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Power LEDs from both 12v constant and ignition

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=140642
Printed Date: May 03, 2025 at 9:08 PM


Topic: Power LEDs from both 12v constant and ignition

Posted By: funky_d
Subject: Power LEDs from both 12v constant and ignition
Date Posted: January 13, 2016 at 2:09 PM

Hi everyone and thanks in advance. I've seen this topic covered in somewhat similar fashion before but have not yet seen a direct answer that was confirmed successful.

I have 4 LED strips, mounted under the dash and seats of my 2000 Civic DX. They are currently powered by a 12v ignition lead from the interior fusebox which connects to an on/off dimmer switch. The voltage is distributed to the 4 LED locations in parallel, and each LED is grounded to the chassis. Works great.

I would like to modify the circuitry so that the LEDs come on at full strength when entering the car. It's quite clear that I would need a 12v constant source and the door switches would connect to ground. I would also like to the LEDs to light at full strength regardless of the state of the on/off dimmer switch.

I'm unsure of how to do this with a single relay (or perhaps multiple ones). I've also seen mention of using a diode in each of the 2 source voltage leads with no relay at all.

For what its worth I can obtain power from either the OEM circuitry or an auxiliary fuse panel I installed in the trunk of the car. Not sure if that would be helpful in any way.

Again, many thanks for your help.

D



Replies:

Posted By: violentmouse
Date Posted: February 14, 2016 at 4:31 PM
two relays.
one triggered by the door ground that has constant hot.
The other triggered by ignition that has constant ground.
use both to send voltage to the LED's




posted_image



Posted By: violentmouse
Date Posted: February 14, 2016 at 4:33 PM
If you dont want to use the relay on the ignition side, you might be able to get away with a diode. but the reason for the second relay is to prevent the door activation from sending power back to your switched ignition circuit. (not cool when you open your doors and the stereo turns on....)




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