Low Profile Switch

You will need:
  • Adhesive copper tape
  • PVC paper
  • Insulation tape
  • Piece of wood for base.
  • 10k resistor
  • Multimeter, scissors, ruler.
This is a design for a low profile switch. There is little or no sense of movement in the switch mechanism as it is pressed and activated therefore it can thought of as a 'touch' switch.
It simply employs two switch contacts made from adhesive copper tape stuck to pieces of plastic sheeting separated by a very thin air gap which is created by an offset created by an insulating tape 'lip'.
fig. 1
fig. 2
Stick a square of copper tape (in this example I have used aluminium tape) onto the base of the switch which in this example is a piece of plywood. There is no strict rule regarding what size this square should be but it will depend on the application. In my example the square is 30 x 30mm which will form a good finger sized switch. The switch relies on the springiness of the plastic sheet to maintain the air gap when the switch is released therefore there will probably be a maximum size this can be made beyond which the switch will be in danger of sagging and making false contact.
Attach a short tab onto one corner of the square. It is important that you use adhesive copper tape with conductive adhesive. Fold this tab over onto itself to create a sturdy tab to which connections can be made later.

Form an outlined square of insulating tape around the piece of copper or aluminium tape. The insulating tape strip should overlap both the metal/aluminium tape square and the wood. This insulating tape 'lip' will prevent the upper and lower switch contacts from touching by maintaining a thin air-gap when the switch is released.
fig. 3
fig. 4
Form the upper part of the switch by sticking another square of copper or aluminium tape onto a piece of plastic/PVC paper. Attach another small tab of copper tape that will be used for making connections to the other contact of the switch.

This square should be slightly larger than the exposed copper tape that forms the lower contact so that it rests on the insulating tape square.

fig. 5
fig. 6
Affix the upper part of the switch using insulation tape or glue. If using glue take care not to get glue on the conductor.

Connect one of the tabs of the sensor to 5 volts (5v) and the other to an analog or digital input of your Arduino (or equivalent). Connect a resistor between the same analog or digital input and ground (see fig. 7). Typically this resistor should be around 10 k.ohms. This resistor is referred to as a 'pull-down' resistor as it pulls the sensor input down to ground potential when the switch is released.
fig. 7

The switch has just two states, on or off, interpretted by a digital input as high or low and by an analog input as maximum (1024 for an 8 bit input or 127 for MIDI) or minimum (0).

A sequence of switches with no interruption can be formed by creating the upper part of the switch with a single piece of plastic. The side of the switch that will connect to 5 volts can be made using a single continuous conductor for convenience - it isn't necessary to make multiple connections to 5v.