40k mcd leds?

I was browsing through ebay looking at the loose leds that are available, and found this:

http://cgi.ebay.com/ebaymotors/Whit...emQQcategoryZ33713QQitemZ8022886090QQtcZphoto

i did a cursory search for 40k, 40000, mcd, etc. but couldn't find anything. i have seen a lot of 35k, 26k, etc.

what do you guys think?

-Melvin

is a supporting vendor...
http://www.besthongkong.com/newsdesk_info.php?newsdesk_id=21&osCsid=ceeb4cc66708d71b7022e7e3e9dc0c0f

what they are selling on ebay vs their website seemed a little different? Part numbers were different?)

also have 80-100K in 10mm

Interesting, I think I still have some 26's and 33's left What're some more when searching for more light :-D

Another seller with similar product. I'm quite curious how these stack up.

haha, yea, that's what i was thinking.

lebox, good eye, i didn't know they were a supporting vendor. you are right though, the model numbers provided on ebay and on their site are different. and from ther site, it is significantly more expensive than from ebay, given there aren't any bids yet. although, i wonder if after this post, there will be some bids... heh.

if people know these to be of 'good' quality, i wouldn't mind doing a group buy of sorts, it's just that i don't know anything about the company or these leds.

also, is the forward voltage of most of the different leds 3.2-3.4 with a max of 3.8? does that mean most of the lights in the keychains are being underdriven (usually at 3.0 volts, i believe, correct me if i am wrong) and would that mean that these wouldn't be significantly brighter in most applications?

-Melvin

edit: found another seller on ebay:

http://cgi.ebay.com/100-Mega-Bright...571938466QQcategoryZ66954QQrdZ1QQcmdZViewItem

the seller name is suspiciously similar to the other link posted by weep.

also, the specs i'm reading from all of these are slightly different. does this mean different manufacturers? or just the vendors misreading the specs?

gnef said:

the seller name is suspiciously similar to the other link posted by weep.

Click to expand...

Well, the "hk" part probably refers to Hong Kong, where the sellers are located. Best Hong Kong and Light of Victory are known to be good sellers, I think, and I think there was a group buy of 35k LEDs from LoV in the past. Now there are 40k LEDs, at least as advertised...and I'm curious... I don't have much of anything to compare them to, if I were to purchase some, however. Anyone else interested in hosting a show?

gnef said:

edit: found another seller on ebay:

http://cgi.ebay.com/100-Mega-Bright-White-LED-5mm-40-000-mcd-Free-Resistor_W0QQitemZ7571938466QQcategoryZ66954QQrdZ1QQcmdZViewItem

the seller name is suspiciously similar to the other link posted by weep.

Click to expand...

This is the seller that I bought 100 40k LEDs from recently.

It is irritating that I find out I paid a little over $12 more for the same thing that the OP posted.

In any case, I bought them to replace the LED's in a cheap hybrid lantern (non regulated) that I bought on eBay.
Here is a link to an eBay auction that shows the type of lantern I am talking about:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=8738827457


It worked fine in the beginning, but eventually, all of the original LED's were either weak, flickering, or dead. I put in all new LED's (and sockets, to make future replacements very simple), and it is now brighter than when I first bought it.
Side note:
Here are links to some "sockets", just in case anyone needs these:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G12996
http://www.allelectronics.com/cgi-bin/category.cgi?category=192&item=SIP-30&type=store
http://www.allelectronics.com/cgi-bin/category.cgi?category=192&item=SIP-81&type=store



I am kind of worried though. I feel that the LEDs may be overdriven, and may also burn out like the originals did.

The lantern uses 4 D cells in a holder, but you could also take out the holder, and use a 6 volt lantern battery instead (which is what I did, although the auction didn't mention you could do that). It has 10 LEDs connected in parallel, with a 2 ohm resistor for each LED.
Is this the right size resistor? Or should it be higher?




edit:
Here is a pic of the bag that the LEDs came in:




NOTE:
The 40K LEDs I recieved were definitely brighter than the old LEDs, but they had a slight blue hotspot, with a slight green ring around it.


