Essential Electronic Components: Relays, Capacitors, and More

Essential Electronic Components

Relays

Relays are components used to control a high voltage current by means of a small current applied to a coil. When an electric current passes through the coil, it acts like an electromagnet and attracts a movable piece of metal that closes two contacts. If an electric current doesn't flow through the coil, the central contact stays joined to the contact on the left.

Capacitors

These are components that can store electric charge. They are made of two conductive plates separated by a non-conductive material called a dielectric. There are two kinds of capacitors: electrolytic and non-electrolytic capacitors. Electrolytic capacitors have terminals of different lengths, while non-electrolytic capacitors have terminals of the same length.

Capacitance is measured in farads.

In direct current circuits, capacitors allow the flow of electrons at the beginning, but with time the flow decreases until the capacitor is totally charged, then the current stops.

Diodes

These are made from semiconductive materials and only allow the current to flow in one direction. Actually, the current flows in the opposite direction to the one indicated by the arrow on the diode symbol.

A particular kind of diode is called an LED (Light Emitting Diode). LEDs emit light when a current flows through them.

Fixed Resistors

Fixed resistors impede the flow of electric currents. Their values are measured in Ω (ohms), and we use a color code to identify them.

Light Dependent Resistors (LDR)

The resistance of an LDR varies according to the amount of light the resistor receives. The resistance diminishes as light increases. They work as light sensors in electronic circuits, commonly together with transistors. For example, they can be used in photoelectric lighting controllers.

Thermistors

A thermistor is a resistor whose value depends on temperature. There are two types of thermistors:

• NTC (Negative Temperature Coefficient): Resistance diminishes as temperature increases.
• PTC (Positive Temperature Coefficient): Resistance increases with temperature.

Potentiometers

A potentiometer is a type of resistor whose value can be modified by a moveable piece. They are used to regulate the amount of electricity passing through a circuit in order to control luminosity, sound, or movement in different receivers. They can also work in electronic circuits together with sensors and transistors.

Transistors

These are basic elements in electronic circuits, made from semiconductive materials. They have three leads: emitter, base, and collector. They operate by a small current flowing into the base, and then a greater amount of current flows across the other terminals, activating the circuit.