“How to test LED screen?”

[Peter Chiu]

Continuous …..............“how to test lcd led backlight?”

Episodes 2 …....... “How to test LED screen?”

[music] https://www.youtube.com/watch?v=CaQzv5nVpac

Review:

Who lights up rock ?................................H J Round
Who lights up liquid ?...............................Friedrich Reinitzer
Who lights up filament ?...........................Thomas Edison
Who lights up my life ?..............................Debby Boone
Who lights up Firefly ?......................... ....God

Bioluminescence more than 95% energy efficiency.
Firefly produce light very little heat is given off which means that not very much energy is wasted at all. This "cold light" has a 96% efficiency rating; which, when compared to an incandescent light that has only 10% efficiency, is rather impressive...... Man has so far no way to create such an efficient light source!...

Reference:
Bioluminescence
http://en.wikipedia.org/wiki/Bioluminescence
Luciferase
http://en.wikipedia.org/wiki/Luciferase#Applications
Bioluminescence: Fireflies and the Future
http://serendip.brynmawr.edu/exchange/node/1721




OLEDs: only 20 percent of the light generated is released from the device. The scientists have designed an OLED that boosts illumination by 60 percent using a combination of an organic grid working in tandem with small micro lenses that guide the trapped light out of the device........$#%@%......Yes.....still can't catch up with Fireflies....

Tips: …........OLED TV has no back-light, it light up by itself.......

LG Shows of 8K TV & Explains why OLED is the Future - CES 2015
https://www.youtube.com/watch?v=17Ua0Bw8pKg

We interview Craig Cunningham, UK product manager.
https://www.youtube.com/watch?v=45WVV2wcQFw

https://www.youtube.com/watch?v=3OnSUxI4NsQ

[chat]
...That's why shopjimmy went to outlet business!.....%$@%%$@^$......... he already knew OLED TV hardly anything for sale........ the screen is what the money at ........ #%@%@^%#^ .......... Yes,I think so, he is smart guy.................A ... man........#have U'een to CES show...... Yes, I've been there twice, one week for each time,To help my friend's product exhibition. ..........# there have Adult Expo...... yes I've been there also ....... #man ..... hot .......@$$#%^^^$ ........... Yes ..I have porn star's photo and signature.....#$%3..7^$^&$&....I don't think the value will go up.....

[Peter Chiu]

Re: “How to test LED screen?”

How to solve the LED's puzzle.

[Music] Leo Rojas- The lonely sheppard
https://www.youtube.com/watch?v=ay6jiKpHSmk


[Example]
I picked up a TV in dumpster, parting out the TV for sale on ebay, I want $ 240 out of it.
Power supply will be 3 times more than T-con.
Motherboard will be 6 times more than T-con
How much should I sale each parts?

[Answer] y+3y+6y=240 y=24

T-con priced at $24
Power supply priced at $72
Motherboard priced at $144
The equation is y+3y+6y=240 24+72+144=240 1+3+6=10

Questions from BUD M

The questions are, without opening the screen how would you know:
1) How many LED strings are inside the TV
2) How many LEDS are in each string, some LED may have two or more LEDs in one body.
3) How the LED strings are connected together, series or parallel, or series-parallel combination.


[ Solution 1] Use mathematics to solve problem.
On the board show pins led1+led1- led2+ led2-
use meter test current from the screen
led1- led1+ tested current at 0.384 A
led2- led2+ tested current at 0.286 A
that's all we need to know....

one set of wires get current 0.384 A
another set of wires get current 0.288 A
We definition of equation X+Y=Z
X= First groups LEDs=0.384 A
Y= Second groups LEDs=0.288 A
Z= Total LEDs

X+Y=Z 0.384 A+ 0.288 A= 0.672A simplified them

0.48A + 0.36A =0.84A simplified again 4+3=7

OK now look this ….. 4+3=7 …..means total has 7 LED strips

First groups LEDs has …...........4 LED strips=X
Second groups LEDs has ….... 3 LED strips=Y
Total has …....….......................7 LED strips=Z

From this equation X+Y=Z 4+3=7 we will get this possibility combinations.
.
.

