor.

• The capacitors in parallel, the equivalent capacitance is equal to the total capacitance of the capacitor combined. C = C1 + C2 + C3
• Withstand voltage of the capacitor voltage was roughly equal with the low voltage capacitors.
• If the convergence of the capacitors must be connected in the same direction and yang.

9.3 - Application of the capacitor.

Capacitors are used in many electrical and electronic engineering, in electronics, the capacitor is an indispensable components, each circuit has a certain utility as signal transmission, interference filters, power filters, oscillators etc. .. ...

Here are some pictures illustrating the application of capacitors.

* Source filter capacitor in the circuit.

Capacitor filter circuit of the source.

• In the filter circuit shown above sources, together with the effect of filtering the DC voltage after rectification is flat to provide load consumption, we can see if there is no convergence, the DC voltage after the diode voltage is undulating, when the filter capacitor voltage is relatively flat, the larger the capacitor DC voltage is more flat.

* Capacitors in the oscillator to two square pulse.

Multi-body oscillator circuit using two transistors

• You can mount on the circuit with the parameters given in the diagram.
• Two bright lights use LEDs in parallel with the positive sign of the two transistors CE, attention and yang, right way.