Redundantly powered and daisy chained power over ethernet

Abstract

According to one aspect, embodiments of the invention provide a distributed sensor network comprising an interface unit and a plurality of sensor strings, each sensor string comprising a plurality of sensor units coupled in series to a port of the interface unit, wherein each one of the plurality of sensor units is configured to be provided both power and network connectivity via a first cable from one of the interface unit and another sensor unit within the sensor string and also to provide both power and network connectivity via a second cable to another sensor unit within the sensor string, and wherein a first string of the plurality of sensor strings is configured to be coupled to a second string of the plurality of sensor strings and wherein at least one sensor unit within the first string is configured to provide power to a sensor unit within the second string.

What is claimed is: 
     
         1 . A distributed sensor network, the network comprising:
 an interface unit comprising a plurality of ports; and   a plurality of sensor strings, each sensor string comprising a plurality of sensor units coupled in series to one of the plurality of ports of the interface unit,   wherein each one of the plurality of sensor units within a sensor string is configured to be provided both power and network connectivity via a first cable from one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string and also to provide both power and network connectivity via a second cable to an adjacent one of the plurality of sensor units within the sensor string, and   wherein a first string of the plurality of sensor strings is configured to be coupled to a second string of the plurality of sensor strings and wherein at least one of the plurality of sensor units within the first string is configured to provide power to at least one of the plurality of sensor units within the second string.   
     
     
         2 . The distributed sensor network of  claim 1 , wherein each one of the plurality of sensor units within a sensor string comprises:
 a first port configured to be coupled to one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string via the first cable; and   a second port configured to be coupled to one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string via the second cable;   wherein the first port and the second port are both configured to be provided both power and network connectivity from one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string via the first cable and to provide power and network connectivity to an adjacent one of the plurality of sensor units within the sensor string via the second cable.   
     
     
         3 . The distributed sensor network of  claim 2 , wherein the second port of the at least one of the plurality of sensor units within the first string is configured to be coupled to the second port of the at least one of the plurality of sensor units within the second string. 
     
     
         4 . The distributed sensor network of  claim 2 ,
 wherein the first port is configured to be coupled to one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string via Ethernet cabling, and   wherein the second port is configured to be coupled to one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string via Ethernet cabling.   
     
     
         5 . The distributed sensor network of  claim 2 , wherein each one of the plurality of sensor units further comprises:
 a switch coupled between the first port and the second port;   a power supply coupled to the switch;   a downstream transformer coupled between the first port and the switch;   an upstream transformer coupled between the second port and the switch;   a downstream center tap coupled between the downstream transformer and the power supply; and   an upstream center tap coupled between the upstream transformer and the power supply;   wherein the downstream center tap is configured to provide power from the downstream transformer to the power supply, and   wherein the upstream center tap is configured to provide power from the upstream transformer to the power supply.   
     
     
         6 . The distributed sensor network of  claim 5 , wherein each one of the plurality of sensor units further comprises:
 a control processor coupled to the power supply; and   a controller coupled to the control processor, the downstream center tap and the upstream center tap,   wherein, in response to the downstream center tap providing power from the downstream transformer to the power supply and to a determination that an adjacent sensor unit has been coupled to the second port, the interface unit is configured to operate the control processor to send a forward power control signal to the controller to operate the controller to forward power from the downstream center tap to the upstream center tap, and   wherein, in response to the upstream center tap providing power from the upstream transformer to the power supply and to a determination that an adjacent sensor unit has been coupled to the first port, the interface unit is further configured to operate the control processor to send a forward power control signal to the controller to operate the controller to forward power from the upstream center tap to the downstream center tap.   
     
     
         7 . The distributed sensor network of  claim 6 , wherein the controller is a “Hot-Swap” controller. 
     
     
         8 . The distributed sensor network of  claim 6 , further comprising an opto-coupler coupled between the control processor and the controller to provide isolation. 
     
     
         9 . The distributed sensor network of  claim 2 , wherein the first string of the plurality of sensor strings is configured to be coupled to a first port of the plurality of ports of the interface unit, wherein the second string of the plurality of sensor strings is configured to be coupled to a second port of the plurality of ports of the interface unit, and wherein the first string and second string are configured to form a sensor loop between the first port and the second port. 
     
     
         10 . The distributed sensor network of  claim 9 , wherein the first port of a first one of the plurality of sensor units within the first string of the plurality of sensor strings is coupled to the first port of the plurality of ports of the interface unit, wherein the first port of a second one of the plurality of sensor units within the first string of the plurality of sensor strings is coupled to the second port of the first one of the plurality of sensor units within the first string, and wherein the first one of the plurality of sensor units within the first string is configured to receive power from the interface unit via the first port and to provide power to the second one of the plurality of sensor units within the first string via the second port of the first one of the plurality of sensor units. 
     
