The Tao of Chinese LED Strip Lights

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texaspyro
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The Tao of Chinese LED Strip Lights

I recently converted all 300+ lighs in my house to LEDs (see My adventures in LED home lighting).   In my master bedroom are two bookcases with under-shelf light strips made up of small incandescent bulbs.   They work,  but have a nasty trait of causing the shelves to pop and creak for over an hour as they heat up the wood.  Plus they are incandescent...  that just won't do for the techno-villa.

If you've ever trolled Ebay, etc for LED stuff you have seen those LED strip lights.  These are strips of LEDs with ballast resistors mounted on an adhesive backed flexible strip.  They are 8mm wide and up to 5 meters long.  You can get them with 60 or 120 LEDs per meter.   The LEDs are configured in groups of (usually) three LEDs and a current limiting resistor.  The LED groups are connected in parallel along the length of the strip.  

You can cut the strips to any length that is a multiple of three LEDs.  You solder wires to small copper dots to make the new connections.  You can get the strips in many colors.  If fact you may get them in colors that you did not order.  I first ordered warm white,  but got a neutral-cool white.

The strips come in two types: "water-proof" and non-water proof.  AVOID THE WATERPROOF STRIPS LIKE THE PLAGUE!  They are waterproofed by coating them in a semi-cured epoxy booger.  It stinks.  It sticks.  It sucks.  And it WILL KILL THE LEDS!. Also,  if you cut the strips, it takes forever to clean it off the electrical contact points.

Back to the IT WILL KILL THE LEDS...  I ordered some non-waterproof strips and got shipped waterproof.  Bummer, but OK.  I made some lights out of them and ran them for a few months.   After that,  the LEDs were almost non-visible DEDs (Dark Emitting Diodes).  A couple of LEDs on each end of the strip were visible.  The epoxy booger had cracked and darkened (but not enough to obscure the LEDs).  I stripped the epoxy off the tops of a few LEDs and they were just as dim.  My theory is the epoxy traps heat that kills the LEDs or somehow leaches into the LED package and kills them.

Later, I found one waterproof LED seller that mentioned the problem with epoxy waterproofed strips.  He sold a version that was in a silicone tube that allegedly does not have the problem... sound reasonable,  but buyer BEWARE if you need waterproof LED strips.

 

When you get the LED strips,  they come on a reel.  The seller most likely has terminated one end of the strips with wires and maybe a barrel connector.  I bought 5 meter reels of 600 leds.  Rated at 4 amps.  I hooked up 12V to the wires and voila.. 2 amps.  Huh?  Another Sino-fraud rating ripoff from our friends in Old Cathay?  Well,  not exactly.  I checked the voltage/current over a 3 LED segment near the wires.  The LEDs were drawing 16.5 mA.   The full strip should have been drawing 3.25 amps...  Hmmm.... It turns out that the flexible copper tape conductors that the LEDs are mounted on cannot handle the current.  There is a big drop in voltage down the length of the strip.  The groups at the far end of the strip were getting less than 10 volts.

Well,  why not just crank up the voltage so the strip draws the full rated current? Because the LEDs nearest the power connector will be seriously overdriven.  The only way to properly drive the strips is to connect the "+" voltage to one end and the '-' voltage to the other end.  This will assure that each LED group on the strip receives the same voltage.  You still have to crank up the input voltage well past 12V to offset the voltage drop in the copper foil connectors.  Driving a full 5 meter, 600 LED strip from each end required 14.25V to get 12V to the LEDs.  So around 1/4 to 1/3 the power you dump into the strip goes to heating copper foil.

You can drive shorter pieces of the strip from one end since the voltage drop won't be too bad,  but beware if you want to drive longer pieces.

JohnnyMac
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Hey, Tex, can you provide a pic of the "waterproof" booger covered strips so we know exactly which ones you are talking about? I have a bunch of red LED strips to put on my Harley and now I'm wondering if they might be the same type you are talking about.

These are the type I have: http://www.tmart.com/60cm-LED-LED-Strip-Car-Flexible-Light-Bar-Line-Red_p92339.html

texaspyro
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JohnnyMac wrote:

Hey, Tex, can you provide a pic of the "waterproof" booger covered strips so we know exactly which ones you are talking about?

I tossed all of those horrid things.  You can tell if they are the epoxy ones because they stink (literally) and they are sticky (at least when new).  Set them down on a surface and you will be pulling them off while referring to chants in the "Drunken Russian Sailor's Book of Curses and Swears".

Also,  some red LED strips may not be arranged in groups of three LEDs since most RED LEDs have a lower forward voltage than the other colors.

texaspyro
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I measured the resistance of the copper foil conductors on a couple of different reels.  They run around 0.2 ohms per meter (1 ohm for a 5 meter reel).  You need to allow for the voltage drop across that resistance when you drive the strip from each end (+ on one end, - on the other).

