Organza touchpad development 2

This month I’ve made quite some progress with the transparent touchpad in metallic silk organza. With thanks to Piem who has sewn the thread paths and did the more difficult fabric crafting, I now have a working prototype touchpad.

Organza touchpad

touchpad internals

The prototype touchpad has 8 sensitive areas roughly the size of a man’s hand. All areas are embedded in a single layer of metallic silk organza. Only a light touch of one or more of the sensitive areas is enough to trigger. In total the pad has five layers (might increase to seven depending on the possible addition of a ground ‘plane’).

  • organza sensitive layer
  • two isolation layers (could be one depending on fabric quality)
  • component layer
  • two isolation layer (could be one depending on fabric quality and presence of ground plane)
  • possible ground plane

The sensing boards are constructed out of copper foil circuit boards (cut with a Roland CAMM-1 vinyl cutter at Protospace fablab Utrecht ) and conductive thread. They work by capacitively coupling a relatively high frequency signal put on the metallic organza sense areas. On the left is the A/D converter board (unfortunately TSOP-16 is too small for cutting).

In the movie I overlayed (slightly out of sync) the touchpad output as a bar graph. Only the first 4 (out of 8) outputs are functional in this test (the most left bars in the graph).

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