Hi,

I’ve finally laid out the circuit board for the LED backlight and fabricated it.
The attached photo is a preliminary electrical test.  I couldn’t do a full test because the power supply that I need is being used by another colleague right now.  The only one that I could find is an 18V supply so it is only half of the necessary bias voltage.  But apparently, it is just enough to turn on the LEDs.     

You can find all the details at:

http://www.waves.utoronto.ca/~joshua/Projects/LED/index.html

Anyway, I think I need to take a break from soldering those LEDs.  The width of the LED strip is only 2.5mm so it is really difficult to do.  :(  :(

Josh.

Oh you da man josh! I am happy to see the new update on this project. I wish I could be like you and fabricate something really useful for the TR laptops.

I am still amazed at all the possibilities the TR has! I will continue to follow you

Intricate soldering….... will these leds give an even enough light spread, I mean the cold cathode gives an even glow along it’s length?

Also would you know if there is any way to replace the circuit boards attached to the Tr’s LCD screen? I have a non cracked one here that just shows a mid grey when used and wonder if it’s one of the two attached printed circuits that are faulty. They seem heat bonded to the lcd’s membranes?

[quote author=“Secure Samurai”]Oh you da man josh! I am happy to see the new update on this project. I wish I could be like you and fabricate something really useful for the TR laptops.

I am still amazed at all the possibilities the TR has! I will continue to follow you

Thanks Secure Samurai.  If there is a local PCB shop around your area, maybe they can fab it for you.  I agree with you that the TR is one of the best laptop that you can mess around with!!  The internal is spacious and everything is well designed so you could fit many extra things in there.
For example, there was another mod that I’ve done on bluetooth antenna.  I used the laptop as an insitu testbed for my own bluetooth antenna.  But I couldn’t post it because that one is actually related to real work.

[quote author=“BladeRunner”]Intricate soldering….... will these leds give an even enough light spread, I mean the cold cathode gives an even glow along it’s length?

Also would you know if there is any way to replace the circuit boards attached to the Tr’s LCD screen? I have a non cracked one here that just shows a mid grey when used and wonder if it’s one of the two attached printed circuits that are faulty. They seem heat bonded to the lcd’s membranes?

Hi BladeRunner,

I got a little excited and forgot to explain how the backlight work.  The picture that you see shows only 1 of the 2 strip.  In the proposed design, I employed two LED stripes arranged as shown in the concept drawing:

where light emits towards the +z direction

In other words, what you see in the photo is only one of them.  During testing, I did not fold the LED strips together.  That is why it appears there is only one strip.  The reason for using 2 stripes is efficiency.  The battery voltage varies approx between 8V to 16V (when AC is plugged in).  There are 32 LEDs in total and each requires at least 3.4V to be fully turned on.  If I only have one strip (which means I am connecting all of them in series, then I will need to step up the voltage to around 100V).  By using two stripes and 4 LED strings (8 LEDs per string), I only need to step up to around 30V.  A lower output voltage means that I can design a more efficient controller which further extend the battery life.

To answer your second question, I don’t think you could replace the PCB that is attached to the LCD panel.  As you have already discovered, they are directly bonded to the silicon glass.  You mentioned that it shows a mid grey when used?  It may be due to the CCFL tube aging or an inverter issue.  CCFL degrade over time and will grow dim.  That is what happened to my C1.  I am not an LCD expert so if the problem has nothing to do with CCFL or inverter aging, then I have no idea.  Anyway, I hope this will give you some light on your problem.

Josh

Not 100% with you, but I understand it’s difficult to explain in text or drawings I guess the finished item will reveal all

Anyhow it’s a great project, and I was more commenting on the type of light emitted, the cathode being similar to a household fluorescent light and the led a ceiling spot light. Florescent lights tend to give a more even light spread and are less prone to pin points or shadow casts than direct / spot type lights. So basically I was wondering if the screen will have bright spots with the leds? what reduction in power do you calculate will this to be over standard CC btw?

