latched relay w/time delay

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=108947
Printed Date: May 10, 2025 at 7:17 AM

Topic: latched relay w/time delay

Posted By: tomtoth
Subject: latched relay w/time delay
Date Posted: November 15, 2008 at 8:36 PM

I'm looking for a Relay That will take a Negative pulse (from alarm) to energize a timed relay. But this relay Also needs to be turned off with a second negative pulse. I have tried an DEI 528T, which works great, but the timed relay function can't be turned off once started. I have seen the diagrams that use multiple relays to achieve this, but never with a timed relay. I Have in fact found a relay that does everything I need (rear defrost) but with one issue.. Its timer is set for 10min.. But I need/want 30 to 45 seconds (I got this idea from a newer volvo that could turn its parking lights on and off, but timed off @30 seconds)

Below is a picture of the relay I have found, The question is, Any idea how to or if its possible to modify this relay for a different time? Thanks, Very much !

Tom

posted_image

Replies:

Posted By: noisy crow
Date Posted: November 15, 2008 at 10:54 PM

Timer circuits usually use a RC network to determine the time delay. Large delays ususally mean largish capacitors.

There are two capcitors on the board. I would try replacing the larger electrolytic cap with a smaller one. I think it says 47microfarads on it.. so try a tenth of that (4.7 microfarads) and go from there. Just unsolder the cap and temporarily solder in a couple of wires so you easily try different values.

Mind the polarity... electrolytics are polarized. Note that smaller valued caps tend to non-electroyltic, and as such aren't usually polarized, in which case you don't need to worry about the polarity.

Posted By: tomtoth
Date Posted: November 16, 2008 at 7:40 AM

Hi,

I suspected the CAP being whats energizing the Relay Also. So I removed the Cap all to gether to see if the relay would work without it...(it shouldn't have) With cap removed the relay still seems to work the same way.. So thats when I posted here :) Perhaps the latching will still work, but without the capacitor, there is now timing delay?

tom

Posted By: dualsport
Date Posted: November 26, 2008 at 9:33 PM

The U6046B integrated timer chip used in that relay has a toggle input that can be used to turn on the relay for the preset time, and a second pulse will turn it back off.
The first pulse starts off the delay, and another one is supposed to turn it off again. If it doesn't do that, they may not have used that input for the relay.
You'll have to trace out circuit used in the relay to see how they used it, and you may be able to modify things to do what you want. Take a look at the datasheet to see what you can do.

You can change the resistor/capacitor combo to get whatever time you want, 600k ohms and 1nF should give you 37 seconds.

Posted By: dualsport
Date Posted: November 26, 2008 at 9:36 PM

Reread your question, and I see the relay does what you want in turning off again with the second pulse, so ignore what I suggested- posted_image

Just change the RC values and you should be all set then-

By the way.. the 47uF cap is NOT the timing cap, it's for power filtering. The cap you want to change is the little yellow thingie.

Double check it and trace it to pins 6 and 7 of the IC. Resistor is across the two pins, and the cap is connected to pin 6.