And here is the link to their LEDs.
NOTE: I could not find the model # of these LEDs in their list
http://www.led-center.com/led_lamps.htm

gnef wrote: "also, is the forward voltage of most of the different leds 3.2-3.4 with a max of 3.8? does that mean most of the lights in the keychains are being underdriven (usually at 3.0 volts, i believe, correct me if i am wrong) and would that mean that these wouldn't be significantly brighter in most applications?"


Most white LED keychain lights of the Photon type actually use 2x CR2016 coin cells in series to give a total nominal voltage of 6 volts - so they are over-driving the LEDs.

Only the Red, Orange and Yellow LEDs which have a lower Vf use single CR2032 coin cells at 3 volts.

SuperNinja said:

I am kind of worried though. I feel that the LEDs may be overdriven, and may also burn out like the originals did.

The lantern uses 4 D cells in a holder (but you could also use a 6 volt lantern battery, although the auction didn't mention that), and it has 10 LEDs connected in parallel, with a 2 ohm resistor for each LED.
Is this the right size resistor? Or should it be higher?

Click to expand...

That value of 2 ohms doesn't sound right. This would give (assuming a LED Vf of 3.6V) (6.0-3.6)/2 = 1.2A per LED.
LED current (on a full battery) = 2.4/R
Do you have a meter you can use to check the value of the resistors?

meteor said:

That value of 2 ohms doesn't sound right. This would give (assuming a LED Vf of 3.6V) (6.0-3.6)/2 = 1.2A per LED.
LED current (on a full battery) = 2.4/R
Do you have a meter you can use to check the value of the resistors?

Click to expand...

1.2A! Yikes!

Another option to simple resistors if you are decent with soldering and finding places to put things (which you seem to be from the sounds of your post) is just to buy an actual regulator from the Shoppe. Something like one of the DownBoy boards would be perfect. The 400 would send 40ma to each LED and I think they would all have a happy life if they are as good as the 35k LEDs from KevinL and you get consistant brightness and I would have to assume you'd see RIDICULOUS runtime.

I bid on a set of these. Check his other auctions, since after bidding, i saw the same set of LED's at $13.xx instead of $17.xx.

A got some of these so-called 40cd leds. Type was Light of Victory.
- measured viewing angle is 12 degrees.
- brightest part of beam was approx. 20% dimmer than a U-bin (15,5-22cd) Nichia CS
- Vf was 3,40V

Other story.

Previously got some 30cd/24 degrees 5mm leds from BestHongKong.
When shipped, labeling said 20 degrees.
Measured 10-11 degrees.
By their datasheet these are min. 20cd max. 30cd in brightness. Very wide range, guess whether you really hit the 30 cd pieces? I don't think so.
(One good point: they were brighter than Nichia CS in their hotspot. It seems that at least the 20-30cd rating is true)

Vendors always make their ads
- by the max candela rating of the given bin
- stating 20 degrees, in reality it is 10-12 degrees. (Interesting: "datasheet" says 20+/-5 degrees (or even 20+/-10! degrees)
It is not the same! In theory the half viewing angle makes a four times candela rating (inverse square rule).

I think this is true for all cheap led sellers on ebay.

meteor said:

That value of 2 ohms doesn't sound right. This would give (assuming a LED Vf of 3.6V) (6.0-3.6)/2 = 1.2A per LED.
LED current (on a full battery) = 2.4/R
Do you have a meter you can use to check the value of the resistors?

Click to expand...

Ok, I just quadruple checked this (tested it with four different meters).
All the meters are coming back with readings in the 2 to 3 ohm range.

And the resistors have this color code - red,black,gold,gold.

When you say the 30k, 24 degrees LEDs were brighter than the CSs in their hotspot, how were you driving them? The CSs hold up fine direct driven on a Lithium Ion cell and driven on one, are WAY brighter than my 35k LEDs in a Dorcy AAA.

