Has anyone modded their B13 dome light to fade out slowly like on a G20? I searched but found nothing.

To get the dome light to fade out you would need to install a capacitor in parallel with the dome light. The bigger the capacitor the longer it will take to fade out.

Figuring out how long a light will stay lit in this type of circuit is a pretty classic physics problem. Go find a physics text book and you should be able to figure out what size of capacitor you need to achieve any desired 'fade out time.' I do believe there is some basic calculus involved.

To get the dome light to fade out you would need to install a capacitor in parallel with the dome light. The bigger the capacitor the longer it will take to fade out.

Figuring out how long a light will stay lit in this type of circuit is a pretty classic physics problem. Go find a physics text book and you should be able to figure out what size of capacitor you need to achieve any desired 'fade out time.' I do believe there is some basic calculus involved.

I thought of a capacitor, too. I know a major geek that could probably tell me off the top of his head what value capacitor to use based on how long I wanted to "fade" to be. I'll shoot him an email right now.....

Let us know what you find out!

Let us know what you find out!

I will, but this guy is a "treat". The answer will probably be some E=MC2 shit...

whoops (double post, can't delete)

I will, but this guy is a "treat". The answer will probably be some E=MC2 sh*t...

His response.....

"A series capacitor will not do what you want. A cap blocks DC voltage so you cannot keep a light bulb lit if you wire a cap in series. Now if you put a large enough cap in parallel with the bulb, it may store enough juice to fade the bulb away"

:confused:

Couldn't find my physics textbook but I did find my EE book.

The equation that applies here is that of a simple RC circuit, here it is already derived:
V(t) = Vo*e^(-t/(R*C))

V(t) = Voltage at time 't'
Vo = initial voltage across capacitor = 12V
t = time in seconds
R = resistance of light bulb, we can figure this out if we know the wattage rating of the bulb and voltage across the bulb with P = VI and V= IR... A 1.5Watt bulb in a 12V circuit is approx 96omhs.
C = capacitance of our capacitor in Farads

Lets say we want our dome light to be at half brightness after 2seconds. So we solve the above equation for C with V(t)=6V and t=2seconds. For half brightness at two seconds would require a capacitance of 30,000 uF.

That is a fairly big capacitor, the biggest capacitor Radioshaft carries is ~5,000uF. You can probably find better selection and prices on ebay. Also remember that the capacitance adds together for multiple capacitors in parallel.

If anyone spots any errors I'd be curious to know, I'm a bit rusty.

Couldn't find my physics textbook but I did find my EE book.

The equation that applies here is that of a simple RC circuit, here it is already derived:
V(t) = Vo*e^(-t/(R*C))

V(t) = Voltage at time 't'
Vo = initial voltage across capacitor = 12V
t = time in seconds
R = resistance of light bulb, we can figure this out if we know the wattage rating of the bulb and voltage across the bulb with P = VI and V= IR... A 1.5Watt bulb in a 12V circuit is approx 96omhs.
C = capacitance of our capacitor in Farads

Lets say we want our dome light to be at half brightness after 2seconds. So we solve the above equation for C with V(t)=6V and t=2seconds. For half brightness at two seconds would require a capacitance of 30,000 uF.

That is a fairly big capacitor, the biggest capacitor Radioshaft carries is ~5,000uF. You can probably find better selection and prices on ebay. Also remember that the capacitance adds together for multiple capacitors in parallel.

If anyone spots any errors I'd be curious to know, I'm a bit rusty.

Thank you Sir. I have a couple "ham radio" geeks on the case on another forum and I'm waiting for one of them to post a definitive answer of some sort. It's funny watching them argue about the values of capacitors and resistors. Hell, and I thought I was a geek. :rofl:

Check it. One of them even posted a YouTube vid to prove the other one wrong...

http://www.youtube.com/watch?v=iMioETNc9NU

http://www.circuitdb.com/circuits/id/196

I will, but this guy is a "treat". The answer will probably be some E=MC2 sh*t...

You mean "E = mc NISSAN"? :D

http://www.circuitdb.com/circuits/id/196

Yeah, I saw this one. I could probably pull it off if I took my time, but I'm gonna try the capacitor first. I've been told a 22000uf, 25 volt cap should fade the bulb over 15 seconds or so, and I had one offered to me for free to test.

I'm gonna pick it up this weekend and give it a shot. :biggthump

Any luck?

Any luck?

Well, the guy I was supposed to get the capacitor from flaked out on me and I haven't been able to meet up with him. I may just pick one up on eBay.

This is not dead yet. I'll keep everyone posted.:biggthump

On the advice of a couple of major geeks I'm going with an LED dome light. The LEDs lower power consumption means I'll be able to use a smaller capacitor, which hopefully can fit up in the fixture itself. I have and LED on order which should be here next week and I've got plenty of junk lying around that I can rip capacitors out of.

I'll post further progress......

This is not dead. I picked up an LED dome light, and tried a few capacitors, but with no good results.

What I did find was an aftermarket delay timer/fader for RV's and conversion vehicles. It wasn't what I'd call cheap @ $55 shipped, but I bit the bullet and I got one on order today. The manufacturer told me they're discontinued, but I found one in stock at one of their distributors.....

http://www.mccampingsupplies.com/images/intellitec/31-0000516000.jpg

It's a big pic, but they told me it's small; 2" x 3" x 1/2" so it should fit up in the headliner.

When wired across the normal door pin switches, it provides five seconds of full brightness light after the doors are closed and then the lights fade out over the next two seconds. This allows the occupants of the vehicle time to fasten their seat belts and to get settled before the lights go out....

The module will carry up to 7.5 Amps of lighting load.



I'll continue to post......

call me a smart a$$ but why not just find a g20 at the junkyard and gank its domelight shit?????

call me a smart a$$ but why not just find a g20 at the junkyard and gank its domelight sh*t?????

Already thought of that. The "timer control unit" in the G20 controls the dome light fade, and a ton of other stuff. It's not a stand-alone dome light module.

I compared diagrams and functions of the G20 and B13 time control units and it doesn't look like they're swapable without major re-wiring.

This is not dead. I picked up an LED dome light, and tried a few capacitors, but with no good results....

Where did you pick up your LED dome light? One of my B13's the dome light is so dim it's useless. Figured an LED replacement might do the trick.

Thanks in advance.