TouchFactors

We created a fully assembled multi-touch surface for the first time the other day. It looks rather nice, and produces good blobs! We believe there are a number of innovations in this process, which really simplified the construction time and cost:

• Use of infrared LED ribbons as our IR Light source
• Use of LED ribbon channel with neoprene spacers for the display frame
• Double-sided taped perimeter for applying Sulky Solvy and Rosco Grey

We captured the process on video and with photos. The photos are numbered and walk you through the whole process step-by-step, assuming you’ve ordered a few supplies first.

[Note: The idea of using IR light with plexiglass (FTIR) is from a paper by Jeff Han (http://www.cs.nyu.edu/~jhan/ftirsense/index.html).  If you are planning to sell something based on this you should probably check with him to make sure it is ok.]

Photos

View the photos with step-by-step instructions.

Video

High-Quality Video

We did a quick test of the infrared LED ribbons to see how well they generated blobs. For this test, we just wrapped part of the LED ribbon reel around the acrylic. In reality, you would trim the ribbon to an L-shaped length. We’re still trying to see if a U-shaped wrap, or a total-perimeter wrap, will produce better results. But wow, the blobs are great with just an L-shaped wrap! Keep in mind this test is showing a direct touch of the acrylic with a person’s fingertips. We’re exploring different compliant surfaces, such as silicone, Lexel, and Sulky Solvy, and will post our findings with them later.

[Note: The idea of using IR light with plexiglass (FTIR) is from a paper by Jeff Han (http://www.cs.nyu.edu/~jhan/ftirsense/index.html).  If you are planning to sell something based on this you should probably check with him to make sure it is ok.]

High-Quality Video

Earlier this year, I was working with flexible LED ribbons for a research project investigating telepresence lighting and glare. I found that the ribbons, connectors and power supplies from EnvironmentalLights.com were pretty handy, and saved a lot of time. So when Jon and I began to build the infrared LED lighting circuit for our multi-touch display, we realized there had to be a simpler way. We looked all over the Internet, but did not find an easily ordered source of LED ribbons in the infrared wavelength.

So we contacted Greg Thorson at EnvironmentalLights, explained our situation, and convinced him there was an army of multi-touch prototypers that would love to simplify the LED lighting step. The result? EnvironmentalLights now has Infrared 940nm LED Ribbon sold by the foot on its web site. If purchased by the foot, it ranges from $20.10 to $14.63 a foot. You can also buy a 5-meter reel for $207. One meter contains 60 LEDs, and can be cut to any length. Don’t feel like soldering? Not a problem. You can purchase a 60-watt 6-12 VDC dimming power supply, a female mini power supply plug, a power line connector cable, ribbon-to-ribbon connectors, and connectors with a bit of wire between them. All of these parts can be found at the bottom of the product page for the reel.

The infrared LED reels we ordered from Greg have arrived, so our next step is to test them with a piece of acrylic, and see how well they produce FTIR blobs.