Apparatus for producing a time-proportioned control signal electronically

• US 4,161,660 A
• Filed: 08/31/1977
• Issued: 07/17/1979
• Est. Priority Date: 08/31/1977
• Status: Expired due to Term

• Current Assignee: Longwood Machine Works Incorporated
• Original Assignee: Longwood Machine Works Incorporated
• Inventors: Gallant, Donald A.
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Ginsburg, Morris
• Application Number:
  US05/829,487
• Time in Patent Office: 685 Days
• Field of Search: 307/118, 307/308, 307/116, 307/117, 307/141, 328/4, 200/61.06, 236/44 R, 236/44 A, 236/44 B, 236/44 C, 236/44 E, 340/602, 340/604
• US Class Current: 307/118
• CPC Class Codes: G05B 11/28 using pulse-height modulation; using pulse-width modulation
• CPC Class Codes: G05D 22/02 characterised by the use of electric means

Abstract

A solid state electronic controller for humidification devices employs an electronic humidity sensor to create an electronic signal proportional to the humidity in the space to be controlled, and massages or processes this proportional signal to create a cyclic series of time-proportioned control signals to cause the operation of the humidification devices in each cycle for a period proportional to the difference between the sensed humidity and the desired humidity.

Claims

1. An apparatus for producing a timed control signal for actuation of a responsive device for changing a condition to a predetermined desired condition, said apparatus comprising

(a) electronic means for sensing the condition;

(b) means for creating electronic signals proportional to the measure of said condition being sensed by said electronic means within a sensitivity range and cyclic electronic ramp signals rising uniformly to a maximum amplitude representing said sensitivity range;

(c) electronic means for processing said proportional signals to create therefrom a series of timed control signals by comparison of said proportional signals and said rising cyclic ramp signals at each cycle thereof and creating one of said timed control signals for the remaining duration of each cycle at the time that each ramp signal rises above each proportional signal.

2. An apparatus for producing a timed control signal for actuation of a responsive device for changing a condition to a predetermined desired condition, said apparatus comprising

(a) means for sensing the condition;

(b) means for creating an electronic signal proportional to the measure of said condition being sensed by said means for sensing;

(c) means for creating electronically a cyclic sawtooth direct current wave form signal of constant maximum amplitude and having a cycle including a uniformly changing ramp signal of like maximum amplitude included as a portion thereof;

(d) means for electronically re-basing and amplifying said proportional signal suitably for comparison with said ramp signal to cover a sensitivity range which has limits set by a proportional signal corresponding to a selected condition and by another proportional signal corresponding to said predetermined desired condition;

(e) an electronic means for comparison of said proportional signal after said re-basing and amplifying with said ramp signal at each said cycle of said sawtooth signal; and

(f) means for electronically creating from said comparison said timed control signal whose duration during each said cycle is directly proportional to the difference between said proportional signal after said re-basing and amplifying and said desired condition signal as related to said maximum amplitude of said ramp signal.

3. An apparatus for producing a timed control signal according to claim 2 and characterized further in that said sensing means senses said condition continuously and said means (b) continuously creates said signal proportional to the measure of said signal being sensed.

4. An apparatus for producing a timed control signal according to claim 3 and characterized further in that said sensing means has an electrical impedance varying generally proportionally to variations in the measure of said condition.

5. An apparatus for producing a timed control signal according to claim 4 and characterized further by an element included in means (b) thereof having an essentially fixed impedance and connected in series with said sensing means and by means included in means (b) thereof for applying an alternating current voltage of constant amplitude across said essentially fixed impedance element and said sensing means in series for producing alternating current voltages across said sensing means and said element respectively proportional to the measure of the condition as sensed.

6. An apparatus for producing a timed control signal according to claim 5 and characterized further in that said alternating current voltage has a frequency selected suitably such that said sensing means impedance and said alternating current voltages proportional to the measure of said condition being sensed vary essentially linearly with variations in the measure of said condition in a suitable range of interest.

7. An apparatus for producing a timed control signal according to claim 6 and characterized further by said alternating current voltage having a sine wave form and a frequency in the order of 10 Hertz, said sensing means sensing relative humidity, and said sensing means impedance varying inversely with the measure of said relative humidity being sensed.

8. An apparatus for producing a timed control signal according to claim 6 and characterized further in that said means included in means (b) thereof for applying an alternating current voltage comprises an oscillator and means for isolating said oscillator from said varying impedance of said sensing means including an operational amplifier receiving at its input said alternating current voltage and operated with unity feedback to its inverting input from its output and its output connected for said applying of said alternating current voltage across said fixed impedance element and said sensing means.