40LEDs +30LEDS=70LEDs

44LEDs +33LEDS=77LEDs

48LEDs +36LEDS=84LEDs

52LEDs +39LEDS=91LEDs

56LEDs +39LEDS=98LEDs
..
.
and so on
form the current relationship this are all we can know....But
…......................................................................................
If we could know one LED's current is 8ma

Then we get all the answers right away

(384 mA+ 288 mA =672 mA)/8 mA

48+36=84
That's means
48 LEDs +36 LEDS=84 LEDs

48 LEDs/4=12 LEDs on each trip

This is the answer:

12 LEDs on each trip

First groups LEDs has …...........4 LED strips=X=48 LEDs
Second groups LEDs has ….... 3 LED strips=Y=36 LEDs
Total has …....….......................7 LED strips=Z=84 LEDs

Total LEDs 84 LEDs


[ Solution 2] Use BUD M's idea, build an adjustable power supply , in darkroom slowly turn up the voltage until you saw white dots just count how many LEDs and which one is not light up …....

[Build instead of buy ]: 1-100 LEDs Tester.....
Make 400 watt MOSFET Sine Wave Inverter Circuit.....

http://www.homemade-circuits.com/201...-inverter.html

Or CCFL tester will do the trick also........

[budm]

Re: “How to test LED screen?”

Sorry, WRONG! WRONG ! WRONG! AND WRONG!
Do you understand what series connection is? Do you understand current flow in series?
Draw up a diagram of what you show in your and use your logic and what you learn to get your EE, plus learn about LED's Current AND VF.
Do the experiment with just one actual LED strip, power it up and measure the current and tell us how you figure out how many LEDs are on the strip.
A clue, the current draw does not tell you how many LED are in the circuit, total Vf will give you close enough (because Vf caries with If) to figure out how LEDs are in the circuit.

[Peter Chiu]

Re: “How to test LED screen?”

Will do real LED TV report to you ....from unopen TV ....test .... and report ...and light up LED strips.....each LEDs current....

But I need to build a LED power supply tester first ....Will you do it ...so, We tested screen and see...
I really don't want buy another JUNKs....

[budm]

Re: “How to test LED screen?”

You can get 5 or 6 white LEDs connected them in series and attach it to your power supply and set the constant current to about 30 mA and take the readings.
Not that complicate is it? simple logic and common sense on trying to solve the problem.

[budm]

Re: “How to test LED screen?”

Look at this and tell me if the current flowing through the LED strips will tell you how many strips and LED there are in the circuit.

[Peter Chiu]

Re: “How to test LED screen?”

one LED I tested is ......... 3.3V @ 12ma
when I use CCFL tester ,, reading is AC current and is not full bright so.....I need good HV power supply .

tested with 6 LEDs is open loop ,still light up, amazing. then I soldered close the loop, got more current....I need good HV power supply .

[Peter Chiu]

Re: “How to test LED screen?”

If led @ 10mA
then first one DRV1=10 LEDs , Drv2=10 LEDs, 2 strips total 20 LEDs
each strip has 10 LEDs

4 strips basic as same as 2 strips, as long as same current..

DRV1=10 LEDs, Drv2=10 LEDs, 4 strips total 20 LEDs
each strip has 5 LEDs

[Peter Chiu]

Re: “How to test LED screen?”

Find one good and cheap, somehow look like @Alastair E's ideas

The variable high voltage power supply 0-300V
http://www.eleccircuit.com/the-varia...supply-0-300v/

Special thank to Alastair E ........I can't believe...... .We make a big circle then come back to his idea......Would save us months of works......

I will built at weekend and come back.... %$%$#^%#^....Good...%$@#^.....smart guy....man.....

[Music] Sleepsong Secret Garden HD

https://www.youtube.com/watch?v=Gq_glz5S6zE

[budm]

Re: “How to test LED screen?”

If led @ 10mA
then first one DRV1=10 LEDs , Drv2=10 LEDs, 2 strips total 20 LEDs
each strip has 10 LEDs

4 strips basic as same as 2 strips, as long as same current..

DRV1=10 LEDs, Drv2=10 LEDs, 4 strips total 20 LEDs
each strip has 5 LEDs

Again, WORNG, WRONG, WRONG, and WRONG.
You just do not get the concept of LEDs connected in series, do you? and the series current reading. And do not understand the relationship between Vf and the current.
Like I said, put LEDs in series and drive it circuit with 10 or 20mA.
What is Vf reading? The total Vf will tell you what the minimum power supply voltage needs to be.

