Capacitive keyboard

Abstract

Abstract PURPOSE:To detect accurately the operations of keys, by delivering a sensing signal when the output pulse width of a sensing amplifier which converts a change of the electrostatic capacity of a key into a voltage signal when the push of the key exceeds a prescribed level. CONSTITUTION:Capacitive keys C11-C65 having electrostatic capacity varied by the operation of each key are provided at the intersecting points of rows and columns of a key matrix 1. These rows are driven successively and selectively by a line driver circuit 2, and at the same time the columns are connected successively and selectively to a sense amplifier 4 via a multiplexer 3. In this case, the multiplexer 3 selects once all columns while a specific row is driven by the circuit 2. Then the output signal of the amplifier 4 is applied to a signal processing circuit 5. The circuit 5 eliminates assuredly a wrong signal having a small pulse width.

Inventors

• 👤 Hiroshi Hasegawa
• 👤 弘 長谷川

Bibliographic Details