Abstract:
To reduce or eliminate difficulties inherent in manual reporting of signal light failures, especially at remote railroad grade crossings, there is provided, in one embodiment of the present invention, a system for monitoring failure of a lighted signal that includes lighting configured to flash during a predetermined alarm condition. The system includes a power supply configured to power the lighting during the predetermined alarm condition and to provide a timing signal indicative of power being applied to the lighting; a detector/transmitter responsive to the timing signal to detect lighting parameters when the lighting is flashed on to generate a signal indicative of the lighting parameters and to generate a signal indicative of the lighting parameters; and a receiver/concentrator responsive to the signal indicative of the lighting parameters to generate a signal indicative of predetermined fault conditions of the lighting.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to methods and apparatus for detection of signal light parameters, and more particularly to methods and apparatus for detecting and reporting flashing signal light failures occurring at remote locations. 
     Railroads are now utilizing remote monitoring of signal locations as a tool for more rapid diagnosis of signaling problems. When such problems are promptly corrected, improved efficiency and safety of operations results. 
     Current methods of monitoring flashing warning lights in railroad applications are labor intensive to install and to calibrate, and do not provide a reliable, unambiguous, long-term indication of lamp performance. 
     One condition presently monitored at signal locations is the presence of AC power. Although backup battery systems are often employed, battery power is sometimes exhausted before AC power is restored and before maintenance personnel are alerted to the problem. To reduce the likelihood of this occurrence, backup battery systems having large reserve capacity are used. However, if an outage is persistent and goes undetected, as for example, when there is an open circuit breaker at the signal location, the first indication of trouble may occur only when the signal location is altogether nonfunctional. Timely reporting of AC power outages would help avoid such delays. 
     Techniques most often employed to report AC power outages measure bulk current through primary conductors supplying external lamps, and draw inferences to determine an exact number of bulbs that are operating correctly. These circuits are highly sensitive and the current detection components themselves (Hall effect devices) are prone to aging drift and nonlinearity. 
     Additional measures have been taken to alleviate problems associated with extended loss of AC power at highway crossings. For example, crossings are designed with separate operating battery and control battery systems. The battery systems have different capacities, so that, when AC power is lost, the operating battery is depleted first. The highway crossing is configured so that, upon depletion of the operating battery, the crossing is activated continuously. Ideally, the crossing will be reported as malfunctioning before the control battery is also depleted. Active crossings are also provided with indicator lights that are continuously lit when AC power is available. Employees are instructed to report an AC power off condition immediately to a dispatcher when they observe that the indicator lamps are off. Equipment houses at active crossing locations are also labeled with site-specific information and a toll-free telephone number that can be used by the public for reporting crossing problems. 
     Even with measures now in place, however, the reporting of crossing problems is still primarily a manual process, with inherent inaccuracies and delays. It would be desirable if these inaccuracies and delays could be reduced or eliminated. Moreover, many other crossing conditions, such as battery voltages and lamp currents, and for highway crossings, gate operation and activation status, are of interest and should be monitored. It has been difficult, however, to obtain timely reports of these conditions from remote locations. 
     BRIEF SUMMARY OF THE INVENTION 
     To reduce or eliminate difficulties inherent in manual reporting of crossing problems, in one embodiment of the present invention, there is provided a system for monitoring failure of a lighted signal having lighting configured to flash during a predetermined alarm condition. The system includes a power supply configured to power the lighting during the predetermined alarm condition and to provide a timing signal indicative of power being applied to the lighting; a detector/transmitter responsive to the timing signal to detect lighting parameters when the lighting is flashed on to generate a signal indicative of the lighting parameters and to generate a signal indicative of the lighting parameters; and a receiver/concentrator responsive to the signal indicative of the lighting parameters to generate a signal indicative of predetermined fault conditions of the lighting. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified block diagram of one embodiment of a light outage detection system of the present invention. 
     FIG. 2 is a drawing of a flasher lamp showing mounting of one embodiment of a detector/transmitter thereon. 
     FIG. 3 is a block diagram of one embodiment of a light outage detection system, showing additional details of the detector/transmitter. 
