Current sensing of capacitive keyboard arrays

Details Current sensing of capacitive keyboard arrays Current sensing of capacitive keyboard arrays

1980-03-03

1983-09-20

Groody, James J.

Communications: electrical

Audible indication

Percussion-type sound producer

200DIG1, 307115, 340365S, G06F 302

Patent

active

044059183

ABSTRACT:
Current sensing circuits especially adapted for use with either capacitive touch plate or mechanical switch keys. The circuits include a transistor whose base is connected to a constant voltage source and whose emitter-collector circuit is connected between the touch plate or switch keys and an input to a comparator. A second transistor and a capacitor are interconnected with the first transistor to provide transient surge protection. The circuits distinguish between differing values of current and activate the comparator which produces a signal indicative of the existing condition.

REFERENCES:
patent: 3492440 (1970-01-01), Cerbone et al.
patent: 3705367 (1972-12-01), Peil et al.
patent: 3971013 (1976-07-01), Challoner et al.
patent: 4176575 (1979-12-01), Munch

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