General Purpose Relays

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OMRON provides General-purpose Relays, I/O Relays, Power Relays, Latching Relays, and Ratchet Relays.

What is a relay?

A Relay is a device that opens and closes a switch in response to an input signal (voltage or current) applied to a coil.

Applications for Relays

Relays are widely used in most machines and devices that use electricity.

Types of relays

There are mainly two types of relays: mechanical relays and solid state relays.
Omron calls mechanical relays “General-purpose Relays.”

These are various types of mechanical relays (General-Purpose Relays)

Hinged Relays

Hinged relays employ a common structure where the electromagnet’s armature rotates around a fulcrum, enabling it to directly or indirectly control contact opening and closing. Omron categorizes relays with contacts, known as General-purpose Relays, based on their applications, as indicated in the following table.

Structure and Operating Principles

General-purpose Relays transfer signals through a mechanical action.
A hinge relay is shown below as an example.
Hinged relays switch contacts by the rotating movement of an armature around a fulcrum

Example: NO contacts (make contacts)

Application Examples:

Latching Relays (Also Called Bistable Relays or Keep Relays)
Magnetic Latching Relays: Two-coil Latching Relays

Relaxed State (after Reset)

Battery not connected to the coil

The diagram depicts the relay in its relaxed state. These relays resemble the hinged relays discussed earlier, with the key difference being that they utilize semi-hard magnetic material for the core, yoke, and armature, and they feature a minimum of two coils.

Operating State (set)

When current passes through coil A, it magnetizes the electromagnet, composed of semi-hard material, causing the armature to be drawn towards the core. Consequently, the moving contact shifts away from the normally closed (NC) contact, turning it OFF, and establishes contact with the normally open (NO) contact, turning it ON.

In the set state, residual magnetic flux in the semi-hard magnetic material, which resembles the properties of a permanent magnet, maintains the armature’s attraction to the core, even when current is no longer flowing through coil A.

Release State (Reset) – Relaxed State

If a current is introduced to coil B, wound in the opposite direction of coil A, it diminishes the residual magnetic flux in the semi-hard magnetic material, weakening the magnetic attraction. The release spring’s force will then surpass the magnetic attraction, causing the armature to release, returning the relay to its relaxed state. When the armature is released, there will be minimal residual magnetic flux in the semi-hard magnetic material.

Note: semi-hard magnetic material differs from the hard magnetic material used in permanent magnets, requiring less energy for magnetization and demagnetization.