Actually,  the positive conductor was 0.88 ohms and the negative 1.10 ohms,  so even driving the strip from the opposite ends,  the voltage to each LED group is not perfectly divided (but is close enough to not really matter).   

dchomak
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Here is the strip lighting that I have.  My brothers kid got them off a remodeling job at a bank or jewelery store. The aluminum strip is a heat sink and gets very warm.  I do not know what LED's are there but they are bright.  All modules run in parallel so I was able to cut smaller strips and install them into a curio cabinet my wife keeps here Swarovski Crystal in.  Spectacular sparkle!.  Those crystals love point source lighting!

Kwak
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Could anybody recommend us any offer of 5050 warm white led strips (preferred eBay)?
Minimum requirements:
● Color: Warm White
● View angle:120°
● Working Voltage: 12VDC
LED Quantity: 300 leds/5 Mete
● Working Current/meter: 1.2A
● Working Tempreture:-20 to 50°
● Protection Rate Sad Non-waterproof)
● Color temperature: 2800-3500K
● Size: L 5 or 1 m

zeremefico
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Great work. I have ordered some 24V 5050 60 led/m led strip from Aliexpress and I intend to put it in a bus.
It is really hard to choose from zillions of led strips, maybe we could create a supplier database, based on the feedback of members.

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texaspyro
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zeremefico wrote:
maybe we could create a supplier database, based on the feedback of members.

I suspect that it would be out of date before you hit carriage-return. I doubt that no two orders, even from the same supplier, would get the same product. There is just so much of it out there. I’ve bought quite a bit of them and no two seem to be quite the same.

theoldbill
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Anyone in the UK wanting LED strips should check out visualchillout.co.uk

Ive ordered from him before, slightly clunky website but quality products. Not as cheap as the bay but you get what you pay for!

I have no connection to the guy, just a loyal customer.

Merry Christmas one and all!

Werner
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I pull this thread back from the grave because I got 5 m ledstrip from fasttech today. Described as 72W.
https://www.fasttech.com/products/1064803
They are not explicit declared as waterproof but it has a siliconstyle waterproof coating which can be peeled off easyly. The full 5m strip pulled only 2.5A, so I was upset first but then I cut 1m.
The 60LeD from one meter strip pull 0.9A, that’s acceptable.
3LEDs pull 16mA.

As you can see there are 3 resistors with 150ohm each, how are thes strips connected? I can’t really figure out how the schematic is.
I will try to remove the resistors but I am confused….?

texaspyro
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Werner wrote:
As you can see there are 3 resistors with 150ohm each, how are thes strips connected? I can’t really figure out how the schematic is. I will try to remove the resistors but I am confused….?

Leave the resistors in, they are needed to limit the current to the LEDs. The strips are arranged as many paralleled groups or parts. Each group is three LEDs and the current limiting resistor in series.

Werner
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But each led has three LEDs in it too…?
I want just to play a bit with them. I have removed the resistors of one 3 LED part, and soldered a wire instead. Now I power them with 0.1A and they are really nice and bright.

I can’t figure out how they are connected…perhaps I am too tired, I will try tomorrow again.

texaspyro
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Did you buy the RGB strip or the white light strip?

texaspyro
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Looking at the photo, there are three resistors per three LEDs on the RGB strip. Should be the same configuration with all three RED leds in series with a resistor, all three GREEN leds in series with a resistor, all three BLUE leds in series with a resistor.

Leave the resistors as-is or you are going to fry some LEDs.

Werner
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I got the neutral white version. I just increase current until color change and then I decrease it…so everything is safe.

The only datasheet of a similar 5050led I found, showed that the parallel legs are one led with forward voltage of 3V or so.
I will try to wire the LEDs parallel and power them with a 7135…

Edit I tried the 3 inner led in every led they seem to work from 2.7-3.7V above that they get blue and then they fry…
I cut the LEDs in single and paralleled 3(6inner leds 3 fried) LEDs and powered them up with 0.4 A. I would be happy if I could do this without ruining the strip, than I would try some kind of 18650 powered lantern or so…

Shadowww
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Werner wrote:
I pull this thread back from the grave because I got 5 m ledstrip from fasttech today. Described as 72W.
https://www.fasttech.com/products/1064803
They are not explicit declared as waterproof but it has a siliconstyle waterproof coating which can be peeled off easyly. The full 5m strip pulled only 2.5A, so I was upset first but then I cut 1m.
The 60LeD from one meter strip pull 0.9A, that’s acceptable.
3LEDs pull 16mA.

As you can see there are 3 resistors with 150ohm each, how are thes strips connected? I can’t really figure out how the schematic is.
I will try to remove the resistors but I am confused….?

