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.
September 23rd, 2008 at 4:18 am
Hi !
I have a Question concerning the LED Ribbon.
The LED’s have a viewing angle of about +/- 120°
I heard that a narrow angle (like 40-60°) is better for a multitouch board.
Does this ribbon really produce precise/good results ?
Do you need resistors for the ribbon,
too ? Or is everything ready to go?
Thx
Florian
September 23rd, 2008 at 5:42 pm
Hi Florian,
I don’t know how much of an affect the viewing angle has on results. It may have a significant effect when you have a limited number of LEDs, and want to direct as much light into the acrylic as possible. Or perhaps if there’s a poor “seal” between the LEDs and the acrylic, which would allow some light to escape.
But this ribbon has tons of LEDs, and the technique we used with the U-shaped channel doesn’t allow for light leakage (at least, we haven’t noticed any). The ribbon is a complete system that includes resistors. All you need to do is buy the appropriate type (850nm or 940nm) and length for your project, add a power supply (or use your own), and perhaps some connectors (if needed).
Hope that helps!
Jim
September 25th, 2008 at 5:59 am
Thank you very much.
Just two more questions:
1. Where is the difference for a multitouch table between the 850nm and 940nm LEDs ?
2. What size is your table ?
Florian