latched on/off output with momentary

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Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=136514
Printed Date: May 15, 2025 at 2:59 PM

Topic: latched on/off output with momentary

Posted By: jabowsi
Subject: latched on/off output with momentary
Date Posted: April 24, 2014 at 11:11 AM

Hi all,
I have wired the diagram as below and tested.
I get the latched on but the next pulse does not unlatch the relays.
What have I got wrong and how to fix it?
Is there something amiss with this diagram?
Any help appreciated.
Thanks

https://www.the12volt.com/relays/relaydiagram23.html

Replies:

Posted By: the12volt
Date Posted: April 24, 2014 at 11:47 AM

Double check that each of your relays are SPDT relays, verify placement/direction of diodes, and that your connections are solid.

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Posted By: jabowsi
Date Posted: April 24, 2014 at 12:00 PM

Hi, Thanks for the response.
I have actually used DPDT BT type 47 relays on a PCB.
Only using one side of the relay of course.
The diagram I have used is here.

https://synel.serveftp.net/photobucket/relaydiag.jpg

Posted By: the12volt
Date Posted: April 24, 2014 at 3:09 PM

I have not tested my configuration/diagram using DPDT relays, though in theory it should be exactly the same. Without having one of your relays to test, I can't say for sure what the issue may be. I'm on my phone at the moment and did not verify your diagram, but will attempt to do so when I can get on my laptop or desktop.

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Posted By: jabowsi
Date Posted: April 25, 2014 at 3:43 AM

That's great,
Thanks so much for your help on this.

Posted By: the12volt
Date Posted: April 25, 2014 at 10:18 AM

Your diagram looks fine.

Here are a couple things to test once it latches on:

Check that 87a on the first relay (far left) has 12V+ and the other relay connections on that wire do as well.

Check the operation of the fourth relay (far right). This is what kills power to the latched relay (middle left).

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