Non-Latching Relays

What Are Non-Latching Relays?

Relays are switches that are operated by electrical impulses. Latching and non-latching relays, the two major types, have this in common, but have differences that make them appropriate for different applications.

If a non-latching relay is a normally closed position, when the relay is depowered, the relay will remain in this NC state, usually with a mechanical or magnetic apparatus keeping the parts in place. When the circuit is powered up, the relay switches to a NO state. This is accomplished with a coil, which generates a magnetic field that keeps the parts in the NO position. After the power is removed from the component, it will go back to its NC state. A normally open latching will function in just the opposite fashion.

These relays need to be installing in circuits with consideration given to the amount of voltage required to make them switch, the amount of power and current they can handle and other safety concerns. If they have too much voltage going through them, for instance, the electricity may arc across the contact, essentially achieving the same end as closing the contacts, at least momentarily and potentially damaging the circuit.

Non-latching relays are mechanical types of relays. The way they are constructed makes them exceptionally durable and they are entirely capable of lasting for the whole lifecycle of much of the machinery on which they are typically installed.


Which Parts Are Inside a Non-Latching Relay?

Relays are switches. They are electrically operating but, at their cores, they are switches and the language of switches can be used to describe both their parts and how those parts function within the device.

The relay has a moveable part called an armature. This armature rests on contacts that allow the current to flow through the switch. The movement is powered by a coil, which produces a magnetic force that holds the relay in a given position. A spring keeps the contacts in the normal position when the device is depowered.

The basic parts that any electromechanical relay will have are the coil, the spring, the armature and the contacts. A yoke connects the switch to the circuit.


How Does a Non-Latching Relay Function?

When current flows through the device, the coil generates magnetic forces that move the armature. The contacts then move, either opening up the circuit or closing it. The armature will remain in this position as long as current remains flowing through the component. When the current is removed, a spring pushes the armature and contacts into the opposite configuration. In a non-latching relay, this predicably moves the relay back to its initial state.

These simple, electromechanical devices have been in use since the early days of telegraphs. Today’s designs are generally housed in a plastic housing. In some cases, this is clear, permitting one to watch the relay in operation as current is added and removed from the circuit.


How Is a Non-Latching Relay Different from a Latching Relay?

A latching relay stays where it was when the circuit was last powered. If it was in an NO position while there was power flowing, it will stay in that position if the power is removed from the circuit. If it was in an NC position, it will retain that state if the power is removed from the circuit. These devices can have one or two coils in them.

A non-latching relay, by contrast, goes back to its normal position when the power is removed from the circuit. This small difference means a lot in terms of the applications that this device is suitable for. Notably, these relays automatically return to a known state if the power is removed from the circuit. This is useful if, when a piece of equipment is powered down, it’s necessary to know the state of some of the relays on the apparatus before it is powered up again.

Outwardly, these devices quite often look very similar. They are usually designed with either plug in or PCB mountings on them and there are many different variables that dictate which one is right for any given task.


Who Manufactures Non-Latching Relays?

Non-latching relays are very commonly used components and, as such, they are available from many different manufacturers. Some of these companies specialize in components for certain industries—aerospace, for example—and others produce an enormous range of products, or may even work in industries aside from the electronics components industry, as well.



Altech is an automation and control component producer that has non-latching relays among


American Zettler

This company specializes in relays, manufacturing them for a variety of different industries and applications.



This company has been in business since 1921 and is very much associated with sensors. They have non-latching relays among their offerings.



An electronics manufacturer with a wide range of monitoring and control products that manufactures non-latching relays.



Manufactures circuit protection devices and products for the aerospace industry, their lines includes non-latching relays.



Finder has a wide range of relays and other control components available on the market.



Fujitsu is a global brand that manufactures a variety of different products, including controllers, microcontrollers, relays and may other types of components.



Honeywell is associated with the aerospace industry as much as they are with consumer level devices. They manufacture relays of various types.



This company manufactures circuit breakers, pilot devices and a variety of different types of relays.



This company is a large manufacturer of controls components for industrial use.



This company makes many types of relays, including non-latching types.


NTE Electronics

This semiconductor manufacturer makes switches and other components for industrial purposes.



Omron is a Japanese company that has been business since the 1930s. The company makes a variety of different electronic components.


Opto 22

This company specializes in industrial electronics, with control and monitoring components and non-latching relays being available from them.



An exceptionally large company based in Japan, this manufacturer products electronic components, but also a huge range of consumer goods, technology and beyond.


