Humidity and/or temperature control device

• US 5,578,753 A
• Filed: 05/23/1995
• Issued: 11/26/1996
• Est. Priority Date: 05/23/1995
• Status: Expired due to Fees

• Current Assignee: Weiss Controls, Inc.
• Original Assignee: Micro Weiss Electronics, Inc.
• Inventors: Jean, Chwen C., Weiss, John
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): WIGGINS, JOHN DAVID
• Application Number:
  US08/450,957
• Time in Patent Office: 553 Days
• Field of Search: 73/335.02, 73/335.05, 73/29.02, 73/29.05, 62/85, 62/176, 62/195, 62/209, 62/214, 62/216, 219/494, 392/501, 392/497, 307/34, 307/35, 307/116, 307/117, 236/10, 236/11, 236/44, 361/93
• US Class Current: 73/335.02
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/88 Electrical aspects, e.g. circuits
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 3/14 by humidification; by dehumidification
• CPC Class Codes: G01N 27/121 for determining moisture content, e.g. humidity, of the fluid moisture content of the tested material G01N27/048
• CPC Class Codes: G01N 27/122 Circuits particularly adapted therefor, e.g. linearising circuits
• CPC Class Codes: G05D 22/02 characterised by the use of electric means

Abstract

A humidity control device includes a microcontroller, a variable impedance humidity sensing circuit and a zero crossing detector circuit. The humidity sensing circuit and zero crossing circuit are provided with an AC line voltage and both have outputs which are provided to the microcontroller. The humidity control device also includes a semiconductor switch circuit which switches the AC line voltage to an external electrical device, such as a dehumidifier or heater, at the zero crossing.

Claims

1. A humidity control device for sensing humidity and for selectively energizing an electrical device connected to an AC line voltage in response to the sensed humidity, which comprises:

a humidity sensing circuit, the humidity sensing circuit including circuit components, at least one of the circuit components being a humidity sensor which is coupled and responsive to the AC line voltage, the circuit components forming a balanced circuit such that the humidity sensing circuit is substantially self-compensating for AC line voltage variations, the humidity sensing circuit sensing the humidity and comparing the sensed humidity with a preselected humidity set point and generating a first output signal in response to the comparison thereof,

a zero crossing detector, the zero crossing detector detecting a zero crossing of the AC line voltage, the zero crossing detector being responsive to the AC line voltage and generating a second output signal indicating the zero crossing thereof,

a microcontroller, the microcontroller being responsive to the first and second output signals of the humidity sensing circuit and zero crossing detector and generating a third output signal in response thereto; and

means for switching the AC line voltage connected to the electrical device, the AC line voltage switching means being responsive to the third output signal of the microcontroller and selectively providing the AC line voltage to the electrical device in response thereto thereby selectively energizing and deenergizing the electrical device in a manner which substantially reduces radio frequency interference.

2. A humidity control device as defined by claim 1, wherein the humidity sensing circuit includes a first electrical path having a first overall electrical resistance, a second electrical path having a second overall electrical resistance, and a voltage comparator, the second electrical path including the humidity sensor, the humidity sensor having a sensor resistance which varies with the sensed humidity, the second overall electrical resistance of the second electrical path including the sensor resistance, the first and second overall electrical resistances respectively of the first and second electrical paths being substantially equal at a particular humidity sensed by the humidity sensor, each of the first and second electrical paths being provided with at least a portion of the AC line voltage to cause a voltage drop across the first and second overall electrical resistances, the comparator being responsive to the voltage drops across the first and second overall electrical resistances respectively of the first and second electrical paths and generating the first output signal in response thereto.

3. A humidity control device as defined by claim 2, wherein at least one of the first and second electrical paths includes means for compensating for temperature variations, the temperature variation compensating means having a resistance which varies with changes in temperature.

4. A humidity control device as defined by claim 1, wherein the humidity sensing circuit includes a comparator, the comparator having at least first and second inputs, the first input having a reference signal provided thereto, the reference signal corresponding to a preselected humidity set point, the second input having a humidity varying signal provided thereto, the humidity varying signal being responsive to changes in the humidity sensed by the humidity sensor and varying in response thereto, the comparator comparing the reference signal with the humidity varying signal and generating the first output signal in response to the comparison thereof.

