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LED Map light 'soft off' circuit

6995 Views 12 Replies 7 Participants Last post by  xero
Inspired by this circuit, I decided to build a soft off circuit for my map lights. The idea is to allow the lights to stay on for a few seconds after I've entered the car.

The basic effect is illustrated in this movie. I increased the delay a bit since this video was taken.

Update See the circuit in action on my map lights: Movie

The version I've constructed is only good for LED lighting applications; I get away with using a small signal NPN transitor for Q2 because my LED map lights draw less then 70mA. Incandescent bulbs could draw upwards of an amp, especially when cold. Replacing Q2 with a MOSFET allows this circuit to be used by those with incandescent lighting as well (see above link). If you build the incandescent version, installation is exactly the same.

Here is the circuit:

It's very simple, as you can see, and component selection is very flexible. All component values were chosen based on what I had on hand. anything reasonably close to the quoted values should work just fine. Delay lasts about 5 seconds with a 100uf C1 and 500R R5. Higher values for C1 and R5 will increase the delay time. Anyone purchasing components for this circuit does not need a 100uf cap, I used it because I had it on hand. 20-30uf should do the trick with a larger R5.

I constructed the circuit on a breadboard prior to soldering, this allows for experimentation and fine tuning of the delay time. If you would like more control over the dimming time a variable resistor can be substituted for R5.

After soldering and testing the circuit, it was time to install it.

I completely removed the map light assembly from the car for the install. Just grip the sides and pull hard; It takes quite a bit of force. Unplug the wire harness, and proceed to the workbench.

Remove the black plastic piece from the gray housing by bending the plastic out at each of the tabs. A small spring and ball bearing will pop out of the "Door-off" switch as you pry out the black plastic. De-solder two wires on one side to allow the board to flip over.

Now we can access the light wiring without damaging the original wiring harness. With a pair of pliers I clipped the trace marked "door switch/trigger". This allows us to wire in our delay circuit. There is no need to cut the other traces, cut only the door switch trace. With this method the delay only functions when the door is opened, not when the map lights are turned on with the switch.

The +12V wire from our circuit should be soldered to the +12V trace and the ground wire should be soldered to the ground trace. The 'door switch' wire and 'trigger' wire are soldered to the cut trace; solder the 'door switch' wire on the side going out to the wiring harness (upper left in the image) and the trigger wire on the map light side of the cut.
Go crazy with electrical tape, and reinstall the black plastic into the gray housing, remembering to re-solder the switch wires and re-install the ball bearing and spring in the "door-off" switch.

Now return to your vehicle, plug the map lights back in and try it out. If you haven't screwed something up your lights will now have a delay and a pleasant dimming effect before turning off completely.

Hope this is useful to someone. Zoom-Zoom :-D
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thats pretty cool, but i dont have the time or the will power to do something that electricaly complicated. good job though!

PS: i need video
My '05 has always faded the lights out gradually when I close the doors. :thinking:

It's really not that bad once you get into it. It looks worse then it is; just leave plenty of time to play with it on the breadboard (they're nice to have for any circuit building), de-soldering and re-soldering gets old real fast.

I tried getting a video on my digi-cam but it came out pretty dark. I'll have to try again.

I have an 06 3i, so that may be an option with touring or GT models. I did notice there's a free pin in the map light connector, this may well be for the dimmer option.
thanks for the info
**WOW** that took some smarts... Good Job!!!
Alrighty, I've uploaded a video of my map lights after installing the circuit. It's in my edited first post, and right here for the lazy: Movie

Can anyone confirm at which trim level the interior lights fade out slowly? I'm curious :)

If anyone is interested in making this circuit, but does not feel comfortable interpreting the circuit diagram, I'd be happy to come up with an easy perf-board layout. This way you just have to put the components where I tell you and solder them together.

Let me know if there are any takers.
that looks really sweet! good job :goodjob:
That is absolutely incredible. I have an 07 S Touring and mine does have a factory fader, but your circuit allows the LEDs to fade more slowly and dramatically and it fades all the way to off, whereas the factory fader is pretty quick and kind of cuts off a bit near the end, since it's designed for the current draw of an incandescent bulb rather than an LED. Well done! :D

I might take a look at my map lights and compare the circuitry with yours to see if I can find the circuit for the factory dimmer. Perhaps a change to one of the resistors might make the factory map lights fade slower with LEDs.

If you rip the map lights down and find a circuit board in there it will likely be very different from what I've constructed here. If you could take a picture of the board, top and bottom, I'd be interested in how they did it (if I can even back it out from a photo).

Hopefully the board is up there and not buried somewhere else in the dash.
Yeah, that's pretty neat, that must have been fun to fiddle with. It looks good also.

I have a 06 3i and mine has always faded although it does fade quickly, however that fits me perfectly. Good job :klavergreg:
RDK87, do you have the touring package?

The only option on my 3 is AC; everything else is completely base. I'm guessing this is why I lack the factory 'fade' functionality.
yep you bet, I have the 3i Touring, I put in the extra grand for that, and got a spoiler / auto dim-mirror, and the cargo net with it.

Maybe that's why.
I have an 06 3s Touring and it fades as well. Good work on the circuit though, if I didn't have the fade already I would definitely get this setup.
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