High led price, better quality?

[bikefreak]

I see some good leds out there for $1 each...

http://www.ledsupply.com/l1-0-g5th45-1.php

and some for a few pennies...

http://cgi.ebay.com/60pcs-5mm-green-sup ... dZViewItem

Both LEDS above are similar, but will the cheaper one break down faster or what?

And a side question, I ordered 6 POV bars and received 2 USB's. Can't I just use 1 USB for all 6 POV bars?

[adafruit]

if you got 6 USB dongles, that was a mistake. you should have received 2. but you can use just one, yes.

[kayrock66]

In general you pay more for efficiency in LEDS. Efficiency being defined as light output divided by power input. When they manufacture a batch of LEDs they get good ones and no so good ones. They sort them by brightness and sell them off asking more for the brightest and less for the weaker ones.

I don't think reliability figures in much since these are solid state devices.

The examples you provided in your post aren't apples to apples comparison, one is a diffused type and the other is a clear wide angle type. The intensity is indicated by the mcd number. In general diffused LEDs aren't as bright as the water clear type.

The thing I'm learning about LEDs in this application is that you aren't so much interested in the intensity but the total luminus flux. The typical high brightness 5mm LED has a very narrow angle (20 degrees). The lens gathers most of the light coming out of the LED chip and concentrates in into a narrow beam, like a flashlight. But from my own Spoke POV and looking at pictures of others I realize that a wide viewing angle is probably more valuable than narrow one, even at the expense of intensity. I want people to be able to see the display over a wide angle, not just straight on. So its a balance between intensity and viewing angle. I saw some jumbo 10mm LEDs with extremely high intensities but realized that this must be at the expense of viewing angle. Specific questions to 2 HK manufactures asking about the apparent paradox of these devices claiming to be just as wide angle, by several times brighter than the 5mm devices went unanswered.

So I'm going to try a stick with LEDs such as:

http://cgi.ebay.com/30x-Red-5mm-Wide-an ... dZViewItem

and see if I can get a better viewing angle One anticipated side benefit of the wide angle devices is that they produce a display with less striation. This is the effect were you can see brighter and darker circles making up the POV display due to the different angles of the individual LEDs in the array. When the LED viewing angle is narrow, small differences in LED mounting make big differences in perceived intensity and thus smoothness of the composite POV display.

[bikefreak]

if you got 6 USB dongles, that was a mistake. you should have received 2. but you can use just one, yes.

Sorry, I meant 2, not 6 USB.

[bikefreak]

In general you pay more for efficiency in LEDS. Efficiency being defined as light output divided by power input. When they manufacture a batch of LEDs they get good ones and no so good ones. They sort them by brightness and sell them off asking more for the brightest and less for the weaker ones.

I don't think reliability figures in much since these are solid state devices.

The examples you provided in your post aren't apples to apples comparison, one is a diffused type and the other is a clear wide angle type. The intensity is indicated by the mcd number. In general diffused LEDs aren't as bright as the water clear type.

The thing I'm learning about LEDs in this application is that you aren't so much interested in the intensity but the total luminus flux. The typical high brightness 5mm LED has a very narrow angle (20 degrees). The lens gathers most of the light coming out of the LED chip and concentrates in into a narrow beam, like a flashlight. But from my own Spoke POV and looking at pictures of others I realize that a wide viewing angle is probably more valuable than narrow one, even at the expense of intensity. I want people to be able to see the display over a wide angle, not just straight on. So its a balance between intensity and viewing angle. I saw some jumbo 10m LEDs with extremely high intensities but realized that this must be at the expense of viewing angle. Specific questions to 2 HK manufactures asking about the apparent paradox of these devices claiming to be just as wide, by several times brighter than the 5mm devices went unanswered.

So I'm going to try a stick with LEDs such as:

http://cgi.ebay.com/30x-Red-5mm-Wide-an ... dZViewItem

And see if I can get a better viewing angle One anticipated side benefit of the wide angle devices is that they produce a display with less striation. This is the effect were you can see brighter and darker circles making up the POV display due to the different angles of the individual LEDs in the array. When the LED viewing angle is narrow, small differences in LED mounting make big differences in perceived intensity and thus smoothness of the composit POV display.

Yeah, I noticed the same thing with the wide angle. With the small angle leds the brightness is only visible when you look at it dead on.

I know I made a mistake in the comparison of the 2 leds, but I still wonder whether its better paying $1 instead of several cents per led. Are you saying that the really expensive leds $1-$2 are expensive not because of the percieved brightness but because they will take up less battery life? Here's an article saying that quality among led manufacturers can differ:

http://www.electronicproducts.com/ShowP ... n2006.html

I found this interesting:

"In fact, a low-quality LED may initially appear brighter than a high-quality one if the low-quality device has a higher drive current. However, the extra current causes the LED to heat up more quickly, and ultimately fade or burnout."

Maybe its pays to have more efficient leds? I don't know.

[kayrock66]

I'd say a dollar is way to much to spend per LED on a project like this. I'm paying around 13 cents each for the ones I've ordered.

Regarding efficiency- in the situation that you're in, where the drive current has already been set by the design done by someone else, the extra efficiency goes towards being brighter, not saving battery. Put another way, if Ladyada has already set the drive current at 10mA, then the better LED you get will just put out more mcd's.

In my situation where I can measure an adjust the current, I'm running without resistor networks (shorted to Vcc) to try to get up to the LEDs' rated 20mA. My red unit with 2 NiMh 1.2V batteries I still only get about 11mA. I hate to leave so many photons on the table but my mechanical contraints limit me to 2 cells on the PCB and I don't want to run 1.5V cells because I'm going to be running this thing all the time.