Prototype 10: Remodelled 5x4 Vibrotactile Array

We have upgraded the structures that hold the electronics and vibrotactile array: replacing gaffer tape and felt with laser cut polycarbonate. The motors are now attached using velcro which makes it easy to reconfigure the pattern and number.

The electronics have also been thoroughly tested (and a few misconnections identified and corrected). We have discovered that low current motors can be run directly from the TLC5940s if sufficient diodes are included in the circuits, whereas before we had been decoupling the chips from the motors using transistors or logic buffers.

The biggest test of the system was on Saturday 21 February when we ran a 'tummy vision' demonstration at Bright Sparks, an event at the Brighton Science Festival. Over 100 children (and a few parents) tried to bat a ball rolling towards them with their hand. After a few trials, nearly all of them were able to hit the ball and experience sensory substitution. The stand was hugely popular and the waiting list was over 2 hours but everyone seemed to enjoy the novel perceptual experience. For 8 hours, the minimal TVSS worked effectively in a wide range of light conditions and on very different body sizes. The only issue we found was that occasionally one of the plugs connecting the motors to the TLC5940 chips would come loose when we were removing the system from a participant. This will be simple to rectify in a future prototype.

We have now demonstrated that a 5x4 array is sufficiently large to enable most people to quickly learn how to track and bat a relatively slow moving ball. The system works with both a head-mounted and fixed camera. For the Bright Sparks event we used a fixed camera as it meant one less thing for the children to put on and take off.