Insulated touch / close proximity sensor?

Other Hardware Sensors
1

Hi,

I'm building a LED strip into my bathroom, right next to the bath tub. The electronics together with the LEDs go behind a frosted glass / acrylic pane. I want it to have one or more touch switches for turning on/off, dimming, cycling through colors, that should be usable from the bath tub. For safety reasons, I'd like to use contactless switches built behind the glass/acrylic pane (so a finger touch on the pane is sensed, but no electrical connection is made with the touching finger). Is this possible with capacitive / resistive sensing, or do I need an IR sensor? All projects I have seen using capacitive sensing always required some electrical contact. I foresee problems with an IR sensor due to the glass pane, though.

Thanks a lot in advance,
Björn

2

Theoretically it's possible, because a thermin works along those lines. However, I haven't seen an DIY application that involves a relatively dense cluster of buttons. That leads me to believe it might be difficult or impractical to achieve.

3

Capacitive sensors are normally (nearly always) used electrically isolated from human contact. Some things that might help are:

  • keep the glass thin, if possible
  • sensor pads not too small
  • if you get too much cross talk, add separation or a ground line between the buttons (not electrically connected)