Relays: Single Throw vs Double Throw

Relays: https://www.rspsupply.com/c-1620-rela...

Today we want to talk in a little more about relays. Specifically, about NO contacts and NC contacts. Why does it matter and how does it affect the type of relay we might need.

All relays have a set of contacts, these contacts allow electricity to pass through them when they are in the closed position (or when they are touching each other)

Depending on the function we need in a relay, we can use a NO contact or a normally closed contact.

o Normally Open Contacts

The contacts will not be touching each other in it’s normal state (that is when the coil is not acting on the contact)

When the coil is energized, the normally open contact will be pulled against the other stationary contact into a closed state

At this point, electricity will be able to pass through the contacts.

A relay that is normally open is providing power when the coil is energized.

Lets look at how this works

o Normally closed contacts

The contacts WILL be touching each other in the relay’s normal state (when the coil is not acting on the contacts)

When the coil is energized, the contact will be pull away from the other stationary contact, thus opening the circuit.

At this point electricity that was previously flowing when the contacts were closed, will no longer be flowing when the coil is energized.

It is important to note that the contact side of a normally closed relay will be energized. So at any given point either the coil side or contact side will have power to it.

Let me show you how this works

o Double Throw Relay

There are also relays that give us both options in the same relay. This is called a double throw relay

What is important to not about a double throw relay is that we have the ability to control two different circuits with the same relay.

So a double throw relay will let us wire one circuit to the normally open side, and another circuit to the normally closed side.

When the coil is energized the normally closed contact will open and the normally open side will close.

They both use the same power, or common.

o Let’s take a look at a few examples to better demonstrate how this works.

Get the FULL video transcript here: https://www.rspsupply.com/education/a...
Want to see similar products to those featured in this video: https://www.rspsupply.com/c-1620-rela...
Check out our full line of Industrial Hardware on our website: rspsupply.com

Additional Links -

Website:
https://rspsupply.com/
Engineering Page:
https://rspsupply.com/engineering/
Panel Fabrication Page:
https://rspsupply.com/panel-fabrication/
Procurement Services Page:
https://rspsupply.com/procurement-ser...
Manufacturers Page:
https://rspsupply.com/manufacturers.aspx
Relays & Timers:
https://rspsupply.com/c-1620-relays-t...
PLCs & IO:
https://rspsupply.com/c-3872-plcs-io....
Panel Hardware:
https://rspsupply.com/c-34-panel-hard...
Enclosures:
https://rspsupply.com/c-1618-enclosur...
Tools & Supplies:
https://rspsupply.com/c-7684-tools-su...