     FIG. 4 is a more detailed block diagram of one embodiment of the receiver/concentrator shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In one embodiment, and referring to FIG. 1, a light outage detection system  10  has two main component systems. The first is a detector/transmitter  12  that detects one or more lighting parameters such as brightness or intensity, lamp head voltage, and flash rates of lamps in a lamp head. The second is a central receiver/concentrator  14  to which information relating to the lighting parameters is sent for analysis of possible alarm conditions. In one embodiment, a receiver/concentrator  14  receives lighting parameter information from up to six detector/transmitters  12  and each detector/transmitter  12  monitors up to four separate lights. The number of detector/transmitters  12  monitored by a receiver/concentrator  14  and the number of lights monitored by each detector/transmitter  12  differ in other embodiments. Most typically, the lights being analyzed are flashing lights, so that lighting parameter information relating to performance data is sent following each flash cycle. In one embodiment, this information is sent via spread spectrum communication, and is transmitted, for example, on power lines  16  for the flashing lights themselves, or as a field radiated signal  18  (i.e., a radio frequency [RF] signal). 
     A typical installation of one embodiment of the present invention is as a light outage detector on a railroad grade crossing signal. In one embodiment and referring to FIG. 2, a detector/transmitter assembly  12  is a small, credit-card sized device  13  mounted in a lamp head reflector  20 , on a two-screw terminal block  22  that interfaces field wiring  16  between a signal bungalow and one or more incandescent or LED lamps  24  located in lamp head  20 . A photodiode or other optical detector  26  of detector/transmitter  12  is configured to receive and detect light directly from lamp  24 . In this embodiment, the lighting includes a plurality of lamps  24  configured to flash during a signaling event, and detector/transmitter  12  is configured to be responsive to lighting parameters of at least some of the plurality of lamps  24 . For example, three additional flashing lamps (not shown) on the same structure are sensed as well. For example, optical light guide (not shown) interface detector/transmitter  12  to adjacent bulbs (also not shown), or additional, multiplexed photodiodes  28  (shown in FIG. 3) are interfaced to adjacent bulbs. In one embodiment, multiple lamps  24  are located in lamp heads  20 , and separate optical detectors  26  are provided for each lamp  24  in a lamp head  20 . In this manner, one detector/transmitter monitors light output at a total of four lamp heads  20  on a single pole. 
     Calibration is accomplished by activating the lamps  24 , which causes all detector/transmitters to receive power in parallel with lamps  24  that are being powered. During each flash cycle, every detector/transmitter  12  measures and transmits status, intensity, and voltage level of a lamp  24  or lamps that it is monitoring to receiver/concentrator  14 . 
     Referring to FIG. 3, during a predetermined alarm condition, such as an approach of a train (resulting in activation of the railroad grade crossing signal), a power supply block  30  converts the flashing 12 volt supply that is delivered to individual lamps  24  when the crossing is activated to a constant 5 volt signal that is used to power detector/transmitter  12 . Thus, no additional power source other than the flashing  12  volt supply that is normally present is required to power detector/transmitter  12 . In addition, for synchronization purposes, power supply block  30  provides a timing signal (“power applied”) that indicates when power is or is not being applied to lamps  24 . This timing signal is used to synchronize times during which the detector function within detector/transmitter  12  is used to verify that lamps  24  are on, and to synchronize times to sense the lamp head voltage. 
     When power supply block  30  indicates that voltage is present, an analog to digital converter (ADC) block  32  digitizes a measurement of the voltage and communicates this measurement to a microprocessor block  34 . Microprocessor block  34  formats and delivers the measurement information to a receiver/concentrator  14  located at signal bungalow  36  controlling the crossing facility. In one exemplary embodiment, ADC  32  voltage measurement has a resolution of 8 bits. 
     Microprocessor block  34  receives lamp intensity information from an optical intensity detector  38  monitoring up to four lamps  24 , along with voltage at a physical/electrical terminal strip interface point from ADC  32 . This information is converted into a suitable form for delivery to receiver/concentrator  14 . For example, the information is converted into a serial bit stream and transmitted via field signal wiring  16  or radiated via an RF signal  18 . In one embodiment, a spread-spectrum modulator/demodulator  40  (for example, an INTELLON® SSC P200 available from Intellon, Inc., Ocala, Fla.) is used to transmit the information via the field signal wiring  16  to receiver/concentrator  14 . In another embodiment, a spread spectrum modulator/demodulator  40  is used in conjunction with a low power RF generator (not shown) for wireless transmission. Flash rate is also determined and included in the message along with a unique detector/transmitter  12  identification number. In embodiments in which more than one lamp  24  is being monitored, a lamp position number (LPN) is also included in the message. Thus, sufficient information is provided for receiver/concentrator  14  is able to determine how many and which, if any, lamps  24  are malfunctioning. 
