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%rframe height=200px% Attach:proto2.jpg | ''2008: Stimtac becomes a portable tactile stimulator''

of the sensor is 170 dpi due to optical constraints and post-treatments.

%lframe height=200px% Attach:proto3.jpg | ''2010: improvement in power consumption''
'''2010: Stimtac is thin, lightweight and sobre.'''

A more convenient design of Stimtac could cut the power losses
down by 90%. Consequently, the tactile plate doesn't get warm, allowing the
user to play a long time with the device. Moreover, the rated power (0.5W) is
sufficiently small to allow a power supply from a lightweight power source, or
directly from an USB port for example.

The idea of StimTac was to produce a tactile device which can render good tactile stimulation, and which can be as small as possible in the same time. « Squeeze film effect » was found to be the interaction process between the vibrating plate and the fingertip. A specific prototype was then manufactured. The design results in a plate, on which a stationary wave propagates. Width and length have been chosen in order to favour squeeze film.

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%rframe height=200px% Attach:proto2.jpg | ''2008: a portable tactile stimulator''
'''2008: A portable tactile stimulator.'''

To operate, Stimtac need an accurate finger position sensor.In order to remove the LVDT, a custom-made optical sensor is thus used to locate the user’s finger. The sensor was built from two white LEDs, a set of mirrors and a linear 200 dpi CCD array. An on-board DSP computes the centroids of two shadow images created by the user’s finger and sends them on a serial line as absolute (x; y) coordinates at a rate of 120 Hz. The final resolution
of the sensor is 170 dpi due to optical constraints and post-treatments.

%rframe height=200px% Attach:stator.jpg | ''2004: stator of USR60''

%lframe height=200px% Attach:proto1.jpg | ''2007: made at the lab''

%rframe height=250px% Attach:stator.jpg | ''2004: stator of USR60''
'''2004: Prehistoric time.'''

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%lframe height=250px% Attach:proto1.jpg | ''2007: made at the lab''
'''2007: First prototypes made at the lab.'''

The idea of StimTac was to produce a tactile device which can render good tactile stimulation, and which can be as small as possible in the same time. « Squeeze film effect » was found to be the interaction process between the vibrating plate and the fingertip. A specific prototype was then manufactured. The design results in a plate, on which a stationary wave propagates. Width and length have been chosen in order to favour squeeze film.

%rframe width=150px% Attach:stator.jpg | ''2004: stator of USR60''
'''The image is right-aligned, and the text wraps on the left side of the
image.'''

First prototype of StimTac used a free stator of an Ultrasonic Motor called USR60. This ring shaped resonator can provide 3µm vibrations at 40kHz. A plastic tape was bonded to level the touched surface, and eliminate the effect of the teeth machined on the original stator. A Linear Variable Differential Transformer (LVDT) was used to detect fingertip's position. This solution wasn't optimal: it's one dimension, with contact, and doesn't measure touch area's position acurately.
[Attach:stator.jpg"2004| [- %newwin% First prototype using an Ultrasonic Motor -]