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Black LEDs?

T

Terry Yager

Veteran Member
Joined
May 1, 2003
Messages
8,763
Location
Saginaw, MI, USA 48601
Does anyone know of a source for very dark LEDs? I'm thinking of a theme for next Christmas' decorations, and I want to do an African-American thing to honor our new (by then) president, using the colors red, green and black. (I was going to decorate the tree with a buncha lil' watermelon slices & chicken legs, but one of my (black) friends suggested that that might not be appropriate).

Seriously tho, need some really dark LEDs

--T
 
A good use for burned-out LEDs; just dip 'em in black paint and Bob's yer uncle!
Whatever happened to uncle Bob BTW?

m
 
I think I saw a circuit where they cut one of the leads on the LED. I'm not sure which one though. I guess you could experiment. Perhaps you could rig a switch of some kind to make it more versatile.
 
I think you should look for some LSD -- Light Sucking Diodes. They'd probably be dark and work as miniature black holes. Better watch out though so a whole array of them don't suck you and the whole tree in.
 
The problem with Light Sucking Diodes and black lights in general, is that they only work in the day time. When it's dark, you can't tell if they're on or not.
 
Terry: Seriously tho, need some really dark LEDs
Click to expand...

Of course, Terry hasn't told us what he really needs here. What's "dark", and what colour are we talking about? If you're actually serious then just remember that R=E/I and find the appropiate resistor. Regular 1/4 or 1/8 watts are fine. Most LEDs that aren't specialty or high output, will prefer around 20ma for max output so try something around 5ma and see if you like it. For a 12V supply thats around 2.4Kohm. For 5V it would be 1K. (Brown/Black/Red) You can always try to find a 1.5 K if you want to keep to your original colour theme on the resistors too. :p
 
I have seen purple LEDs,but they may not be deep enough. They usually end up looking pink. Maybe you could try using tri-color LEDs and vary the color intensities until you come up with a deep enough color?
 
Deep Purple

Deep Purple

There's also violet ones that might work (InGaN-based).
Or, a white led blackened by magic marker, soot, etc ?
Or, an alternate way to get violet light, courtesy of Wikipedia,

an ordinary NPN bipolar transistor will emit violet light if its emitter-base junction is subjected to non-destructive reverse breakdown. This is easy to demonstrate by filing the top off a metal-can transistor (BC107, 2N2222 or similar) and biasing it well above emitter-base breakdown (≥ 20 V) via a current-limiting resistor
Click to expand...

patscc
 
Ole Juul said:
Of course, Terry hasn't told us what he really needs here. What's "dark", and what colour are we talking about?:p
Click to expand...

Actually, I was thinking of the UV LEDs, just wondering if anyone had first-hand experience with any. I'm assuming they are not all created equal, but from a catalog, can't really tell which company's might be darker than another's. Also, some hints on darkening them more, while still being able to tell they're lit up. I'd thought of the marker trick, but haven't begun experimenting yet. Also thinking of trying different color combinations, such as blue marker on red LED, etc, to try and come up with the right effect.

--T
 
right effect

right effect

Terry Yager said...right effect
Click to expand...

You remeber those dark red & dark green plastic panels they used to put in front of led displays on alarm clocks ? There's a small window like that on a lot of remotes that sometimes is a real dark red or purple. Or welding glass from a welding mask ? Maybe sticking led's behind something like that ?

patscc
 
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