High CRI LED tape got cheaper

[Phil Rhodes]

I notice that the low-cost online sellers are starting to offer LED tape advertised as having a 93 CRI:

 

http://www.ebay.com/itm/121666577526

 

This sort of thing has been available from specialist suppliers for a while, at swingeing cost. It's considerably more expensive than the cheapest LED tape, but very reasonable compared to the competition at about $10 a meter, where a meter represents 90 LEDs and about 20W of power dissipation.

 

We can assume there are caveats, of course. These numbers may be inaccurate, but if the 93 CRI claim is legitimate it's probably about as good as the first generation of LED lighting. TLCI analysis would, of course, better show the flaws. Most of the LED strip I've seen has been rather ambitiously rated as regards power level, too, so it may not be as bright as 20 watts per meter suggests because it may not really be 20 watts a meter.

 

Still, no bad thing for those of us on a budget.

 

P

[Adrian Sierkowski]

Good find.

[Akos Baranya]

I got some of these delivered to me, the light seems nice, but it looks more like 5W/m rather than the stated 21W/m . It comes with more documentation than expected for a chinese led strip. I have no means to test the CRI of the strip I have. Be careful, I wanted to order warm but accidentally ordered super warm, totally my fault but the ebay listings could be a tad more clear.

[James Daggy]

I got these in as well and when using a more powerful power supply from 2a to 5a the thing got much brighter... Still waiting to try it on a 10A. Will be ordering the 4000 to 5000 version next.

[Phil Rhodes]

Perhaps I'd better put in for a few. Anyone tried Yuji LED, as well?

 

If that stuff really is 24W/metre, it would need 2A/metre at 12V to run correctly. To run the entire strip ought to require 10A, and that's actually more than I'd trust the little copper tapes in it to carry, so you may wish to cut it into shorter lengths and power them independently.

 

It may not actually be 24W/m, but I would strongly recommend choosing a power supply of 25% to 50% greater capacity than is needed, for long life and reliability. Again, this may mean subdividing it, as a 15A 12V power supply is a large, heavy, expensive, possibly fan-cooled and noisy item. This is why some places do a 24V version, too.

 

Use a multimeter to measure the voltage. If it's significantly under 12V on load, your power supply is struggling.

 

P

[Akos Baranya]

Had a chance to check with just a 1 meter length, a proper power source and a multimeter and I was very pleasantly suprised. The ~24 W/m claim seems legitimate after all if it isnt being underpowered. I am very satisfied.

[Guy Holt]

 

If that stuff really is 24W/metre, it would need 2A/metre at 12V to run correctly. To run the entire strip ought to require 10A....

 

 

Calculating the Amps drawn by LED ribbons is straight forward when powering them with DC, but when you need to plug them into the wall things get complicated because a lot of LED AC power supplies are not power factor corrected. Which means that if you do not take their poor power factor (which can be as low as .45) into account when running LED Ribbons you can find yourself tripping breakers because the lights will draw twice the AC current you would think. A good example of this was a Christmas movie shot here this last January. The set decorators dressed a large tree (20’ high) with hundreds of LED strings. Where each string was just a few watts they figured they could plug them all into one circuit. After the breaker tripped several times, only then did they call in the electricians to sort out the mess. But of course now the production is waiting for the tree lights to come on before they can shoot and the electricians caught the blame.

 

(Even the premium priced LiteGear RGB Lite Ribbon pictured above has a pf of .45)

 

Unfortunately, the manufacturers of LED Light fixtures generally do not give power factor specifications for their products. One would think that the less expensive LED lights would not be pfc, while the more expensive ones would, but that proved not to be the case in recent testing of fixtures. Over half of the fixtures that I tested at random (from the inventories of Boston area rental and lighting sales companies) were not pfc. With power factors ranging from .45 to .63, these fixtures generated considerable harmonic distortion (THD ranged from 75-85%.) Even those that were pfc generated harmonic currents when dimmed. For instance, the pfc of the new Litepanel Astra 1x1 below dropped from .99 to .54 when dimmed 50% (THD increased to 83.2%.)

 

 

One could argue that the wattage of LED fixtures is so low that the harmonics they draw and kick back into the electrical distribution system is so low that it does not matter from a practical standpoint.

 

While that is true to a degree, when used as the predominant source of light in a studio, like the new BSkyB studio pictured above, or for a night exterior powered by a portable generator, the harmonics generated by even small LED fixtures will accumulate and effect their power source adversely. To see which LED lights are power factor corrected or not, use this link to see some of the results of my tests.

 

 

Guy Holt, Gaffer

ScreenLight & Grip

Lighting Rental & Sales in Boston

[JD Hartman]

OMG! Doom and Gloom. What say ye, Phil Rhodes?

[Phil Rhodes]

The sort of light tape stuff I mentioned in the original post is likely to be run from fairly small, individual 12V DC power supplies in the 25-100 watt range, which are indeed almost always uncorrected for power factor.

 

Guy, why don't you commission one of the big Chinese factories to produce a PFC 12V power supply at say 50W, then we could all use them!

 

P

[John E Clark]

The sort of light tape stuff I mentioned in the original post is likely to be run from fairly small, individual 12V DC power supplies in the 25-100 watt range, which are indeed almost always uncorrected for power factor.

 

Guy, why don't you commission one of the big Chinese factories to produce a PFC 12V power supply at say 50W, then we could all use them!

 

P

 

There are open frame power factor corrected powers supplies... From a quick search here's one for 50W

 

http://www.trcelectronics.com/View/Cosel/LFA50F-12.shtml

 

The price seems to be about $45 USD... the 100W version is about $62.

 

I've not had the time to find out what power supplies that are used in my day job application, and I don't know if PFC-ness was part of the consideration. Our unit is certified for FCC Class B use, but that does not consider low frequency crap that Guy Holt is discussing.

 

As for quantity pricing, and why LED manufacturers don't just use PFC devices in the first place... well say the above 50W item could be had for $25 in large quantities... that still may be too much for the LED panel manufacturer in their pricing scheme.

 

 

Edited August 14, 2015 by John E Clark

[Phil Rhodes]

As for quantity pricing, and why LED manufacturers don't just use PFC devices in the first place... well say the above 50W item could be had for $25 in large quantities... that still may be too much for the LED panel manufacturer in their pricing scheme.

 

This is really the question.

 

The things one assumes one is paying for, with these big-brand devices, is attention to exactly this sort of detail in the engineering. It's very disappointing to discover the truth.

 

That said, this is really only ever going to be a problem on extremely upscale jobs.

 

Or, I suppose, small jobs running from battery-powered inverters.

 

P

[James Daggy]

Hey all

 

If it's any interest I took some pics a while back when I first got them... Very make shift china lantern ball shoot to see what we're dealing with- I really like them-

 

 

[Phil Rhodes]

Hi James

 

Perhaps it's time to pick up a Macbeth chart.

 

P

[JD Hartman]

A more honest test would be seeing the same space lit with an HMI, a Joker 400 maybe and the LED paper lantern. Could you tell the difference without seeing the light source?