[sdiy] White LED Source

[Harry Bissell Jr]

I jst bought some white LEDs from a well-known
  surplus dealer. Maybe 30% of them were defective.
  The bad ones did not light up... and had a forward drop of only
  1.6V instead of the normal 3.5V (or so). Probably, they
  are static damaged.   Beware !!!
  
  I will work it out with the retailer (they are reputable) but I got
  way less yield than I needed...
  
  H^) harry

clark at andrews.edu wrote:  
> Be careful with the Hong Kong sellers... many are probably reliable, but I
> won & paid for a batch of Red/Blue bicolor LEDs from the seller "*
> spectrumleds*"
> 23 days ago and have had no communication and no LEDs so far... waiting
> for
> a reply to my "contact this seller" attempt, but suspecting that the money
> is gone and I will need to try again.  No point complaining to Baywatch,
> as
> they don't care the tiniest bit about ripped-off buyers as long as they
> get
> their cut of the take.
> As always check feedback and seller's history... happy hunting
>
> On 1/15/06, Colin Raffel  wrote:
>>
>> Check eBay.  There are lots of sellers from Hong Kong who sell white
>> LEDs for cheaper, they just have fairly high shipping prices.
>>
>> Here are some for 19c apiece shipped, a tiny bit cheaper...
>>
>> http://cgi.ebay.com/New-100-Mega-Bright-10000mcd-3MM-White-LED-Free-
>> R_W0QQitemZ7580316357QQcategoryZ66952QQrdZ1QQcmdZViewItem
>>
>> Wrong size....
>>
>> http://cgi.ebay.com/Lot-of-100x-Ultra-Bright-White-LEDs-5mm-
>> dia_W0QQitemZ7579578236QQcategoryZ66954QQrdZ1QQcmdZViewItem
>>
>> Give it a try.
>>
>> -Colin
>>
>>
>> On Jan 14, 2006, at 1:21 PM, xamboldt wrote:
>>
>> > Anyone know a good source for relatively cheap white LEDs? The best
>> > I found was $0.20 for 3mm here:
>> > http://www.rjmods.com/product_info.php?products_id=90
>> >
>> > But this seems so much cheaper than every place else (around $1.00/
>> > each for the cheapest), it seems kind of fishy. Has anyone heard of
>> > rjmods before?

   Hi Chris,

   I'd be very wary of cheap white LEDs.  Of course my concern is largely
centered around two issues:

   1) White "color"
   2) Color matching between LEDs.

   Most "white" LEDs that I've seen are really a "blue" color, some so
significantly so that I don't know why they don't sell them as "light
blue" LEDs and not "white".  Getting a more neutral (or warm) colored
white is difficult and not many suppliers carry them.
   I've gotten some nice warm white LEDs from this company:

   http://www.ledtronics.com

   They aren't cheap, but again, it's very hard to come by true warm white
LEDs.

   The second issue, color matching is pretty critical if you are going to
have more than one or two of these LEDs together.  My company has a
product which is lit by yellow LEDs.  We initially went with some of
the cheapest LEDs we could get our hands on, only to find out that the
manufacturer doesn't bin-sort the LEDs according to color.  So we'd
have some which were a lemon-yellow and some that were almost a dark
orange!
   So I went back through various supplier data sheets until I found one
from Agilent which are bin-sorted for color.  These were almost as
cheap as the ones we'd been using but dead-on accurate in color.

   So, just be aware that a 20 cent white LED may not get you what you
really want...

   Good luck!

   Tony
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