Abstract:
A power distribution unit with voltage and current sensors and a display which displays inverted characters when the power distribution unit upside down as sensed by a tilt sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority under 35§119(e) to U.S. Provisional Patent Application No. 61/390,805 filed Oct. 7, 2010, which is hereby incorporated by reference in its entirety herein. 
     
    
     BACKGROUND 
       [0002]    The invention relates to Power Distribution Units (“PDUs”), and more particularly relates to the displays on PDUs. In one or more specific applications, the invention relates to the orientation of a display on a PDU. 
         [0003]    IT equipment rooms (also known as data centers) utilize hundreds or even thousands of separate units of IT equipment, such as servers, switches, and routers. These units are typically mounted on racks. Each unit of IT equipment typically receives power from of a rack mounted power distribution unit (“PDU”). A PDU has multiple appliance outlets designed to distribute electric power within a rack. PDUs are used for taking the supplied voltage and current and distributing it electrically to more common outlets, for example from 240 V 30 A single phase to multiple 120 V 15 A or 120 V 20 A plugs. Rack-PDUs can be dumb—meaning that they have no instrumentation and are not manageable, or they can be metered—meaning that they are equipped with a display that shows current, voltage or power drawn for each outlet. PDUs typically look like a very large “power strip” and are not mounted in the rack like servers but mounted at the back of the rack in various orientations. In such mounting, the orientation of the PDU has one of 4 options. Typically the PDU is mounted vertically. The display is oriented so that the numbers are readable when the PDU is mounted in a vertical orientation. To a technician presented with a PDU at the rear of the rack, trying to read the display, the vertical orientation is legible, and the horizontal orientations are legible by a simple tilt of the head. However, the anti-horizontal orientation is relatively illegible as the displayed numbers will be upside down. As the orientation of the PDU is typically determined by the available space due to servers and cabling in the rear of the rack, and as such sometimes the anti-horizontal orientation is required. Therefore, there remains a need in the art to allow such an anti-horizontal orientation to be legible to a technician. 
       SUMMARY OF THE INVENTION 
       [0004]    In one or more specific embodiments further described herein, the present invention provides for a power distribution unit (PDU). The PDU has a power input penetrating said vertical strip enclosure. The PDU has a plurality of power outputs disposed along a face of the length of the strip enclosure. Each among the plurality of power outputs is connectable to a corresponding one of said one or more electrical loads. The plurality of sensors monitors the plurality of power outlets and the power input. The PDU has a CPU coupled to the sensors. The PDU has a display coupled to the CPU disposed on the vertical strip enclosure coupled to the power input and the plurality of power outputs and capable of displaying characters. The PDU has a tilt sensor coupled to the CPU disposed within the enclosure vertical strip enclosure such that when then tilt sensor vertical is along the length of the vertical strip enclosure. The CPU receives the sensor information and selects and displays the sensor information. If the tilt sensor is more than a specified angle off of tilt sensor vertical, the display displays the characters in an inverted orientation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Exemplary and non-limiting embodiments of the invention are illustrated in the Figures. The drawings may not be to scale, various details may be enlarged or reduced for clarity, and the illustrate values of any electrical components are merely exemplary and not limiting. 
           [0006]      FIG. 1  shows a power distribution unit (PDU). 
           [0007]      FIGS. 2A-2B  show the two relevant orientations of a prior-art PDU deployed at the rear of a server rack. 
           [0008]      FIG. 3  shows a schematic of one embodiment of the present invention. 
           [0009]      FIG. 4  shows the tolerances of a tilt sensor in an embodiment of the present invention. 
           [0010]      FIG. 5  shows a flow chart of an embodiment of the present invention. 
           [0011]      FIG. 6  shows one embodiment of the present invention wherein the LCD display is inverted. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A PDU  100  including a high power inlet  102  from which it receives power (typically from a panel board), multiple lower power outlets  104 - 114 , display  116  and display controls  118 . Display  116  is a liquid crystal display (LCD). ( FIG. 1 ) Display controls  118  select from the outlets  104 - 114  which will have their data displayed, and/or what information to display (current or voltage or power). 
         [0013]      FIGS. 2A-2B  shows the possible orientations of a prior art PDU.  FIG. 2A  shows PDU  200  having display  202  in a vertical orientation. The display  202  displays the number “94”.  FIG. 2B  shows PDU  204  in anti-vertical (upside down) position. Note that display  206  shows the number “94” upside down. 
         [0014]      FIG. 3  shows the internals of one embodiment of the present invention. A schematic of a portion of a PDU  200  is shown having a control board  302  on which a CPU  304 , a tilt sensor  306 , and a communication circuits  308  are mounted. The tilt sensor  306  and a display  310  are each coupled to the CPU  304 . The display  310  may be an LCD display. A data bus  311  connects to a relay board CPU  312 . This data bus runs the length of the CPU. The data bus connects to circuits on relay board  313 . There are multiple relay boards running through the PDU working with groups of outlets like outlets  322  and  324 . The relay board CPU  312  is coupled to the energy measuring integrated circuit  316 , which in turn coupled to the voltage sensor  320  and the current sensor  318 . In operation electricity through the outlet is measured by sensors  318  and  320 , which in turn pass the data to the circuit  316  which in turn passes the data to relay board  312  which in turn passes the data to main CPU  304 . It is understood that this process is repeated in the other outlets of the PDU. From the many simultaneous measurements the CPU  304  selects which measurement to display and cause the display  310  to display it. 
         [0015]      120  Tilt sensor  306  can be one of a variety of tilt sensors Tilt sensors are well known in the art. For example, The SQ-SEN-6xx series tilt sensor acts like a position sensitive switch that is normally open when vertical and normally closed below the switch angle. Gravity determines the vertical. It is designed to be non-sensitive to vibration in the vertical position. When at rest in a vertical position, the sensor will settle in an open state. When tipped down from vertical to the “switch angle” it will produce continuous on/off contact closures while in motion. When at rest below the switch angle, it will settle normally closed. The operation the sensor is described in U.S. Pat. Nos. 7,326,866, 7,067,748, 7,326,867, and 7,421,793. The tilt sensor will send this open or closed signal to the CPU  304 . 
         [0016]      FIG. 4  shows the tolerances of a tilt sensor in one embodiment of the present invention. Angle  402  determines at what point the sensor sends a closed signal. The sensor is available in switch angles of 75°, 60°, 45°. In the preferred embodiment of the present invention, the switch angle is chosen as 60°. 
         [0017]      FIG. 5  shows the procedure  500  for using the tilt sensor in one embodiment of the present invention. Step  502  the CPU polls the tilt sensor to see of it is open or closed. If the signal is open then CPU  304  proceeds to step  504 . In step  504  the CPU causes the voltage, sensor, or power measurements to be displayed without alteration. If the signal is closed the CPU  304  will proceed to step  506 . In step  506  the CPU causes the measurements to be displayed upside down in inverted operation. The CPU will periodically poll the tilt sensor to monitor the PDU orientation. 
         [0018]      FIG. 6  shows an embodiment of the present invention. PDU  602  is in the vertical position and shows display  604  is the standard way. PDU  606  is shown in an anti-vertical position but the LCD display  608  display the measurement right side up. 
         [0019]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.