Abstract:
A pump control unit incorporates an accelerometer as a sensor. Responsive to outputs from the sensor, electrical load driving signals can be provided to energize a pump motor to reduce a fluid level in an enclosure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 61/027,076 filed Feb. 8, 2008 and entitled “Decelerometer Switch”. The &#39;076 application is incorporated herein by reference. 
    
    
     FIELD 
     The invention pertains to pump control units. More particularly, the invention pertains to control units to turn pumps on and off to maintain fluid levels in a container within predetermined levels. 
     BACKGROUND 
     Various types of sump pump on/off switch units are known. One such configuration has been disclosed and claimed in U.S. Pat. No. 7,307,538, entitled Pump Connector System which issued Dec. 11, 2007 and which is assigned to the assignee hereof and incorporated by reference. 
     While known switches have been effective control elements, they operate in difficult environments and are subject to arcing as well as electrically induced contact erosion where relays are used to switch turn-on/turn-off motor currents. The noted operating conditions can lead to shortened lifetimes and switch failures. 
     There is thus a continuing need for improved pump on/off switch units. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a block diagram of a pump control system in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION 
     While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, as well as the best mode of practicing same, and is not intended to limit the invention to the specific embodiment illustrated. 
     Embodiments of the invention incorporate an accelerometer as a sensor of an ambient condition, for example a fluid level. Signals from the sensor can be coupled to control circuits which can generate control output signals to activate an AC switch, and/or a relay. In one aspect of the invention, a solid state switch with a thermal sensor can be used in combination with a non-solid state switch to take into account heating of the semiconductor switch during extended on intervals. 
     In another aspect of the invention, acceleration sensing elements facilitate solid state switching over any increment in a circle, 360 degrees. Where such pump control units are encased in a float-type housings, they can be configured to move through a spherical locus in response to a fluid level in a tank, for example. 
     In a further aspect of the invention, the control circuits can incorporate a programmable processor and associated control program stored on a computer readable medium such as read only memory, programmable read only memory without limitation. Switching increments can be established using the pre-stored programs which can incorporate programmable on/off parameters, for example over a 360 degree circle defined on the spherical locus of the respective housing. 
       FIG. 1  is a block diagram of one embodiment of the present invention. It will be understood that other embodiments come within the spirit and scope of the invention. 
     In  FIG. 1 , a motor control unit  10 , and an associated pump P are illustrated installed in a tank T of fluid F. The unit  10 , and pump P can maintain the fluid F between a selected level L 1 , or, a level L 2  greater than the level L 1  as desired. 
     A sealed, hollow, switch housing  12  can float in the fluid F and change position/orientation in response to the fluid level rising and falling. Housing  12  carries an accelerometer  20  which generates an output signal indicative of movement of housing  12 , on line  20 - 1 . Line  20 - 1  is coupled to a signal conditioner  22  which in turn proves a conditioned version of the accelerometer signal, via line  22 - 1  to control circuits  26 . 
     Control circuits  26  can include a programmable processor  26   a , various types of storage units  26   b , including random access read-write memory, electrically erasable read only memory and flash memory. Units  26   b  provide computer readable storage units which can carry control programs or software, executable by processor  26   a.    
     Circuits  26  include one or more input ports, such as an analog input port coupled to line  22 - 1  which includes an analog-to-digital converter  26   c  which provides digital representations of the signals from sensor  20  to processor  26   a.    
     A digital output interface  26   d , coupled to processor  26   a , can produce first and second output control signals  28   a,b . Signals  28   a,b  buffered by amplifiers/drivers  32   a,b , can in turn be coupled to a motor control switching element  34 . 
     Element  34  can include a solid state switch, such as a Triac  34   a , and a relay  34   b , parallel coupled to one another. Control signals, coupled via lines  34 - 1 - 2  can be used to switch Triac  34   a  and relay  34   b  into a conducting state to provide a switched output on a line  38 . 
     As those of skill in the art will understand, electrical energy coupled from connector C, via cable C 1  and line  38   a  into housing  12  can be provided as a switched output, via line  34   a  cable C 1 , connector C and cable C 2  to pump P thereby activating same to pump fluid F from the tank T down to level L 1  for example. In the embodiment of  FIG. 1 , utility supplied, or locally generated, AC-type electrical energy can be coupled to unit  10  and pump P to activate pump P. In other embodiments, DC-type electrical energy can be coupled to a switching unit, such as unit  10 , without departing from the spirit and scope of the invention. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.