Are you saying these 30ks driven hard are brighter than the CSs driven hard or if you put them both in something like a keychain light, the 30ks are brighter?

cratz2 said:

Another option to simple resistors if you are decent with soldering and finding places to put things (which you seem to be from the sounds of your post) is just to buy an actual regulator from the Shoppe. Something like one of the DownBoy boards would be perfect. The 400 would send 40ma to each LED and I think they would all have a happy life if they are as good as the 35k LEDs from KevinL and you get consistant brightness and I would have to assume you'd see RIDICULOUS runtime.

Click to expand...

This sounds great!

I didn't know you could get regulators (didn't see any sold on the websites I went to)

Do you have a recommendation for a site for downboy boards, or any other regulators?



edit:
I think I might be confused here. You weren't responding to my post, were you?

SuperNinja said:

Ok, I just quadruple checked this (tested it with four different meters).
All the meters are coming back with readings in the 2 to 3 ohm range.

And the resistors have this color code - red,black,gold,gold.

Click to expand...

So there are 10 2-ohm resistors in the circuit (one per LED). Are there any other resistors on the board or in the light? If you remove the batteries can you measure the resistance between the positive battery contact and any of the 2 ohm resistors?

Although I've probably read hundreds of topics this is my first post. Forgive me if I'm poorly informed or am rehashing something you all have discussed before.

I have heard that these low cost high candela LEDs actually become less efficient in terms of the light output relative to power consumption (or rather increase dissipation as heat disproportionably). Is there any truth to this? has anyone tested these specific high output (non luxeon) LEDs? I've been planning a few large array projects and deciding unit brightness vs array size has kept me walking in circles for weeks.

P.S.
I also find it interesting that BestHongKong sells 25CD, 11CD, and 8CD LEDs for less (at unit) than the 40CDs. What's wrong with this picture?

Cheers,
Rob

cratz2 said:

When you say the 30k, 24 degrees LEDs were brighter than the CSs in their hotspot, how were you driving them? The CSs hold up fine direct driven on a Lithium Ion cell and driven on one, are WAY brighter than my 35k LEDs in a Dorcy AAA.

Are you saying these 30ks driven hard are brighter than the CSs driven hard or if you put them both in something like a keychain light, the 30ks are brighter?

Click to expand...

They were driven at the same current: 20mA.
My Nichia CS had a 3,36V@20mA, BestHongKong 30cd was approx 3,49V@20mA (and 10-11 degrees viewing angle instead of the advertized 24 degs). So it needs more power also.

If a mega-hyper-superbright led happens to be brighter than the good old ("only" 15,5-22cd rated) 15 degrees Nichia CS that because they have a narrower beam. And not because they are two years ahead the LED technology.

edit: corrected Vf@20mA

Based on my limited testing and only using crude measurement devices (ie crappy DMM from Harbor Freight), I don't think you'll see significant increases running the cheapest LEDs much over about 30ma. You might see some, and it you pop one in a light that is going to send more than that to the LED, I'm not saying it will always be worth the effort to replace the circuit to get the current down, but they usually don't 'overdrive' quite like the super bulbs where if you give them just a little more current or voltate they get radically brighter.

SuperNinja, here is a link to the Shoppe's converters. Another forum member (who can feel free to chime in here) built a couple lights based on Nichia CS LED swaps running on either the DB400 or DB500. I bought the light modded with the DB400 and six Nichia CS LEDs and it was impressively bright... The brightest small light I've ever seen or owned that used 5mm LED. I'd think 10 of those even running in the cheapest DB400 would make an excellent lantern mod for your lantern. I have never used the 40k LEDs so I can't say anything about them one way or the other but I do know that the CS LEDs can take a beating and if you wanted to try running them on the 750 they'd probably take it for quite a long time and should be a bit brighter than on the 400 or 500, but if it was me, I'd probably just go with the cheapie $9 DB400.

As long as you realize you aren't going to get much throw out of them, I have no doubt that you would be very happy with the 10 CS LEDs running on the DB400. Minus your resistors, of course.