DIY Multi Touch Surface on a Budget (FTIR)

A borrowed projector, acrylic sheet, tracing paper, OHP mirror, £5 Asda Webcam and a job lot of security camera IR LEDS and filter from eBay are the main components in this project, along with some freely available software from the NUI Group and the University of Durham (links below).

Accuracy is not it's strong-point but it does work reasonably well and I learned some valuable lessons from it. A few pointers for those trying to make a similar display:
1) Get the most powerful IR LEDs you can find (forward current 100mA +), and lots of them (80 - 100). I had a false start thinking I could get away with being cheap and buying a few very weak ones. eBay is your friend.

2) Surprisingly, most of the accuracy comes from having a decent power supply to power them! I started off with a decent regulated bench PSU, and the results were much better than seen here. Also it has to be quite large to power them all (1 - 2 Amps). If the voltage/current drops across the LEDs and resistors, the brightness will constantly change. This 'noise' makes the work of Touchlib / other vision system harder, as the background image isn't static.

3) Mounting the LEDs is a pain. They must always remain static relative to the acrylic. I found the best solution was to use plastic 'C' Section ducting from B&Q, with holes drilled for the LEDs.

Software:
http://nuigroup.com/touchlib/ - TouchLib converts the images of blobs from the camera into OSC instructions.

http://tel.dur.ac.uk/synergynet/ - Java Platform for writing multi-touch applications, focused on educational uses and provides a vast amount of multi-touch ready UI components for writing your own applications, and sample apps (shown in the video).

Category:

Science & Technology

Tags:

• Multi-Touch
• Surface
• HCI
• Interactivity
• SynergeyNet
• Durham

[ifyoure555thenim666]

What would you say the overall cost of this project would be, if I were to start from scratch?