Fault detection for traffic light systems using electronic...

Details Fault detection for traffic light systems using electronic... Fault detection for traffic light systems using electronic...

2001-04-19

2003-06-24

Mullen, Thomas (Department: 2632)

Communications: electrical

Traffic control indicator

Traffic control or local controller failure indicator

C340S331000, C340S642000, C340S691800, C340S815450

Reexamination Certificate

active

06583731

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to traffic light systems. In particular, this invention relates to fault detection in traffic lights systems that use electronic lighting elements such as light emitting diodes (LEDs) to provide light signals at desired colors.
BACKGROUND OF THE INVENTION
A common fault detection technique applied in existing traffic light systems is to determine power consumption of traffic lights. Typically, the power consumption is determined by monitoring the current drawn by the traffic lights. Hence, when the current supplied drops below a predetermined value, control circuits for such traffic light systems generate alert signals to indicate a fault.
However, monitoring the current drawn at the system level is a problem because of inaccuracies. For example, leakage currents in cables or wires that supply power to the traffic light systems can lead to incorrect current measurements. Also, poor electrical contact between lighting elements of a traffic light system and power supply cables or wires causes the current to be supplied intermittently. Hence, such poor electrical contact leads to inaccurate fault detection.
Furthermore, in traffic light systems that use incandescent lamps or halogen bulbs, an alert signal does not provide a clear indication of which lamp or bulb is malfunctioning. In these traffic light systems, additional time and effort is required to trace a fault and this is unproductive for maintenance.
As is known, electronic lighting elements such as light emitting diodes (LEDs) have better durability compared with electrical lighting elements such as incandescent lamps and halogen bulbs. Consequently, an LED traffic light system generally has lower maintenance costs for lighting elements compared with traffic light systems that use incandescent lamps and halogen bulbs.
However, monitoring current supply in an LED traffic light system is difficult because LEDs typically consume less current than electrical lighting elements. Furthermore, detecting the failure of a single LED is not practical for the LED traffic light system. This is because failure of that single LED does not necessarily prevent the remaining LEDs in an LED assembly from continuing to provide a light signal. Hence, existing fault detection techniques applied in traffic light systems using electronic lighting elements and based upon current supply monitoring is difficult and do not reliably detect faults.
Therefore, what is clearly needed is an apparatus that enables improvements in fault detection for traffic lights systems that use electronic lighting elements such as, for example, LEDs.
BRIEF SUMMARY OF THE INVENTION
The present invention seeks to provide an indicator controller, an optical assembly having the indicator controller, a traffic light system that comprises at least one of the optical assembly and a method for fault indication by the indicator controller.
Accordingly, in one aspect, the present invention provides an indicator controller for a traffic light system, the indicator controller comprising:
a control signal generator having at least one control input and a control output; and
a power control section having an actuating input and a blocking section, the actuating input being coupled to the control output, the blocking section being coupled to a power control circuit associated with a plurality of electronic lighting elements of the traffic light system.
In another aspect, the present invention provides an optical assembly for providing lighting signals in a traffic light system, the optical assembly comprising:
a plurality of electronic lighting elements;
a power control circuit coupled to the plurality of electronic lighting elements;
a monitoring circuit having a monitoring input and a monitoring output, the monitoring input being coupled to the power control circuit; and
an indicator controller comprising:
a control signal generator having at least one control input and a control output; and
a power control section having an actuating input and a blocking section, the actuating input being coupled to the control output, the blocking section being coupled to the power control circuit and at least one electronic lighting element of the plurality of electronic lighting elements.
In a further aspect, the present invention provides a traffic light system to provide traffic light signals, the traffic light system comprising:
at least one optical assembly having:
a plurality of electronic lighting elements;
a power control circuit coupled to the plurality of electronic lighting elements;
a monitoring circuit having a monitoring input and a monitoring output, the monitoring input being coupled to the power control circuit; and
an indicator controller comprising:
a control signal generator having at least one control input and a control output; and
a power control section, having an actuating input and a blocking section, the actuating input being coupled to the control output, the blocking section being coupled to the power control circuit and at least one electronic lighting element of the plurality of electronic lighting elements.
In yet another aspect, the present invention provides a method for fault indication in a traffic light system, the method comprising the steps of:
receiving a comparator input signal when the amplitude of a monitored signal exceeds a predetermined threshold relative to a reference setting;
comparing the comparator input signal with a comparator threshold;
disabling a control signal based upon the comparing step; and
blocking current flow through at least one electronic element of a plurality of electronic lighting elements of the traffic light system.


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English-language Abstract of French publication 2724749 A1 (Mar. 22, 1996), Derwent Acc. No. 1996-181513.

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