Key input device

• US 4,872,008 A
• Filed: 10/20/1987
• Issued: 10/03/1989
• Est. Priority Date: 10/20/1986
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited 1006 OAZA Kadoma-Shi Osaka Japan
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Fujii, Yasutel, Ohtsuka, Akinori, Kurita, Hitoshi
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Queen, Tyrone
• Application Number:
  US07/110,327
• Time in Patent Office: 714 Days
• Field of Search: 340/365 S, 340/365 R, 340/365 A, 340/309.15, 341/22, 341/26, 341/34, 200/5 A, 200/5 R, 219/10.55 B, 219/10.55 R, 364/189
• US Class Current: 341/26
• CPC Class Codes: H03M 11/24 using analogue means , e.g. by coding the states of multiple switches into a single multi-level analogue signal or by indicating the type of a device using the voltage level at a specific tap of a resistive divider

Abstract

In a key input device, the depression of any one of the keys of a keyboard applies a voltage to an analog-digital conversion input terminal and to one of a plurality of ordinary input terminals so that in accordance with the resulting analog-digital input terminal voltage and ordinary input terminal voltage, a microcomputer discriminates the depressed key.

Claims

1. A key input device comprising:

control circuit means including a microcomputer having an analog-digital conversion input terminal and a plurality of ordinary input terminals and having programming functions; and

a keyboard for applying input signals to said microcomputer,

said keyboard including a plurality of separate-key-contact circuits, a first portion of said circuits connected through one of a plurality of predetermined resistances to said analog-digital conversion input terminal and a second portion connected to said ordinary input terminals, and

a plurality of keys, each of said keys corresponding to a selected one of said keycontacts for applying a voltage to said analog-digital conversion input terminal through one of said resistances and to one of said ordinary input terminals so that, said microcomputer discriminates said depressed key through analysis of said input terminals and said analog-digital terminal.

2. A key input device comprising:

control circuit means including a microcomputer having an analog-digital conversion input terminal and a plurality of ordinary input terminals; and

a membrane-type keyboard for feeding input signals to said microcomputer,

said keyboard including a character sheet indicating positions of a plurality of keys, a conductive sheet having a conductive lower surface and arranged below said character sheet, a spacer sheet arranged below said conductive sheet and formed with a plurality of openings each opening corresponding to one of said keys, and a contact sheet arranged below said spacer sheet and formed with first, and second groups of contacts, with one contact of each of said groups provided for each of said keys, each contact of said first group being connected to a corresponding one of said ordinary input terminals of said microcomputer through a low-resistance pattern, each said contact of said second group being connected to said analog-digital conversion input terminal of said microcomputer through one of a plurality of predetermined resistance means, and

said conductive sheet being connected to a power source of said microcomputer whereby when said character sheet is depressed at any one of said key positions, said conductive sheet simultaneously contacts one contact of each of said first and second contact groups through one of said openings formed in said spacer sheet, thereby connecting said power source through said conductive sheet to said contacts of said first and second groups.

3. A device according to claim 2, wherein said plurality of predetermined resistance means are resistance patterns printed in an open space among said contact groups on said contact sheet.

4. A device according to claim 2, wherein a voltage output of said power source is applied to said first and second contact groups only upon depression of said contact sheet, thereby maintaining said groups at an equal potential in the absence of depression.

5. A device according to claim 2, wherein said conductive sheet is connected to the power source of said microcomputer and to a ground of an apparatus employing said keyboard.

6. A key input device comprising:

control circuit means including a microcomputer having an analog-digital conversion input terminal and a plurality of ordinary input terminals; and

a membrane-type keyboard for feeding input signals to said microcomputer,

said keyboard including a character sheet having a print, indicating positions of a plurality of keys and providing an external appearance, a conductive sheet having a conductive lower surface and arranged below said character sheet, a spacer sheet formed with a plurality of openings each corresponding to one of said keys and arranged below said conductive sheet, and a contact sheet arranged below said spacer sheet and formed with first, second and third groups of contacts, with one contact of each of said groups provided for each of said keys, each contact of said first group being connected to one of said ordinary input terminals of said microcomputer through a low-resistance pattern, each contact of said second group being connected to said analogdigital conversion input terminal of said microcomputer through one of a plurality of predetermined resistance means printed on said contact sheet, and said contacts of said third contact group being connected to a power source of said micrcomputer whereby when said character sheet is depressed at any one of said key positions, said conductive sheet simultaneously contacts one contact of each of said first, second and third contact groups through one of said openings formed in said spacer sheet.

7. A key input device comprising:

control circuit means including a microcomputer having an analog-digital conversion input terminal and a plurality of ordinary input terminals and having programming functions; and

a keyboard having a plurality of keys,

circuit means connected to said keyboard for detecting actuation of at least one of said keys and for applying a first input signal of a predetermined voltage level corresponding to said actuated key to said analogdigital input of said microcomputer, and a second input signal to a selected one of said ordinary inputs corresponding to said actuated key,

said microcomputer further comprising means for identifying said actuated key based on said voltage level and said corresponding ordinary input.