Changing from CCFL to LED Display

The original inverter with the bulb in full brightness consumes [email protected]. To increase the battery runtime I was thinking of installing an LED-Light into the display. I was looking a long time for a small LED stripe, which can fit into the little gap of the metal bracket on the display. Finally I found it here: http://www.led-tech.de/en/Chip-On-B...hip-On-Board-SLIM-Module-LT-1446_134_141.html . I bought 2 of them for my CF-29 to connect them together and cut of the last 6 LEDs. They are brighter than the original CCFL!
Additionally I bought also the constant current power supply
(which replaces the inverter): http://www.led-tech.de/en/Chip-On-B...ply-for-COB--180mA,-30V--LT-1534_134_141.html which works very efficient and did not produce unnecessary heat and also have the possibility to regulate the brightness.
The power consumption is now 110mA in full brightness!
But now I have a problem: if I use the pwm controller of the toughbook the brightness is inverted, which means:
Ur toughbook is off -> LEDs are full on
Toughbook is on and Brightness is full -> Brightness is down
Toughbook is on and Brightness is down -> Brightness is full

I was trying of using an logic-inverter, but to my bad I was soldering at the PWM-pin in a unheeding moment, as the machine was on
Now I have no signal on the pin. I destroyed probably IC106 or IC107 (in the well known schematic of CF-29 Main14 LCD I/F 5F). And at the moment I have no idea, where to find the chips on the mainboard for repair.

Anyone can help me out?


Pics:

dismantling the display
don't touch the front of the display without gloves
dismantling the screen

 

next 6 pics:
dismantling the CCFL-bracket
on the pic with the connector from the inverter u can see 2 cutted wires- this are the plus wires. The next 2 wires right of them are ground and the last one is the pwm-signal.

 

And another 5 pics:
cut the LED-stripes
isolate the backside of them with tape
Testpictures

 

Is this a picture of the screen with the led installed? All I can say is good job if that is the case.

 

onirakkiss -

Well done, as usual. Are these strips wired in series or in parallel? What is the operating voltage of the full strip?

I AM curious about these things, though I am leery of the lifespan. However... for $45-50US, it seems like not a terribly expensive experiment.

mnem
Let's get dangerous!

 

@Klonsdale: Yes, this are testpics with the LED-stripes. Really bright! But on the bottom of the screen u can see the brighter points, where an led on the stripe is. I will also install an translucent plastic-stripe between the LED-stripe and the glas of the display to avoid this.

@mnementh: 3 LED are in series, 9 of them = 27 LED on one stripe. My second stripe I have parallel soldered on the first stripe and u can cut every 3. LED, if the stripe is too long. They work on 9,6V@180mA. Hope they will work a long time

 

This sounds very interesting, when you get all the details done would love to see a tutorial, this seems like it would help us cf-28 users whose screens are not as bright as the CF-29 with the added benefit of lower power consumption and increased battery life. Please keep us posted on your progress.

 

Wow, quite a re-engineering; I am very impressed! I am sorry for you setback but look forward to reading more.

 

Simply amazing!

 

Onirikkiss... With you being in the top 1% of the "wicked smart" crowd here... I'm left wondering who has enough brain power to help you.

Kudos to you! Looks like a fantastic mod and can hardly wait to see how this turns out. I don't have any spare monitors to play with but the first I do I'd like to help out.....

Please list tutorial when possible. We'll sticky it somewhere!

 

I do have a spare CF-28 monitor to play with, can't wait for more details, sorry about the bump in the road, maybe someone with CF-29 experience can help you out.

 

son of a gun, i am new to the forum but this guy does all kinds of interesting things. he is definitely a reverse engineer, most of its very technical even for myself none the less very cool.

but the led display i may just have to research more as a very smart idea it provides 2 pros which are better battery life and brighter screen

 

I would suggest cutting a strip of some of the 2nd thin layer of plastic between the LCD and the main thick plastic substrate harvested from a dead LCD panel; the stuff that looks like a diffraction grating, not the stuff that looks like a fresnel lens (if it has that fresnel sheet - many do not anymore); that diffraction/diffusion sheet is MADE to diffuse light in the manner you need.

