Abstract:
A pump controller is provided for removing liquid condensate from a reservoir in a condensate pump removal system which collects condensate from an air conditioning/refrigeration system. The pump controller comprises a liquid level sensor in the form of an acoustic transmitter and acoustic receiver which are used to measure the time of flight of the acoustic signal, to thereby indicate the level of the liquid and determine whether the pump should be switched on and off.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a pump controller using an acoustic liquid level sensor for condensate removal. 
         [0002]    The operation of air conditioning and refrigeration units, including those used to cool down computer rooms, results in condensate on the cooling coils. The condensate collects, typically in a reservoir, and the condensate needs to be pumped out to another location, sometimes with lift of 50 feet or more. 
         [0003]    In order to control the pump operation, a standard mechanical float mechanism has been used. Condensate pump reservoirs often will develop mildew, sediments, and other foreign debris. Over time, the presence of this material can foul the mechanical float mechanism requiring cleaning, servicing, or even rendering it inoperable. 
         [0004]    Capacitive type sensors have also been used, where the capacitor is submerged in the liquid, but residue affects the capacitive readings leading to incorrect operation and eventually failure. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a pump controller for removing condensate from a liquid reservoir or tank, which controller uses an acoustic level sensor to sense the liquid level and control the pump operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1A  is a top plan perspective view of a pump controller according to an embodiment of the invention; 
           [0007]      FIG. 1B  is a top perspective view of the pump controller of  FIG. 1A ; 
           [0008]      FIG. 1C  is a side elevational view of the pump controller of  FIG. 1A ; 
           [0009]      FIG. 1D  is a front elevational view of the pump controller of  FIG. 1A ; 
           [0010]      FIG. 1E  is the same view as  FIG. 1A , but with a cover removed; 
           [0011]      FIG. 1F  is the same view as  FIG. 1B , but with the cover removed; 
           [0012]      FIG. 1G  is the same view as  FIG. 1C , but with the cover removed; 
           [0013]      FIG. 1H  is the same view as  FIG. 1D , but with the cover removed; 
           [0014]      FIG. 1I  is a top perspective view of the sub-module of the pump controller; 
           [0015]      FIG. 1J  is a bottom perspective view of the sub-module of  FIG. 1I ; 
           [0016]      FIGS. 2A-2F  together show an electric schematic of a pump control circuit according to an embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    A preferred embodiment of the invention will be described, but the invention is not limited to this embodiment. 
         [0018]      FIG. 1  shows a pump controller for removing condensate from a liquid reservoir according to the present invention. 
         [0019]      FIGS. 1A-1J  show a housing  12  for the pump controller  10  according to an embodiment of the invention. 
         [0020]      FIG. 1A  shows a motor  14  which is used to drive a pump  16 . The housing  12  includes a cover  18  and a bottom portion  20 . The housing  12  is adapted to sit in an AC condensate reservoir, where water collects and needs to be pumped out. 
         [0021]      FIGS. 1E-1H  show the same as  FIGS. 1A-1D , respectively, but with the cover  18  removed to show the pump controller module  30 .  FIGS. 1I and 1J  show the pump controller module  30  removed from the housing  12 . 
         [0022]      FIG. 1I  shows the module  30  as having an overflow safety switch comprising a ball  32  adapted to move within a cage  34 . When the housing  12  is in the reservoir and water rises, if for some reason the pump controller fails to detect the rising water level to turn on the pump (using the circuitry described below in connection with  FIGS. 2A-2G ), the ball will rise within the cage, closing a switch which is wired directly to the air conditioner or refrigeration unit to cut power so that the condensate level does not continue to rise, at least appreciably, to avoid an overflow condition. 
         [0023]    As shown in  FIG. 1J , the module  30  comprises an opening  40  with angled walls, at the bottom of which is an acoustic transmitter TX 1  and receiver RX, which will be described below in connection with  FIGS. 2A-2G . The angled walls will reduce noise from the transmitter and receiver. 
         [0024]      FIGS. 2A-2G  show an electrical schematic of the controller.  FIG. 2A  shows one part of the controller which comprises an AC/DC power converter adapted to receive 110 VAC power and to provide a VDD of about 9 volts DC. The circuit employs a U 3 -Viper  16  chip, commercially available. 
         [0025]      FIG. 2B  shows another part of the controller also comprises a voltage regulator which receives the VDD 9 VDC voltage signal and conditions and regulates it using a U 1 -TPST 1001  chip to provide a VCC of about 5 volts DC. 
         [0026]      FIG. 2C  shows one part of the controller which includes an acoustic transmitter circuit which receives the VDD power signal and a control signal at point P 1 . 0 , supplied by a micro-controller circuit described below. The micro-controller provides the transmitter circuit with an 8 cycle burst of a 40 kHz square wave which is amplified by a bridge circuit with hex inverter gates U 2 -CD 4049  and drives acoustic transmitter TX 1 . When the burst occurs, a timer feature is turned ON and the controller waits for the acoustic sound signal to return. 
         [0027]      FIG. 2D  shows the part of the controller which includes an acoustic receiver circuit comprising an acoustic receiver RX which receives the acoustic wave transmitted from the transmitter TX 1  after it is echoed or reflected off the liquid in the reservoir or tank. The received signal is amplified through two amplifiers U 5 :A and U 5 :B (U 5 -TLV 2772 ) and output at point P 1 . 1  to the micro-controller. The amplification of the signal triggers a capture of a time duration. The capture count provides a measure of time indicating how long the signal transmitted from the transmitter takes to reach the liquid level, and bounce or echo back to the receiver. The time measure provides an indication of the height of the liquid level. 
         [0028]      FIG. 2E  shows the micro-controller circuit, which comprises mainly a micro-controller MSP 430 , processes the time signal and compares it to values indicating the high liquid level (where the pump should be turned on) and the low liquid level (where the pump should be turned off). Of course, the high and low liquid levels are appropriately spaced to prevent hunting and excessive switching on and off of the pump. 
         [0029]      FIG. 2D  shows that the controller circuit also comprises an LED D 4 , which is controlled through point P 1 . 5  of the micro-controller, which indicates whether the controller is operating. 
         [0030]      FIG. 2F  shows connections for points P 1 . 3 , P 1 . 6 , and P 1 . 7 . The main controller chip provides at output point P 1 . 4  (at pin  6 ) a signal to indicate pump motor ON and OFF. 
         [0031]      FIG. 2G  shows that this signal is provided to U 4 -MOC 3052  which provides a low-voltage to high-voltage trigger to turn on the pump motor through Triac Q 2 - 2 N 6344 . The motor for the pump is connected to J 2 . 
         [0032]    While one embodiment of the invention has been described, the invention is not limited to this embodiment, and the scope of the invention is defined by the following claims.