[budm]

Re: “How to test LED screen?”

https://www.badcaps.net/forum/attach...5&d=1429804566
What is the Vf of that strip?

[Peter Chiu]

Re: “How to test LED screen?”

Use Vf is good idea.
I use my Fluke 77
1 LED=0.76v
2 LEDs=1.53v
3 LEDs=2.29v
4 LEDs=no reading
5 LEDs=no reading

[budm]

Re: “How to test LED screen?”

BTW: from the person that provide the circuit and the video:
"6P1P says:
October 5, 2014 at 10:08 pm
The video is belong to my experiment, I have slightly modified the circuit to maintenance 300VDC, I add a 100K resistor in between B+ and 500K , and i add a 24V x 12 = 294V zener parrallel with 500K.

I didn’t use MOSFET because i don’t have on hand i ‘m using FGA25N120ANTD 1200V 25A IGBT , i think any MOSFET will work as long as the Vds can withstand 400V and above.

I’m Using the transformer is design for valve/tube amplifier, having output 230V and 6.3V, the 6.3V winding i use to power the digital voltmeter for voltage and current as well.. the current actually is 1V meter with 1 ohm resistor in low side sense as shunt.

Good luck"

Good luck alright! The MOSFET will never be fully turned on due to fact that it is being use as the HIGH supply for the load.
Putting 294V to the output of the B+ which is about 325V without current limiter for the Zener, good luck with that also. Notes: as you can see, the 500K pot is connected to the output of the main rectifier and filter cap, so he added 100K in parallel with 500K pot and the 294V Zener with 100k and the 500K pot.
Also that 12V ZENER in parallel with the BC junction of Q2, REALLY?

http://www.eleccircuit.com/the-varia...supply-0-300v/

[budm]

Re: “How to test LED screen?”

Use Vf is good idea.
I use my Fluke 77
1 LED=0.76v
2 LEDs=1.53v
3 LEDs=2.29v
4 LEDs=no reading
5 LEDs=no reading

"1 LED=0.76v" that is FUNNY!

Again, what is the Vf of this strip?
https://www.badcaps.net/forum/attach...5&d=1429804566

[Peter Chiu]

Re: “How to test LED screen?”

with power supply
1 LED=2.5v
2 LEDs=5.01v
9 LEDs=22.74v

[budm]

Re: “How to test LED screen?”

with power supply
1 LED=2.5v
2 LEDs=5.01v
9 LEDs=22.74v

And how much current is flowing through that 9 LEDS (which are connected in series + current limiting resistor I hope!)?

[budm]

Re: “How to test LED screen?”

BTW, what is the FLUKE meter model number?

[retiredcaps]

Re: “How to test LED screen?”

BTW, what is the FLUKE meter model number?

Hi Budm,

From the last picture, it is a Fluke 77IV.

The 77IV is not True RMS probably made specifically for some of the government/militiary that had older generation of non True RMS meters with tons of custom documentation.

[budm]

Re: “How to test LED screen?”

Thanks retiredcaps, now it makes sense as to why his reading is so far off trying to read high frequency AC amp when the meter that only has 1KHz bandwidth.
That high voltage generator is >30KHz, that FLUKE is not gong to read it properly and it is not T.R.M.S either.
Peter, you should learn about your tool limitation next before start testing and report the invalid results.

Do you really think that your CCFL High voltage generator can put out 0.640A AC or more than 700mA AC? That CCFL tester output voltage is over 1000V (at least 1500VAC to start the lamp).
778mA AC through that LED strip, sure! You also taking a big chance damaging the meter with that high voltage CCFL tester.

I am really curious as to why you keep posting all these invalid results. You also still do not understand that the LEDs are connected in series (so the current flowing through each LED on the strip will be same and that is why you CANNOT use the current to determine the QTY. of the LEDs on the strip) in each backlights LED strip, that is why when one LED goes open circuit, the whole strip will not light up.

If led @ 10mA
then first one DRV1=10 LEDs , Drv2=10 LEDs, 2 strips total 20 LEDs
each strip has 10 LEDs

4 strips basic as same as 2 strips, as long as same current..

DRV1=10 LEDs, Drv2=10 LEDs, 4 strips total 20 LEDs
each strip has 5 LEDs

[budm]

Re: “How to test LED screen?”

LEDs drivers.
BTW, FYI: you do not add current draw of each component that are connected in SERIES to get TOTAL CURRENT DRAW.