So... Each strip has 9 banks of 3 LEDS in series at 180ma total for the strip? This means each LED is operating at a forward voltage of 3.2V, with each 3 LED bank drawing 20ma?

Are all banks wired in parallel to 2 common solder pads or can you light up each bank individually?

mnem
Lit.

 

Any way to do this with just two led's on each and of a thin glass rod or fiber optic cable? This would allow you to mount in the same place as the original ccfl and use the existing reflector.

 

@Mnementh: Ur idea is great, will try it tomorrow. My girlfriend cutted one stripe of thicker plastic foil and uses a sandpaper on both sides do create an diffusor. I have to try this first ;-)
U are also right with the operating of the stripes. But u can't light up each group individually, except if u cut the conductive paths on the stripe.
@tough-2-go: all the parts, which I use, found their place, where the original parts normally are. So no need for me to develop an version with only 2 LEDs.
@all: Thank u for ur mental support!
It's not a big thing. The difficulty is to disassemble and rebuild the display without destroying anything. Use gloves and ground urself to the chassis of the toughbook. This has to be without any power and batterie. And don't use an soldering iron, if the toughbook has power!
The LED-stripes fit exactly in the place, where the ccfl was. I used an thin pair of cable, cropped from a harddisk flat cable, to connect the LED-stripe to the BUCK. On the original-connector of the highvoltageinverter u find 15.9V, ground and the pwm-signal (nearly 6.7V in full brightness). Use an other socket for the plug and connect it to the BUCK. Thats the point, where I'm standing now. If it rains today I will work on the inverting if the PWM-signal and repairing of the mainboard-failure.....
Denis.

 

I found the ICs IC106 and IC107. U can see them in the attached pic. But also I found, that the resistance between pin 2 and 4 of IC107 is 200kOhm. I will verify the signals on the ICs hopefully tomorrow. Too much work, too less sleep .
Anyone, who know if the resistor group located left of the ICs in the picture included R745 of the schematic? In the schematic it is a zero resistor, but on the pic it is a 100kOhm group...The 3. of top of the group has a connection to pin 4 of IC107 on one (right) side and the other side (left) is grounded. It's different than in the schematic.

 

Only for update: I'm still waiting for the new IC's ....

 

I was rereading your first post on this project where you were having difficulty controlling the brightness and the old adage of a little bit of knowledge can be a dangerous thing certainly applies to me. But if you used a full wave bridge rectifier and a proper resistor would you be able to use the factory inverter so that you could then control the brightness in the normal manner?

 

No This will not work. It is completely different. Have a look into the picture. Top is before and on the bottom is after. Red is plus, blue is minus and green is the PWM-signal ( http://en.wikipedia.org/wiki/Pulse-width_modulation ). To invert the signal I want to use an normal CMOS-Logic-inverter like 4093.
The only one simple thing where I failed was to use an soldering iron, because I didn't notice, that the Laptop was powered on at this time.

 

The older I get the less I know, I get the jist of the PWM-signal article, I will go back and reread it after I have had a conversation with "Jack" LOL.

I see where you are going with this now that I am familiar with PWM, keep up the good work. As soon as I can find the cash I will get the parts and try to follow along.

Keven

 

So folks, I got it working

I unsoldered the defective chip, routed new thin wires (+,-,signal from board, signal to the BUCK) to a logic-inverter, which also in my case worked as the logic-AND (additional signal from the SCC (Mitsubishi)), because i destroyed one...

 

On this pics can u see the pull-up-resistor which u have to use to shut-off the display; an LED-stripe in NEW and the LED-stripe in the gap, where the CCFL was; an pic with CCFL and an pic with LED backlight.

