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thender
Screen tycoon
Premium Member
join:2009-01-01
Brooklyn, NY

thender

Premium Member

LED strip differences

Can someone more knowledgeable about LEDs than I am explain why two different SMD5050 strips with the same amount of LEDs across the same 5' have completely different characteristics in light dispersion & output?

I believe you get what you pay for, so I understand I should get better light out of the $120 product than the $16.50 one with free shipping on eBay. I am curious though, what is actually different? They're both being powered off the same PCI-E graphics card 12v connector of a PCP&P computer power supply.

mackey
Premium Member
join:2007-08-20

mackey

Premium Member

Actually the light from the $120 one will be the exact same as the $16.50 one. You will probably get a fancier/nicer package with the more expensive one though (it'll feel more "polished"). Or it might just be the exact same thing with 'phile pricing... "It's much more expensive so it MUST be better!" The only exception to this is if you're looking for a specific wavelength with a tight tolerance; those cost more due to them taking the time to test and "bin" the LEDs so they're an exact color.

As for the light output, that's going to be determined by the LED. All LEDs have a lens of sorts built into them, and assuming they put out the same amount of total light (wattage and efficiency is the same) the one with a wider beam angle will have a lower intensity due to the light being spread out more.

It would help if you could post links to the modules you're looking at.

/M

thender
Screen tycoon
Premium Member
join:2009-01-01
Brooklyn, NY

thender

Premium Member

Click for full size
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I'm discussing what I've already purchased. I spent about $120-$150 the first time around. I wanted to try the $16 eBay one this time, and I was very disappointed. A few things of note:

a) The $120-$150 ones, I could link 4-5 of these together in a row with no loss of luminance. With the $16 ones, by the second strip, it was half as bright as the first strip. I was hooking them up in series, one after the other. The quality strips could be linked serially, the $16 ones could not as there would be a great loss of power from one strip to the next even if I used 12 3" runs of 12 gauge wire soldered directly to the terminals on the strip.

b) The $120 ones had a much wider dispersal angle, and much more light output.

The cheapie one is on the bottom of the table. The expensive one is mounted on the shelf. The cheapie one is for when tiny screws/washers are dropped, to help locate them. I have always dreamed of having a floor light for this purpose.

I have also tried running these in parallel so that there is no loss from the resistance of going from one strip to the next, with the same result. The cheapie one puts out light, it just sucks by comparison. The cheapie is advertised as 300 SMD5050 LEDs in a 5' strip. SMD5050 is supposed to be incredibly bright, but if it is, why is it having its ass kicked by the 300 LEDs in the above 5' strip?

I truly believe science has more to do with it than branding and price. I just want to know why so I can be an educated consumer for next time.

mackey
Premium Member
join:2007-08-20

mackey

Premium Member

I've used quite a few 5 meter rolls of this stuff, though most have been "digital RGB" (both 12v WS2801 based and 5v WS2812 based) and not single color. If it's dimming when wired in parallel then something's wrong with your power supply. If I put 2 5 meter RGB rolls together (almost 33') I only get a little dimming when full white.

/M

thender
Screen tycoon
Premium Member
join:2009-01-01
Brooklyn, NY

thender

Premium Member

They don't dim in parallel, only in serial.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

1 edit

SparkChaser to mackey

Premium Member

to mackey
said by mackey:

Actually the light from the $120 one will be the exact same as the $16.50 one. You will probably get a fancier/nicer package with the more expensive one though (it'll feel more "polished"). Or it might just be the exact same thing with 'phile pricing... "It's much more expensive so it MUST be better!" The only exception to this is if you're looking for a specific wavelength with a tight tolerance; those cost more due to them taking the time to test and "bin" the LEDs so they're an exact color.

As for the light output, that's going to be determined by the LED. All LEDs have a lens of sorts built into them, and assuming they put out the same amount of total light (wattage and efficiency is the same) the one with a wider beam angle will have a lower intensity due to the light being spread out more.

It would help if you could post links to the modules you're looking at.

/M

The SMD5050 has a definitive spec. If they are using the 5050 it should come close to it, 120° with a flat lens. Assuming these are white and not RGB the symptoms sound like the way they are being driven.

edit: LED spec
61238-32700.pdf
226477 bytes

mackey
Premium Member
join:2007-08-20

mackey

Premium Member

said by SparkChaser:

The SMD5050 has a definitive spec. If they are using the 5050 it should come close to it, 120° with a flat lens.

Are you sure about that? I was pretty sure "SMD5050" simply meant it's a Surface Mount Device that's 5.0mm x 5.0mm; beyond that anything goes. While it is true the vast majority are 120°, I thought that was simply because that was the easiest angle to get with that package; while you could make one with a different angle, it's simply easier to do it with a different style package.

What was the point of posting that datasheet? It does not mention either "SMD" or "5050" even once.

/M
mackey

mackey to thender

Premium Member

to thender
Do you have a link for the "cheap" one? I'd like to look at the actual specs. With the $2.20/meter warm white LED strips I bought, 2 runs are enough to light up a rather large room even though I'm running them at 11.4v instead of 12v...

/M

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser to mackey

Premium Member

to mackey
said by mackey:

said by SparkChaser:

The SMD5050 has a definitive spec. If they are using the 5050 it should come close to it, 120° with a flat lens.

Are you sure about that? I was pretty sure "SMD5050" simply meant it's a Surface Mount Device that's 5.0mm x 5.0mm; beyond that anything goes. While it is true the vast majority are 120°, I thought that was simply because that was the easiest angle to get with that package; while you could make one with a different angle, it's simply easier to do it with a different style package.

What was the point of posting that datasheet? It does not mention either "SMD" or "5050" even once.

/M

Sorry about that, I should have explained it. The spec was from Mouser and was the same as about 5 others I saw from people selling the light strips. It happened to have a manufacturers name on it so I used it.

I was basically trying to show that there is little difference in the LED and it is probably in the application of it.

The 120° comes from Lambert's cosine law and not from a lens.