Capacitive sensor control system

• US 4,323,829 A
• Filed: 07/28/1980
• Issued: 04/06/1982
• Est. Priority Date: 07/28/1980
• Status: Expired due to Term

• Current Assignee: Barry M. Fish
• Original Assignee: Barry M. Fish
• Inventors: Visser, Harry, Witney, Gary
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Indyk, Eugene S.
• Application Number:
  US06/172,529
• Time in Patent Office: 617 Days
• Field of Search: 318/55, 318/257, 318/341, 318/662, 318/599, 307/116, 340/365 C, 324/60 C, 324/61 R, 328/5
• US Class Current: 318/55
• CPC Class Codes: A61G 2203/16 Touchpads
• CPC Class Codes: A61G 5/045 Rear wheel drive
• CPC Class Codes: H02P 5/68 controlling two or more dc dynamo-electric motors H02P5/46, H02P5/60 take precedence

Abstract

An electronic control system for controlling the operation of electromotive apparatus utilizes a capacitive sensor for sensing human touch and producing a command signal whose magnitude corresponds to the contact area of the contact. The sensor command signal is applied to an oscillator which produces a series of output width pulses having a frequency corresponding with the magnitude of the sensor command signal. A discriminator detects the trailing edge of the oscillator pulses and produces a series of fixed width pulses and an integrator produces a D.C. voltage signal corresponding to the discriminator output, which voltage signal corresponds to the area in proximity to and thereby stimulated by the human body. A comparator is employed to produce a pulse-width modulated rectangular pulse output whose duty cycle corresponds to the integrator D.C. voltage by comparing the integrator D.C. voltage with a reference triangular waveform. The comparator output is applied via power circuit to drive the electromotive apparatus which may typically comprise one or more D.C. electric motors.

Claims

1. An electronic control system for controlling the operation of electromotive means, comprising:

electronically capacitive sensing means for detecting proximity thereto by a portion of a human body,

oscillator means responsive to said sensing means operative to produce a series of output pulses having a frequency in accordance with the capacitance input thereto by said sensing means,

discriminator means for detecting the trailing edges of said oscillator pulses and producing a series of fixed width pulses in response thereto,

integrator means operative to produce a D.C. voltage in accordance with said discriminator pulses, said D.C. integrator voltage corresponding to the magnitude of the coupled capacitance sensed by said capacitance sensing means.

2. An electronic control system as defined in claim 1 further comprising reference waveform generating means for producing a triangular reference waveform,

comparator means operative to compare said integrator D.C. voltage and said triangular reference waveform and to produce a series of rectangular pulses having a duty cycle determined by the difference between said compared D.C. voltage and said triangular waveform, and

power circuit means for applying said pulsed D.C. output to said electromotive means.

3. An electronic control system as defined in claim 1 wherein said oscillator means output pulses comprises a changeable rectangular waveform, the frequency of which changes with the amount of capacity sensed.

4. An electronic control system as defined in claim 3 wherein said discriminator means comprises a one-shot delay flop circuit operative to produce a series of rectangular pulses of fixed pulse width whose leading edges are respectively time coincident with the trailing edges of said oscillator means output pulses.

5. An electronic control system as defined in claim 4 wherein said integrator means is operative to produce a D.C. voltage signal corresponding to the discriminator output which voltage signal corresponds to the amount of capacity sensed.

6. An electronic control system as defined in claim 5 wherein said reference waveform generating means comprises reference oscillator means operative to produce a series of rectangular pulses having a fixed pulse frequency and reference integrator means operative to produce a series of triangular pulses having a frequency equal to said reference oscillator rectangular pulses.

7. An electronic control system as defined in claim 6 wherein said comparator means is operative to produce a zero output when said integrator D.C. voltage is less than the inverse peak voltage of said reference integrator triangular pulses.

8. An electronic control system as defined in claim 7 wherein said comparator means output pulses have a substantially one hundred percent duty cycle when said integrator voltage exceeds the peak voltage of said reference integrator triangular pulses.

9. An electronic control system as defined in claim 8 wherein the duty cycle of said comparator output pulses is linearly dependent on the level of said D.C. integrator voltage.

10. An electronic contol system as defined in claim 9 including power circuit means having an input terminal for the application thereto of said comparator output pulses and an output terminal for connection to said electromotive means.

11. An electronic control system as defined in claim 1 wherein the capacitative output signal produced by said sensing means varies in accordance with the area of the said human body proximity.

12. An electronic control system as defined in claim 11 wherein said sensing means comprises a plurality of sensing areas, each of said sensing areas representing corresponding directional command signals for said electromotive means.

13. An electronic control system as defined in claim 12 wherein each of said sensing areas has associated therewith a channel comprising said oscillator means, said discriminator means, said integrator means, said reference waveform generating means, said comparator means, said power circuit means and a motor.

14. An electronic control system as defined in claim 13 wherein said electromotive means comprises four sensing areas representing forward and reverse direction drive for each of said motors.