Patent Grant
7211771
The present invention relates to LED traffic signals, and, more particularly, to a circuit for detecting and eliminating the buildup of snow and ice on the lenses of LED traffic signals.
Before light emitting diode (“LED”) traffic signals began replacing traffic signals using incandescent bulbs, the buildup of frozen matter, such as snow and ice, on the viewable faces or lenses of incandescent traffic signals was not an issue. Typically, the incandescent signals required an amount of power that was much larger than that required by LED traffic signals. The large amount of power used by incandescent traffic signals was converted to heat and dissipated through the face or lens of the traffic signal, resulting in the melting of most, if not all, snow and ice on the lenses of the incandescent traffic signals.
With the introduction of LED traffic signals, a significant reduction in power consumption over that used by incandescent signals was realized. The LEDs used in such signals convert the input power more efficiently and thus dissipate much less heat through the lens of the traffic signal. However, this significant improvement in power efficiency provided by the LED traffic signals eliminated the inherent benefit of the incandescent signals to reduce or eliminate the buildup of frozen snow and/or ice on the lenses of the traffic signals. This dangerous buildup of snow and/or ice on the LED signals has caused many accidents, and is a major concern for the safety of the motoring public.
Thus, it is desirable to provide a circuit that would detect and eliminate the buildup of ice or snow on the lenses of LED traffic signals.
The present invention is directed to a circuit that detects and eliminates the buildup of frozen matter, such as snow or ice, on the viewable face or lens of an LED traffic signal. The circuit of the present invention monitors the ambient temperature within the traffic signal, and when the temperature falls below a certain set point where snow and/or ice accumulation can occur, the circuit begins looking for the buildup of snow and/or ice on the lens of the traffic signal. When the circuit detects the buildup of frozen matter, the circuit “warms” the face or lens of the traffic signal so as to defrost, and thereby eliminate, the frozen matter buildup. The circuit of the present invention uses a heating element or a plurality of elements that are mounted on, or in proximity to, the face or lens of the LED traffic signal to warm the face or lens of the signal. The heating elements are activated only when a sensor detects the buildup of frozen matter on the lens of the signal. The heating elements can be any device that produces heat when power is applied to them. Preferably, the heating elements are a plurality of high wattage resistors.
The circuit of the present invention includes a microcontroller that monitors ambient temperature within the LED traffic signal using an internal sensor. If the ambient temperature is above a temperature set point where ice and/or snow can form, the microcontroller takes no action. If the ambient temperature is below the set point, the microcontroller begins looking for the build-up of ice or snow on the lens of the LED traffic signal. Using an internal analog-to-digital converter that receives a signal from a photodiode light sensor, the microcontroller measures the ambient light level external to the signal. The measure of ambient light is used by the microcontroller as a baseline to reduce or eliminate false triggering of the circuits used to detect the buildup of ice or snow due to external light sources, such as sunlight, street lights, etc.
The circuits used to detect the buildup of ice or snow on the lens of an LED signal preferably include an infrared LED as a transmitter. The gain of the transmitter is continuously adjusted by the microcontroller using the ambient light level measurement received from the photodiode light sensor. Using an internal digital-to-analog converter, the microcontroller adjusts the gain of the infrared LED transmitter by adjusting the voltage applied to the base of a transistor that controls the operation of the infrared LED. This adjustment to the gain of the transmitter, in turn, controls the transmitting power of the infrared LED transmitter. Preferably, the microcontroller applies to the base of the transistor a 40 kHz signal modulated at 100 Hz, the signal being generated by the microcontroller.
Preferably, an infrared receiver looks for a signal that is reflected from the lens of the LED traffic signal. The reflected signal occurs when there is a buildup of ice and/or snow on the lens of the signal. When the reflected signal is received by the infrared receiver, it demodulates the transmitted signal and sends a 100 Hz signal to the microcontroller. The signal sent by the receiver is analyzed by the microcontroller to determine if it is a valid reflected signal, or if it is noise from an outside light source. The microcontroller determines if a signal is a valid reflected signal by counting the pulses received. If it is a correct count, +/−5, then the signal is valid. If it is a valid reflected signal, the microcontroller then turns on the heating elements. For this purpose, the microcontroller turns on a triac, which applies AC power to the heating elements from an AC power source. Preferably, the heating elements are a series of high wattage resistors located near or on the lens of the traffic signal. However, it should be noted that other heating elements could be used, such as ceramic elements, resistive wire, resistive coatings, filaments, ultrasonic heaters, microwave signals, and Peltier thermoelectric devices. The heater will continue to heat the signal lens until the temperature measured by the microcontroller rises above a controlled set point, or the snow and ice condition no longer exists.
h are plan and side elevational drawings showing alternative heating elements that can be used and locations of such heating elements relative to the lens of an LED traffic signal.
The present invention is directed to a circuit 10 for detecting the buildup of snow and/or ice on the lens of an LED traffic signal and for eliminating the buildup of the snow and/or ice from the lens of an LED traffic signal.
