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wiring relay latch/switch

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=95432
Printed Date: May 08, 2025 at 8:05 PM


Topic: wiring relay latch/switch

Posted By: nick88
Subject: wiring relay latch/switch
Date Posted: July 08, 2007 at 4:16 AM

Hey guys, got a bit of a problem and after some help, now i have a bit of electronic knowledge but not heaps...anyway, today i had a go at making a latch circuit with two relays so that i can still have my radio on with the ign key off but when i open the drivers door, it switches off...exactly like the VZ commodores do.
I found a tut thing on a website (Special Applications with SPDT Relays) and it does work, just the opposite way to what i need, lol....so when the door is closed the radio goes off but with the door open and i turn the key to off the radio stays on! posted_image

I had a bit of a muck around with the wiring and adding another relay to the circuit to try and make the circuit open when door is open and circuit closed when door is closed, but as it is with just the two relays is the other way(circuit open when door closed circuit closed when door open)

Can anyone please help me with this and tell me how to re-wire it or wire in the 3rd relay to make it work?
Thankz
Nick



Replies:

Posted By: hotwaterwizard
Date Posted: July 09, 2007 at 11:12 PM

Okay Show me what you did?

Is the door switch used for anything else?

Is this door switch open when the door is closed or closed when the door is closed?



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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: hotwaterwizard
Date Posted: July 09, 2007 at 11:28 PM

Exactly how would you like it to work?

1) Turn the key on and the relay latches

2) Turn the key off and nothing happens

3) Open the door and off it goes.

4) No power drawn from the circuit when in the off position.



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: hotwaterwizard
Date Posted: July 09, 2007 at 11:38 PM

What is wrong with the diagram you linked to?

posted_image



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: hotwaterwizard
Date Posted: July 10, 2007 at 12:01 AM

Something is wrong with this circuit.

posted_image



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 10, 2007 at 2:23 AM

Hey,  yes the door switch is used for the interior lighting,  the door switch grounds when the door is open to turn the lights on and is disconnected from ground when the door is closed to turn the lights off...

How i want it to work is when i turn the key to off(with the door closed) is stays on but as soon as i open the door it turns it off,  so kind of reversing the switch but only for the door trigger wire not the interior lighting wire

and i cant see whats wrong with the circuit(not that i know what im looking for....lol)

Thankz

Nick




Posted By: hotwaterwizard
Date Posted: July 10, 2007 at 9:46 PM

Nick, I drew this one for you.

The first relay is inactive until the second one is latched. The key switch signal latches it on. The diode stops the voltage from going back into the key switch circuit. Almost any Diode will work.

When the Relay latches it gets power from the hot wire. Voltage goes thru the first relay 87a to 30 then to the coil of the second relay. When the key is off the first relay still has a hot on pin 85 but nothing happens because the door switch provides the ground for the other side of the coil.

When the door is opened it will give relay 1 a ground and unlatch the second relay and drop the power to it's self as well. No power goes to it untill the key is back on.

posted_image



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 11, 2007 at 3:38 AM

Awsome,  thankz for your help hotwaterwizard...

so that new diag u drew me is how i should set it up yea? i dont have to do anything with the door switch to reverse the switch?

Also,,  is the diode the lil triangle thingy with a line? what diode should i get? i do really need it?

Nick




Posted By: nick88
Date Posted: July 11, 2007 at 8:33 AM

ok, just tried it then...and didnt work:(....although i didnt put the diode thingy in, does that matter? or should it still work?

it was doin the exact same thing as before, turns off with the door closed but stays on with the door open....damn thing!

Nick




Posted By: hotwaterwizard
Date Posted: July 11, 2007 at 8:38 AM

You can try it without the Diode but I would put one in  myself.

posted_image



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 11, 2007 at 8:39 AM

is there a way i can reverse the switch just for that wire and not have it afftect the rest of the interior lighting? like with another SPDT relay or sumthin?




Posted By: hotwaterwizard
Date Posted: July 11, 2007 at 8:44 AM

Put a diode on the wire to the pin switch backwards of the one in there. The light is probably affecting the relay.

posted_image



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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: hotwaterwizard
Date Posted: July 11, 2007 at 8:48 AM

Work it out step by step. on the bench with a light bulb. Then install it in the car. Use a wire to simulate the pin switch.

First make the latch then make the latch breaking circuit.

posted_image



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 11, 2007 at 8:50 AM

alright,  ill go buy some diodes tomorrow, any one in particular and how do i know which way to install them? hopefully this works...didnt think itd be so hard! lol

Nick




Posted By: hotwaterwizard
Date Posted: July 11, 2007 at 8:50 AM

Gotta go to work now. Will check back later to see how it went.

Post the results for me please.

Or I won't sleep good tonight. LOL



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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: hotwaterwizard
Date Posted: July 11, 2007 at 8:52 AM

posted_image 

1N4001 1N4002 Or equivelent

1 amp to 3 amp rating at 50v or so should be fine



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 12, 2007 at 10:45 PM

ok,  just tried it then with some diodes...and guess what...........STILL DIDNT WORK! lol,  damn thing

what other wiring options could we try?

Nick




Posted By: hotwaterwizard
Date Posted: July 13, 2007 at 12:17 AM

Your switch is not what it apears to be.

Try it on the bench.

Do you have a test light? Hook one side to the switch output and the other to a hot and see if it lights up when the door opens.

Take a picture of your hook-up and post it or email it to me. We will figure this out.

I will build the circuit on the bench to verify the wiring diagram I sent.



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 13, 2007 at 10:53 PM

YAY finally got it to work!  and even works with the original diag i linked to in the first post!

if you lived in Aus ud prolly kill me now,  the reason it wasnt working is cause i didnt have the right relays! lol,  such an idiot i am,  i just grabbed the first 5 pin relay i saw and thought it was the one,  but it wasnt cause i realised that the 87 pins are both connected to each other and when the relay comes active, pin 30 and the two 87's have continuity....so i went back to autobarn n had a look at the others and sure enough they had some with an 87 and 87a terminals SEPERATE from each other!....man i fell stupid, lol

Thankz for all your help anyway hotwaterwizard, ur a champ

Nick




Posted By: hotwaterwizard
Date Posted: July 13, 2007 at 10:59 PM

LOL 

You got me rolling around on the ground laughing.

OOPS I gotta Go to the restroom.



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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !



Posted By: nick88
Date Posted: July 13, 2007 at 11:49 PM
lol,  thought u might say sumthin like that....haha i feel soooo stupid:P



Posted By: hotwaterwizard
Date Posted: July 15, 2007 at 1:10 PM

No disrespect Intended. The funny part was how you told the story.

I can relate because I have ben there and did the same type of things.



-------------
John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !


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