Interior Light Delay Shut-off

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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=77056
Printed Date: May 18, 2024 at 9:14 AM

Topic: Interior Light Delay Shut-off

Posted By: jeepicon1022
Subject: Interior Light Delay Shut-off
Date Posted: April 30, 2006 at 2:47 PM

I've got a 2004 Jeep Rubicon that is heavily modified for rock krawling. I have installed "rocklights" under the vehicle which consist of 6 55 watt halogen lights actuated by two bosch relays. No problem there ...this works fine.

When I exit my Jeep the dome light comes on and then fades out about 30 seconds after the door is closed. I would like the rocklights to come on and then fade with the dome light. I can make the rock lights come on and go off with the dome light, but I want the fade. Is this fade or dimming performed by some type of relay?

Thanks,

Jim

Replies:

Posted By: bigscratch
Date Posted: May 01, 2006 at 9:08 AM

You would not use a relay for the application you describe. One way of doing it is to make a voltage follower circuit using an op-amp. You would have an R-C network, as the input to the op-amp, charge up while the lamps are on through your existing circuit. Once you shut the door the power circuit would drop out and the voltage follower would supply voltage following the discharge rate of the RC network. The RC network would determine how quickly the lamps would dim to full off. You would have to have a constant power supply to the voltage follower circuit of sufficient capacity for the two lamps. Look up Voltage follower on Google. I once saw a schematic on a web site intended to do exactly what you describe but cannot recall where. If you look up automotive lamp dimmer you may find what you are looking for.

Posted By: hotwaterwizard
Date Posted: May 02, 2006 at 11:33 PM

Why can't you just make a voltage follower from a 2N3055?

Just like they do with this Zener Diode.

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

Posted By: hotwaterwizard
Date Posted: May 02, 2006 at 11:39 PM

Or like these Regulators.

posted_image

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

Posted By: jeepicon1022
Date Posted: May 07, 2006 at 10:00 AM

hotwaterwizard wrote:

Or like these Regulators.

Thanks... I'm going to give this a try. I appreciate everyones input.

Jim