Interactive Multitouch Display

Step 3 Led rails

The leds are mounted in extruded aluminum c-channel, pressed into holes. The channel serves to hold the leds in place as well as providing a baffle to direct the light into the edge of the acrylic. Additional spacer blocks cut from acrylic keep the panel from sliding around and pushing the leds out of their holes.

Comments

[psalanoa]

how do you press the holes into theextruded aluminum c-channel?

[danny9893]

Hey just a question but do the LEDs go all the way around the board?

[automata]

How far apart are the LED holes in the aluminum frame? Do both vertical bars and horizontal have the same spacing or is it different. I am assuming the IR's make a grid and the grid should have equal units between each IR. Thanks in advance

[Treknology]

 It's not about creating a grid, it's about creating a uniform distribution of IR throughout the acrylic sheet, in the same way that you want uniform distribution of visible light in an LCD panel.

"Frustrated" Infra-Red remains trapped between the two outer surfaces of the acrylic, and the presence of a finger causes an image to be produced underneath which I'm guessing in future steps will be detected by IR cameras.

I just don't understand why TWO sheets were used.

[turkey tek]

welllll...the screen is 30x36 inches and there are 88 leds distributed around the perimeter so 1.5 inches.

[Rjessick]

Hey, I commented on an earlier step... Just a thought. Adding like two times the amount of LED's would really improve how well the table senses your finger touches.

[Zero-Vision]

Ok, so I'm working on a modified version of what you did here. A couple questions reguarding LED, and rail placement. 1) What degree of spread were your led's. I'm considering using ones with 40 degree angle. The assumption being wider spread, less led's needed. You also used 950nm range leds. Could I use slightly lower range ones, since cams tend to be more sensetive to closer range Light waves? say 800nm or so?

[mustafa.alrefaee]

what are the spacer blocks and where exactly to do you place them... are they only placed on the edges or between every led?

[turkey tek]

i only placed the spacer blocks in the corner, at the very end of each strip. it might have been good to have a couple in the middle as well but i put them in as sort of an afterthought to keep the acrylic from resting on the leds and pushing them out of the holes.