led triggered by dome light and on/off/on
Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=115480
Printed Date: June 06, 2024 at 9:42 AM
Topic: led triggered by dome light and on/off/on
Posted By: jewster
Subject: led triggered by dome light and on/off/on
Date Posted: August 05, 2009 at 1:50 PM
Here is what i want to do:
2008 Nissan Pathfinder:
Switch Position 1(ON): LEDs to come on with dome lights.
Switch Position 2(OFF): LEDs OFF
Switch Position 3(ON): LEDs to come on regardless of dome lights.
Note: The dome trigger is (-) and my switch has its own led that I would like to stay illuminated at all times(unless ign is off ofc)
Thanks for the help cause I am lost. I have tried searching around, but I really never found a concise answer to this.
Replies:
Posted By: t&t tech
Date Posted: August 05, 2009 at 8:09 PM
you would need a relay, a toggle on/off switch and two one amp diodes, do it lke this the relay- pin 30 and 86-to twelve volts permanent fused at ten amps pin 87 to the positive leads of the leds pin 85 - diode the output of the dome light an the toggle switch into this pin (bands facing away from relay) the other side off the toggle switch is grounded along with the negative leads of the legs
Posted By: jewster
Date Posted: August 07, 2009 at 12:15 PM
awesome thanks...that makes sense now
Posted By: jewster
Date Posted: December 14, 2009 at 4:35 PM
Okay its been a while since I posted this thread, but I just got a bunch of stuff to start this out and I actually needed the info for an on/off/on switch since i would like to be able to not have the leds come on at all. Any help with that?
Posted By: jewster
Date Posted: December 14, 2009 at 5:12 PM
Would it just be the same except wire the off position to acc+ to illuminate the switch?
Posted By: t&t tech
Date Posted: December 14, 2009 at 8:04 PM
You want it so that the led on the toggle switch is off! Assuming here that the led is powering from a twelve volt permanent source, then yes just eliminate this connection and connect this to an ignition or acc wire!
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COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF.
PSALMS 37:5
Posted By: jewster
Date Posted: December 14, 2009 at 10:39 PM
Okay, please bear with me, and my mspaint skills. (what software do you guys use to create diagrams?) How does this look? Will this accomplish what I am after?
Thanks again.
Posted By: jewster
Date Posted: December 14, 2009 at 10:44 PM
Also. Why would I not want the switch led to be illuminated when in the off position? Oh and my leds already have resistors.
Posted By: oldspark
Date Posted: December 15, 2009 at 12:51 AM
The complexity is the illuminated switch unless its lamp can be separated to the switch contacts (ie, it is merely connected between IGN & ground).
The circuit otherwise is almost in parallel to the dome lights.
EG - same "always hot" power to LED+. The switch connects LED- to dome trigger - ie ground via door switches (Pos #1 - on with domes), Pos #2 is open (NC); Pos #3 to ground.
Posted By: jewster
Date Posted: December 15, 2009 at 10:06 AM
Okay, my diagram is good then. I should just omit the acc+ connection for pos#2 and not worry about the illuminated switch?
Posted By: KPierson
Date Posted: December 15, 2009 at 11:27 AM
In your drawing the LED would always come on with the dome light - there is no "off" position.
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Kevin Pierson
Posted By: jewster
Date Posted: December 15, 2009 at 11:31 AM
KPierson wrote:
In your drawing the LED would always come on with the dome light - there is no "off" position.
So I should leave the middle pins of the switch not connected instead of acc+?
Posted By: jewster
Date Posted: December 15, 2009 at 11:34 AM
Like this?
Posted By: oldspark
Date Posted: December 16, 2009 at 2:53 AM
I was thinking something like below with your switch illumination connected however you like.
Posted By: jewster
Date Posted: December 16, 2009 at 11:15 AM
That would work if you could get between the dome light and dome light switch, but you cannot.
Since the dome light trigger is (-), i will be using this:
Posted By: KPierson
Date Posted: December 16, 2009 at 12:21 PM
If you supply 12vdc directly to the LEDs and run a ground through the switch you can eliminate the relay (like oldspark showed).
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Kevin Pierson
Posted By: jewster
Date Posted: December 16, 2009 at 12:47 PM
KPierson wrote:
If you supply 12vdc directly to the LEDs and run a ground through the switch you can eliminate the relay (like oldspark showed).
