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How a Relay Functions

How a Relay Functions

What Is a Relay?

A relay is a switch that may turn a circuit on or off and is electrically operated. Relays may perform a variety of tasks, depending on the application. Relays can be used as amplifiers to amplify tiny currents into bigger ones or as switches to turn things on and off. They can also be utilized when a low power signal is required to control a circuit or when a single signal needs to control several circuits.

Relays come in two varieties: solid state and electromechanical. We'll be concentrating on electromechanical relays and their operation in this piece.

Simple Parts of a Relay

Armature- Is a simple metal component that is supported by a pivot or a stand. It is regarded as the relay's "moving arm." It establishes or sever the connection with the associated contacts.

Spring- Is attached to one end of the armature and, in the absence of electricity, forces the armature back into position.

Electromagnet- Consists of a metal wire around a metal core. Although the wire doesn't naturally possess magnetic properties, an electrical signal can turn it into a magnet.

Yoke- Is a tiny metal component attached to a core that, when the coil is activated, draws, and holds the armature.

Contacts- Conducting substance within the object whose physical touch initiates or terminates a circuit.

Break- Refers to how many points on a circuit a switch may use to start or stop the flow of electricity. Single breaks and double breaks are both possible in electromechanical relays. With low power devices, a single break is often employed, whereas high power devices typically require a double break.

Pole- Refers to the maximum number of circuits that a switch may accommodate for relays. A single pole contact can only conduct current in one circuit, but a double pole contact can do so in two.

Throw- relates to the quantity of unique wiring pathways. One of three connections, rather than one, can be used to connect a triple throw switch, for instance.

The Way Electromechanical Relays Work

A tiny circuit in an electromechanical relay can use an electromagnet to turn a bigger circuit on or off using contacts. Depending on how the relay is used, certain contacts have varying configurations, such as typically open relays and normally closed relays.

Contacts on a normally open (NO) relay are open when no current is flowing through them. The electromagnet will turn on once electricity is applied. The armature is drawn to the electromagnet's magnetic field when it is charged, which shuts the contacts.

When no current is flowing via a normally closed (NC) relay, contacts are closed. Unlike usually open relays, normally closed relays force the circuit to open and the current to cease flowing when they are engaged.

Different Kinds of Electromechanical Relays

General purpose relays, machine control relays, and reed relays are the three main groups of electromechanical relays that may be distinguished.

General Relay Duties

Relays with a general purpose are electromechanical switches that generally use a magnetic coil to operate. General purpose relays frequently operate at voltages including 12V, 24V, 48V, 120V, and 230V using an AC or DC current. They can also control currents between 2A and 30A. Due to their wide range of switch configurations and low cost, these relays are in high demand.

Machine Control Relays

Machine control relays work similarly to general-purpose relays in that a magnetic coil drives them. These reliable relays are frequently used to manage starters and other industrial components. Although this increases their longevity, it also makes them less cost-effective than general-purpose relays. They do, however, have an advantage over general purpose relays thanks to extra accessories and capabilities.

Reed Relays

Reed relays are made up of two reeds that an electromagnet may use to open or close. These tiny relays, which are commonly found inside electromagnetic coils, have a capacity of eight reed switches. The reeds revert to their initial open posture when the magnetic field is released. Reed relays function swiftly because the reeds are only a small distance apart from one another. A reed relay has various advantages because of its hermetic seal, which stops pollutants from passing through. This seal also makes it possible for reed relays to flip reliably.

When selecting a relay for a project, there are several factors to take into account. A relay's lifespan, working conditions, mechanical stresses, size, and the quantity and kind of contacts are all crucial considerations.

Electromechanical Relay Pros and Cons

Although electromechanical relays are useful in a range of applications, they might not always be the ideal choice because various ones call for different automation tools. We have highlighted some of the benefits and drawbacks of electromechanical relays below to assist you in deciding if they are right for you.


  • Accelerated operation and reset
  • Clearer ON/OFF
  • Simple and most trustworthy


  • Experiences the effects of aging
  • No directional features
  • Need a lot of input power to function.

Identify a Faulty Relay

Relays are thought of as dependable systems, although they are susceptible to failure. A multimeter may be used to quickly and simply identify whether you have a defective relay.

Here are some pointers for testing a relay with your multimeter:

  1. Relay the fuse box or vehicle by removing it.
  2. Identify the locations of the relay's input and output points for the circuit.
  3. Ensure that ohm is selected on your multimeter.
  4. To measure resistance, place the multimeter's leads across the pins at the entry and exit. The ideal range for the reading is 50 to 120 ohm.
  5. You may have a faulty coil winding and need to replace the relay if your multimeter reads Open or Out of Range.
  6. Connect the leads to the switch pins if the reading appears to be accurate. You ought to see an OL or Open reading.

If you need assistance in finding the drive, motor, or servo system you require, just let us know. We have access to a worldwide supply chain network and can locate exactly what you need. We also offer a wide range of other parts and components for a variety of machines and equipment, including:

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