hotwaterwizard: dome delay relay

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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=47908
Printed Date: May 05, 2024 at 7:20 AM

Topic: hotwaterwizard: dome delay relay

Posted By: Vortec4800
Subject: hotwaterwizard: dome delay relay
Date Posted: January 17, 2005 at 12:58 AM

I have here a diagram that you drew up for a dome delay circuit. I'm curious if you know how long this will stay energized after the ignition power is released.

Also, I'm trying to figure out exactly how the circuit works, and I'm not sure the purpose of the second diode making the loop on the relay. Care to enlighten?

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2000 BMW 540i 6 speed

Replies:

Posted By: misterjimbo
Date Posted: January 17, 2005 at 12:36 PM

that depends on the draw from the dome light. if you use it and the delay is or isnt long enough you can always put in a different cap.

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Posted By: misterjimbo
Date Posted: January 17, 2005 at 12:38 PM

for the diode i think that is to keep the 12volt from backing up through the relay. audiovox relays come with that diode already on them

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Posted By: xetmes
Date Posted: January 17, 2005 at 1:54 PM

not trying to step on peoples toes but you better put a resistor on the base of the transistor, granted the coil will provide some but a mere 200 ohms or so. The time on is a result of the transistor base current draw but is determined by a resistor (not shown?). Personally I would run an NPN in common emitter or use a PNP to switch the high side since the current in the relay will drag the emitter voltage up, but thats just me...

Posted By: Vortec4800
Date Posted: January 17, 2005 at 3:50 PM

Well the draw of the lights shouldn't change the time, because the lights are on the other side of the relay.

As far as the resistor, that is all greek to me. My knowledge in electronics is very basic, and while I always try to understand what's going on adding things isn't my specialty.

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2000 BMW 540i 6 speed

Posted By: xetmes
Date Posted: January 20, 2005 at 3:09 PM

posted_image

Here is another one you can try if you want, should give a delay of about 30 seconds

Posted By: hotwaterwizard
Date Posted: January 21, 2005 at 1:25 AM

Have you tried this circuit? I have never seen a 3100 uF Capacitor.

With my 3 min timer you only need 470 uF

posted_image

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

Posted By: Vortec4800
Date Posted: January 21, 2005 at 1:29 AM

Well I only need a 30 second timer. I built the one xetmes drew up, and it clicks on the relay when power to the ign is applied but the voltage to the relay never drops low enough to click the relay off.

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2000 BMW 540i 6 speed

Posted By: hotwaterwizard
Date Posted: January 21, 2005 at 7:30 AM

try mine with a 47uF cap

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

Posted By: hotwaterwizard
Date Posted: January 21, 2005 at 7:30 AM

try mine with a 47uF cap or a 10uF

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