Patent Application
20150029693
This disclosure generally relates to a vehicle instrument panel assembly, and more particularly relates to modulating light sources used in the assembly so a light detector can be used to determine if each of the light sources are operating properly.
Customers of vehicle instrument panel assembly suppliers often ask that the assemblies be able to confirm that a light source on the assembly, a light emitting diode (LED) indicator or telltale for example, is in fact working properly. Typically, the suppliers rely on either a voltage or current measurement of the LED circuit to infer that the LED is working properly. However, such inferences are not the same as verifying that a particular light source is actually emitting light. LEDs with built in light detectors have been proposed. However, the additional part cost, additional wiring complexity, and the increased number of inputs into a controller operating the instrument panel assembly make this alternative financially undesirable.
In accordance with one embodiment, a vehicle instrument panel assembly configured to verify that light sources of the assembly are operating properly is provided. The assembly includes a first light source, a second light source, a light detector, and a controller. The first light source is operable to emit light having a first modulation. The second light source is operable to emit light having a second modulation distinguishable from the first modulation. The light detector is configured to detect light emitted by the first light source and the second light source. The controller is configured to receive a detection signal from the light detector effective for the controller to determine if the first light source and the second light source are operating properly.
Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings.
The present invention will now be described, by way of example with reference to the accompanying drawings, in which:
The assembly 12 generally includes a housing 20 that may include features to aid attaching the assembly 12 to the dashboard 16 of the vehicle 10, as will be recognized by those skilled in the art. The assembly may also include one or more pointers 24 (only shown in
Backlighting of the applique 18 is generally provided by a number of light sources, for example a first light source 26, a second light source 28, and a third light source 30. These light sources are preferably light emitting diodes (LEDs), for reasons that will become apparent in the description that follows. However, the assembly 12 described herein is not limited to using LEDs as light sources. LED's are preferable as the intensity of light emitted by an LED responds quickly to changes in the voltage or current applied to the LED. In particular, it is desirable for the first light source 26 to be operable to emit light having a first modulation 36, and the second light source 28 to be operable to emit light having a second modulation 38 distinguishable from the first modulation 36. As used herein, the terms first modulation 36 and second modulation 38 are used to describe a variation in light intensity emitted by the first light source 26 and the second light source 28, respectively, in response to a variation in the voltage and/or current applied to the respective light sources. The advantage of modulating the light sources with distinct modulations or distinct modulation patterns will become apparent in the description that follows.
The assembly 12 described herein is generally configured to directly verify that light sources (26, 28, 30) of the assembly 12 are operating properly. As opposed to detecting voltage or current applied to the light sources, the assembly 12 directly detects that the light sources are actually emitting light using a light detector 32 configured to detect light emitted by the first light source and the second light source. However, instead of providing a distinct light detector for each light source, the assembly 12 described herein reduces costs by using one light detector to detect light emitted from a plurality of light sources. It is recognized that more than a single light detector may be needed to detect light emitted from every light source in a typical vehicle instrument panel assembly. Proof-of-concept testing that relies on light being reflected by the lens 22 toward the light detector 32 suggests that two light detectors should be sufficient to discriminate all of the light sources in a typical vehicle instrument panel assembly, which may have as many as twenty distinct light sources.
The assembly may include a controller 34 in electrical communication with the light sources 26, 28, 30 and the light detector 32. The controller 34 may include a processor such as a microprocessor or other control circuitry as should be evident to those in the art. The controller 34 may include memory, including non-volatile memory, such as electrically erasable programmable read-only memory (EEPROM) for storing one or more routines, thresholds and captured data. The one or more routines may be executed by the processor to perform steps for determining if signals received by the controller 34 from the light detector 32 correspond to the distinct modulations (36, 38) as described herein. Preferably, the controller 34 is configured to output the modulation signals to the respective light sources, and is configured to receive a detection signal from the light detector 32 effective for the controller 34 to determine if the first light source 26 and the second light source 28 are operating properly. Alternatively, each light source may be configured to autonomously emit light with a unique modulation characteristic, and so the controller may merely output an ON/OFF signal to each light source.
Preferably, the modulation of light is not detectable by the human 14 viewing the assembly 12. If the frequency of modulation is above one-hundred Hertz (100 Hz), the human 14 will not detect the modulation. If the modulation is detectable by the human 14, it may be distracting and/or annoying to the human 14. Several different forms of modulation are described below with regard to the first modulation 36, which is applied to the first light source 26. It should be understood that these various forms of modulation are equally applicable to the second modulation 38, which is applied to the second light source 28, and the modulation of any other light source of the assembly 12, for example modulation of the third light source 30. In the description that follows, the intensity of light emitted by any light source will be described in normalized terms where 100% corresponds to a signal (i.e. voltage and/or current) being appliqued such that the light source emits the maximum light intensity possible or recommended for that light source. Likewise, 50% means that the light source is being operated to emit light at an intensity level that is about half of its maximum capability. Furthermore, the modulation examples presented will include ON/OFF operation of the light source as detecting the proper operation of telltales such as a low-oil-pressure indicator or a service-engine-soon indicator is the primary motivator for the detection scheme described herein. However, it should be recognized that modulation may also be used to detect the proper operation of light sources that are used for general backlighting, i.e. are always on when the vehicle is operating.
Returning to
Accordingly, a vehicle instrument panel assembly (the assembly 12) configured to verify that light sources of the assembly are operating properly is provided. By modulating each of the light sources with a unique modulation signal, a single light detector can be used to determine if a plurality of light sources are operating properly. This provides a solution to the long felt need of being able to directly determine that telltale indicators of a vehicle instrument panel are actually emitting the light that is expected when a signal to activate the light in question is emitted by, for example, a controller. In one example, a high frequency modulation signal is super-imposed on top of the intensity dimming PWM signal. This high frequency modulation would be unnoticed by the driver and have no impact on the intensity dimming PWM. Each telltale LED would have a different high frequency modulation. Most of the light from these LEDs passes through the lens but a small amount of the incident light wave is reflected on the inside surface of the lens. The light detector (e.g. a photo diode or photo transistor) would detect this reflected light and be electrically amplified and passed to a controller. The high frequency modulation of each individual LED is then detected using the software in the controller.
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
