Removal of an accumulated frozen substance from a cooling unit

Abstract

An embodiment of a probe includes a sensor and a support. The sensor is operable to provide an indication of a thickness of a frozen substance that has accumulated between the sensor and a cooling fin of a cooling unit, and the support is operable to hold the sensor spaced apart from the cooling fin. For example, a defrost controller may use an embodiment of such a probe to monitor an amount of frost build up on the fin or fins of a cooling unit (e.g., a refrigeration or freezer unit) so that the controller may initiate a defrost cycle only when warranted. Such a probe may be more reliable than other defrost-detection techniques, and such a defrost controller may increase the cooling and energy efficiencies of a cooling unit as compared to a cooling unit having a conventional defrost controller.

What is claimed is: 
     
         1 . A detector, comprising:
 a first input node configured to receive, from a frost-detection probe, a signal that indicates a thickness of a frozen substance on a fin of a cooling unit; and   a processing circuit configured
 to compare the signal to a threshold that corresponds to a threshold thickness of the frozen substance on the fin of the cooling unit, 
 to generate a comparison result in response to comparing the signal to the threshold, 
 to generate an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the comparison result indicating that the thickness of the frozen substance on the fin of the cooling unit is greater than the threshold thickness, 
 to send the indication that the cooling unit is ready to a defrost unit, 
 to receive an indication that a defrost cycle performed by the defrost unit is complete, and 
 in response to receiving the indication that the defrost cycle is complete, to recalibrate the threshold in response to the signal. 
   
     
     
         2 . The detector of  claim 1  wherein the processing circuit is further configured:
 to determine a difference between the signal after receiving the indication that the defrost cycle is complete to the signal after having received an indication that a defrost cycle previously performed by the defrost unit was complete; and 
 to recalibrate the threshold by adding the difference to the threshold to generate a recalibrated threshold. 
 
     
     
         3 . A method, comprising:
 receiving, from a frost-detection probe, a signal that indicates a thickness of a frozen substance on a fin of a cooling unit;   comparing the signal to a threshold that corresponds to a threshold thickness of the frozen substance on the fin of the cooling unit;   generating a comparison result in response to comparing the signal to the threshold;   generating an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the comparison result indicating that the thickness of the frozen substance on the fin of the cooling unit is greater than the threshold thickness;   sending the indication that the cooling unit is ready to a defrost unit;   receiving an indication that a defrost cycle performed by the defrost unit is complete; and   in response to receiving the indication that the defrost cycle is complete, recalibrating the threshold in response to the signal.   
     
     
         4 . The method of  claim 3  wherein recalibrating the threshold includes:
 determining a difference between the signal after receiving the indication that the defrost cycle is complete to the signal after having received an indication that a defrost cycle previously performed by the defrost unit was complete; and 
 generating a recalibrated threshold equal to a sum of the difference and the threshold. 
 
     
     
         5 . A detector, comprising:
 a first input node configured to receive a first signal that indicates a thickness of a frozen substance on a fin of a cooling unit;   a processing circuit configured to generate an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the signal indicating that the thickness of the frozen substance is greater than a threshold thickness;   a second input node configured to receive a calibration signal;   wherein the processing circuit is configured to set a threshold signal value substantially equal to a value that the signal has at substantially a time that the calibration signal is received, the threshold signal value corresponding to the threshold thickness; and   wherein the processing circuit is configured:
 to generate an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the signal having a value that has a predetermined relationship to a signal threshold value that corresponds to the threshold thickness, 
 to determine a post-reducing value of the signal, and 
 to adjust the signal threshold value in response to the post-reducing value of the signal. 
   
     
     
         6 . The detector of  claim 5  wherein the processing circuit is configured:
 to generate an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the signal having a magnitude that is greater than a signal threshold value that corresponds to the threshold thickness; 
 to determine a first post-reducing value of the signal after the thickness of the frozen substance is reduced; 
 to adjust the signal threshold value in response to the first post-reducing value of the signal; 
 to determine a second post-reducing value of the signal after determining the first post-reducing value but before the thickness of the frozen substance increases to the threshold thickness; and 
 to adjust the signal threshold value in response to the second post-reducing value of the signal if a magnitude of the second post-reducing value is less than a magnitude of the first post-reducing value. 
 
     
     
         7 . The detector of  claim 5  wherein the processing circuit is configured:
 to generate an indication that the cooling unit is ready for reducing the thickness of the frozen substance in response to the signal corresponding to a capacitance value indicating that the capacitance value is greater than a capacitance threshold value that corresponds to the threshold thickness; 
 to determine a post-reducing capacitance value corresponding to the signal after the thickness of the frozen substance is reduced; and 
 to adjust the capacitance threshold value in response to the post-reducing capacitance value. 
 
     
     
         8 . The detector of  claim 5  wherein the processing circuit is configured to generate a reduce-thickness signal as the indication that the cooling unit is ready for reducing the thickness of the frozen substance. 
     
     
         9 . The detector of  claim 5 , further comprising:
 a second input node configured to receive a second signal that indicates a temperature near the fin; and   wherein the processing circuit is configured to generate an indication that the cooling unit is ready to end a frozen-substance-thickness-reducing cycle in response to the second signal indicating a temperature that has a predetermined relationship to a temperature threshold.