Capacitive sensor and method and apparatus for controlling a pump using same

Abstract

Methods relating to varying capacitance of a capacitive sensor and controlling a pump based on the level of a liquid. A pump controller for controlling the level of a liquid in a reservoir includes a controller and a capacitor. The capacitor is adapted to provide an activation signal to the controller when the liquid in the reservoir reaches a first predetermined level relative thereto.

What is claimed is: 
     
         1 . A method of operating a pump, comprising:
 detecting a capacitance for a capacitor at least partially submerged in a liquid having a level that changes in relation to the capacitor, the capacitor having a plurality of capacitances with each capacitance corresponding to a different liquid level;   activating a pump when a first capacitance is detected;   determining when the pump should be deactivated when a second capacitance is detected; and   deactivating the pump as determined when the second capacitance was detected.   
     
     
         2 . The method of  claim 1 , wherein determining when the pump should be deactivated comprises determining a run-time for the pump based on when the second capacitance was detected relative to when the first capacitance was detected or when the pump was activated. 
     
     
         3 . The method of  claim 2 , wherein deactivating the pump comprises deactivating the pump after the run-time has expired. 
     
     
         4 . The method of  claim 1 , wherein deactivating the pump comprises deactivating the pump when the second capacitance is detected. 
     
     
         5 . The method of  claim 1 , further comprising;
 providing an alternating current power supply to power the pump; and   detecting the capacitance of the capacitor at a zero-crossing of the alternating current power supply.   
     
     
         6 . A method of operating a pump, comprising:
 activating the pump when a level of a liquid in a reservoir reaches a first predetermined level;   detecting when the level of the liquid reaches a second predetermined level in the reservoir;   determining a run-time for the pump based on when the level of the liquid reached the second predetermined level relative to when the pump was activated or when the controller determines the pump should be activated, the run-time corresponding to how long the pump should be activated to move a predetermined amount of liquid out of the reservoir; and   deactivating the pump after the run-time passes.   
     
     
         7 . The method of  claim 6 , further comprising using a sensor to detect when the level of liquid reaches the first predetermined level and the second predetermined level. 
     
     
         8 . The method of  claim 7 , wherein the sensor is a capacitive sensor having a capacitor with a plurality of different capacitances, each capacitance corresponding to a different level of liquid being present in the reservoir, and the method further comprises using the sensor to detect when a first capacitance is reached corresponding to the first predetermined level of liquid being reached and when a second capacitance is reached corresponding to the second predetermined level of liquid being reached. 
     
     
         9 . The method of  claim 7 , wherein the sensor includes first and second capacitive sensors and the method comprises using the first capacitive sensor to determine when the first predetermined level of liquid is reached and using the second capacitive sensor to determine when the second predetermined level of liquid is reached. 
     
     
         10 . The method of  claim 7 , wherein the sensor includes a circuit board, the method further comprising dissipating heat from a component located on the circuit board with a heat sink. 
     
     
         11 . The method of  claim 10 , further comprising positioning the heat sink below the liquid level. 
     
     
         12 . The method of  claim 10 , wherein the component of the circuit board is a switching device, the method further comprising attaching the heat sink to the circuit board with the switching device, wherein the thermal metallization of the switching device is a thermal and mechanical bridge between the heat sink and the circuit board. 
     
     
         13 . A method of operating a pump for controlling a level of a liquid in a reservoir, the method comprising:
 providing an alternating current power supply;   detecting a level of the liquid in the reservoir at a zero-crossing of the alternating current power supply; and   activating the pump upon detecting the level of the liquid at a first predetermined level in the reservoir.   
     
     
         14 . The method of  claim 13 , wherein detecting the level of liquid in the reservoir comprises using a sensor for detecting the level of liquid in the reservoir. 
     
     
         15 . The method of  claim 14 , wherein the sensor is a capacitive sensor having a plurality of capacitances, with each capacitance being associated with a different level of liquid in the reservoir, the method further comprising detecting the level of the liquid by determining the capacitance of the capacitive sensor. 
     
     
         16 . The method of  claim 14 , further comprising determining a run-time for the pump upon detecting the level of the liquid at a second predetermined level in the reservoir; and
 deactivating the pump when the run-time has expired.   
     
     
         17 . The method of  claim 16 , wherein the sensor is a capacitive sensor having a plurality of capacitances, with each capacitance being associated with a different level of liquid in the reservoir, the method further comprising detecting the level of the liquid by determining the capacitance of the capacitive sensor wherein detecting the trigger signal from the sensor includes detecting a trigger capacitance from the capacitor of the sensor.