Thread: So, give us new LCD touchscreen options!

I am slightly confused by what you have there. In your right hand is that the whole LCD assembly and that is just a stainless steel box you made?

I can see the inverter wires comign form the edge of the think in you hand.

The backlight works as follows: Perimeter of CCFL light shines sideways intio the plexi light guide. This light guide has a texture pattern ont he back so the light leaves the plexi at the rear. It then hits a white reflector ands bounces back out straight through the plexi - through various diffuser sheets and polarizer sheets (may be refelctive) and throught the LCD.

the 16 bulb is a lot. you want to concentrate on the total length and getting the light distribution as even as possible. The plexi does that perfectyl as the CCFL is shielded from directly shinging through the diffuser and creating a a bright edge. We are cramming so much tube in there we hope it will be nice and even whent he diffuser do their work. If not we have solutions to try.

The diamters you see gve out different light intensities. ie the smaller tubes have a hight cd/m2 but over 1 m a larger diamter has more surface area so with the lower cd/m2 rating gives abotu the same output.

The smaller tubes are just more compact but they do have a lower life and the running voltage is slightly higher. The larger bulbs however are available in longer lengths. The running and starting voltage goes up with length so to get the same amount of light out of a wide tube you need to have it longer and thus need higher voltages as this outweighs the lower voltage from the smaller diameter. It is trade off with tube life, diameter/length and running voltage (and starting voltage as a long thick tube may be damn hard to start as you need 3000V).

LAST PARA EDITED AS I WAS HALF ASLEEP.

Looking good there turbocad, being that it's so far back your probably going to need a good amount of tubes. or something like below.

if your going for the wave pattern your only going to be able to get 2.6MM. Like scouse said, smaller tube more light. Bigger tube less light. But for what it cost me to get these samples, you might be better off just ordering a bunch of straight tubes and get a big inverter.

I would start with 8 tubes and go from there.

yeah i would jsut use about 8-16 tubes and 1 inverter.

Do a trade off of tube diaVnumber of tubesVinverter output. Do wattage calcs.

I haven't read all bazillion pages of this thread, however I browsed a few.

I work at a dealership, and all of the vehicles with the nav screens I can say this - they all have the exact reflective issues of the Lilli's and Xenarcs. However, a majority of OEM's mount the screens in such a way, and design their interiors, so it minimizes reflective problems.

For instance, in the Honda Accords, you'll still get a washout if the sunlight is coming through the rear windshield, or through the sunroof. In alot of the GMC's such as Envoys and Yukons, the way they tint their windows and orient the angle of the windows, almost all of the exterior lighting is kept away from the dash area. Plus, the screens are mounted far enough from the drop-angle of the front windshield, so nothing up front can get it either.

Alot of it has to do with placement really. Alot of the places I could put my screen are simply inconvenient. You'll notice a majority of OEM vehicles put the screens in a spot which almost makes you take your eyes (safely) off the road.

Where I want mine, I would only need to move my eyes a hair to the right to see it -- and I can still see the entire road. The downside: washout is possible, even with Xenarcs.

That's just my 3 cent.

scouse...the rear layer that reflects the original backlight has been removed...my thoughts are to let more light in from the rear....I cut out most of the back so I'm thinking that I may not even need the original tube for illumination...possibally only if the edges are a little dark. I thought about leaving the rear reflective sheet in place also, as it is not totally light blocking...but I thought it may block a lot of light..do you think I should have left it in? as far as the box & confussion, here is a shot of it all assembled.....as far as the distance & depth...I needed the depth for the board that had to be folded back, but that doesn't mean that I couldn't move the bulbs closer to the lcd...I also thought of putting a mirror reflector behind the tubes to try to get as much front projection as possible......I'm hoping that I can contact one of these vendors & have them tell me what I need.....if I have to do all of the calculations myself then I'm going to have to learn more about this stuff as far as start up voltages & formulas for calculations...I'm hoping I could just tell them that I need the power supply for 16 bulbs & I need 16 bulbs that are approx 10" long......can it be that simple or am I just oversimplifying it........I want to just order what I need & get to the dash fabrication done

I did notice that the screen looks like crap without the rear reflector layer as most of the orig. backlight is projecting out of the rear of the panel at this point, but I thought that was a good thing at this point...also the viewing angle has decreased with the rear reflctor removed so I guess backlight does play a part in viewing angles...if only in the fact that well lit helps on a view on an angle.....

this is the exposed rear.....

and this is what I removed....

thank you guys for sharing your research with me...had I not seen this thread I would have been soldering many super bright lcd's togeather right about now.........

another question.....in looking at ccfl's I have seen them in 6000k, 8500k..& I think several others..now I know that this is the color temperature of the lighting...but how do I know what I need......if I use the new bulbs exclusively can't I just adjust the propertys of the display to correct color acuracy or is there more to consider? Thanks...

& as far as factory screens being shielded...that should always be considered in your design but some times it is unavoidable.....I have worked with many new cars & there are times that the factory setup gets washed out as you said willow...I have noticed the last lexus that I worked on had a coating on the touchscreen that is very familiar to me...it kinda looks purple....it is an anti-glair coating.....panasonic uses it on some of there toughbook models & it helps alot when trying to view in sunlight.....it makes a difference enough that it is viewable...but not the same as having the brightness to begin with...I wish this coating was available either liquid or spray....but I have searched a bit to no avail......anyone see this?

Turbocad, the rear reflector helps a HUGE AMOUNT! without it you ar eonyl getting a fraction of the light given off by your tubes. Imagine a nice perfectly white and shiny room with a strip light in it and imagine that is you standing inside your backlighting box (that is how i think of it!). YOu want a nice clean box withnothing that can cause discolouration or trap light. Every reflection removes intensity.

that part you removed i would say is needed.

As for using the original CCFl to light edges that shouldnt be needed if you distribute the CCFLs, use diffusers and have a nice clean box free from artifacts. Most LCD backlights have nice white reflectors - keep them. They are the best you will get - anything else could cause funny colours from refraction and reflection from the LCD etc.

I would keep the existing backlight enclosure and just put strips of CCFLs in running up and down or left to right. Not sure if any has an advantage - i doubt it as the diffusers are there to spread the light out.

Make sure you space the tubes out and dont be greedy as you might go too bright or too hot.

YOu have the option of lots of short tubes across or less longer ones. I woudl think the longer ones would be easier as they would be less things to mount and less connections and complications.

The colour temps you mentioned are the Chromacity (cant spell it or say it). look back a few pages to whern i requested the data sheets and you will see why. Look up CIE charts and these give the colour temps. The typical vaues seem to be around x=0.31 and y=0.32 but if you take both to the 0.3 mark you get away from the yellowing (Xenarc). too far it might go blue (lilliput). This is a pain it the *** as we have no data for either screen. But i got a data sheet (the most amzing data sheet ever) for my new sharp 7" digital panel (yeah i'm boasting) and it gived a range of 0.27 up to 0.34 or summit. with typical around those I metioned earlier. If you get a good chart you will see the tempertaure marked on the plot.

We will jsut have to use the graphics card to tweak the colours. A bodge!