latching relay problem
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=116772
Printed Date: May 13, 2025 at 8:01 AM
Topic: latching relay problem
Posted By: eddi38
Subject: latching relay problem
Date Posted: October 07, 2009 at 7:10 AM
Hi im new here so bear with me here goes my prob,- i have a 12 vdc radio remote switch with a relay inside that only activates when i hold down the keyfob switch when i release keyfob switch it deactivates.This is not what i want, i want the 12vdc output of the remote switch to switch a relay on when i press keyfob and release keyfob it stays on ,then i press keyfob and release- it pulses again and turns the relay off. This is to be used to switch a 100W outside light on as i approach my house in the dark,then when im at front door i can turn it off again via keyfob. Can anyone help me with a relay circuit that will do what i ask? The output of the remote switch is momentary 12vdc it only outputs while button is held down. The relay needs to switch 5A ~240v.
Replies:
Posted By: KPierson
Date Posted: October 07, 2009 at 9:26 AM
It may be easier to put the light on a delay timer. Say, a 10 minute delay. Then, once you press the button the light will come on and then stay on for 10 mintues. If you need it on longer you could just push the button again. If the module you are using doesn't have latching ability and that is definately what you want, you may need to look in to finding a similiar module with programmable outputs. Otherwise, you will need some circuity between the output of the module and the relay that controls the light - like a D flip flop set up to toggle. ------------- Kevin Pierson
Posted By: ckeeler
Date Posted: October 07, 2009 at 9:27 AM
you can use this setup to accomplish what you need 
Posted By: eddi38
Date Posted: October 07, 2009 at 12:22 PM
just looked at above circuit would green and black represent + and - output from the reciever? Then 12v red and blue be replaced by 240v a/c in and out,typically using 4 identical 8A 240va/c switching relays?
Posted By: eddi38
Date Posted: October 07, 2009 at 12:33 PM
Ok my bad dont reply with abuse my error what i just said is wrong that would mean 24va/c going across a 12vdc coil,my bad:),this is used to power the main relay which switches the 240va/c ,i think please reply to confirm. Ive not used relays like this b4.
Posted By: KPierson
Date Posted: October 07, 2009 at 12:39 PM
The 12vdc output would drive your relay that controls the light. So, in addition to the relays above, you would need a relay(s) with a 12vdc coil and contacts rated to at least 240vac and 5A. In all the years I have been on this forum I have never seen anyone post that they got this relay configuration to work, so if you use it and it works be sure to post back. ------------- Kevin Pierson
Posted By: eddi38
Date Posted: October 07, 2009 at 1:25 PM
could anyone here draw this as a circuit diagram showing coil contacts and switching contacts having to refer to a little drawing of a relay then looking at this wiring picture is hard ,anyone game?
Posted By: hotwaterwizard
Date Posted: October 10, 2009 at 2:01 PM
 ------------- John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !
Posted By: eddi38
Date Posted: October 11, 2009 at 3:12 PM
Thnx for giving it a go but you have missed out a relay and 2 diodes i just looked it over and it wont work, i said it is a 12vdc pulse coming out of reciever and i want to switch 240v a/c this will not work i need this circuit to work switching a 12v dc coil which then switches a 240va/c load.please try again for me .
Posted By: hotwaterwizard
Date Posted: October 13, 2009 at 12:49 AM
 ------------- John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !
Posted By: eddi38
Date Posted: October 13, 2009 at 12:58 PM
Thnx very much, i just wanted it to switch 1 load so i remove the right hand relay just to make it easier for myself.I am looking forward to trying this out i just need to get to my local scrap yard and get some relays out of some cars and i am ready to go. If i use the small circuit board sized relays connected to a bigger one at the end of the circuit to carry the 240va/c 5A load i could make this quite compact and fit into a small box. THAT would work as well wouldnt it? i just need to get the same layout relays they are only working on a small load ,oh and i added a diode on the circuit otherwise when power was pressed on the pulse would initially go to the main relay and switch it on before it got to the 2 relays that starts it all going.It would take the pass of least resistance and fire the main relay first unless its coil was a higher resistance than the first 2, take a look and follow the pulse in thru switch on relay 1 then straight up to right thru that switch on relay 2 and out,Do you see?
So if i put a diode in the line directly to the left of relay 2 with stripe facing down towards relay 1 it will force power thru relay 3 and relay 1 thus completing circuit. Next pulse goes thru switching 30 and 87 on relay 1 powering up relay 2 which switches off 87a and 30, thus killing power on relay 3 and relay 1 and ultimately killing output to 240va/c relay.Sorry for long post but i sat and looked at this long and hard.I think im right ,just let me know what you think of my diode idea.thanks very much for your help,how are you on LM555 timer circuits :)
Posted By: hotwaterwizard
Date Posted: October 15, 2009 at 8:13 AM
With 220 volts it is common practice to switch both of the lines for a single load. That is why 2 relays. Both lines are 120v Hot to ground so you switch both, ------------- John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !
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