Circuit layout arrangement for key switch signal recognition

Details Circuit layout arrangement for key switch signal recognition Circuit layout arrangement for key switch signal recognition

2001-02-07

2004-01-20

Edwards, Timothy (Department: 2635)

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

C341S026000, C400S477000, C200S0050EA

Reexamination Certificate

active

06680678

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a key switch signal recognition circuit, and more particularly to a simple circuit layout of key switch signal recognition circuit.
2. Description of the Prior Art
Key switch circuits are intensively used in office automation equipment, industrial instrument, electric and electronic consumer products, and electric home appliances to serve as input interface means between the user and the machine. According to the conventional key switch circuit designs, one key switch button is matched with one circuit loop. The key switch buttons can be switches, micro switches, and membrane switches.
FIG. 1
shows a prior art switch button type key switch signal recognition circuit including a number of key switches. According to this design, a number of key switch contact areas may be arranged on a substrate
10
such as a printed circuit board, and a number of key switch buttons
11
are suspended above the key switch contact areas. Each key switch contact area is generally formed of two corresponding copper foil wires
12
and
13
. One copper foil wire
12
is connected to a common point, such as a grounding terminal or a power source terminal. The other copper foil wire
13
is connected to a first connector
14
. The pins of the first connector
14
are respectively connected through a cable
15
to a second connector
17
mounted on a circuit board
16
. The second connector
17
of the circuit board
16
is further connected to a key switch signal reading interface
18
or a key switch signal processing circuit. According to this conventional key switch circuit design, a number of independent circuit loops are needed to transmit click signal from the key switch buttons, the cable
15
must have a number of wires, and the connectors
14
and
17
each must have a number of pins and one grounding wire. Further, when the numbers of the key switch button are changed, the model of the connector, the number of wires of the cable, and the number of pins of the key switch signal reading interface must be relatively changed.
In some key switch circuit designs, an encoder is used to achieve the object of using a limited number of wires to recognize a number of key switch buttons. However, the use of the encoder greatly increases the cost of the key switch circuit. Therefore, these conventional key switch circuit designs do not satisfy current market requirements. For example, in the design of a key switch circuit for a scanner, the factors of ease of use, highly expandability, less number of component parts, and lost cost must be taken into account.
Therefore, it is desirable to provide an improved key switch signal recognition circuit to mitigate and/or obviate the aforementioned problems.
SUMMARY OF THE INVENTION
Accordingly, the primary object of the present invention is to provide a key switch signal recognition circuit, which uses the architecture of a circuit layout to achieve accurate signal recognition of a number of key switch buttons, so that the number of key switch contact wires, the number of wires of the cable, and the number of pins of the related connector can be minimized.
It is another object of the present invention to provide a key switch signal recognition circuit, which uses a limited number of wires to achieve signal recognition of a number of key switch buttons. No signal encoder is required.
The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the accompanying drawings, in which:


REFERENCES:
patent: 4567469 (1986-01-01), Danish et al.
patent: 5153590 (1992-10-01), Charlier
patent: 5534860 (1996-07-01), Phillips et al.
patent: 5831556 (1998-11-01), Niot

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