pulsed relay continuous on

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=112585
Printed Date: July 22, 2025 at 12:24 AM

Topic: pulsed relay continuous on

Posted By: rfhelp
Subject: pulsed relay continuous on
Date Posted: March 23, 2009 at 2:01 AM

I am wanting to drive a 12v circuit with an rfid unit. I want the circuit to stay energized once the fob has energized the circuit and then is moved away. With a single relay when I remove the fob the rfid module closes and power shuts off.

I heard of a dude doing this with two diff relays and an on off switch connected to the rfid module. sorry guys I am electronically impedant so any reply will need to be structured for simplicity.

thanks.

Replies:

Posted By: ckeeler
Date Posted: March 23, 2009 at 4:26 PM

at the top of the page in the "relay" section, there is a diagram for a "momentary to constant" setup.

Posted By: rfhelp
Date Posted: March 23, 2009 at 4:55 PM

thanks for the quick reply. I found the diagram thank you. Can you explain to me HOW the second relay stays active when the first one shuts down? I understand if you don't. I like to know how stuff works and I am new to electronics.

I am trying to make this happen between a 5a mini pcb 6 connector relay (don't know the configuration of the connectors on it)

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and a standard automotive relay as diagramed in the section you pointed me to. I am told I need the pc relays lower power because the auto relays can burn out the circuit board over time. I am using a 1N4007 diode as well for spike protection.

Posted By: ckeeler
Date Posted: March 23, 2009 at 5:12 PM

notice the second relay on the right in the diagram has pin 85 connected to 87 also? once the second relay is activated, the12v that is on pin 87 via pin 30 keeps feeding pin 85 which in turn keeps the coil energized and the relay on until a strong jolt to the outter case knocks the internal contacts loose or either power is removed from pin 30 or the ground is removed from pin 86 resetting it.

Posted By: rfhelp
Date Posted: March 23, 2009 at 6:13 PM

does this work?

right now I have the neg output to 85 from the rfid and the pos to 85.

[img]https://www.robwilton.com/rfid/mco.gif[/img]

Posted By: rfhelp
Date Posted: March 23, 2009 at 6:28 PM

OOOOHhhhh Maaann!!!!

I will be happy when I get edit status...I think we all will

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Posted By: the12volt
Date Posted: March 23, 2009 at 6:45 PM

Note: Rookie members can not edit or delete their posts. Standard members may edit their posts if it is the last in the thread, and upload images. Silver and Gold members may upload file attachments to posts as well as delete their posts. Platinum members may create polls (more info).

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Posted By: rfhelp
Date Posted: March 23, 2009 at 11:06 PM

Would this work?

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Posted By: rfhelp
Date Posted: March 23, 2009 at 11:08 PM

I guess I forgot to put in how I was going to shut it off?

Posted By: dualsport
Date Posted: March 24, 2009 at 12:55 AM

Once it's latched on, it'll remain on until you actually remove power from the fused +12V.

How were you planning to turn it off? A second pulse from your RFID circuit? you'd need an impulse relay or an electronic circuit to toggle the outputs with a single pulsed input line.