5. A humidity control device as defined by claim 1, wherein the humidity sensing circuit includes a first resistor divider network and a second resistor divider network, at least a portion of the first and second resistor divider networks being provided with at least a portion of the AC line voltage and respectively generating first and second voltage drops in response thereto, the second resistor divider network including the humidity sensor, the humidity sensor having a sensor resistance which varies in response to the humidity sensed by the humidity sensor;

and wherein the humidity sensing circuit further includes a voltage comparator, the voltage comparator being responsive to a comparison of the first and second voltage drops respectively generated by the first and second resistor divider networks and generating the first output signal in response to the comparison thereof.

6. A humidity control device as defined by claim 1, wherein at least a portion of the AC line voltage is provided to the humidity sensing circuit, and wherein the humidity sensor is an AC resistive type humidity sensor.

7. A humidity control device as defined by claim 6, wherein the humidity sensing circuit includes a comparator, the comparator having at least first and second inputs, the first input having a reference signal provided thereto, the reference signal corresponding to a preselected humidity set point, the second input having a humidity varying signal provided thereto, the humidity varying signal being responsive to changes in the humidity sensed by the humidity sensor and varying in response thereto, the comparator comparing the reference signal with the humidity varying signal and generating the first output signal in response to the comparison thereof.

8. A humidity control device as defined by claim 1, wherein the humidity sensing circuit includes:

a first resistor divider network, the first resistor divider network being provided with at least a portion of the AC line voltage and generating a first AC voltage drop in response thereto;

a second resistor divider network, the second resistor divider network being provided with the at least portion of the AC line voltage and generating a second AC voltage drop in response thereto, the second resistor divider network including the humidity sensor, the humidity sensor being an AC resistive type sensor, the second AC voltage drop being at least partially across the humidity sensor;

means responsive to the first AC voltage drop for generating a first DC voltage in response thereto, the first DC voltage being proportional to the first AC voltage drop and corresponding to a preselected humidity set point;

means responsive to the second AC voltage drop for generating a second DC voltage in response thereto, the second DC voltage being proportional to the second AC voltage drop and varying with the humidity sensed by the humidity sensor; and

a voltage comparator, the voltage comparator comparing the first DC voltage and the second DC voltage and generating the first output signal in response to the comparison thereof.

9. A humidity control device as defined by claim 8, wherein at least one of the first and second resistor divider networks includes means for compensating for temperature variations, the temperature variation compensating means having a resistance which varies with changes in temperature.

10. A control device for one of providing power gradually to and removing power gradually from an electrical device connected to an AC voltage, which comprises:

means for determining when power is to be applied to the electrical device, the power determining means generating a first output signal indicative thereof;

a zero crossing detector, the zero crossing detector detecting a zero crossing of the AC voltage, the zero crossing detector being responsive to the AC voltage and generating a second output signal indicating the zero crossing thereof;

a microcontroller, the microcontroller being responsive to the first output signal of the power determining means and the second output signal of the zero crossing detector and generating a third output signal in response thereto; and

means for switching the AC voltage connected to the electrical device, the AC voltage switching means being responsive to the third output signal of the microcontroller and selectively providing the AC voltage to the electrical device in response thereto thereby selectively energizing and deenergizing the electrical device;

the third output signal of the microcontroller being in the form of electrical pulses of voltage timed to selectively switch on and off the AC voltage switching means for half cycles and full cycles over a predetermined number of cycles of the AC voltage provided to the electrical device.

11. A control device for one of providing power gradually to and removing power gradually from an electrical device connected to an AC voltage, which comprises:

a zero crossing detector, the zero crossing detector detecting a zero crossing of the AC voltage, the zero crossing detector being responsive to the AC voltage and generating a first output signal indicating the zero crossing thereof;

a microcontroller, the microcontroller being responsive to the first output signal of the zero crossing detector and generating a second output signal in response thereto; and

means for switching the AC voltage connected to the electrical device, the AC voltage switching means being responsive to the second output signal of the microcontroller and selectively providing the AC voltage to the electrical device in response thereto thereby selectively energizing and deenergizing the electrical device;

the second output signal of the microcontroller being in the form of electrical pulses timed to selectively switch on and off the AC voltage switching means for half cycles and full cycles over a predetermined number of cycles of the AC voltage provided to the electrical device.

