Hello everyone,


This is my first time here on this forum. I have started my first LCD based FTIR multitouch. As this is my first project, i didnt want to buy an LCD and therefore am doing it with a spare 19” LCD monitor i had around. I have seperated the actual LCD panel from the backlight and have tested it and it works fine.


I have a few questions that I am hoping someone can help me on here.


1) With the LCD seperated from the backlight and powered on, i can see the picture, i can also see through the lcd panel. Do I need to put some sort of layer beneath the LCD panel?

2) I’ve read on a few threads about the use of tracing paper. I’m not sure where exactly the tracing paper is used? is it beneath the lcd?

3) For this first test project, I am using thick Plexiglass Acrylic panel. But in the future i was considering using glass. Would glass be ok or is acrylic prefered?

4) How do you calculate the distance between the leds?

5) Does the acrylic sheet have to sit on the LCD panel? or can i leave a slight gap and suspend it so that the acrylic sheet doesnt damage the lcd panel?

6) Finally, do I need to do anything special to the acrylic sheet other than attach the leds along the sides?

I would really appreciate some advice on these questions.


I do appologise if i’m asking questions that may have been answered already. I couldnt seem to find answers using the search feature.


Many thanks

Hi and welcome!
I recommend taking a look at these links and if you got anymore questions, fire away!
http://wiki.nuigroup.com/Documents_and_tutorials
http://nuicode.com/projects/wiki-book/files
http://wiki.nuigroup.com/Hardware

Good luck with your project!

+1, plz read the forum and wikis before posting

Thanks for your replies.

I have actually been on that wikki and read it before. But it never covered the issue with the LCD being transparant and what to do and whether to let the acrylic sit ontop of the lcd or have it suspended to not let the weight of the acrylic effect it.

The wikki does cover the issue with compliant surface. I’m not sure if i am 100% understanding the issue with the compliant surface. This is what i understand of it: By using LEDs with acrylic by itself, i may get the finger positions recognized and showing as blobs, but if i drag and move my fingers along it wont work and thats where the compliant surface issue comes in. Am i right?

Can i not apply the silicon method directly onto the underneath of acrylic (in between the lcd and the acrylic)

Many thanks

OK it seems like i will have to have some sort of compliant surface and from what i’ve been reading, a vellum sheet coated with some layers of silicon is best. From what i read also, it seems this compliant layer is the final layer that is touched with the finger and the rubber silicon side of it faces downwards and is touching the acrylic.

I can see a possible problem with this: If the rubber silicon coated side of the vellum is facing downwards onto the acrylic, then this means the user finger input is on the otherside of the vellum which wouldnt really feel very good. Has anyone trying to add some other layer on top of this to give it a good finish and texture?

Thanks

I am testing some different materials for this. I tried the siliconlayer this weekend although i sprayed a thin siliconmix directly on the acrylic. Did not like the results though. Prolly my fault in some way.
Today I got some plasticfilm used for car-graphics. It’s a uv-filter aswell.
we will see about this. Stay tuned in my projectthread! Dunno the URL, I’m on my iPhone! Oh, talking about iPhone I tried some of the protectivefilms you can buy for phones and that worked great. It’s sold in small ready-to-apply pieces though.

thanks for your reply.

any ideas what i can put beneath the lcd panel to prevent the transparancy issue. At this current moment I have the LCD mounted and beanth that i have all the space in the cabinet for wires and things and then i have backlight. however, if i look carfully i can actually see through the lcd into the cabinet

Well, you could use parts of the backlights diffuser, although I use a semitransparent coverplastic sheet. Works ok for me and I don’t want to dissamble the backlight.