You should connect + from one side, and – from other side, otherwise you have huge voltage drop across the stripe (causing the under-spec current).
After doing that, adjust the voltage of power supply so that voltage across + and – lines in the MIDDLE of strip is exactly 12.0V.
Werner
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I think it isn’t possible to use these strips in full power without additional wiring in either way connection. Increase voltage will lead to overdriving some LEDs…inconsistent brightness in either way.
Edit: I have thought about your tip and I will try this tomorrow, if I connect one connection to every side the resistance to every strip should be equal…that’s clever

I think I have measured the current for 3 LEDs incorrect…will do that tomorrow again.

As I can live with 1 m strips brightness at0.9A I will parallel 3 strips and glue them on a piece of aluminium and screw that underneath a shelf to enlighten my desk. That was the plan and still is. Also I have wrote fasttech a message to ask if they have additional info or tips regarding the 72W thing….
But it would really be fun if I could use some of the strips for battery application

My other parts dimmer and so on I ordered for this project on the same day as the strip but from DX are just departed, and this is just a partial shipment…DX is so slow…

I have somewhere a 12V 3A power supply laying around and I will test to power the strips with that tomorrow…

And yes they smell

Shadowww
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Werner wrote:
I think it isn’t possible to use these strips in full power without additional wiring in either way connection. Increase voltage will lead to overdriving some LEDs…inconsistent brightness in either way.
Edit: I have thought about your tip and I will try this tomorrow, if I connect one connection to every side the resistance to every strip should be equal…that’s clever
Yup, it took some time to come up with this solution – but after I implemented it, each and every triplet (is that even a word?) of LEDs measures exactly 12V, no matter if I measure it on either of ends, in the middle, or in any other place.
texaspyro
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By connecting the + to one end of the strip and the – to the other end, the LED voltages along the strip are fairly well equalized. Driving each end with + and – is even better. Diving long strips from one end only is bad. The LEDs at the far end are starved for current due to voltage drop along the strip.

Shadowww
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texaspyro wrote:
By connecting the + to one end of the strip and the – to the other end, the LED voltages along the strip are fairly well equalized. *Driving each end with + and – is even better. * Diving long strips from one end only is bad. The LEDs at the far end are starved for current due to voltage drop along the strip.

Oh crap, how could I overlook a idea that’s so simple yet makes so much sense.. Silly
Thanks for this, I’m going to re-wire a few LED strips I have around the house now.
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So I have used some meters of this strip and it is ugly blue…okay for my worktable but a neutral tint would be better. The good thing is it has stopped stinking, after laying around outside off the bag and powering it up some hours it does only smell if you go nearer than 50mm.
We will see how long the sticky tape on the back lasts, as it gets hot about 55°C=130°F. One element needs 50mA, one meter has 20 elements(60 LEDs ) and pulls around 900mA.
I use 3 strips of 0.95m(57 LEDs ) in parallel powered with 11.9V and about 2.6A. I have them connected on each side.
They are far away from 72W like described from fasttech so i got 30% of the money back and they have removed them until they have cleared things with the suplier.

I found out what my problem was. Each of the pads needs to be soldered, three are negative one is positive.
So 3inner leds(one of each 5050) are in series with one resistor, and three of these groups are in parallel.

texaspyro
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The problem that I found with those stinky, sticky epoxy-ish coated strips is that they soon die. It looks like the epoxy stuff traps heat and/or reacts the the LED surface. The end leds on each 16” strip of mine were fine, but all those in the middle died and were barely visible. This occurred after a couple of months of 24/7use.

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I have cold white and RGB strips, waterproof, dunno what it is but even after 3 years? It’s still soft when I press it with a nail. It did not crack, nor discolor.
They did smell when new that’s for sure, but not once installed and in the open.

Work fine for 2 years now?

The only tiny discoloration is from the copper at the places where the copper traces for cutting the strips are.

I think they are the smaller type 3528 and around 2m length.

Werner
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Mine are also still fine but I only use them a couple of hours a day and I glued them on a aluminium rod. They also stopped to stink.
I hate the bluish colour, If I had to do it again I would probably use some of the 12V LEDs, these have much nicer colour temp. So I have laying around about 1.5m without use…

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New to the forum, just found this! I’m an amateur LED enthusiast that last year made a go at turning this knowledge in to products. I started with high quality cree stuff and hand assembling my own circuit boards but am ever intrigued by the cheap Chinese light strip product as it is super cost effective for $/lumen.

Yes. Tieing the back to the front will get you even voltage across. That is how super regulated power supplies work. You bring a wire from the far side back to a voltage input on the supply and it automatically adjusts so that it accounts for voltage drop over the wire. Voltage drop over distances will happen. I haven’t studied this on a lot of the strip light but will look in to. It is a real phenomenon but dont know how drastic it is in this case. Wiring up to the strip with 18ga or bigger will definitely help for higher current draws of your whole system because that will be a choke hold.

