Heater diagnostics and electronic control for a clothes dryer

• US 5,281,956 A
• Filed: 11/22/1991
• Issued: 01/25/1994
• Est. Priority Date: 08/11/1989
• Status: Expired due to Term

• Current Assignee: Whirlpool Corporation
• Original Assignee: Whirlpool Corporation
• Inventors: Bashark, Larry T.
• Primary Examiner(s): Crosland, Donnie L.
• Assistant Examiner(s): Lefkowitz, Edward
• Application Number:
  US07/797,446
• Time in Patent Office: 795 Days
• Field of Search: 340/310 R, 340/310 A, 340/660, 340/538, 340/640
• US Class Current: 340/660
• CPC Class Codes: D06F 2103/32 Temperature
• CPC Class Codes: D06F 2103/44 Current or voltage
• CPC Class Codes: D06F 2105/28 Electric heating
• CPC Class Codes: D06F 34/14 Arrangements for detecting or measuring specific parameters
• CPC Class Codes: D06F 37/304 Arrangements or adaptations of electric motors
• CPC Class Codes: D06F 58/34 characterised by the purpose or target of the control
• CPC Class Codes: G01R 31/2825 in household appliances or professional audio/video equipment testing LAN's H04L43/50; testing TV systems H04N17/00; testing loudspeakers H04R29/00
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: H02P 25/04 Single phase motors, e.g. capacitor motors

Abstract

A control for a clothes dryer with an induction drive motor and an electric resistance heater element. A single sense winding is threaded through sensors monitoring drive motor current and heater current, generating an output voltage each time the alternating motor or heater current passes through a zero-crossing. The control monitors the ON/OFF condition of the heater and samples the lagging phase angle of the motor current, and provides an improved system of detecting when the clothes load is dry. The control provides a clothes cool-down period with controlled moisture regain as per the user dryness selection. Numerous heater related diagnostic conditions are monitored at the start of each cycle, or, throughout each cycle, including: heater ground fault detection; 208 or 240 VAC service voltage identification; heater open/short circuit detection; open door detection; heater box thermostat cycling; and restricted air flow detection.

Claims

1. A method of determining the voltage of an AC power source having a first hot side, a second hot side, and a neutral side, said AC power source supplying AC power to an appliance having a three wire connector interconnectable to said AC power source, said method comprising the steps of:

sensing the zero crossings of the AC power source between said first hot side and said second hot side;

sensing the zero crossings of the AC power source between said first hot side and said neutral side;

wherein at least one of zero said crossings is measured by using a core wound about an electrical line between two sides of said AC power source; and

comparing the relative timing between said zero crossings.

2. A method of determining the voltage of an AC power source having a first hot side, a second hot side, and a neutral side, said AC power source supplying AC power to an appliance having a three wire connector interconnectable to said AC power source, said method comprising the steps of:

sensing the zero crossings of the AC power source between said first hot side and said second hot side;

sensing the zero crossings of the AC power source between said first hot side and said neutral side; and

wherein at least one of said steps of sensing zero crossing comprises sensing zero crossings of the AC power source through a component of said appliance such that at least one step provides, in addition to information about the type of AC source, information about the operation or inoperation of said component; and

comparing the relative timing between said zero crossings.

3. The method of claim 2 wherein said appliance is a dryer and said component is a heater connected between said first hot side and said second hot side such that said step of sensing the zero crossings of the AC power source between said first hot side and said second hot side comprises sensing zero crossings of the AC power through said heater.

4. A method of determining the voltage of an AC power source having a first hot side, a second hot side, and a neutral side, said AC power source supplying AC power to an appliance having a three wire connector interconnectable to said AC power source, said method comprising the steps of:

sensing the zero crossings of the AC power source between said first hot side and said second hot side;

sensing the zero crossings of the AC power source between said first hot side and said neutral side;

comparing the relative timing between said zero crossings;

providing a record indicative of the detection of a 240 VAC power source if said timing of said zero crossings is substantially less than 45 electrical degrees different; and

providing a record indicative of the detection of a 208 VAC power source if said timing of said zero crossings is approximately 90 electrical degrees apart.

5. The method of claim 4 wherein said appliance is a dryer having a heater connected between said first hot side and said second hot side and wherein said step of sensing the zero crossings of the AC power source between said first hot side and said second hot side comprises sensing zero crossings of the AC power through said heater, thereby providing information about the operation of said heater.

