Constructing a Keyboard with E-Field Touch Feature

The E-field touch keyboard was designed in order to eliminate the use of mechanical keyboard switches which can reduce the strain of finger muscles.

The design of the E-field touch keyboard involves two thin and small electrodes of triangular shape placed below the sheet denoted with keyboard letters as they form a 9 columns and 4 rows matrix. The presence of finger near the matrix will be detected by the electrodes where the signal is sent to the E-field sensor board. The key will be further identified and decoded before sending through Serial signal or PS/2 compatible signal to a PC.

An analog multiplexer with very low capacitance and very high speed is used to multiplexed the signal to/from electrodes since there are only 9 electrodes available in E-field sensor that divide the keyboard into group of 9 keys. A 9×4 matrix was developed from the 36 keys which can be increased further by choosing different analog multiplexer or switches.

The MC33794 is used to build the 36-key E-field touch keyboard along with the E-filed sensor evaluation kit. The key pressed can be read by a freely available COM File Software.

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