Electric lamp and discharge devices: systems – With radiant energy sensitive control means
Reexamination Certificate
1999-07-23
2001-07-10
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
With radiant energy sensitive control means
36
Reexamination Certificate
active
06259211
ABSTRACT:
BACKGROUND OF THE INVENTION
Vending machines in the field include interior fluorescent lamps that illuminate a large front panel typically having a sign advertising the items available for vending. These illuminated vending machines attract consumers. But studies show that vending machine sales drop off dramatically when one or more of the lamps go out because customers perceive that the vending machine is broken. Thus, there is a need for a device to alert the vending machine owner when one or more of the lamps are showing signs of failing.
SUMMARY OF THE INVENTION
The invention concerns a non-contact fluorescent light tube detector (FLD) circuit for mounting within a vending machine. In particular, a photodetector monitors one of the fluorescent tubes, and is connected to a means for compensating for ambient light entering through the front panel. An output signal indicative of the status of the light tubes is generated on an output line. The output line may be connected to a microcontroller, such as a digital signal processor, a microprocessor or other control circuit, which monitors the phase shifts in the pulses generated by the FLD circuit. Based on the output of the FLD circuit, the microcontroller can determine when one or more fluorescent light tubes is going bad. In one implementation, the detector circuit may be housed in a collimator tube.
An implementation of a non-contact fluorescent light tube detector circuit for a vending machine includes a photodetector, circuit means connected to the photodetector to compensate for ambient light entering through the front panel, and an output line.
Implementations of the invention may include one or more of the following features. The light detector circuit may be housed within a collimator tube. The circuit means for compensating for ambient light may be an automatic gain control circuit, or may be a high pass filter. A microcontroller may be included to monitor the phase shifts in the pulses generated by the detector circuit, and may generate a fluorescent tube failure signal if at least one fluorescent light tube is faulty. The tube failure signal may be transmitted to a remote site. The microcontroller may be operable to detect when mains power has been removed to minimize false fluorescent tube failure signals. The microcontroller may also be operable to monitor a jitter signal for a predetermined time interval and to generate the fluorescent tube failure signal if the jitter exceeds a predetermined threshold value within the time interval. Alternately, the microcontroller may calculate a time interval based on monitored activity and use the time interval to monitor a jitter signal and then generate a fluorescent tube failure signal if the jitter exceeds a predetermined threshold value.
In another implementation, disclosed is a method for detecting when at least one fluorescent light tube in a vending machine is failing. The method includes positioning at least one fluorescent light tube detector adjacent at least one of the fluorescent light tubes, generating signals with the light tube detector, measuring the timing of a cycling waveform induced by the fluorescent light tube to detect any jitter, and generating a fluorescent light tube is failure signal if a jitter condition is detected.
Implementations of the method may include one or more of the following features. The jitter condition may comprise monitoring the jitter for at least one predetermined time interval, and indicating fluorescent tube failure if the jitter exceeds a predetermined threshold amount within the time interval. Alternately, the jitter condition may comprise monitoring the jitter for at least one calculated time interval, and indicating fluorescent tube failure if the jitter exceeds a predetermined threshold amount within the calculated time interval. The method may also include indicating that a fluorescent light tube has failed if no signals are detected and mains power has not been removed. The method may also include transmitting the failure signal to a remote location, and an audit system may transmit the failure signal. The method may further include logging the total amount of time that a fluorescent light tube has been illuminated, and transmitting a warning signal indicating that a light tube is nearing the end of its useful life if the time logged exceeds a predetermined threshold.
Advantages of the invention include the ability to measure the timing of a 60 cycle waveform (50 cycles in parts of Europe), such that any jitter detected in the timing pulses, or detection of missing pulses, indicates a fluorescent tube that is flickering. Such flickering is an indication that the fluorescent tube is about to fail, and thus a vending machine owner can be notified in a timely manner to install a new tube. Further, the FLD does not contact or couple to any of the fluorescent light tubes, which means that it can be retrofit to existing machines in the field, and that no special adaptations of the light tubes is required.
The invention also detects that a tube has failed, and the information can be used by the microprocessor to request service. In addition, the amount of time that a particular tube has been illuminated can be logged, which can be used to predict the useful life remaining in the fluorescent tube.
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Fish & Richardson P.C.
Mars Incorporated
Tran Chuc
Wong Don
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