     In an embodiment in which information is transmitted via field signal wiring  16  to receiver/concentrator  36 , the “power applied” signal from power supply block  30  is used by microprocessor block  34  to time delivery of information to coincide with the voltage present state, to ensure that a metallic path exists back to receiver/concentrator  14 . Signal coupler block  42  comprises circuitry to couple transmissions from spread spectrum modulator  40  onto field signal wiring  16  for delivery to receiver/concentrator  14 . 
     Referring to FIG. 4, receiver/concentrator  14  receives an asynchronous message burst each flash cycle from all monitored active detector/transmitters  12 . If receiver/concentrator  14  expects but does not receive lighting parameter information affirming that illumination, flash rate, and lamp head voltage are within preselected limits, it delivers an alarm signal  44  to an external alarm communication device (not shown). If a power applied signal is present but receiver/concentrator  14  receives no incoming information affirming the illumination and flash rate status of connected lamps  24 , then receiver/concentrator  14  delivers an alarm signal  44  to the external alarm communication device. Alarm signal  44  is thus indicative of predetermined fault conditions of the lighting. 
     A power supply block  31  provides a constant  5  volt DC voltage to power receiver/concentrator  14 . In addition, an input from a flashing relay (not shown) provides power supply block  30  with timing information to produce a “power supplied” signal that is used to synchronize microprocessor block  48  of receiver/concentrator  14 , and to synchronize transmissions from a number of detector/transmitters  12 . 
     In one embodiment, a power line signal coupler  46  of receiver/concentrator  14  contains circuitry configured to couple a lighting parameter information signal on field signal wiring  16  to a demodulator  48 . (In embodiments in which an RF signal  18  is transmitted, couplers  42  and  46  are replaced by an RF transmitter and receiver [not shown], respectively.) 
     In one embodiment, an INTELLON® SSC P200 spread spectrum modulator/demodulator  48  is used to demodulate a spread spectrum signal delivered via field signal wiring  16  to receiver/concentrator  14 . Using a “power applied” signal from power supply block  31 , a microprocessor block  50  is synchronized with incoming serial data. The use of a spread spectrum signal and multiple repetitions of serial information in one embodiment ensures that microprocessor block  50  experiences a high success rate in sorting and correctly receiving asynchronous data from a number of different detector/transmitters  12 . 
     Microprocessor block  50  receives and interprets incoming serial asynchronous data from a number of detector/transmitters  12 . In one embodiment, upon initialization, receiver/concentrator  14  dynamically takes inventory of lamps  24  that are activated, based upon signals received from detector/transmitters  12 . In this manner, receiver/concentrator  14  is able to “remember” what lamps  24  should be active when the crossing is active. When at least one lighting parameter such as flash rate or lamp head voltage is outside predetermined values, or when an insufficient number or an unacceptable combination of lamps  24  are operating, microprocessor block  50  delivers an alarm signal to an external alarm communication device. Microprocessor block  50  also includes a communication port  52  (for example, a serial port) configured for communication with an external device, such as a laptop computer (not shown). Microprocessor block  50  is configured to provide the current status of all lamps, flash rates, and voltages to the external device through communication port  52  so that this information can be displayed, such as on a graphic user interface application running on the laptop computer. Because of the multiplicity of lamps  24  in a crossing warning device, and/or a multiplicity of lamps  24  in a single lamp head  20 , a successful warning event may be considered to have occurred despite one or more lamp  24  failures. Therefore, in one embodiment, microprocessor block  50  is configured to receive information relating to the numbers or combinations of operating lamps required to comprise a successful crossing warning event via communication port  52 , thereby providing adjustment of thresholds for triggering warnings or failure indications as desired. 
     Memory (not separately shown in FIG. 4) associated with microprocessor block  50  is provided to archive crossing activation performance data, including, but not necessarily limited to, triggering warnings and failure indications. (For example, failures of individual lamps  24  even during warning indications meeting the threshold for a successful event are recorded in one embodiment.) This archived data is accessible via communication port  52 , so that a user is able to diagnose past crossing activation performance. 
     From the preceding description of various embodiments of the present invention, it is evident that problems inherent in manual reporting of railroad grade crossing problems are reduced and eliminated. 
     Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. For example, in other embodiments, modifications are made to more suitably accommodate other types of signaling devices. Accordingly the spirit and scope of the invention are to be limited only by the terms of the appended claims and their equivalents.