Relays

Relays are an extremely common type of switching device used in electronics and in electrical work in general. There are many different types of relays and many may seem dissimilar when looked at but all act upon the same basic principle.

A relay is an electromechanical or solid-state device operated by variations in the input which, in turn, operate or control other devices connected to the output. It is through this action that they can act as switches.

Relays are used in a wide variety of applications, such as in telephone exchanges, automobile engines, computers, industrial motors and sequencing controls, and modern automation systems. Highly sophisticated relays are commonly used to protect electric power systems from power surges and blackouts as well as to regulate and control the generation and distribution of power along the transmission lines.

Relays are also used in smaller devices such as refrigerators, dishwashers, and heating and air conditioning controls. Although relays are generally associated with electrical circuitry, there are many other types, such as pneumatic and hydraulic. Input may be electrical and output mechanical, or vice-versa.

Relays using discrete solid-state components, operational amplifiers, or microprocessors can provide more sophisticated designs. Their use is increasing, particularly in applications where the relay and associated equipment are packaged together.

In its basic form, a relay is an electrical switch that allows a low power source to control a higher power source. In other words, a small current energizes the relay, which closes a gate, allowing a large current to flow through. In this example, gate and switch are synonymous.

Relays are also used in radio technology. In this area, the relay is a device that receives a signal from a low-power or distant transmitter. It then retransmits it on the same or different frequency in order to increase the broadcast area.

For example, the signal from a broadcast facility in a valley would only be available within that valley. A relay site at the top of a mountain could rebroadcast the original signal to a wider audience. This is why you often see relay towers on high places.

As you might imagine, relays are an essential part of modern electronics. Their use is widespread and this trend will only continue as more technology is discovered and made into practical devices. A study of relays is just as essential for anyone serious about entering the electronics field. An online search will provide much information on this interesting subject.