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