Phoenix Contact

This company specializes in automation technology, including offering many different types of relays.



This company specializes in relays and offers an impressive amount of options among its products.



RS is a major distributor of electronic components for the industrial, scientific and manufacturing world, as well as for consumer level components. It is a UK based company that spans the globe and that has been in business since the late 1930s.


Schneider Electric

This company emphasizes energy as one of its focuses, and provides a range of automation equipment and components.


SE Relays Magnecraft

This is a division of Schneider Electronic that produces relay as a specialty.



Siemens is a very large corporation that produces well for a variety of different industries. They are headquartered in Germany and have been in business since the mid-1800s.


Song Chuan

Song Chuan produces relays for the automotive industry and other industries, including many specialized designs.


TE Connectivity

This components manufacturer provides products for the aerospace industry, the telecommunications industry and more. They make many different types of electronic components.



This is a global company that is headquartered in the US. They produce many components that are aimed at the aerospace industry and the defence industry.



This manufacturer makes products that are used in automation and other industrial applications. They have non-latching relays and other types among their line.



This company, as their name suggest, is associated with timekeeping devices, though they also manufacture control products.



Wieland is a growing international company that produces electrical components for several different industries.


What Is the Contact Configuration of a Non-Latching Relay?

The contract configuration of a non-latching relay describes the switch at its core. They are described in familiar terms such as 3-pole double throw (3PDT), Normally Open vs. Normally Closed and so forth. This is the depowered state of the relay.


What Is Considered the Coil Voltage of a Non-Latching Relay?

The coil voltage describes the voltage required to actuate the magnetically-operated switching mechanism in the relay. The magnet is magnetized by the current, producing a force that is stronger than the spring—or, in some cases, the other magnet—that holds the relay in its normal position.

The coil voltage is one of the basic specifications that are given for relays. It has to be matched to the circuit in which the device is going to be used. The two consequences of using a voltage that is too high or low are the device being damaged or not having enough power to open, respectively.


What Is the Coil Resistance of a Non-Latching Relay?

This describes the amount of resistance, in ohms, that the coil introduces into the circuit.


What Is the Maximum Switching...

There are several specifications that are prefaced maximum switching. Their meanings are straightforward enough, but matching these to the circuit being build or repaired is imperative to ensure reliable function and that no damage comes to the component.


Current AC

This is the maximum amount of current—amps—that can flow across the relay with the relay still functioning as designed. The relay can be opened or closed as long as it is operated within this limit.


Current DC

This is amount of DC current that can flow through the device while ensuring that it functions as designed. Exceeding this amount may damage the component.


Voltage AC

This is the highest voltage in AC power that the relay can operate at. Exceeding this limit may result in electricity arcing across open contacts, unintentionally closing the circuit.


Voltage DC

This is the same as maximum voltage AC but for DC circuits. The same arcing issues can occur if this figure is exceeded during the operation of the circuit.


Power AC

This is the maximum amount of power that the relay can handle safely. Exceeding it may result in damage to the component.


Power DC

This is the maximum wattage that the component can handle in a DC circuit. It is measured in watts.


What Is Considered the Coil Power of a Non-Latching Relay?

This is the amount of power that the coil in the relay is designed to operate at, measured in watts. It has to be matched to the circuit to ensure that the device functions properly.


Which Applications Require Non-Latching relays?

Non-latching relays are used for a variety of automotive purposes. They are also used in telecommunications applications.

Some of these relays are specialised for use in applications that require high currents or voltages. They are useful in any instance where the switch needs to return to a predictable position when a circuit is depowered. This makes them ideal for safety and signalling uses, as well as their many other applications.

Non-latching relays are integral enough to modern electronics that they are used in the most advanced applications, as well. They are used in the aerospace industry to build sophisticated systems and beyond. They are really only one type of relay and relays in general are enormously useful and versatile components.


What Is Used as Contact Material for Non-Latching relays?

Non-latching relays have contacts made out of a variety of different materials. Gold is popularly used, as are other precious metals, including palladium. Silver, nickel, tin oxide, ruthenium and other materials are used, as well. The materials are often alloyed to gain specific properties.

Tungsten is used in the contacts, in some cases. Silver tin oxide is particularly popular, as are silver nickel contacts.


What Is Considered as Isolation Coil to Contact?

A relay needs to have two circuits passing through it. The contacts complete the circuit to which the relay is attached. The second circuit is that which controls the coil itself. They may require different voltages, currents or even types of power to function. This requires that the relay have a coil that is isolated from the contact. This figure shows the safe levels where this can be assured.


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