Things I’ve done before if there’s strips side by side is pull the plus and minus from strips nearby in the middle so that even if there is voltage drop its from the middle and not the ends so the light doesn’t look increasingly dim from left to right or top to bottom if you’re going in one end and out the other.

I’ve bought the eBay and DX stuff that doesn’t come as described or isn’t the same twice. Amazon has some cheap reels but I feel like that is blow out product and when they’re out they’re out and you never know how accurate their specs are.

I found a great Chinese vendor at a trade show that makes super high quality strip light (they only sell business to business). I’ve bought multiple samples from them and the quality has been super high and lumen output is very high. They provide light files and everything.

Anyways quality stuff is out there its just hard to know what is good or bad on a website. I would say if something doesn’t give you Volts, Amps, Lumens, and Color Temp then stay away. These are specifications every person making a LED product should know even if its theoretical from data sheets. A lot of strip light on websites if it does have lumens don’t tell you if that lumens is for the reel, per meter, per foot, per cut strip or what.

I like to look at total lumens when comparing products. It is the most simple and is the easiest to compare what you’re paying for. I believe some manufacturers use lux (lumen per square meter) ratings though for incandescent equivalents. Go to Home Depot’s website and look at a Cree A19 and Cree BR30. A19 is 800 lumens and 60W equivalent and the BR30 is 650 lumens and a 65W equivalent. How could it be less lumens but a higher equivalent? I use incandescent wattage x 15 lumens/watt and then compare to what my LED total lumens are.

I launched a kickstarter this month for a 12VDC light that uses 12v product from the vendor I spoke of earlier as the light engine and I corded it with a car plug. I’m making the housing. I am including a wall adapter for a car plug so you can use it indoors. Its 300 lumens in 11”. Really bright for tape light! Tape light that has to have a heat sink.

https://www.kickstarter.com/projects/1749518521/mount-anywhere-led

Anyways check it out or support the cause for one if you’re interested in seeing the tape light and how cool and finished a product you can make from it.

I’ve got some experience in this if you want to ask me questions.

The bulb is dead

texaspyro
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[quote=lightvision1A19 is 800 lumens and 60W equivalent and the BR30 is 650 lumens and a 65W equivalent. How could it be less lumens but a higher equivalent? I use incandescent wattage x 15 lumens/watt and then compare to what my LED total lumens are.[/quote]

BR/PAR lights are reflector lights and you lose quite a bit of output there. LED equivalents don’t have the reflector losses but do have losses in their optics.

Also, a better number for USABLE incandescent output is 10 lumens/watt. Most decent LED bulbs deliver 50-60 lumens/watt once you get all the losses figured in… larger sized bulbs are usually more efficient than the smaller ones.

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texaspyro, or anyone else willing to weigh in… I’m looking for recommendations for power supplies for these bad boys. I’ve got a 5m strip of 5630 WW leds that I’ll cut into appx. 4’ sections (75 emitters). These will be used outdoors (under canopies, so not super-exposed), so would like a tidy-ish box as opposed to a harvested PC power supply.

It seems like 1.25m wants 18 watts… does that number fit your experience? And wattage-wise, are the specs of transformers on ebay kinda like the chinese lumens problem? Should I shoot for a bit of headroom? These aren’t going to be in 24/7 service, but I really want them to run all night without failure.


 

texaspyro
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You might look into using something like a regulated wall-wart or laptop supply. My dining room table (http://budgetlightforum.com/node/16538) used 10 meters of strip and draws around 6 amps on high. I needed around 14 volts to overcome wiring losses and used an efficient 15V power supply adjusted down until the “bulbs” saw their rated 12V.

When driving longish pieces of strip you need to feed the “+” voltage into one end of the strip and the “-” into the other end. Otherwise the LEDs on one end will be overdriven and those on the other end will be starved for power.

Werner
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I used a 12V power supply I bought from a shop which sells cheap electro parts, which they buy in large quantities. It’s a small black box like a laptop power supply and I mounted a DC socket on the strip to plug it in.
My strips are only one meter long and I fed them from both sides because even on this small distance I saw a to high voltage drop. Check post #20 for my current measuring.
It works but if I had to do it again I would do it like Tp recommended and tweak the max out of it.

There are tons of nice DCDC step down modules on ebay, one of this and a laptop power supply might work well.

ruffles
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Thanks for the info.

As a total side note, Werner, I suspect that the 72w number refers to the entire 5m string. Of course, finding accurate numbers on ali/ebay/ft/etc is ridiculously hard.


 

texaspyro
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BTW, I was testing a strip while it was still on the reel… it melted the reel rather quickly.

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