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SENSOR FOR ILLEGAL TOUCH ON MEMBRANE SWITCHES

IP.com Disclosure Number: IPCOM000025761D
Original Publication Date: 1987-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 56K

Publishing Venue

Xerox Disclosure Journal

Abstract

Membrane and capacitive switches often operate to give continuoushon-discrete output. A one dimensional switch is shown in Figure 1 (2 dimensional devices are more common and work in like manner). The physical position on the switch arrow is proportional to output voltage. R2 is very high. However, if two positions are selected, the output voltage is ambiguous. Two methods for detecting this problem are shown in Figure 2.

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XEROX DISCLOSURE JOURNAL

SENSOR FOR ILLEGALTOUCH ON MEMBRANE SWITCHES U.S. C1.200/5A Craig A. Smith

Proposed Classification

Int. C1. B65d 6/00

FIG. I

FIG. 2

Volume 12 Number 6 November/December 1987 259

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SENSOR FOR ILLEGALTOUCH ON MEMBRANE SWITCHES (Cont'd)

Membrane and capacitive switches often operate to give continuoushon- discrete output. A one dimensional switch is shown in Figure 1 (2 dimensional devices are more common and work in like manner). The physical position on the switch arrow is proportional to output voltage. R2 is very high. However, if two positions are selected, the output voltage is ambiguous. Two methods for detecting this problem are shown in Figure 2.

Dual depressing indicated by two arrows, results in a short circuit between the two points A and B. The decreased impedance will cause a lower voltage at C because increased current will flow thru R1.

The voltage V will be a step function from zero to the correct first read when first touched to some other voltage when the second touch takes place. Correct output cannot be guaranteed until the voltage returns to zero.

Either of these conditions can be sensed to indicate that two buttons (touches) are made.

260 XEROX DISCLOSURE JOURNAL

Volume 12 Number 6 November/December 1987

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