Generally, touch switches cannot be used through glass.
How Touch Switches Work
A touch switch is a switch that uses human body induction as its control. It primarily uses electrostatic induction from the human body to open or close the circuit, making it a very common electronic component. Touch switches control the switch by sensing the weak current from the human body, without requiring a physical button press.
How Glass Can Block Touch Switch Operation
Many people believe that touch switches can be operated through glass, but this is incorrect. The induced electric field of a touch switch radiates outward from its sensor surface. When the touch switch is a certain distance away from an object, the signal of the induced electric field is attenuated by the object, thus preventing the switch from working. Although we may see the light under the touch switch illuminate, the switch is not actually being controlled.
Touch Switches Made of Special Materials
While touch switches generally cannot be operated through glass, there are exceptions when using transparent materials. For example, some touch switches have a special anti-reflective coating on the glass surface, or the glass surface has been treated to be transparent. Under these conditions, the touch switch can still function normally through the material.
In short, although touch switches have become common components in modern homes, they cannot be used through glass, requiring a thorough understanding of how they work. If a switch needs to be used on glass, a special transparent material or a specially developed air-touch sensor must be chosen.