[GI] Interior light dimmers

[Demonic1]

So, I've been working on an electronics project. I'm still in the testing phase... But once I get my prototype working I was wondering if members of the forum would be interested in buying these.

Basically it's interior "Theatre" style lighting. When you shut the car door the light will stay on for a set period of time, and then dim over a period of time. If you turn the car on (or to ACC.) the lights will automatically start to dim. The design I'm working on will have 2 adjustment points. The first for length of full brightness, and the length of dimming time.

The circuit board will be small enough to mount behind the headliner, and will need to be patched into the wires (I'll write up how to later)
I'm thinking around $25 (+ shipping) to get these out the door.

Who thinks they would want one?

[_-Night-Shade-_]

I'd be interested. Would give the car a more moddern appeal. Let us know more info such as how the adjustments would be made, etc.

[Demonic1]

I've got two POT switches wired in. One would control the length of full power after the doors are closed, and the other controls the speed of the fade out.
They're adjustable with a screwdriver, but it'd be something you set and then hide behind the headliner. Not something you could adjust on a whim.

Also, in case you're unsure what a pot switch is:
These are the exact ones I'm using (small size, easy adjustments)
http://media.digikey.com/photos/Panason ... SERIES.jpg

I'm also unsure about the maximum settings under a larger load (stock bulbs). I'm using LEDs, but I also have a large group of them pulling power. I have 5 SMD LEDs and 5 5mm LEDs off each light socket. I'll do the math later when I'm not sleepy.

[Mooneggs]

yeah I would be interested

[Demonic1]

I got the final 2 pieces for it today. I should have a working prototype this week and will get a video of it (if/)when it works.

[onlytrueromeo]

I have LEDs so this is not an option for me, but good luck!

Mooneggs, don't you too?

[_-Night-Shade-_]

This can't be made to work with LEDs?

[onlytrueromeo]

Dimming LEDS is a bit more complicated and not as simple as sticking a capacitor into the mix. Can be done with "mixed" results, but different procedure than incandescent bulbs. Ever seen a dimmable LED flashlight? They exist but are rare.

[Demonic1]

Dimming LEDs isn't all that complicated either. LEDs have a low tolerance for input voltage to visible light output. Basically, if an LEDs max voltage is 3.2v it will put out light all the way up until 3.2v (failure point). The visible light may not appear until 2.3v and ramp up quickly until failing.

At 2.3v it may put out 10% light, and at 2.5v it puts out 15% light... 2.7v = 50%, 2.9v = 80%, 3.2 = 100%

This is just a loose example, but a good estimate. The problem with dimming LEDs is that the light output is not linear across the power band. An incandescent bulls is. (example below)

100 watt bulb reference: at 10w = 10% light, 20w = 20%, 30w = 30% and so on...

There are two methods used for dimming LEDs, limiting voltage and rapid power cycling. Limiting the voltage is difficult because of the power curve, but the power cycling involves a larger circuit to control the rate/speed of the flash.

-------------------- That being said... ---------------

There is a way to stretch the power curve for LEDs by wiring a number of LEDs in series (most LED replacement bulbs use this) and using the appropriate resistor. My LED setup is set up this way and should function normally (except my floor lighting).
I am using a POT (potentiometer) to limit the voltage and with the right adjustments should work correctly with LEDs.

A capacitor is used as a power source, not a limiter. It holds a charge similar to a battery. There is a capacitor on my design to hold a charge after the voltage has be removed (closing the door). Resistors will limit voltage input to the bulbs (LED or incandescent) and a POT will control how much the resistor limits....

[_-Night-Shade-_]

Hey man I'm not an electricity ace but I've got faith in you and if it works I'm in!

[Demonic1]

So, I finished my first prototype yesterday...
First run, I turned the adjustments all the way to the max (longest timing). The timer of full brightness went for about 50 seconds and then when the dimming portion kicked in, I blew an IC and a diode.
I'll have to replace them before I get another built...
I noticed my error and a transistor was wired wrong. I corrected it and I'll be set to do another test run soon.

Stupid dyslexic me... read the diagrams right!

[mikeinaus]

any luck on a beta 2? im definitely interested in grabbing one once you get these up and running.

+1 for led dimmer...

[Demonic1]

I had some issues finding the IC I used. the place I originally got them from was out of stock, and had to find another place. I got them ordered, and paid for... Then my unemployment ran out, my car started running like s---, etc. This project took a side spot for a bit, but I have all the parts waiting for when I get back to it.

Also was working on getting custom circuit boards printed out. They'd make assembly easier, and if someone wanted a discount I could sell kits. But right now I have to get the base designed and then work from there.

I should be able to get back to it soon. Within the month or so.