Capacitors - juxtapix/IMA_E4I GitHub Wiki

Intro to Capacitors:

Capacitors are a fundamental part of many electrical circuits because they have the ability to store electric charge. They are like a small charged electric battery. A very simple capacitor can be made from two conductive plates sandwiched with an insulating layer, aka a dielectric.

There are many types of capacitor but they can be categorized in two groups: polarized and non-polarized. They are both represented by a different circuit symbol.

There's a wide range of applications for capacitors in a circuit. The most common applications for capacitors include smoothing power supplies, signal filtering and timing circuits.

Polarised capacitors

Polarized capacitors have a positive(+) and negative(-) leads and must be connected in the right way. The negative side is usually marked on the body of the capacitor.

The most common types of polarized capacitors are electrolytic and tantalum.

Non-Polarised capacitors

Unpolarized capacitors are usually small in value, generally less than 1µF. They can be connected in any direction.

Identifying Capacitors

  • Symbols
  • Types
  • Values
  • Codes
  • Voltage rating

Capacitors in Series and Parallel

Capacitors in Series

Total capacitance calculation for capacitors is the opposite from the resistor calculation. For N capacitors in series, the total capacitance is the inverse of the sum of all inverse capacitances.

C(total) = 1/C1 + 1/C2 + 1/C3 ...

Capacitors in Parallel

The total capacitance of multiple capacitors connected in parallel is calculated as the sum of all the capacitance combined.

C(total) = C1 + C2 + C3 ...

Substituting capacitors

Substituting
It is generally okay to substitute a capacitor of a close value for a specific value. Just be sure to choose a substitute capacitor that is rated at the expected maximum voltage.

Precautions
When choosing a capacitor for your circuit, make sure to choose one that exceeds the required voltage rating. If the circuit voltage is above the rating, the capacitor may be fried by the stored charge. The voltage rating is usually noted on the capacitor.

Safety

Capacitors are able to store a charge for a very long time, even after their power supply has been cut off. A large charged capacitor can be very dangerous since they discharge at a very fast speed. For example, high voltage capacitors inside old TV units and photo flashers can store a charge forceful enough to throw you across the room and can sometimes be lethal. Be careful to NEVER touch the leads of such a capacitor.

RC Time Constant

2.23.8 RC Time Constant

Charging a Capacitor
When connected to a power source, the capacitor is charged immediately. To slow down the charging time, a resistor can be placed between the capacitor and the power source because it can limit the current flow into the capacitor.

Discharging a Capacitor
Similarly, capacitors can discharge immediately when the leads are connected. To slow down the rate of discharge, connect a resistor across it to limit the flow of electrons.

Capacitor circuits (examples)

  • Decoupling (Bypass) Capacitors
  • Power Supply Filtering (Power Conditioning)
  • Energy Storage and Supply
  • Signal Filtering (High-pass and low-pass filters)

References:

https://electronicsclub.info/capacitors.htm
https://learn.sparkfun.com/tutorials/capacitors