     
         11 . A method for providing power to a distributed sensor system, the distributed sensor system comprising an interface unit having a plurality of ports, and a plurality of sensor strings, each sensor string comprising a plurality of sensor units coupled in series to one of the plurality of ports of the interface unit, the method comprising:
 providing power from at least one port of the interface unit to a first port of a first sensor unit of at least one of the plurality of sensor strings;   powering up the first sensor unit;   forwarding power from a second port of the first sensor unit to a first port of a second sensor unit of the at least one of the plurality of sensor strings;   powering up the second sensor unit;   monitoring the plurality of sensor strings for a fault condition; and   in response to detecting a fault condition in a first sensor string of the plurality of sensor strings, providing power from a second one of the plurality of sensor strings to the first sensor string to provide power to at least one of the plurality of sensor units within the first sensor string.   
     
     
         12 . The method of  claim 11 , wherein monitoring the plurality of sensor strings for a fault condition comprises monitoring the second port of the first sensor unit for an open-circuit or short-circuit condition while power is being forwarded to the first port of the second sensor unit. 
     
     
         13 . The method of  claim 11 , wherein forwarding power from the second port of the first sensor unit to the first port of a second sensor unit comprises:
 providing power from the second port of the first sensor unit to the first port of a second sensor unit at a first current level, the first current level sufficient to power only the second sensor unit;   determining if the second sensor unit has powered up correctly in response to the power provided by the first sensor unit at the first current level; and   in response to a determination that the second sensor unit has powered up correctly, providing power from the second port of the first sensor unit to the first port of a second sensor unit at a second current level, the second current level greater than the first current level and sufficient to power a third sensor unit coupled to a second port of the second sensor unit.   
     
     
         14 . The method of  claim 13 , further comprising:
 forwarding power from the second port of the second sensor unit to a first port of the third sensor unit powering up the second sensor unit; and   powering up the third sensor unit.   
     
     
         15 . The method of  claim 11 , wherein providing power from the second one of the plurality of sensor strings to the first sensor string in response to detecting a fault condition in the first sensor string comprises:
 identifying a location of the fault condition within the first sensor string; and   providing power from the second one of the plurality of sensor strings to a group of sensor units within the first sensor string, the group of sensor units within the first sensor string coupled between the second sensor string and the location of the fault condition.   
     
     
         16 . The method of  claim 15 , wherein providing power from the second one of the plurality of sensor strings to a group of sensor units coupled between the second sensor string and the location of the fault condition comprises:
 forwarding power from a second port of a third sensor unit within the second one of the plurality of sensor strings to a second port of a third sensor unit within the first one of the plurality of sensor strings;   powering up the third sensor unit within the first one of the plurality of sensor strings; and   monitoring the second port of the third sensor unit within the second one of the plurality of sensor strings for a fault condition while power is being forwarded to the second port of the third sensor unit within the first one of the plurality of sensor strings.   
     
     
         17 . The method of  claim 16 , further comprising:
 in response to a determination that a fault condition at the second port of the third sensor unit within the second one of the plurality of sensor strings does not exist, forwarding power from a first port of the third sensor unit within the first one of the plurality of sensor strings to a second port of a fourth sensor unit within the first one of the plurality of sensor strings;   powering up the fourth sensor unit within the first one of the plurality of sensor strings; and   monitoring the second port of the third sensor unit within the first one of the plurality of sensor strings for a fault condition while power is being forwarded to the second port of the fourth sensor unit within the first one of the plurality of sensor strings.   
     
     
         18 . The method of  claim 11 , further comprising
 providing data from the at least one port of the interface unit to the first port of the first sensor unit of at least one of the plurality of sensor strings; and   forwarding data from the second port of the first sensor unit to the first port of the second sensor unit of the at least one of the plurality of sensor strings.   
     
     
         19 . A Power over Ethernet (PoE) distributed sensor system, the system comprising:
 an interface unit comprising a plurality of ports;   a plurality of sensor strings, each sensor string comprising a plurality of sensor units daisy chained together and coupled to one of the plurality of ports of the interface unit; and   means for intelligently passing power from sensor unit to sensor unit within each one of the plurality of sensor strings, powering each one of the plurality of sensor strings,   wherein each one of the plurality of sensor units within a sensor string is configured to receive power and data from one of the interface unit and an adjacent one of the plurality of sensor units within the sensor string and also to provide power and data to an adjacent one of the plurality of sensor units within the sensor string.   
     
     
         20 . The distributed sensor system of  claim 19 , further comprising means for providing redundant power between at least two of the plurality of sensor strings. 
     
     
         21 . A PoE sensor unit; the sensor unit comprising:
 an Ethernet switch; and   a plurality of ports coupled to the Ethernet switch, each one of the plurality of ports being configurable to both receive power from an Ethernet cable coupled to the port and to provide power to an Ethernet cable coupled to the port, and each one of the plurality of ports being configurable to both receive data from an Ethernet cable coupled to the port and to provide data to an Ethernet cable coupled to the port,   wherein the Ethernet switch is configured to forward data received at one of the plurality of ports to another one of the plurality of ports, and   wherein the plurality of ports is configured to forward power received at one of the plurality of ports to another one of the plurality of ports.