On the LCD I have a few cracked ones so was hoping there might be a way to swap the PCB’s the LCD in question had coffee spilt on it (so I’m told) so I’m unsure what is dead but I have tried it in a good base unit with good CC and inverter. wouldn’t have thought the screen it’s self was fried more likely the PCB or components (nothing obviously dead or burnt). The membrane is part of the LCD, but is soldered or bonded to the PCB, with a little heating from a hairdryer it will peal off but I’m unsure if there is anyway to rebond another one… just seems a shame to loose a non cracked LCD as I have a few spare PCBs that should be good   :cry:

Congratulation for the update .. hope to see the final result  

[quote author=“BladeRunner”]Not 100% with you, but I understand it’s difficult to explain in text or drawings I guess the finished item will reveal all

Anyhow it’s a great project, and I was more commenting on the type of light emitted, the cathode being similar to a household fluorescent light and the led a ceiling spot light. Florescent lights tend to give a more even light spread and are less prone to pin points or shadow casts than direct / spot type lights. So basically I was wondering if the screen will have bright spots with the leds? what reduction in power do you calculate will this to be over standard CC btw?

Hi BladeRunner,

I think I understood what you meant by bright spots.  Theoretically speaking it shouldn’t.  But practically, it is very severe as you can see from the photo below.  I used my C1 as a testbed and inserted one LED strip into the screen.  The voltage to around 20V which is approx 2/3 of the design voltage.  But already, there are severe bright spots at the bottom.

The good news is that power consumption is only 0.4W as oppose to 3W and equally if not brighter.  That is approx 87% reduction in power.  Qualitatively speaking, there is also no detectable heat dissipated which is also nice.  The picture is taken with the screen facing the window in my office to give you a feel of how bright the backlight is.

Now, what is shown in the picture has only one LED strip and no current regulation so the brightness is not uniform.  What I need to do now is to finish building the controller and the brightness control circuit.  I will also need to optimise the homogeneity of the light intensity across the screen.  I believe this should improve when I insert the second LED strip into the screen.

Anyway, I think the result is encouraging and provides serious reduction in power consumption.

Josh.

I want to grow up to be like you Josh. lol I really wish I would have been able to grasp electronics at a much earlier age.

I like your laptop as well. There are a couple of those on Craigslist all the time, one of which is the same guy ALWAYS selling his for $1K.

Anyway, I can see the light, I can see the light!

Oh my Gosh .. Josh   ..

By the way .. And as you an electrical expert ..
Could we increase TR’s speaker volume ? .. I mean by replacing the speaker with other one which have a louder volume ?

Thanx ,

[quote author=“Q80”]Oh my Gosh .. Josh   ..

By the way .. And as you an electrical expert ..
Could we increase TR’s speaker volume ? .. I mean by replacing the speaker with other one which have a louder volume ?

Thanx ,

Hi Q80,  I’ve asked the same question myself a year ago.  Unfortunately, none of the speakers that are capable of louder volume will fit in the TR.  Well, at least the ones that I’ve found on digikey didn’t fit.  :cry:

But we can always hope that something will come up in the future :wink:

That effect is what I was thinking…. a few ideas… would it be possible to have a full run of LEDs and reduce the light emitted from each? or maybe shroud them with something of high opacity, (like a thin piece of white model plasticard for instance). Have the LEDs pointing downwards and use a mirror effect to spread the overall light back up….. just thinking out loud really 8)

[quote author=“josh”]
Hi Q80,  I’ve asked the same question myself a year ago.  Unfortunately, none of the speakers that are capable of louder volume will fit in the TR.  Well, at least the ones that I’ve found on digikey didn’t fit.  :cry:

But we can always hope that something will come up in the future :wink:

Is the problem because of other speakers’ size ?

If yes , I found that the T laptop have a different speaker but with the same TR speaker’s size (1.6 CM ) and it has louder volume & higher price !

This’s TR’s speaker :
http://www.nexttronicsparts.com/sony/store/comersus_listItems.asp?strSearch=182544911

And that’s T’s speaker :
http://www.nexttronicsparts.com/sony/store/comersus_listItems.asp?strSearch=182597211

Hope that helps .. 

Hi, I just tried that.  The photo that you see below consists of two LED strips resulting in an effective LED spacing of 7mm (centre to centre).  As you can see, there are still bright spots at the bottom but it is definitely an improvement.

I was talking to some of my colleagues from the photonics group and they suggested using an optical fibre.  Apparantely, the latest research trend in LCD backlight is to use an optical slab with micro trenches on the surface as the backlight solution.  Anyway, I don’t how far I want to take this since it is not my area of research expertise.