Let's Make Robots!

A Large Touch Surface Brainstorm

Something I was thinking about was what if you were to build a surface that had fast moving linear  sensors on the side. These sensors could be moved maybe with a stepper motor and a timing belt. So you have a sensor moving in the x direction and one in the y direction. Now you should be able to put your finger on this surface and the sensors would detected it. The x and y coordinates could be figured out and boom, you have a large touch surface. Maybe these sensors could be IR range sensors, or a laser and photo cell. I think it could be a fun idea to play with if I could get the sensors to move fast enough. Once the sensors found your finger, they would then make minute movements to follow your finger. This touch surface could then be used to control a robot with gestures. 

Practical? Crazy? Not going to work? Already been done? 

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I might end up tearing apart a wii controller to play with the camera if I can find a cheap one that will work. Will have to talk to The Carpenter, Grog, or Gareth to see if they found cheap ones that worked. 

I've seen that being done using a sheet of clear plastic, a camera and LEDs arround the edge, too.

It worked basically like this:

There is a processing library for this. Have a look here: http://www.tuio.org/?processing


In order to make a fast scanner, you must keep the moving parts as light as possible.

Take a cue from a laser cutter: laser stays put. Mirrors move and deliver the energy where it's needed.

I recently disassembled a laser printer. Also very educational. It uses a rotating mirror (six of them on a wheel) to scan a line with a laser dot. A little sensor in the corner synchronises all the action.

I imagine two rotational IR sensors in the corners of a table could produce polar coordinates of one finger's location.

Yes a mirror could reflect the laser across the surface and then another, longer mirror (angled up a bit) on the other side could reflect it into a photodiode that is placed above the mirror that is moving back and forth. Hmm, there must be a way to make the photodiode stationary also. 

Polar coordinates might work also. 1 sensor might be able to do this. That is if IR sensors have a fast update rate. 

I believe the infamous Sharps work at 1000 measurements per second. At least they produce a nasty 1 kHz noise on the power bus.

Sharp would probably work then. Laser would be the best option in my opinion.

WiiDar would work but the surface would be a cone shape, not a square. The scan rate would probably be faster than a rig with servos, since then energy/effort needed to swing a laser on a pivot is much less.

I can imagine a different setup with a laser on the edge of a room going through multiple splitters - and then a photo-transistor on the opposite side of the room, wherever the laser was split.  This would be instantaneous detection without scanning.  It could be done with multiple pen lasers if splitters were more expensive.   2 Grids of these and you have a touch-floor-pad.


the wii cams out put would give you some sort of multi touch system aswell. i know it out puts the co-ordinates of several bright points.

hey Pat,
could you not try using a wiimote camera and some sort of glass panel so the camera only sees when youve touched the screen?

I have not looked much into the wiimote camera. Just did and it does look pretty handy. I see why some guys around here are using it.