LED Dash lighting?

[Brett Dikeman]

On Dec 23, 2005, at 12:20 PM, Ingo Rautenberg wrote:

> So, since I'm going to be replacing the dash pad and some  
> instrument cluster lights, etc. tonight, I was wondering if anyone  
> has done LED lights for the 200/V8 instrument cluster?  I know  
> people have done so with the window switches, dash switches, etc.   
> Or do they not dim like traditional light bulbs?  If they do dim,  
> I'd like to know which ones to get (want to keep red lighting).   
> And, yes, I can solder...

This has been mulled over for years on the mail list, and I'm not  
sure anyone actually did it.

I have a tach courtesy Mike Sylvester (thanks Mike!) that I was  
playing around with- the lighting scheme is actually pretty complex.   
The tach for example is lit by no less than FOUR bulbs, and the gauge  
face is a multi-layer setup that has patches of different levels of  
translucency.

The plastic light guide (which is also the body of the gauge itself)  
has prisms(basically just 45 degree faces) cast into it around the  
shaft for the needle; the needle is open in back and uses a prism   
incorporated into the shape of the clear plastic to bounce light  
coming straight out from the gauge face.  The two bulbs on the  
outside edges of the face supply light to the pointer; light is  
bounced at the gauge edge (again, a 45 degree face which acts like a  
mirror) into the center, then straight out via the cast prisms  
previously mentioned.

You could most likely get away with LEDs on the outside bulb  
positions because they collect light mostly dead-on, but the inside  
bulbs are used for dial face illumination and light is transmitted  
via cylinders which have an inside beveled edge (again, acting like a  
prism- the bevel is probably level with the filament.)  An LED would  
work, but only if it was the kind that casts light full-circle to the  
sides.   They do make LEDs with integral reflectors for this kind of  
dispersal pattern, if you poke through a catalog like Mouser or Digikey.

This is another solution to the problem:

http://img.ebigchina.com/cdimg/325915/1241243/0/1110537806.jpg

Note the 45 degree prism face to distribute light to the sides.  Too  
big, however, for the dash...wrong bulb base style as well.

This place, however, has bulbs that might work:
http://www.superbrightleds.com/cgi-bin/store/commerce.cgi?product=CAR

Page two, skip down to the T1.5 twist-lock bulb.  Pretty much the  
same idea.

As for color-matching, yes...there are a wide variety of "red" LEDs  
at different wavelengths, but as long as the instrument cluster is  
all the same and not very amber-ish, that's good enough for me.

Anyone already have their cluster out, so they can check to see how  
even the illumination would be with these bulbs?  Actually, I think  
Lee Levitt was going to take his out to fix a mis-installed warning  
light.  Maybe he has yet to do it and wouldn't mind being guinea  
pig?  I'd do mine, except I absolutely HATE removing my cluster, so I  
don't want to be the guinea pig.  I do have a few bulbs out in the  
cluster though...mostly the ancillary gauges.


Brett