Low-cost devices for touch control

• US 5,283,558 A
• Filed: 01/27/1992
• Issued: 02/01/1994
• Est. Priority Date: 10/16/1989
• Status: Expired due to Fees

• Current Assignee: James K. Chan
• Original Assignee: James K. Chan
• Inventors: Chan, James K.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): LAO, LUNYI
• Application Number:
  US07/826,363
• Time in Patent Office: 736 Days
• Field of Search: 341/34, 340/712, 340/706, 178/18, 178/19, 338/99, 200/512
• US Class Current: 345/168
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Low-cost devices for touch control by using a matrix of discrete composite switch contacts in close proximity, and x and y terminal measurable parameter such as resistance for touch position sensing and encoding. When a touch position is touched, the corresponding composite switch contacts simultaneously short a proportional portion of the x and y terminal resistance. These terminal resistance values are then converted to digital x and y cordinates of the touched position by A/D converters. Also, that the resistance between the last position sensing conductor and the ground return is three to five times larger than the resistance between all the other position sensing conductors of the first and second sheet eliminates the occasional error of detecting the normally untouched state as a touched state.

Claims

1. A touch pad or a touch screen comprising:

a. a first sheet of insulating material with one surface coated with a first plurality of parallel position sensing conductive strips which are connected at one end with a resistive coating strip having a first terminal resistance value except the last position sensing conductor;

b. a second sheet of insulating material with one surface coated with a second plurality of parallel position sensing conductive strips which are connected at one end with a resistive coating strip having a second terminal resistance value except the last position sensing conductor;

c. a ground return network of a plurality of parallel conductive strips coated on the same position sensing conductor surface of either the said first sheet or the said second sheet of the insulating material, each strip of said network interleaved with said plurality of position sensing conductive strips such that each conductive strip of said ground return network is in close proximity to an associated position sensing conductive strip;

d. means for orienting said first sheet of insulating material and said second sheet of insulating material such that the conductive strips of the two sheets are facing each other in orthogonal orientation and such that by pressing a selected point on the oriented sheets, a selected one of said plurality of conductive strips on one sheet come into contact with the interleaved conductive strips of the other sheet, thereby changing the terminal resistance values of said resistive coating strips proportionally to the touched position;

e. means for connecting said resistive coating strips to analog-to-digital converters to determine the x- and y-digital coordinates of the point of contact; and

f. means of having the resistance between the last position sensing conductor and the ground return three to five times larger than the resistance between all the other position sensing conductors of said first and second sheet.

2. A touch floor mat comprising:

a. a first sheet of insulating material with one surface stiched or glued with a first plurality of parallel position sensing conductive wires which are connected at one end with resistors having a first terminal resistance value except the last position sensing conductor;

b. a second sheet of insulating material with one surface stiched or glued with a second plurality of parallel position sensing conductive wires which are connected at one end with resistors having a second terminal resistance value except the last position sensing conductor;

c. a ground return network of a plurality of parallel conductive wires on the same position sensing conductor bearing surface of either the said first sheet or the said second sheet of the insulating material, each wire of said network interleaved with said plurality of position sensing conductive wires such that each conductive wire of said ground return network is in close proximity to an associated position sensing conductive wire;

d. means for orienting said first sheet of insulating material and said second sheet of insulating material such that the conductive wires of the two sheets are facing each other in orthogonal orientation and such that by pressing a selected point on the oriented sheets, a selected one of said plurality of conductive wires on one sheet come into contact with the interleaved conductive wires of the other sheet, thereby changing the terminal resistance values of said resistors proportionally to the touched position;

e. means for connecting said resistors to analog-to-digital converters to determine the x- and y-digital coordinates of the point of contact; and

f. means of having the resistor between the last position sensing conductor and the ground return three to five times larger than the resistors between all the other position sensing conductors of said first and second sheet.

3. A stylus-type touch pad comprising:

a. a first sheet of insulating material with one surface coated or glued with a first plurality of parallel position sensing conductive strips which are connected at one end with a resistive coating strip having a first terminal resistance value except the last position sensing conductor;

b. a second sheet of insulating material with one surface coated or glued with a second plurality of parallel position sensing conductive strips which are connected at one end with a resistive coating strip having a second terminal resistance value except the last position sensing conductor;

c. means for providing a mobile ground return for the position sensing conductive strips of the said first and second sheet through the tip of a stylus or mouse contact;

d. means for orienting said first sheet of insulating material and said second sheet of insulating material such that the conductive strips of the two sheets are facing each other in orthogonal orientation and such that by pressing with said stylus or mouse contact on a selected point on the oriented sheets, a selected one of said first plurality of conductive strips comes into direct contact with a selected one of said conductive strips of said second sheet and both in contact with the said ground return tip, thereby changing the terminal resistance values of said resistive coating strips proportionally to the touched position;

e. means for connecting said resistive coating strips to analog-to-digital converters to determine the x-and y-digital coordinates of the point of contact; and

f. means of having the resistance between the last sensing conductor and the ground return three to five times larger than the resistance between all the other position sensing conductors of said first and second sheet.