12. A control device as defined by claim 11, wherein the second output signal of the microcontroller includes:

a first plurality of electrical pulses, each electrical pulse of the first plurality of electrical pulses having a first pulse width equal to about one half cycle of the AC line voltage and being periodically spaced apart from each other; and

a second plurality of electrical pulses, the second plurality of electrical pulses following the first plurality of electrical pulses, each electrical pulse of the second plurality of electrical pulses having a second pulse width equal to about a full cycle of the AC line voltage and being periodically spaced apart;

wherein the first plurality of electrical pulses selectively switches on and off the AC switching means for half cycles of the AC voltage provided to the electrical device; and

wherein the second plurality of electrical pulses selectively switches on and off the AC switching means for full cycles of the AC voltage provided to the electrical device.

13. A control device for providing power gradually to an electrical device connected to an AC voltage, which comprises:

a zero crossing detector, the zero crossing detector detecting a zero crossing of the AC voltage, the zero crossing detector being responsive to the AC voltage and generating a first output signal indicating the zero crossing thereof;

a microcontroller, the microcontroller being responsive to the first output signal of the zero crossing detector and generating a second output signal in response thereto; and

means for switching the AC voltage connected to the electrical device, the AC voltage switching means being responsive to the second output signal of the microcontroller and selectively providing the AC voltage to the electrical device in response thereto thereby selectively energizing and deenergizing the electrical device;

the second output signal of the microcontroller being in the form of electrical pulses timed to selectively switch on and off the AC switching means for half cycles and full cycles of the AC voltage provided to the electrical device, wherein the second output signal of the microcontroller includes a first plurality of electrical pulses having a first pulse width and a second plurality of electrical pulses having a second pulse width, the first pulse width being equal to about one half cycle of the AC voltage and the second pulse width being equal to about a full cycle of the AC voltage, at least some of the electrical pulses of the second plurality of electrical pulses being interspersed with at least some of the electrical pulses of the first plurality of electrical pulses over a predetermined number of cycles of the AC voltage.

14. A method of one of providing an AC voltage gradually to and removing an AC voltage gradually from an electrical device selectively connected to an AC voltage source, which comprises the steps of:

generating a first plurality of electrical pulses and a second plurality of electrical pulses, each of the electrical pulses of the first plurality of electrical pulses having a first pulse width equal to about one half cycle of the AC voltage, each of the electrical pulses of the second plurality of electrical pulses being equal to about one full cycle of the AC voltage;

arranging the first and second pluralities of electrical pulses such that the first plurality of electrical pulses precede the second plurality of electrical pulses over a predetermined number of cycles of the AC voltage when providing power gradually to the electrical device and follow the second plurality of electrical pulses over a predetermined number of cycles of the AC voltage when removing power gradually from the electrical device; and

selectively switching the AC voltage provided to the electrical device in response to the first and second pluralities of electrical pulses thereby selectively energizing and deenergizing the electrical device.

15. A method as defined by claim 14, which comprises the further step of:

detecting the zero crossing of the AC voltage; and

timing the occurrence of the electrical pulses of the first and second pluralities of electrical pulses such that the AC voltage provided to the electrical device is selectively switched in response to the first and second pluralities of electrical pulses at the zero crossing of the AC voltage.

16. A method of providing an AC voltage gradually to an electrical device selectively connected to an AC voltage source, which comprises the steps of:

generating a first plurality of electrical pulses and a second plurality of electrical pulses, each of the electrical pulses of the first plurality of electrical pulses having a first pulse width equal to about one half cycle of the AC voltage, each of the electrical pulses of the second plurality of electrical pulses having a second pulse width equal to about one full cycle of the AC voltage;

arranging the first and second pluralities of electrical pulses such that at least some of the electrical pulses of the second plurality of electrical pulses are interspersed with at least some of the electrical pulses of the first plurality of electrical pulses over a predetermined number of cycles of the AC voltage; and

selectively switching the AC voltage provided to the electrical device in response to the first and second pluralities of electrical pulses thereby selectively energizing and deenergizing the electrical device.

17. A method as defined by claim 16, which comprises the further steps of:

detecting the zero crossing of the AC voltage; and

timing the occurrence of the electrical pulses of the first and second pluralities of electrical pulses such that the AC voltage provided to the electrical device is selectively switched in response to the first and second pluralities of electrical pulses at the zero crossing of the AC voltage.