Many PIC microcontrollers have built in touch pad capability. The PIC 16F1937 for example has 16 inputs for the capacitance module. These allow for a simple and inexpensive way to add buttons to your project without adding physical switches. Nice thing about these switches is that they will not fail after a certain number of uses like a physical switch will. Our friend Giorgos Lazaridis from PCB Heaven has designed a circuit which uses the PIC 16F1937 Capacitance inputs to make a keypad which outputs BCD.
“The fundamental rule when designing a touch-pad is this: Keep the wires as close as possible. When i designed my keycode doorlock project, i had only one PIC to handle everything including the touchpad. But the PIC was hidden inside the door, so i had long wires (about 10-15cm) to connect the pads with the PIC. That was a bad idea. So, i came to the conclusion that the touchpad must have a dedicated PIC on-board to minimize the wire length.”