 

The difficulties are:
-dismantling the TFT to get the CCFL out
-find a point, where to get 3V for the V4093 (got it from the IC on top of the connector CN9)
-to find an location, where I can fix the V4093 on the board (under the modem-board, flipped on the top, fixed with tape and the pressure of the modem-board)
-create an diffusor for the LED-stripes (an plastic-foil rubbed with sandpaper)
-rebuild the TFT in the housing.

So I mean it's only for users, who know, what they are doing.

And a big "Thank u" goes to PANASONIC for this great, also electronical robust laptop and also to this forum

 

onirakkiss.... What a great mod.... Rep to you! Glad you are part of our group!

 

Wow, very impressive! I am sitting here wondering if I have the nerve to give it a try!

 

I have to agree, as someone who has replaced a CCFL and it was a royal pain, I can say that is probably the easiest part of your mod. Again well done.

 

Dewed...

If you ever get your laptop scanned by Air TSB, they're gonna look at all those extra wires and ship you and your Toughbook straight to GITMO for a full cavity search FOR BOTH OF YOU.

WELL DONE!!!

mnem
bring a sponge.

 

I would let my advocacy say: He have done all this things with the help of some guys in the TB-forum....

 

You are a MAD genius eh,eh I dare you to send the unit to Panasonic for warranty repair. On a side note if you ever develop a kit along the lines of the GPS kit from that Norwegian site you will be a rich man.

 

Were not worthy!

 

Brilliant !!

Reps to you

 

Thank u all for pating me.

I only want to add, that it is not needful to change anything on the mainboard. U can also locate the logic inverter simple inline near the BUCK, where the original CCFL-inverter was located and connect the IC with the original wires and the plus for the IC u have to get from the touchscreenboard. No need to soldering on the mainboard.
All the pics from the mainboard, which u can see are because of the fault to use an soldering iron during the laptop has power. It was my inattention. :/



I hope mnementh is now dry.
And I don't want to make money with such simple ideas....I want to share and spread it, so anybody can do it on his own liability

I will do it again for myself on my CF-19 nexttime...

Denis

 

Dwagon-momma sez I'm juicy... whatever that means.

mnem
Life is messy.

 

What is the color rendering like? do the test images look good on your laptop?

 

no problems.

 

onirakkiss -

I believe Pantha is asking how the upgraded light source renders colors as a "color-calibrated display". The test patterns are typically compared against a lightbox with a colored cell to validate "color correctness"; this is important with commercial publishing and photo editing scenarios.

Pantha -

I'm just guessing, but I don't believe onirakkiss was really too concerned about absolute color purity; I think he just wanted to get decent brightness again and hopefully save a few watts to extend battery life with decent picture quality.

mnem
lit.

 

I had used an HP 'eye one' to calibrate and generate profiles on all of my monitors and printers -> no problems so far

 

Ah, i don't have the equipment to generate color profiles. What was the colour like before you calibrated it? significantly erroneous?

I think i could make the led strip myself from cheaper leds from ebay. Although i doubt i could find simething similar to that driver

http://forum.notebookreview.com/att...67-changing-ccfl-led-display-ledbacklight.gif

Wait a sec, if you used that circuit with that 180ma led strips with the 180ma current source, how did the leds light? they shouldn't have enough current to be bright. You soldered them in parallel so presumably they only get 90ma each. By any chance did you time division it? so that only half of those leds are ever on at one time?

 

with leds the picture was a little cooler than with ccfl.

would be nice if u will make pictures for us.

good question!
No, I used 1 and an part of an second stripe (u can cut them) to get the full length of my display. You are right about the current, but 1.: it's even brigther than the ccfl and secondly: if it is not bright enough for u, u can change an resistor in the circuit to get more power.

 

onirakkiss -

I was looking at this again and I realized I was right the first time; they drive the entire output at a fixed 180ma, which means that one BUCK is intended to drive one LED strip at full intensity.

As I suggested, you're essentially driving 1 7/9 of those strips at the current level intended for 1 of those strips, so you are driving them at approximately (Hmmm... lets do the math here...)

