5630 LED Strips / Ebay - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: September 09, 2015, 12:13:43 pm
content: Hello,Has anyone purchased 5630 LED strips on ebay? Such as these5M 5630 LED Strips?They state 30W (I assume per 5M), so 6W / Meter. Now, if you look at the 3rd picture, it shows a 390Ohm resistor. I've also confirmed this with the seller.This would mean the following assuming a 3.3Vf drop on each led:12V - 9.9V = 2.1V / 390 = ~ around 6mA current through the leds.OK, if this is the case, I calculate the power dissipation of the LEDs to be (6mA x 9.9V = ~ 60mW). The resistor power dissipation is (6mA * 6mA * 390 Ohm ~ 14mW). Total power dissipation for one "unit" of 3 LEDs + Resistor ~ 75mW. OK, there are 20 of these such units per meter (60 leds / 3 = 20 units), so 75mW x 20 = 1.5W / Meter. 5meters worth of strip is thus 7.5W of total dissipated power.My questions are obvious:1 - Why would they rate it at 30W if the total power is 7.5W( I will assume Chinese "Marketing" tactics).2 -MORE IMPORTANTLY, Why in the hell are they UNDER-DRIVING these LEDs by 95%?6mA / 150mA = 4-5%?? Let's play it safe and assume they are 5630 LEDs that can do 50mA - 100mA, that's still only 6% - 12% of their potential??? Why are they wasting so much LIGHT???Has anyone bought such strips that use a proper resistor which will allow these units to run closer to 100mA / LED?

author: Augustus
author_rank: Regular Contributor
timestamp: September 09, 2015, 12:33:02 pm
content: It's 39 Ohms (39 times 100) - now redo your calculations

author: made2hack
author_rank: Frequent Contributor
timestamp: September 09, 2015, 07:10:10 pm
content: that makes things a little better

author: SeanB
author_rank: Super Contributor
timestamp: September 09, 2015, 07:44:45 pm
content: I had some of those strips, and they drop in lumen output rather fast. I decided to underdrive the rest using thin wire ( saved looking for a low value resistor by just using some 28AWG network cable instead) so they run cooler and dimmer, but last longer. Do not expect stellar performance from them, I use them as a ;ight in the rear luggage compartment, as they are a lot better than the original festoon lamp in the nearly hidden holder.

author: Augustus
author_rank: Regular Contributor
timestamp: September 09, 2015, 08:50:05 pm
content: The quality of these cheap Chinese LED strips is very questionable... For your enjoyment, this is what you get from Banggood, if you order one of their 50cm 5630 36 LED Waterproof Rigid Strip Cabinet Lights (SKU140236):It's brandnew, advertising on their website states"*Grade A Led chip guarantee, it is same brightness and color match for each Led chipand with aging procedure"... Yeah, sort of...Should have known better...

author: made2hack
author_rank: Frequent Contributor
timestamp: September 11, 2015, 03:07:41 pm
content: the thing is i don't have the patience or wherewithal to hand solder 300 of these suckers (if I buy the individual leds).Not to mention I don't have the flex pcb either.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 11, 2015, 03:18:59 pm
content: ..and Vf is more typically 3.0v

author: Chris C
author_rank: Frequent Contributor
timestamp: September 11, 2015, 06:45:37 pm
content: I can't explain that resistor value. But  is right, running those at 100% of the rated LED current typically results in them losing half their lumen output in less than a year, sometimes just a few months. The strip those LEDs are mounted to just doesn't dissipate enough heat.Running them at 33-50% of rated current works better. A few people have affixed the strips to aluminum heatsinks using thermal glue, and managed to run them at 100% long-term without issues.And the pic  showed is fairly typical too, but know that a camera tends to process light more linearly than the human eye. In person, looking at that exact same strip, you might not notice much of a brightness difference between individual LEDs at all.