ELECTRONIC TRAFFIC SIGNAL CONTROL SYSTEM

• US 3,810,084 A
• Filed: 03/23/1971
• Issued: 05/07/1974
• Est. Priority Date: 03/23/1971
• Status: Expired due to Term

• Current Assignee: Harold C. Hoyt Jr
• Original Assignee: Harold C. Hoyt Jr
• Inventors: Hoyt, Harold C. Jr.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Myers, Randall P.
• Application Number:
  US05/127,134
• Time in Patent Office: 1,141 Days
• Field of Search: 340/35,36,37,40,41
• US Class Current: 340/931
• CPC Class Codes: G08G 1/085 using a free-running cyclic timer

Abstract

An electronic traffic signal control system. Logic circuitry is included for providing a sequence of timed changing logic states which define operating periods for a plurality of signal lights. Control means is responsive to the changing logic states for selectively energizing predetermined ones of the signal lights during each of respective operating periods defined by the logic states. Timing circuitry generates timing pulses for causing successive changing of the logic states. Provision is made for manually varying the timing of generation of the timing pulses for preselecting the lengths of the respective operating period defined by each of the logic states.

Claims

1. A solid state electronic traffic signal local controller for controlling a plurality of traffic signal lights, comprising:

logic means for providing a sequence of timed changing logic states which define operating periods for said signal lights;

control means responsive to said changing logic states for selectively energizing predetermined ones of said signal lights during each of respective operating periods defined by said logic states;

timing means operative to generate timing pulses for causing successive changing of said logic states;

means for adjusting the timing of generation of said timing pulses thereby to preselect the length of the respective operating period defined by each of said logic states; and

means for causing accelerated generation of a timing pulse by the timing means in order to shorten the operating period defined by at least one of said logic states in response to the presence of an externally generated master controller synchronizing signal, thereby to synchronize control of said signal lights with the master controller.

2. A traffic signal controller as set forth in claim 1 wherein said synchronizing means includes delay means for manually preselecting a time delayed response to said master controller synchronizing signal.

3. A traffic signal controller as set forth in claim 1 wherein said synchronizing means comprises further logic means for preventing said altering of the timing of changing logic states if the presence of said synchronizing signal is irregular thereby to preclude improper synchronizing of said signal lights.

4. A solid state electronic traffic signal local controller for multiphase control of a plurality of traffic signal lights at a traffic intersection, comprising:

logic means including a code generator for generating a repeating coded sequence of timed logic states and a decoder for defining operating periods for said signal lights according to said coded sequence;

control means including a plurality of semiconductor current switching devices operative in response to said decoder for selectively energizing predetermined ones of said signal lights during each of respective operating periods defined by said logic states;

timing means responsive to selective energization of said signal lights and operative to generate timing pulses for causing said code generator to generate successive logic states;

means for manually varying the timing of generation of said timing pulses thereby to preselect the length of the respective operating period defined by each of said logic states;

flasher control means; and

fault monitoring means for terminating traffic control operation of said controller in response to concurrent energization of an unsafe combination of said signal lights in different phases permitting conflicting traffic within said intersection, said fault monitoring means operating upon said unsafe combination to disconnect said controller from a source of power therefor and concomitantly to connect said flasher control means to predetermined ones of said signal lights.

5. A traffic signal controller as set forth in claim 4 wherein at least one of said logic states defiNes an operating period for at least one signal light signalling a turn for traffic, said system further comprising means for manually preselecting system operation to prevent energization of said turn signal light.

6. A traffic signal controller as set forth in claim 5 further comprising means operative when energization of said turn signal light is prevented to accelerate the generation of a timing pulse for causing accelerated changing of the logic state defining an operating period for said turn signal light, said accelerated changing of the logic state preventing erroneously long operation of signal lights normally operated with said left turn signal light.

7. A traffic signal controller as set forth in claim 4 wherein said fault monitoring means comprises fault logic circuitry for detecting concurrent energization of predetermined respective signal lights controlling intersecting traffic.

8. A traffic signal controller as set forth in claim 7 wherein said fault monitoring means further comprises means for causing flasher operation of red signal lights in response to detection of said concurrent energization.

9. A traffic signal controller as set forth in claim 8 further comprising flasher means for providing said flasher operation of signal lights, said flasher means comprises at least one triggerable semiconductor current switching device operable, when triggered, to energize signal lights, and timing means for causing periodic triggering of said switching device thereby to cause said flashing energization of signal lights.

10. A traffic signal controller as set forth in claim 9 wherein said flasher means comprises a pair of triggerable semiconductor current switching devices each operable, when triggered, to energize ones of said signal lights, a flip-flop having a pair of outputs each connected for causing triggering of a respective one of said switching devices, and a timing circuit operative to provide pulses for causing periodic toggling of said flip-flop, thereby to cause alternate triggering of said switching devices for causing said flashing energization of signal lights.

11. A traffic signal controller as set forth in claim 4 wherein said means for manually varying timing includes a first plurality of manually variable impedance devices interconnected with said control means and further comprising auxiliary means for manually varying the timing of generation of said timing pulses, said auxiliary means including a second plurality of manually variable impedance devices interconnected with said control means, and switching means for causing said first plurality of devices to become inoperative and said second plurality of devices to become operative in response to said operation of a clock switch.

12. A traffic signal controller as set forth in claim 11 further comprising a plurality of indicator lights adapted to be energized concomitantly with respective ones of said signal lights, said indicator lights being positioned for all being viewed simultaneously thereby to facilitate adjustment and testing of said system.

13. A solid state electronic traffic signal local controller for controlling a plurality of traffic signal lights, comprising:

logic means for providing a sequence of timed changing logic states which define operating periods for said signal lights;

control means responsive to said changing logic states for selectively energizing predetermined ones of said signal lights during each of respective operating periods defined by said logic states;

timing means operative to generate timing pulses for causing successive changing of said logic states;

means for adjusting the timing of generation of said timing pulses thereby to preselect the length of the respective operating period defined by each of said logic states;

flasher control means for terminating traffic control operation of said system and initiating flasher operation of predetermined one of said signal lights, and thereafter reverting to traffic control opEration, said flasher control means comprising flasher logic means for permitting initiation of said flasher operation only during a predetermined one of said logic states and for permitting reversion to said traffic control operation only during a predetermined one of said logic states, thereby to permit transistion between flasher operation and traffic control operation only during safe traffic conditions.

14. A traffic signal controller as set forth in claim 13 wherein said flasher logic means comprises a first logic gate responsive to a predetermined one of said logic states, a second logic gate responsive to a predetermined one of said logic states, and a flip-flop adapted for being set by said first logic state to cause flasher operation and for being reset by said second logic gate to cause traffic control operation.