The heart of circuit 10 is a microcontroller 12, which senses ambient temperature within the LED signal, initiates the function of looking for snow and/or ice buildup when the ambient temperature falls below a certain set point and initiates the operation of a heater to eliminate ice and/or snow when it is detected. Preferably, microcontroller 12 is a CY8C27143B programmable microcontroller manufactured, for example, by Cypress Semiconductor Corp. Microcontroller 12 is shown as component U1 in the schematic of circuit 10 shown in
As shown in
Using the information obtained from ambient light sensor 14, microcontroller 12 adjusts the gain of an infrared LED transmitter circuit 16 to reduce or eliminate false triggering due to external light sources, such as sunlight and streetlights. The information received by microcontroller 12 from ambient light sensor 14 is used as a baseline by microcontroller 12 to reduce or eliminate false triggering due to the external light sources.
Infrared LED transmitter circuit 16 includes an infrared light emitting diode D1, which functions as a transmitter. Preferably, diode D1 is an LTE-4208C Infra-red LED Emitter manufactured, for example, by Lite-On Technology Corporation. Microcontroller 12 adjusts the voltage on the base of a transistor Q1, which controls the forward bias of infrared LED D1, as transistor Q1 is turned on. Transistor Q1 is preferably a 2N3904 PNP transistor. As shown in
As shown in
Microcontroller 12 turns on heater circuit 20 by turning on a triac U2, which applies AC power from an AC power source 22 to heating elements 21. Preferably, heating elements 21 are a plurality of high wattage resistors R5–R16 connected in series between triac U2 and the AC power source 22. Although it should be noted, however, that other heating elements could be used, such as ceramic elements, resistive wire, resistive coatings, filaments, ultrasonic heaters, microwave signals, and Peltier thermoelectric devices. Regardless of the type of heating element used, microcontroller 12 would turn on triac U2 to apply a voltage that turns on heater circuit 20. Thus, for example, if heater circuit 20 were an ultrasonic heater, heater circuit 20 would be comprised of an ultrasonic emitter with its associated drive circuitry powered by triac U2 under the control microcontroller 12.
Heater circuit 20 continues to heat signal lens 19 until the temperature measured by microcontroller 12 through its internal sensor rises above the temperature set point, or the snow and/or ice condition on lens 19 no longer exists. In the latter case, signal 17 transmitted by transmitter circuit 16 is no longer reflected by snow and/or ice on lens 19 so as to be received by receiver circuit 18.
a through 7h are plan and side elevational drawings showing alternative heating elements 21 that can be used in heater circuit 20 and locations of such heating elements 21 relative to the lens 19 of an LED traffic signal 30.
a and 7b are plan and side elevational drawings, respectively, of an LED traffic signal 30 including heating elements 21 in the form of a plurality of resistive coatings 32 located on the lens 19 of traffic signal 30 and positioned in multiple iterations of a back and forth pattern across lens 19 to heat lens 19. Preferably, resistive coatings 32 are connected in series between triac U2 and the AC power source 22.
c and 7d are plan and side elevational drawings, respectively, of LED traffic signal 30 including heating elements 21 in the form of a resistive wire 34 located on the lens 19 of the traffic signal 30 and positioned in multiple iterations of a back and forth pattern across lens 19 to heat lens 19. Preferably, resistive wire 34 is connected between triac U2 and the AC power source 22.
e and 7f are plan and side elevational drawings, respectively, of LED traffic signal 30 including heating elements 21 in the form of a plurality of resistors 36, shown as resistors R5 through R16 in the schematic of
g and 7h are plan and side elevational drawings, respectively, of LED traffic signal 30 including heating elements 21 in the form of a resistive wire 38 located on the lens 19 of the traffic signal 30 and positioned, to heat lens 19, in a multi-loop circular pattern on lens 19 where such lens is in close proximity to the circuit board 40 on which the array of light emitting diodes are mounted. Preferably, resistive wire 38 is connected between triac U2 and the AC power source 22.
The power supply used by circuit 10 for its operation supplies a voltage of VCC, which is typically 5V DC. As shown in
The circuit 10 of the present invention for detecting and eliminating the buildup of ice and/or snow from the lens of an LED traffic signal can be used with a single array of LEDs that form one of the signal lights of a traffic signal, such as the red, amber and green signals that are typically included in traffic signals. The circuit 10 can also be used with multiple arrays of LEDs that form the red, amber and green signals included in traffic signals. In the latter instance, it would be necessary to have an ambient light sensor circuit 14, a transmitter circuit 16, a receiver circuit 18, and a heater circuit 20 for each of the LED arrays; however, a single microcontroller 12 could be used to interact with and control these circuits in each of the LED arrays.
While the invention has been described in connection with what is presently considered to be the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4724304 | Teshima et al. | Feb 1988 | A |
| 4729076 | Masami et al. | Mar 1988 | A |
| 5782555 | Hochstein | Jul 1998 | A |
| 5785418 | Hochstein | Jul 1998 | A |
| 6045240 | Hochstein | Apr 2000 | A |
| 6282969 | Daniel | Sep 2001 | B1 |
| 6354714 | Rhodes | Mar 2002 | B1 |
| 6430996 | Anderson et al. | Aug 2002 | B1 |
| 6601983 | Runfola et al. | Aug 2003 | B1 |
| 20030002179 | Roberts et al. | Jan 2003 | A1 |
| 20050063182 | Birch et al. | Mar 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 2003303399 | Oct 2003 | JP |
