Using a DC voltage to drive a relay to interrupt a power supply

[ash1204]

Hi,

I am very new to Electronics, and was just hoping someone could help me with this:
I have a 24 V power supply. I wish to connect a relay to the connections that will interrupt the power supply when an external DC voltage (of 24 V as well) is supplied.
Can this sort of connection be made, and what sort of relay would I need?
Many thanks,
Ash

 

[AnalogKid]

You need a DPDT (Double Pole Double Throw) relay with a 24 Vdc coil. The relay contacts must be rated for more than 24 V, and the current rating for the contacts should be at least twice the power supply output current that is being interrupted.

Connect the power supply output to the relay armature connections, and the downstream circuit/device) that previously was connected to the supply) to the relay NO (Normally Open) contacts. Be sure to observe the supply polarities, so the + output of the supply is connected to the same contact pair as the + input of whatever is downstream.

Also, the relay should have a rectifier diode across its coil connections to reduce generated interference and help preserve the switch contacts.

Traveling today, so no schematic. Someone else probably will create one.

ak

 

[ash1204]

Many thanks for this. I will study it, give it a try, and come back here with an update

 

[Delta Prime]

Many thanks for this. I will study it, give it a try, and come back here with an update

A belated Welcome to Maker Pro!
Quick question:Are you using two separate 24 Vdc power supplies?

 

[Bluejets]

that will interrupt the power supply when an external DC voltage (of 24 V as well) is supplied.

Are you sure you want negative logic?
If so you need to consider what will happen when the mains supply goes down.

 

[ash1204]

Thank you everyone for the feedback.
Yes, I am using two 24 V dc power supplies.

Allow me to show you what I mean, and give you more context:

The video below shows something similar to what I wish to do:

 

[Delta Prime]

I think you want a magnetic door lock. When the door is closed the relay coil is energized the door being a switch that is closed connecting one of two 24 Vdc power supplies across the relay coil energizing the relays armature connection common to normally open contact connection. When the door opens it de-energizes the magnetic field surrounding relays coil which disengages the armature to the normally closed contact cutting off power to the second 24 Vdc power supply momentarily until the door closes again applying power to the coil creating the magnetic field which actuates the armature once again to its normally open contact.

Low Volt Wiring – Unit 4 – School of Lock and Electronic Security

schooloflock.com

 

[Delta Prime]

I have a better understanding because you used that video as an example you can achieve your goals with less components, 1, 24 volt power supply & a single pole double throw SPDT Normally closed common relay. The same 24 volt DC supply will be connected without having to energize the coil to make that connection and when the door opens it will supply power across the coil contacts momentarily energizing the relay and disconnecting the armatures normally closed contact to normally open just like the door. The link I supplied was just to give you more information, variations that you can implement to achieve your goals.