Capacitive keyboard operable through a thick dielectric wall

Details Capacitive keyboard operable through a thick dielectric wall Capacitive keyboard operable through a thick dielectric wall

1985-10-16

1990-05-08

Yusko, Donald J.

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

341 26, 200600, 4004791, H03M 1100, H03K 17955

Patent

active

049242229

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

This invention relates to a novel type of capacitive keyboard and the procedure to scrutinize the action of the keys. One will consider this scrutinization as the way to record, versus time, the state of each key on a complete and systematic way. There are many touch-sensitive devices based on capacitive effects either static or utilizing repetitive scrutinization and comparison. The subject of the present invention is related to a judicious combination of electronic and mechanical devices in view of completely solving the specific problem of man-machine interaction when they are separated by a thick dielectric panel like a shop window.
The device consists in a keyboard of standard dimension which can be activated with full reliability through glass thickness up to 30 mm. When keyboards are extensively operated, like in public telephones, or automatic bank terminals, or information terminals, they are often subject to breaks due to improper or too repetitive actions on the keys. Furthermore, whenever one must activate these keyboards with dusty or wet fingers, contamination by water or dust on the associated electronic circuitry is likely to occur. The present invention offers, among other features, the avoidance of these drawbacks by permitting a thick dielectric wall to be interposed in between the keyboard and the operator. The operator can activate a given key by just putting his finger in front of the selected key and possibly obtaining a visual or audio validation signal, enabling him to check his action.
The keyboard, subject of the present invention, utilizes as the activation indicator the dynamic capacitive effect created on an electronic oscillator by the operator's finger which is separated from the key by a thick dielectric wall. The frequency variations of these oscillators is then analyzed.
This keyboard can be, in a few seconds, put on a window and maintained with simple means like double-sided adhesive, and connected at noticeable distance (several meters) to the user of the electronic system with the help of a cable with a very limited number of wires (around five). This number of wires does not change whatever in the number of keys.
Furthermore, the device contains a programmed internal logic which enables it to emulate any traditional keyboard by providing standardized signals (for instance parallel ASCII, RS232C and so on), or more generally create a signal slaved to a particular sequence of action (coded lock). All of these applications can be determined without impact on the hardward but by a proper software selection. Such a type of keyboard is conceived to satisfy usual applications like office data processing, systems to be accessed by a large public, interactive information or advertisement through shop windows, security devices like digital locks for entry doors, safes or cars, keyboards to be utilized with wet or dirty fingers like scales for vegetables, meat, fish, etc.
It is easily understandable that a keyboard which can be operated through a wall constitutes a solution to a growing request in many domains of application when direct contact with the operator is to be avoided for security, reliability or ease of installation reasons, or in the scope of new types of applications like office data processing, information processing, advertisements through shop windows, and industrial equipment. For example, the presently known information and advertisement systems in shop windows always utilizes passive means, because of the presence of a thick window. No interaction can occur in between the street-walker and the inside of the shop. With the help of the present invention, communication can take place through a shop window, enabling an interactive control by the keyboard of any equipment installed inside the shop.
The originality of the present invention versus other known capacitive devices lies in a special scanning technique which leads, in spite of the extremely low capacitive effect as generated by the operator's finger through more than 15 mm. of glass, to abso

REFERENCES:
patent: 3696409 (1972-10-01), Braaten
patent: 4257117 (1981-03-01), Besson
patent: 4263659 (1981-04-01), Hirata et al.
patent: 4290052 (1981-09-01), Eichelberger et al.
patent: 4305135 (1981-12-01), Dahl et al.
patent: 4373124 (1983-02-01), Frame
patent: 4374381 (1983-02-01), Ng et al.
patent: 4495651 (1985-01-01), Froeliger

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