Except there isn't enough space between dome light switch and dome light to add a circuit. Even if there was, I would have to dig through the ceiling and feed wire. Simpler to tap the dome light trigger from the BCM at the driver's feet and use a relay in my opinion. I do appreciate the help though.
Posted By: KPierson
Date Posted: December 16, 2009 at 2:55 PM
You would still use the (-) dome light wire at the BCM, you just wouldn't need a relay: 
------------- Kevin Pierson
Posted By: oldspark
Date Posted: December 16, 2009 at 5:46 PM
jewster wrote:
That would work if you could get between the dome light and dome light switch, but you cannot
I assumed you could since you specified " Switch Position 1(ON): LEDs to come on with dome lights" (without using current or voltage sensing techniques). (Else how would you have done it? Or should I review that relay version?)
So Position #1 becomes "on with dome (door etc) triggers" instead of "on with dome light".
Just move the LED/3-way section down so Pos #1 joins BELOW the dome selector switch (above any door <whatever> trigger).
IE - connect Pos #1 to what you called "Dome light (-)" in your diagram.
It is still the same solution - no relay is needed. (Unless your LEDs/load draws several Amps.)
Posted By: jewster
Date Posted: December 17, 2009 at 11:13 AM
KPierson wrote:
You would still use the (-) dome light wire at the BCM, you just wouldn't need a relay:
ha! Wow that was easy. Dang. Why is the fuse on the other side of the battery though?
Posted By: jewster
Date Posted: December 17, 2009 at 11:28 AM
Although that circuit is simpler for omitting the relay, I think I will go with the relay instead. This is becuase I will likely add LEDs to this circuit, but in other locations and having the power source and dome light trigger junctioned for additional circuits would be more convenient than running more wire all over the place.
Is there any real drawback to using a relay here?
Posted By: KPierson
Date Posted: December 17, 2009 at 3:23 PM
Sorry about the fuse being in the wrong place, I just copy and pasted your diagram and hacked it up a bit. There isn't a drawback, we just like to keep things simple and not use parts if they are not necesarry. ------------- Kevin Pierson
Posted By: jewster
Date Posted: December 17, 2009 at 3:30 PM
Okay, that is what I thought. Thanks very much again for the help.
Posted By: petertfm
Date Posted: January 24, 2010 at 12:46 PM
Hi I am new here but I was searching for this exact solution.
I have wired my 2002 sunfire just like the diagram from jewster made
without the switch, but the problem is when the dome light dims at the end my relay buzzes.
my question is"is there a transistor or something I can put in the circuit to fix this?"
maybe a transistor connected to dome light ground that can trigger the relay
that transistor would have to be able to work under low voltage and up to 12 or 14 volts
any help would be greatly appreciated.
Posted By: oldspark
Date Posted: January 24, 2010 at 7:48 PM
Exactly.
If they are LEDs, do not use the relay - it is not needed.
Otherwise you could use a transistor with a current capability sufficient for the load (lights). In this case it would be a PNP. A FET may also be suitable - especially for dimming.
The circuit depends on whether full brightness or dimming.
Posted By: petertfm
Date Posted: January 25, 2010 at 6:59 PM
I found a solution to the relay buzzing
https://www.the12volt.com/installbay/forum_posts.asp~TID~114184~get~last#585248
I just didn't want to run any thing extra on the circuit for the dome light. and I also plan on adding more to the circuit for my leds
Posted By: oldspark
Date Posted: January 25, 2010 at 7:14 PM
But that might blow the dimming circuit (if it can't handle the cap current).
Besides, why the heck use a relay if it is for LEDs?
Posted By: 97accord
Date Posted: April 17, 2010 at 8:00 PM
does anyone know what does the dot's mean
that kpierson draw
Posted By: KPierson
Date Posted: April 17, 2010 at 8:16 PM
What dots?
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Kevin Pierson
Posted By: oldspark
Date Posted: April 17, 2010 at 10:01 PM
The only dots I see are the symbolic contacts - ie, switch contacts.
Also, if the wiring is done similar to my fig on the last page (ie, LEDs or relay powered by separate +12V - not what the dome-bulb sees (since it is being dimmed), then no dimming or chattering should occur.
But if the only +12V accessable is the dome light bulb's power, then you need some sort of hysteresis to stop relay chatter - eg, an RC circuit, Schmidt trigger or other buffer circuit; maybe a timer.
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