6. A sensor circuit for determining if a heater coil line is receiving power and for monitoring the current through the winding of a motor used in conjunction with said heater, said sensor circuit comprising:

a first core winding wound about said heater coil line;

a second core winding wound about said winding of said motor; and

a sense winding wound through said first core winding and said second core winding, said sense winding providing;

a first series of voltage spikes indicating zero crossings of the current through said heater, such that the absence of said first series of voltage spikes is indicative of the absence of current through said heater; and

a second series of voltage spikes indicting zero crossings of the current through said winding of said motor.

7. The sensor circuit of claim 6 further comprising sensor means for monitoring the current through the winding of a motor used in conjunction with said heater.

8. The sensor circuit of claim 7 wherein said means for monitoring comprises a second core wound about said winding of said motor, said sense winding being further wound through said second core such as to provide a second series of voltage spikes indicating zero crossings of the current through said winding of said motor.

9. The sensor circuit of claim 8 further comprising current pulse means connected to said sense winding, said current pulse means receiving voltage spikes from said sense winding indicative of said zero crossings and generating a signal having current pulses corresponding to said voltage spikes.

10. The sensor circuit of claim 6 further comprising microcomputer means for generating a record indicative of the existence or non-existence of said voltage spikes.

11. The sensor circuit of claim 6 further comprising thermometer means for detecting the temperature of an environment heated by said heater.

12. The sensor circuit of claim 11 wherein said thermometer means comprises:

means for providing a pulse representation of the temperature of said environment.

13. A sensor circuit for determining if a heater coil line is receiving power, said sensor circuit comprising:

a core winding wound about said heater coil line;

a sense winding wound through said core winding, said sense winding providing a first series of voltage spikes indicating zero crossings of the current through said heater, such that the absence of said first series of voltage spikes is indicative of the absence of current through said heater;

thermometer means for detecting the temperature of an environment heated by said heater; and

means for controlling said heater in response to said voltage spike and said temperature detected by said temperature means.

14. The sensor circuit of claim 13 further comprising microcomputer means for generating a record indicative of the existence or non-existence of said voltage spikes.

15. A sensor circuit for determining if a heater coil line is receiving power, said sensor circuit comprising:

a core winding wound about said heater coil line;

a sense winding wound through said core winding, said sense winding providing a first series of voltage spikes indicating zero crossings of the current through said heater, such that the absence of said first series of voltage spikes is indicative of the absence of current through said heater; and

thermometer means for detecting the temperature of an environment heated by said heater and for providing a pulse representation of the temperature of said environment, wherein said thermometer means further comprises;

a comparator having an inverting input, a non-inverting input, and an output;

a thermistor connected to said inverting input of said comparator;

a resistor of known resistance connected in parallel with said thermistor to said inverting input of said comparator; and

means for alternatingly supplying a source of DC power to said resistor and to said thermistor; and

to said non-inverting input of said comparator, such that said output of said comparator supplies a pulse of a width determined by the temperature of said thermistor.

16. The sensor circuit of claim 15 further comprising current pulse means connected to said sense winding, said current pulse means receiving voltage spikes from said sense winding indicative of said zero crossings and generating a signal having current pulses corresponding to said voltage spikes.

17. The sensor circuit of claim 16 further comprising microcomputer means for generating a first record indicative of the existence or non-existence of said voltage spikes and a second record indicative of the temperature measured by said thermometer means.

18. The sensor circuit of claim 15 further comprising sensor means for monitoring the current through the winding of a motor used in conjunction with said heater, said means for monitoring comprising a second core wound about said winding of said motor, said sense winding being further wound through said second core such as to provide a second series of voltage spikes indicating zero crossings of the current through said winding of said motor.

19. A control circuit for an appliance having a heater and a motor for determining if a heater coil line of said heater is receiving power, for monitoring the current through a winding of said motor, and for controlling the operation of said appliance, said sensor circuit comprising:

a first core winding wound about said heater coil line;

a second core winding wound about said winding of said motor; and

a sense winding wound through said first core winding and said second core winding, said sense winding providing;

a first series of voltage spikes indicating zero crossings of the current through said heater, such that the absence of said first series of voltage spikes is indicative of the absence of current through said heater;

a second series of voltage spikes indicating zero crossings of the current through said winding of said motor;

thermometer means for detecting the temperature of an environment heated by said heater;

means for generating a record indicative of the existence or non-existence of said first series of voltage spikes, a second record indicative of the temperature measured by said thermometer means, and a third record of preselected characteristics of said second series of voltage spikes; and

means for controlling said heater in response to said first and second records and for controlling said motor in response to said third record.