Touchscreen Progress 2
Yesterday I did my first trial wiring up of the LEDs - all went well. I'm doing groups of 7 IR LED's with a 15 ohm resistor in a series running off the 12v rail on an old PC power supply. This will no doubt be part of my tutorial when I write all this stuff up. Right now I am kind of stumped on how to enclose this thing. Ideally I'd like some kind of aluminum bracket style frame which goes around the edge of the acrylic and protects the LED's. Any ideas? Ideally I'd like to find some kind of pre-built picture frame to do the job, but so far I haven't found anything suitable.
posted by David Wallin at 5:48 AM
14 Comments:
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aliminum window companies ? or some one like this http://www.saf.com/alumextru.html
Hmmmm extrusion eh?.. That's exactly the kind of thing I want but the prices are a bit steep. I'll see if I can find any for cheeper. I think I found a picture frame that will work out otherwise.
sweet i am just about to oder a 2.m meter by 1.2 meter sheet of acrylic shoud have it in about 2 - 3 weeks. then I will be looking at the framing wat sort of stuff are you using for the screen
I'm using a piece of 1/4" thick Acrylite I got at the local window and glass company (they sell acrylic scraps for cheap too). I'm making the screen ~24 x 18 (0.6 x 0.45 meters) since that should match the aspect ratio of the projector and not be too big to have to worry about the LED brightness (plus I don't have a lot of space in my apartment ;) That's a pretty big screen you are making! If you search Flickr.com for Jeff Han you can see some other close ups of his screen. It looks like he left the side edges uncovered and just has a piece of aluminum on the top and bottom (probably where his LED's are). I think his looks pretty slick. There are also some wall sized ones that he did that have a frame going all around. I figure some kind of channel shaped extruded aluminum would fit the bill of holding everything together and protecting the LED's.
Just got some aluminum extrusions off ebay. Thanks for the idea!
Thats cool . one of the things i noticed while playing with red LED's is alot of light escaples the edges and i am thinking if a laser cut the edget to get a perfect finish and then lay a mirror or something reflective down the edges this would help get a nice charged screen. i may be wrong with this but in theory its sweet
Polishing the edges is definately important - did you try polishing them with sandpaper and buffing them? How much does laser cutting usually run?
I flame polished my sheet yesterday and it came out really well this time. I sanded it first as best I could then just ran a small torch along the edge until it melts slightly.
I should have read these more-recent comments prior to adding to David's older posts.
Ray, I like the "charged screen" idea. Perhaps a reflective tape applied to the edge? And I agree with David - that's a whomping big prototype you're making. Do I understand correctly that you've already experimented on a smaller sheet with red LEDs?
Yeh , it was just to understand the concept. it made me realise about the leakege from the edges and tim importance of haing somthing to refelect the runoff back into the screen. the only problem i am having at the moment harware wise is finding a materal to project onto
There's an article on Makezine.com that talks about using Tyvek house protector paper (that they use during construction) as a projector screen material. You can buy it at home/hardware stores. It briefly mentions rear projecting. Might want to take a look at that.
A bunch of my stuff from Austrialia serindipitously arrived on Friday. Included was a small 5" x 5" x 1/4" piece of Stewart Film Screen TechPlex 150. This is acrylic with a built-in rear-projection surface. I plan to attach a few LEDs and test its FTIR properties tomorrow. TechPlex isn't cheap, but it could be a nice solution in a production system.
i have seen this stuff used here in shops , dont think it would work too well as the surface is frosted (Could sandwitch it between a clear sheet ), i might look into draughting paper we used of copying images in tech drawing ,
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