CAPACITIVE KEYBOARD

• US 3,750,113 A
• Filed: 11/12/1971
• Issued: 07/31/1973
• Est. Priority Date: 11/12/1971
• Status: Expired due to Term

• Current Assignee: Cencel J. Arthur
• Original Assignee: Cencel J. Arthur
• Inventors: Cencel, J. Arthur
• Primary Examiner(s): Fears, Terrell W.
• Application Number:
  US05/198,268
• Time in Patent Office: 627 Days
• Field of Search: 317/242 340/173SP
• US Class Current: 365/149
• CPC Class Codes: H03K 17/975 using a capacitive movable element
• CPC Class Codes: H03K 17/98 having a plurality of control members, e.g. keyboard
• CPC Class Codes: H03M 11/20 Dynamic coding, i.e. by key scanning H03M11/26 takes precedence

Abstract

A n-key capacitive keyboard is coupled to an n-bit shift register. Each key is sequentially '"'"''"'"''"'"''"'"'interrogated'"'"''"'"''"'"''"'"' and, if actuated, an output pulse appears which is applied to the input of the shift register. The output pulse is also compared to the output of the shift register, corresponding to the '"'"''"'"''"'"''"'"'state'"'"''"'"''"'"''"'"' of the key in the prior cycle. An output pulse is generated on the first occurrence of a signal representing actuation of the key. The output of the shift register is also applied to make the key circuit more sensitive and therefore require less key travel to pass the interrogating pulse.

Claims

1. A data entry comprising, in combination:

a. pulse generating means;

b. an output terminal;

c. a plurality of keys adapted for individual actuation, each key having a different significance in the entry of data;

d. a corresponding plurality of capacitive elements, each connected to a respective key and adapted to have the capacitance modified in accordance with the actuation of the corresponding key, for selectively transmitting pulses applied thereto; and

e. addressing means commonly connected to said capacitance elements and to said pulse generating means and output terminal for sequentially applying pulses to said capacitance elements and for applying the selectively transmitted pulses therefrom to said output terminal in a predetermined order.

2. The data entry system of claim 1, above, further including:

low-impedance sense amplifier means commonly connected to said capacitance elements through said addressing means for providing an output signal representative of and corresponding to an actuated key.

3. The data entry system of claim 2, above, wherein said low-impedance sense amplifier means operates in the current amplifying mode.

4. A data Entry system comprising in combination:

a. pulse generating means;

b. a plurality of keys adapted for individual actuation, each key having a different significance in the entry of data;

c. a corresponding plurality of capacitive elements, each connected to a respective key and adapted to have the capacitance modified in accordance with the actuation of the corresponding key, for selectively transmitting pulses applied thereto;

d. input addressing means commonly connected to said capacitance elements and to said pulse generating means for sequentially applying pulses to said capacitance elements in a predetermined order; and

storage means, including a plurality of storage elements each respectively corresponding to a different key, coupled to said capacitive elements, said storage means operating in synchronism with said input addressing means for applying the output representative of each key to the storage element respectively corresponding thereto.

5. The data entry system of claim 4, above, further including hysteresis means coupled to said storage means and responsive to output signals therefrom representing an actuated key for increasing the sensitivity of the capacitive element corresponding to the selected key, thereby permitting the transmission of pulses over a wider range of key actuations.