Light emitters for optical traffic control systems
Various approaches for activating a traffic control preemption system. The traffic control preemption system has a receiver with a photodetector and circuitry that produces a number of electrical pulses in response to each detected light pulse. For each detected light pulse the number of electrical pulses represents a level of radiant power of the light pulse. A threshold number of electrical pulses and an activation frequency at which the threshold number of electrical pulses is repeated activates preemption. Control circuitry is coupled to a light emitter and controls the light emitter to emit bursts of light pulses. Each burst includes at least two light pulses and the control circuitry controls the frequency of light pulses in each burst and the frequency of the bursts to cause the receiver to produce at least the threshold number of electrical pulses at the activation frequency and activate the preemption.
1. An apparatus for use with a traffic control preemption system that has a receiver with a photodetector and circuitry that produces a number of electrical pulses in response to each detected light pulse, wherein for each detected light pulse the number of electrical pulses represents a level of radiant power of the light pulse, and a threshold number of electrical pulses and an activation frequency at which the threshold number of electrical pulses is repeated activates preemption, comprising:
a light emitter;
control circuitry coupled to the light emitter and controlling the light emitter to emit bursts of light pulses, wherein each burst includes at least two light pulses and a frequency of light pulses in each burst and a frequency of the bursts cause the receiver to produce at least the threshold number of electrical pulses at the activation frequency and activate the preemption.
2. The apparatus according to claim 1 , wherein the light emitter device comprises a plurality of LEDs.
3. The apparatus according to claim 2 wherein the LEDs are infrared LEDs.
4. The apparatus of claim 2 , wherein the plurality of LEDs include a plurality of visible light LEDs and a plurality of infrared LEDs.
5. The apparatus of claim 2 , further comprising a plurality of lenses that disperse the light pulses emitted by the plurality of LEDs.
6. The apparatus of claim 5 , wherein lenses in a first subset of the lenses have a first dispersion angle and lenses in a second subset of the lenses have a second dispersion angle that is narrower than the first dispersion angle.
7. The apparatus of claim 2 , further comprising a light bar for mounting to a vehicle, and the plurality of LEDs are mounted in the light bar.
8. The apparatus of claim 1 , wherein the light emitter device comprises a plurality of gas discharge lamps, and for a first pulse of the burst, the control circuitry triggers at least a first one of the gas discharge lamps, and for a second pulse of the burst, the control circuitry triggers at least a second one of the gas discharge lamps and not the first one of the gas discharge lamps.
9. The apparatus of claim 1 , wherein the light emitter device comprises a plurality of halogen lamps, and for a first pulse of the burst, the control circuitry triggers at least a first one of the halogen lamps, and for a second pulse of the burst, the control circuitry triggers at least a second one of the halogen lamps and not the first one of the halogen lamps.
10. The apparatus of claim 1 , wherein the light emitter device comprises a plurality of light sources, at least a first one of the light sources is of a first type, at least a second one of the light sources is of a second type that is different from the first type, and for a first pulse of the burst, the control circuitry triggers the first light source, and for a second pulse of the burst the control circuitry triggers the second light source and not the first light source.
11. The apparatus of claim 1 , wherein the light emitter device comprises a single gas discharge lamp.
12. The apparatus of claim 1 , wherein the light emitter device comprises a single halogen lamp.
13. The apparatus of claim 1 , wherein the light emitter and control circuitry are disposed in a hand-held housing.
14. A method for operating a traffic control preemption system that includes a receiver with a photodetector and circuitry that produces a number of electrical pulses in response to each detected light pulse, wherein for each detected light pulse the number of electrical pulses represents a level of radiant power of the light pulse, and a threshold number of electrical pulses and an activation frequency at which the threshold number of electrical pulses is repeated activates preemption, comprising:
activating a light emitter to initiate traffic control preemption;
in response to the activating, triggering emission of a plurality of bursts of light pulses, each burst including two or more light pulses; and
controlling a frequency of light pulses in each burst and a frequency of the bursts to cause the receiver circuitry to produce at least the threshold number of electrical pulses at the activation frequency to activate the preemption.
15. The method of claim 14 , wherein the triggering emission includes applying power to a plurality of LEDs.
16. The method of claim 15 , wherein the plurality of LEDs are infrared LEDs.
17. The method of claim 15 , wherein the plurality of LEDs include a plurality of visible light LEDs and a plurality of infrared LEDs.
18. The method of claim 14 , wherein the triggering emission includes applying power to a plurality of gas discharge lamps, and for a first pulse of the burst, the triggering at least a first one of the gas discharge lamps, and for a second pulse of the burst, the triggering at least a second one of the gas discharge lamps and not the first one of the gas discharge lamps.
19. The method of claim 14 , wherein the triggering emission includes applying power to a plurality of halogen lamps, and for a first pulse of the burst, triggering at least a first one of the halogen lamps, and for a second pulse of the burst, triggering at least a second one of the halogen lamps and not the first one of the halogen lamps.
20. The method of claim 14 , wherein the triggering emission includes applying power to at least a first one of a plurality of light sources of a first type for a first pulse of the burst, applying power to at least a second one of a plurality of light sources of a second type for a second pulse of the burst without applying power to the first light source, wherein the second type of light source is different from the first type of light source.
21. The method of claim 14 , wherein the triggering emission includes applying power to a single gas discharge lamp.
22. The method of claim 14 , wherein the triggering emission includes applying power to a single halogen lamp.
23. A light emitter for activating preemption in a traffic control preemption system that has a receiver with a photodetector and circuitry that produces a number of electrical pulses in response to each detected light pulse, wherein for each detected light pulse the number of electrical pulses represents a level of radiant power of the light pulse, and a threshold number of electrical pulses and an activation frequency at which the threshold number of electrical pulses is repeated activates preemption, comprising:
a power supply;
a plurality of LEDs coupled to the power supply;
a switch coupled to the plurality of LEDs for controllably switching power on and off to the plurality of LEDs;
a microcontroller coupled to the power supply and to the switch, wherein the microcontroller is configured to control the switch for powering on and off the plurality of LEDs to emit bursts of light pulses to activate the preemption, wherein each burst includes at least two pulses and the microcontroller controls a frequency of the light pulses in each burst and a frequency of the bursts to cause the receiver to produce at least the threshold number of electrical pulses at the activation frequency for activating the preemption.
24. The light emitter of claim 23 , wherein the plurality of LEDs comprises a plurality of channels of LEDs, each channel being powered separate from the other channels.
25. The light emitter of claim 24 , wherein each channel includes a respective capacitor coupled between the power supply and the LEDs in the channel and a respective voltage controlled current source that is coupled to the LEDs in the channel, switch, and microcontroller, wherein the microcontroller is configured to adjust current in one or more of the LED channels in response to a lack of current level in one of the channels of LEDs.
26. The light emitter of claim 23 , further comprising a temperature sensor coupled to the microcontroller, wherein the microcontroller is configured to adjust pulse amplitude and pulse width via the trigger in response to a temperature indicated by the temperature sensor.
27. The apparatus of claim 23 , further comprising a hand-held housing, wherein the power supply, plurality of LEDs, switch, and microcontroller are disposed in the housing.