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Keyboard Scanned Capacitive Joy Stick Cursor Control

IP.com Disclosure Number: IPCOM000051438D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 4 page(s) / 84K

Publishing Venue

IBM

Related People

Fox, JE: AUTHOR

Abstract

The use of joy stick devices for controlling the position of a cursor o a graphic display is common practice. Typically, these devices consist of a plurality of potentiometers and a mechanism to allow sensing of the direction of travel of the stick by the variation in the resistance of the potentiometers. These devices are usually expensive and tend to be unreliable so that they have limited applications to alphanumeric CRT display terminals. The result is that typical CRT display terminals employ four or more keys on a keyboard which are dedicated to moving the cursor in the four basic directions of up, down, left and right. These keys will operate in an automatic fast repeat mode after a fixed delay if the key is held depressed. This method of operation has several disadvantages.

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Keyboard Scanned Capacitive Joy Stick Cursor Control

The use of joy stick devices for controlling the position of a cursor o a graphic display is common practice. Typically, these devices consist of a plurality of potentiometers and a mechanism to allow sensing of the direction of travel of the stick by the variation in the resistance of the potentiometers. These devices are usually expensive and tend to be unreliable so that they have limited applications to alphanumeric CRT display terminals. The result is that typical CRT display terminals employ four or more keys on a keyboard which are dedicated to moving the cursor in the four basic directions of up, down, left and right. These keys will operate in an automatic fast repeat mode after a fixed delay if the key is held depressed. This method of operation has several disadvantages. First, the delay between the time the key is depressed and the time the rapid repeat entry, which causes the cursor to move quickly, occurs cannot be overridden easily. This wastes time when multiple cursor move characters are required, but the delay is necessary in order to generate a single character when desired. Secondly, the automatic repeat keying rate is fixed, and there must be some compromise between being so slow that it takes too long to move the cursor and too fast so that the cursor would override the stopping point desired. Additionally, motion at a 45 degree angle cannot be accomplished without multiple key depressions or adding further keys to define the vector move.

This article solves the above problems and utilizes the existing capacitive scanned matrix keyboard technology. In Fig. 1, the basic mechanism consists of the capacitive circuitboard 1 bearing capacitive or conductive circuit patterns (not shown in Fig. 1). A housing 2 attached to the overall cover for the keyboard 3 contains a spherical ball joint coupling 4 for a lever 5 having an extension 6 with an aperture 8 therein. A spring 7 in aperture 8 forces a movable plunger 9 outward to contact a depression 10 in a conductive slider member 11 used for capacitively coupling the conductive areas on circuitboard 1. Springs 12 attached to a mounting block 13 mounted on stem 6 of lever 5 center the mechanism in the framework 2. Motion in any direction can be achieved by moving lever 5, as will be readily understood. The motion of slider 11 will change the coupling between the various conductive patterns on the circuitboard 1, as will now be described.

In Fig. 2, the circuitboard pattern appearing on circuitboard 1 is shown. It consists of a conductive ring of copper 14, a central conductive pad of copper 15, and several annularly spaced conductive pads 16. Suitable connections 24, 25, and 26 exist on the underside of the circuitboard 1 to supply electrical signals to the outer drive ring 14 or the inner drive contact 15 and to take coupled signals from the pads 16.

In Fig. 3, the overall configuration of the system is schematicall...