2.8. Basic Electronics concepts

The goal of this chapter is to provide some basic information about electronic circuits.

Types of electronic components

We can identify two types of electronic components:

  • Passive components
  • Active components

Passive components

The resistor

We can define a resistor as a two terminal passive component which implements electrical resistance as a circuit element.

Ohm's Law

The current through a resistor is in direct proportional to the voltage across the resistor’s terminals. I = U/R

Why do we need resistors?

  1. Resistors are used to limit the current.
    • Let's suppose that we have an LED which allows 10mA through it's junction and a 9V battery.
    • If the LED is connected directly to the battery , a large amount of current flows through the junction due to its low resistance. Due to the large amount of current, the junction is destroyed and we can say that we have a burned LED.
    • Applying Ohm’s Law we can calculate a resistor which should be connected between a pin and one battery terminal.
    • E.g. I = U/R; U = 9V; I = 10mA = 0.01A; ⇒ R = 9/0.01⇒ 900Ω
  2. We can also use resistors to ensure a default value inside of a circuit (E.g. pull-up or pull-down resistor)
    • If the switch is closed, the state is well defined.
    • If the switch is opened the state becomes undefined and it can fluctuate.
    • If the switch would be connected to Vcc and Ground, when the switch is closed, a short-circuit is produced.

Other types of resistors

  • potentiometer – a resistor with three pins and a wiper. Usually the wiper is connected to the middle pin. The value between the middle pin and one near it’s vicinity, depends on the wiper position.
  • photoresistor – is a resistor which is composed of a light sensitive material. When is exposed to light, the value of the resistor decreases.

Using the color code, we can easily calculate the resistor's value.

Resitor color code

The inductor - coil

The inductor is a passive component which can accumulate magnetic energy. When current is flowing through the wire, it generates a magnetic field. In order to generate a useful magnetic field, the wire is wrapped around a core. That core can be air, ferromagnetic material, etc.

Usually, coils, are used in filters and power transformers.


The capacitor

A capacitor is an electric passive component which stores energy. It’s made of two conductive armatures (metal plates) separated by a dielectric material.

The capacity is the main characteristic of capacitors.

Types of capacitors

We can divide capacitors into two main categories:

  • Polarized capacitors (also known as electrolytic capacitor)
  • Non-polarized capacitors

Most commonly used are aluminium electrolytic capacitors. The armatures are made from aluminium and are separated by a chemical compound. When voltage is applied, the chemicals form a thin insulating layer. If a reverse voltage is applied, the capacitor is destroyed.

Negative lead visible on the left side.

Active components

The diode

A diode is a two terminal active component which contains a PN junction. The diode’s most common use is to allow current flow in one way, and to block the flow in the opposite way.

Types of diode
  • Normal diode
  • Zenner diode
  • LED
  • Photodiode
  • Schottky diode
  • Tunnel diode

Usually, diodes have multiple uses:

  • Converting AC into DC
  • TV and radio tuning
  • Lighting ( LED )

Other types of active components are the transistors, but they aren't covered in this chapter.


roboticsisfun/chapter2/ch2_8_basic_electronics.txt · Last modified: 2012/12/03 06:29 by liviu.radoi