White LEDs... Who wants to get 'em in bulk?

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Greetings from the OddOne!


I saw in a previous thread that folks were looking for white LEDs and one supplier of small quantities was found ("Hosfelt Electronics (no web site) at 1-800-524-6464 has the Nichia bright white LEDs as part # 25-353 for $3.99 each.") The idea of a white LED appealed to my old-school gadget-loving tinkerer side from the first moment, so I flung some quick E-mail at the right people and came up with the full specs on the company, their entire line of white LEDs, and pricing informaiton for most any size order.


Here's the scoop. If there is enough interest I might be able to bulk-buy the LEDs (in particular the most suitable model for flashlight, etc. use, their NSPW500BS, which is a T-1 3/4 (5mm wide) cased LED rated at 2 cd minimum, 4 cd typical at a 20 degree from straight spread (compared to Radio Slack's brightest orangish-red 10mm wide LED which puts out 12 cd at the same 20 degree angle), needs 3.6-4.0 VDC at about 50 mA of current.


Nichia wants $ 2.80 per LED in quantities of 100, $ 2.20 per for 500 quantities, $ 1.60 each by the thousand, and so forth. I personally would like to order a hundred or so but if enough people on the forum want to order enough at a whack to justify buying a huge case of the suckers, the price per unit will drop to MUCH lower than the $ 3.99 per unit that Hosfelt Electronics wants for one. So, my first ? is, who would want how many of them? If I get enough people saying they want 25, 50, 100, 1,000, whatever, I'll start putting an order together. (Responses via E-mail work if in-forum makes you uncomfortable.)


Second ? is how best to set up the payment for them. Nichia doesn't deal with distributors but since I can funnel them through my company (an OEM among other things) I can order them in bulk without problems. They will require payment in advance for a large order like this since it'll be the first order from my company. I don't know who'd be willing to kick out their hard-earned cash in advance for LEDs that would take two weeks to get, but if anyone has suggestions for viable and safe to all parties collection methods to pay for X hundereds or thousands of LEDs, please let me know. (Again, responses via E-mail work if in-forum makes you uncomfortable.)



OddOne, who thinks the folks using alternate energy sources could have a field day with a few hundred of these LEDs and a little creativity... Can you say "totally off-grid with high-efficiency lighting"?


-- OddOne (mocklamer@geocities.com), March 02, 1999


With some project instructions for those of us with only half a clue, I'd be interested. One could put together flashlights or other small lighting devices. Could make great barter items.

Does Hosfeldt sell bulk rechargeable Nicds?

Then build a small solar setup with ability to recharge the Nicds, and you'd be ready to barter your services! (Or just buy a bunch of solar battery chargers. CCrane company has a good price on these.)

(All this could be fairly expensive to set up initially, but definitely more fun than keeping a garage full of toilet paper) :-)

-- Debbie (dbspence@usa.net), March 02, 1999.

I'll take a couple dozen to experiment with or give away.

-- kiyoinc (kiyoinc@IBM.net), March 02, 1999.

If you could xerox some instructions on how to use the dratted things, I'd be up for a couple dozen too. When you get ready to order, post again and I'll send you my real e-mail address. Thanks very much for thinking of such a useful idea and letting us have a share of it.

-- Nontechnical Old Git (anon@spamproblems.com), March 02, 1999.

I'd be interested in 25 and your suggestion(s) on construction.

-- RD. ->H (drherr@erols.com), March 02, 1999.

Since there's apparently a bit of interest, I think I can scare up or create a schematic diagram for a variable-brightness driver to pump one to several LEDs or more at a time with minimal current drain. It'd be based on the CMOS version of the famous and widely available 555 timer chip.

Of course you can take one and wire it directly to a 3V source (2 AAs, etc.) since they require 3.6-4.0 VDC. Better bet would be three in series across a 12v battery of some sort (A small 12v 4Ah gel-cell would run three of these at 50 mA per for months!) or six in two sticks of three or whatever.

I'd need to tinker with them and a 555 or two to get the best combo for a particular number of LEDs and operating voltage, but construction details should not be a problem.

OddOne, who has built many a thing with a 555 timer chip...

-- OddOne (mocklamer@geocities.com), March 02, 1999.

That's a pretty good price! Pity I'm in the UK, and shipping, banks and duties would eliminate the savings on any smallish quantities.

I'd be most interested in seeing the 555 circuitry. The simpleminded way to drive an LED is to connect them across batteries in series with a ballast resistor. 3 AA cells is 4.5V; the white LEDs I've seen take 3.6V, so you need a resistor that passes the rated current at 0.9V. For 50mA, that's 18 ohm. Attempt at a schematic (-->|-- is the LED)

+4.5V---------18ohm--------->|-----+ | 0V---------------------------------+

Same for the common cheap amber 20mA LEDs is a 56 ohm resistor and two cells = 3V (amber LEDs usually take about 1.8V leaving 1.2V across the resistor). Am about to convert a few cheap torches. (break the bulb and solder the LED and resistor to the metal remains). You'd need a big 3-cell torch to convert to a white LED, but 3 D cells would run an LED for a lot of days!

-- Nigel Arnot (nra@maxwell.ph.kcl.ac.uk), March 03, 1999.

The schematic got mangled: here it is on one line

-- Nigel Arnot (nra@maxwell.ph.kcl.ac.uk), March 03, 1999.

A little bit of digging on the Web (I couldn't find my 555 booklet that had this same stuff in it) revealed this diagram:



Obviously it's a lamp driver, but if you replace the lamp with a string of LEDs in parallel, stick a single 50 ohm resistor on the opposite side of the transistor from the LEDs, and put 12VDC to it, you'll have a variable-brightness LED array that uses less average power than just hardwiring LEDs and resistors to a power supply.


All it is is a pulse-width modulated driver running at what looks like about 250 Hz or so. By varying the duty cycle (what % of the time it's off as compared to on) you can vary the brightness.


Further reducing the overhead from a drain perspective can be achieved by replacing the 2N3055 in the right diagram with an IRF511 (the IRF series MOSFETs are static-sensitive so take suitable handling precautions), removing that 100 ohm 2 watt resistor that ran to the 3055's base, and using a CMOS version of a 555 (T7555, TLC555, etc.) Radio Crack calls their CMOS version (which is a TLC555) a cat. # 276-1718 and demands $1.39 for one. Radio Crack also carries an IRF510, which will work albeit with less current capacity. Their cat. # is 276-2072 and they want $1.99 for one. Using the CMOS goods should drop the driver circuit's drain down to 20mA or so less the LED drain. The IRF510 should be able to pump a dozen or more LEDs.



I might swing by Radio Crack this afternoon and snag a few items to tinker with. If I create a viable circuit I'll post a diagram.



OddOne, who knew he could find a diagram somewhere...


-- OddOne (mocklamer@geocities.com), March 03, 1999.

Argh, stupid thing decided to insert a stock size value. Grrrr.





-- OddOne (mocklamer@geocities.com), March 03, 1999.

News flash...

If you want to get in on the deal, hit this thread for the details:

White LEDS and buying in bulk. Pooling orders together...


-- OddOne (mocklamer@geocities.com), March 04, 1999.

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