For those people, that are being to lazy to visit my Flickr and view my photo’s over there.Here are a couple of pictures taken with my old Sweex webcam in infrared modus.
Laptop turned on, inside windows. No image visible in infrared.
Coca Cola is actually transparent in infrared.
50 euro in infrared. I think the same effect is being created in stores at the cash register. They have these special blue colored thingies they, which they point at your money to verify that it indeed is real money.
2 infrared blobs created by two tv remotes.
View the white terminal strips / connector strips (in Dutch: “kroonsteentjes”) to the right. They hold the leds and connect them with the wire. So from the side the IR gets beamed into the acrylic. Because I was so anxious to put it all together, I made a mistake. The leds should have been put along the long horizontal side (bottom and top) of the acrylic, which I lateron corrected. This is because of a better optical performance. You could also put leds along all 4 sides of the acrylic. That’s up to you.
Notice the camera (with the small green light) behind the acrylic to detect the IR blobs as soon as a finger touches the acrylic.
I created a simple circuit just for testing purposes. PSU (power supply unit, red wire (plus), resistor, led, black wire (minus).
I cut a piece of Rosco rear projection screen and put it on top of the acrylic. Now a beamer can beam an image on this screen. Downside is, there is hardly any FTIR effect if you touch the projection screen. The blobs are really vague and unusable.
I’ll talk about this problem in future posts.
This is the uncut Rosco rear projection screen that got shipped from the UK. It was about 40 euros including VAT and shipping costs. Size 1.20 * 1.40 m or so. Eventhough it’s a perfect projection screen, I wouldn’t suggest buying it since the material is not good as a surface compliant overlay. You might as well use tracingpaper, which is alot cheaper. 25 eurocents for a a3 piece or so. You’ll be amazed how clear this tracingpaper displays the beamed image.
The first shabby crap ass prototype of our screen, with the Rosco projection screen placed below the acrylic.
My wooden frame has arrived. My uncle makes wooden frames for paintings and since they only cost 5 euro I asked him if he could make one for me. The acrylic/aluminum part leans on the wooden frame on the left and the right side and a little bit on the top and the bottom as well. Notice I have space left on the bottom and the top side to wire the leds and resistors.
February 26, 2007
For those of you interested, there’s a Flickr and Youtube group around our Multi-touch Open Source community.
Feel free to join our Flickr or Youtube group.
We also have a blog, wiki and forum related to multi-touch hard- and software, in case you haven’t read about it before.
LEDs (Light Emitting Diodes) need a power source to produce light.
Image above is one IR led powered by a 5 volt USB connection.
There are several ways to power your leds. For example by batteries (1,5 volt), USB (5 volt) or a 12 volt adapter. But you could also connect your led’s to the 12 volt molex connector on an old pc power supply. Since I’m going to use 100 (mA) miliampère leds, I’m going to need a pretty good power source.
Using batteries doesn’t make alot of sense, since you would need quite a few and you would need alot of wire as well, because of the inefficient power circuits.
Using USB is possible, but I would only choose that option, if you are going to use 20/30 (mA) led’s and even than, an old pc power supply would make more sense, since you can put more led’s in a row.
Why not use an old pc powersupply? Your screen is going to be near a 220 volt power source anyway, since you have to use a beamer and a pc as well.
You could use one of the molex connectors on the computer you are working on, to supply the leds with power. But you could also use it without the motherboard in between.
Image above: 6 IR leds powered by a 12 volt molex connector inside a pc.
Because basically there’s a pretty easy solution to hotwire that old pc powersupply.
If you look at the ATX connector, you see several colored wires:
To hotwire your pc powersupply, simply connect the green wire with any black wire (ground) of the pin out and you will be able to connect your leds to one of the molex connectors, without the help of a motherboard, turning the power supply on.
February 24, 2007
I got some more information about my graduating project.
If all goes well I’ll be heading to Sweden by the end of April, for a period of about 3 months, to do research on the campus of the Lulea university in Skelleftea (north Sweden, just below Lulea). I’ll be meeting up there with assistant professor Dr. Johannes Hirche, which I met online, during community activities related to multitouch. We’ll be working on multitouch applications, especially education games. I’m really looking forward to go there and work on the project, getting to know the culture and the language.
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