1 7/9 = 1.7777777

1/1.7777777 = 0.5625; shift the decimal 2 places to get 56.25%, and

180ma x .5625 = 101.25ma

Actually, I'm not NEARLY so leery of this setup now as I was the first time we talked about this; I couldn't for the life of me figure how you were getting full power from only 110ma input at the BUCK.

Driving these LEDs at that low level should ensure good long life as well as ensuring we don't get any melted plastic substrate under the LCD panel.

These new generations of excited-phosphor LEDs run REALLY HOT! I've gotten burns from some of the CREEs I tinker with on my flashlights; but that is usually only from running them at maximum output. When you decrease the drive current even by 20%-30%, heat generation drops dramatically.

Oh ,and one last point... I'm so proud of you for figuring out the PWM signal inverter setup; I would have probably taken the lazy way out and relabeled the function keys, then gotten disgusted by the results and done the inverter ANYWAYS. AGAIN - WELL DONE!!!

Pantha -

I would suggest trying to keep your setup in this current range for the above reasons; it will be at least a good safe starting point to mod from. I also suggest you'll not likely be able to duplicate these results by building it yourself because of:

A) The tight space constrictions; these strips are 2.5mm wide, which is what you need to fit inside your LCD panel.

B) The PCB provides necessary heat dissipation and permits the wiring to each individual LED to be kept at this very tiny design size.

C) Availability of the individual LEDs will be hard to match at the cost point; by the time you buy a small batch of these LEDS (50 or so) and cut the PCB, I'm sure you'll be quite hard pressed to build it yourself for the approx $11 EACH plus shipping these strips cost, and that's if you don't value your time at all.

mnem
Oooh... my electrons are getting all excited!!!

 

30.88 Euros + P&P is more than i plan on spending. I also want to run closer to the actual current limit. I also don't plan to use a pcb, i'll glue the leds streight onto some heat resistant material which will slot onto the lcd

 

I wish you the best of luck; my time is worth more than that.

mnem
*Walks away shaking his head*

 

I don't think it'll take that long, wiring an array of leds should be simple enough. The circuitry powering it would be the hardest thing. I'll be using 3mm LEDs instead of SMDs.

 

Keep on the camera, while u are on working
Maybe u can find an better way, than I.

 

Unfortunately i don't have a decent camera, not a high quality one. Just one in my phone and the laptop's webcam.

I am writing down my procedure so i can explain the steps

 

I've ordered the leds and that alone has cost me 20.41 Euros including p&p. I've been looking at driver circuits and it comes to over 20 Euros which ever way i try to design it. However that driver circuit is completely inadequate for my design. It would never have been good enough

The main problem is the space in the bezel, there is enough depth but not height for the led legs and wiring. I'll put the leds in place before i order the driver circuit because i don't think they'll fit.

Might actually get a good camera if this goes well

 

Could u show me the schematic of ur driver circuit and which type of LED?

 

I was referring to the 180ma current source board you used for your laptop mod. No way i can run 100 leds from it.

I'm using 3mm LEDs and i'm using 100 of them, they require 20ma forward current with 3.4v accross them.

So the maximum power will be 6.8W. I plan to run them below that at about 15ma, so 5.1W. Assuming the power board is 75% efficient the power from the battery will be 6.8W. Since i'll rarely use it at max brightness it will be fine.

I've seen pwm controlled led driver boards on ebay. I'll just grab one of those and then wire the LEDs accordingly.

But i'll first put the leds in their place and see if it all fits.

 

They have BUCKs with PWM for 120,180,350,500,700 and 1000mA.

I would try 3 of them in serial, like it is on the COB-boards, so u will come to 33*15mA=495mA and can use an ready-to-go BUCK.

Yep, that's the hardest part normaly.

 

Which tool would i need to make holes in this metal strip? Holes or thin slits for led legs to slide into place. I will insulate and avoid shorts appropriately.