led

Ok, I've probably ridden in too many new cars or something but I really like how the dome light in newer cars dims off instead of just shutting off suddenly. I found a simple circuit (below) on a website and since I've found that I have quite sometime to loose, decided to give it a try. So, do you guys think this is doable? Anyone with some circuit knowledge have any suggestions, comments or anything? I thought there was another thread about this but I couldn't find it.

Circuit information

Skip

Do a search here and over at the rennlist email list (924/944) - I believe Martin Taylor built one of these for his car... if it wasn't him, he'll know or was involved in the discussion. He makes the Window Express kits we sell - smaht fella - from NZ.

Too many years since the military's feeble attempts to train me in circuit theory to keep from getting shocked

Good Luck!

Mr. Avionics

Circuit looks good, only thing I noticed is the door switch is switching the hot side to the RC time constant network. The door switches, at least in my 83, only provide a ground for the light. One side of the switch is actually mechanically grounded to the chassis when it is installed so one would have to replace the switch with a ground isolated switch for the circuit above, but would be a nice addition.
Bill

led

I get what you're saying. What if I make the circuit so that it is placed between the dome light and the switch. Have the two plugs that connect to the dome light connect to the respective points for 12V and ground on the circuit and then have two cables coming out, G and 12v again but this time coming from the part of the circuit that has the bulb to the dome light itself.

Ken D

BTW, if you don't feel like making one yourself, Performance Products sells a dimmer kit for 944s. Should take about 2 minutes to install.

led

ok I realized that I need a constant 12v at the light so basically what I said befor won't work... I'll keep thinking but if there are any suggestions please post them.

Edit: I thought there was someone who sold those dimmers but since I couldn't find out who, I went through this, I'll give it a shot anyways and maybe even do a write up if succesful.

Edit 2: Ken, is this what you mentioned? http://www.performanceproducts.com/P...producttype=20
If so we are talking about slightly different things I'm no particularly interested in the dome light staying on a while longer after I close the doors, I want them to turn off gradually, dim off. Anyways $47 is to much for something you can build for way less than $20

Zero10

My only worry is that you are running the power for the dome light through the transistor, and I am not certain what the current for the dome light is, so you would have to keep that in mind when selecting a transistor.

led

Well, I don't know the current rating but it is a 2N3055 Power transistor which IIRC should handle a few amps.

Melchior

I was involved in this thread a long time ago and stated that if someone built one that worked they could sell it to over half the people on this list: including me.

Sam Lin

I installed the Paragon one, knew it was overpriced for what it was, but wasn't going to spend the time to hunt my own parts and make one - I like it.

Sam

Mr. Avionics

2N3055 transistors can handle at least 10 Amps. they are a good choice for high current dimmer circuits. No problem there. I'll cobble up the circuit some time and let you all know how it works. I know I have all the parts in some junk boxes out in the shop some where. As far as the switch goes, it would not be too hard to come up with an isolated switch I'm sure.

Bill

Zero10

I would like to build one that would keep my inside light on for a little bit after the doors are closed. Would your design work for that too?

led

FWIW, I don't think I would be willing to sell them but will attempt a write up if I'm succesful.

Bill, I ordered the parts and a breadboard to test it that should be arriving this coming week. I've been thinking all day about how to work around the switch while leaving the car's wiring intact but so far I don't think I have anything. If you think of something PM me to let me know.

Zero10, the design isn't mine, I found out on a website... That being said, no it won't work to keep the light on. It will in a sense but it will start dimming as soon as the door is closed. There is a potentiometer that can be adjusted to make the light dim faster or slower so it might work but I can't say for sure. If I can make this work maybe I'll learn later how to do what you want.

led

I think I know how to workout the switch problem but it would involve getting a wire from the switch to the lamp or vice versa from each door, how hard is that?

Melchior

Any updates?