9. An apparatus for producing a timed control signal according to claim 6 and characterized further by means included in said means (b) thereof for converting one of said condition proportional alternating current voltages to a periodically updated continuous direct current voltage varying essentially linearly directly proportionally to the measure of said sensed condition in a suitable range of interest.

10. An apparatus for producing a timed control signal according to claim 9 and characterized further by means included in means (b) thereof for suitably referencing said updated direct current voltage to a zero signal for reading a referenced signal in volts directly representing said condition to a suitable scale.

11. An apparatus for producing a timed control signal according to claim 9 and characterized further in that said converting means comprises a buffered differential amplifier for producing at its output an isolated amplified condition proportional alternating current voltage wave form, a sample and hold circuit having an input connected to said buffered output and capable of being triggered for momentary opening thereof for reception of a direct current voltage signal into said sample and hold circuit for retention therein and transmission therethrough to the output thereof pending a subsequent triggering and opening of said input for reception of a subsequent said direct current voltage signal for said retention and transmission, and means actuated by said isolated amplified condition proportional alternating current wave form for triggering and opening momentarily said sample and hold input at a like selected point in each cycle of said wave form for receiving an effective momentary direct current signal therefrom and thereby producing at the sample and hold output said continuous direct current voltage updated at each cycle of said wave form to a value equal to the instantaneous direct current value of said wave form at said selected point thereof.

12. An apparatus for producing a timed control signal according to claim 11 and characterized further in that said sample and hold circuit includes a time delay circuit for varying the position of said selected point in said wave form and a second time delay circuit for selectively determining the duration of said momentary opening of said input.

13. An apparatus for producing a timed control signal according to claim 2 and characterized further in that said means for creating a sawtooth signal includes a raster circuit for creating said ramp signal and returning said ramp signal to a starting point for a subsequent ramp signal essentially instantaneously at the end of said ramp signal for said sawtooth signal creating thereby.

14. An apparatus for producing a timed control signal according to claim 13 and characterized further in that said means for creating a sawtooth signal includes means for selectively adjusting the cycle time of said cyclic sawtooth wave form signal.

15. An apparatus for producing a timed control signal according to claim 14 and characterized further in that said raster circuit is isolated by transmitting said sawtooth signal through an operational amplifier operated with unity feedback to its inverting input.

16. An apparatus for producing a timed control signal according to claim 2 and characterized further in that said means (b) includes means for producing a direct current voltage signal proportional to said measure of said sensed condition and said re-basing and amplifying means includes means for producing a re-basing direct current voltage signal corresponding to said one of said proportional signals corresponding to a selected condition for subtraction from said proportional direct current voltage signal to produce a re-based condition proportional direct current voltage signal.

17. An apparatus for producing a timed control signal according to claim 16 and characterized further in that said re-basing and amplifying means includes for amplifying said re-based direct current voltage signal for producing a re-based and amplified condition proportional direct current voltage signal suitable for said comparison with said ramp signal in that a re-based and amplified signal corresponding to said selected condition has an amplitude equal to the minimum amplitude of said ramp signal and a re-based and amplified signal corresponding to said desired condition has an amplitude equal to the maximum amplitude of said ramp signal.

18. An apparatus for producing a timed control signal according to claim 2 and characterized further in that said comparison is made of said proportional signal after said re-basing and amplifying as it exists at a selected time in each said cycle of said sawtooth signal.

19. An apparatus for producing a timed control signal according to claim 18 and characterized further in that said means for comparison includes a sample and hold circuit for retaining the value of said proportional signal after said re-basing and amplifying existing at said selected time in each said cycle of said sawtooth signal for comparison with said changing ramp signal thereafter in each said cycle.

20. An apparatus for producing a timed control signal according to claim 19 and characterized further in that said means for creating a sawtooth signal includes a raster circuit for creating said ramp signal and returning said ramp signal to a starting point for a subsequent ramp signal essentially instantaneously at the end of said ramp signal for said sawtooth signal creating thereby and in that said selected time in each said cycle of said sawtooth signal occurs upon said returning said ramp signal to said starting point.

21. An apparatus for producing a timed control signal according to claim 2 and characterized further in that said means for comparison comprises an operational amplifier whereat said proportional signal after said re-basing and amplifying is applied to one input thereof and said changing ramp signal is applied to another input thereof for comparison thereby.

22. An apparatus for producing a timed control signal according to claim 21 and characterized further in that said operational amplifier reverses its output essentially at the time when the value of said changing ramp signal starts to exceed the value of said proportional signal after said re-basing and amplifying and remains reversed while said ramp signal exceeds said proportional signal after said re-basing and amplifying.

23. An apparatus for producing a timed control signal according to claim 22 and characterized further in that said means for creating from said comparison said timed control signal comprises an electronic relay connected for operation by said reversed output of said operational amplifier.