Capacitive transistorized signaling device

• US 3,958,239 A
• Filed: 09/27/1973
• Issued: 05/18/1976
• Est. Priority Date: 03/24/1972
• Status: Expired due to Term

• Current Assignee: Robert E Green
• Original Assignee: Robert E Green
• Inventors: Green, Robert E.
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US05/401,261
• Time in Patent Office: 964 Days
• Field of Search: 340/365 S, 340/365 C, 340/365 R, 178/19, 178/17 C, 179/90 K, 197/98, 200/DIG. 1
• US Class Current: 341/24
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors
• CPC Class Codes: G01K 7/34 using capacitative elements capacitors per se H01G
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 9/0005 using variations in capacitance G01L9/0072 takes precedence
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04
• CPC Class Codes: H03F 3/45071 with semiconductor devices only
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• 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

Abstract

An electronic device incorporating a circuit for providing a signal with respect to an on or off mode dependent upon the degree of capacitance. The invention comprises a first and basic embodiment utilizing a signal source having a slope of a step function or specifically one having a fast rise time initiated for example by a clock element. The operative signal criteria demands that the length and slope thereof respectively have an effective amplitude and an effective frequency compatible with the circuit components.

The signal source is fed to a transistor or suitable amplifier having its base connected to a capacitance sensing means. Resistors are provided for appropriate biasing, current limiting and drain functions as well as capacitors for capacitance balancing purposes. The capacitance sensing means can comprise a touch switch which when touched has its capacitance increased causing the device to function. The transistor or amplifier is connected to a load so that when a change of capacitance is sensed, the change will be registered. Other embodiments can incorporate differential amplification means and means to drive the active components with the voltage of the signal source or the clock voltage.

Alternative embodiments of this invention incorporate capacitance sensing means in the form of transducers which can operate in a linear or a sequential mode. The transducers functionally incorporate a change of capacitance by means of moving mechanical elements so that when such change in capacitance is detected by the circuit it will provide an on or off sensing for the circuit or an analog of the change in capacitance. Thus, a reading of the extent of mechanical movement of a mechanically moving object can be transduced into an electrical function or output having substantial linearity.

In summation, the circuit of this invention can be used for a transducer, or a solid state switch.

Claims

1. A switch comprising:

a capacitive registering element having a conductive surface for purposes of acting as a capacitive element in conjunction with a second body placed in proximity thereto;

a means for generating a signal having sufficiently the slope of a step function to cause the switch to function as a slope differentiation detector with respect to the second body placed in proximity to said capacitive registering element;

means for connecting said conductive surface of said capacitive registering element to said signal generation means so that a change in capacitance between said capacitive registering element and a second body will change the rise time of the slope;

an amplifier connected to said conductive surface and said signal means; and

,

an electrical load connected to said amplifier.

2. The switch as claimed in claim 1 wherein:

the amplifier is a transistor; and

,

the emitter of said transistor is connected to said signal generating means, and the collector of said transistor is connected to said load.

3. The switch as claimed in claim 2 further comprising:

a capacitor connected across the base and emitter of said transistor

4. The switch as claimed in claim 2 further comprising:

a resistor placed across the base and emitter of said transistor.

5. The switch as claimed in claim 1 wherein:

said amplifier is a differential amplifier.

6. The switch as claimed in claim 1 wherein:

said means for generating a signal provides the power to said amplifier.

7. The switch as claimed in claim 1 further comprising:

the combination device of at least a second switch having the elements of the switch in claim 1 wherein said means for generating a signal is in singular form and utilized for both switches by being connected in parallel thereto.

8. The combination device as claimed in claim 7 wherein:

said switches are connected to a keyboard formed with the capacitive coupling elements therein as its keys; and

,

a diode decode matrix is interposed between said capacitive coupling elements and the remainder of the switches.

9. A transduction device comprising:

a capacitive registering element having a first conductor capable of being capacitively coupled to a second body wherein said first conductor is suitably exposed for increases in capacitance with respect to an external body;

a differential amplifier connected to said first conductor of said capacitively coupled element;

a signal production means producing a signal having a substantially rapid rise or fall time connected to said differential amplifier so that said differential amplifier can differentiate changes in slope caused by changes of capacitance with respect to said capacitance registering element; and

,

biasing means for appropriate operation of the differential amplifier.

10. The device as claimed in claim 9 further comprising:

a capacitor connected to said differential amplifier to compensate for stray capacitances within the circuit.

11. The device as claimed in claim 9 further comprising:

a signal production means having sufficient power to operate and power the elements of said differential amplifier.

12. The device as claimed in claim 11 further comprising:

a capacitor connected to said signal production means for reducing transient spikes emanating from said signal producing power means.

13. A device as claimed in claim 9 wherein:

a capacitor is provided for coupling any negative feedback of the amplifier.

14. A capacitive transduction device comprising:

a capacitive coupler having a first conductive member adapted and placed for capacitive coupling with a body that can move with respect to said first conductive member;

a signal source providing a signal having the slope of a step function; and

,

an amplifier connected for amplification of a signal developed in response to the change of the slope of the step function between said capacitive coupler and said signal source.

15. A device as claimed in claim 14 wherein:

a dielectric shield is internally positioned of said first member of a dielectric material;

the body is positioned for movement within said dielectric member for purposes of providing changes in capacity;

connection means for connecting said first member of said capacitive coupler to said amplifier; and

,

means for providing a lower potential for said body than that of the connection point of said first member.

16. A device as claimed in claim 14 wherein:

said first member and said body are concentric cylinders.

17. The device as claimed in claim 14 further comprising:

an insulated tank designed to receive said body;

said first conductive member is placed on the outside of said insulated tank;

a second conductive member on the outside of said tank to register changes in capacitance between said first and second conductive members when said body changes position in said tank.

18. The device as claimed in claim 14 further comprising:

a non-insulated tank designed to receive said body; and

,

said first conductive member is placed in said tank and insulated from contact with said tank and any body therein.

19. A device as claimed in claim 14 wherein:

a second conductor is placed in non-conductive relationship from said first conductive member;

said body is a dielectric for movement between said first and second conductive members;

means for connecting one of said conductors to said amplifier; and

,

means for coupling one of said conductors to a lower or ground potential with respect to said amplifier.

20. A device as claimed in claim 14 wherein:

said conductive member is connected to said amplifier;

a movable conductive block to change the space between said block and said first conductive plate to create changes of capacitance with respect thereto; and

,

a second conductor in adjacent relationship to said conductive block for providing a lower potential with respect to said first conductive member.

21. A device as claimed in claim 14 wherein:

said body comprises a deformable member placed in spaced juxtaposition to said first conductive member; and

,

means for maintaining the potential of said deformable members below that of said amplifier so that as the deformable member moves, it changes the degree of capacity between said spaced first conductive member and said deformable member.

22. The device as claimed in claim 14 in combination with a cathode ray tube further comprising:

a dielectric material for placement over said first conductive member in a manner whereby the display on the cathode ray tube can be seen through said dielectric material.

23. The device as claimed in claim 22 wherein:

said dielectric material forms a panel substantially covering a portion of the cathode ray tube.

24. The device as claimed in claim 22 further comprising:

an array of conductive members deposited on the side of said dielectric material facing said cathode ray tube to provide switch functions relating thereto; and

,

a decoding means for decoding the respective positions representing the respective switches.

25. The device as claimed in claim 24 further comprising:

a computer interfaced with said cathode ray tube and said positions for recording the particular location which has been touched; and

,

a screen between the conductive member and said cathode ray tube for eliminating interference by said cathode ray tube.