Light responsive switching circuit

• US 3,901,813 A
• Filed: 07/12/1974
• Issued: 08/26/1975
• Est. Priority Date: 07/12/1974
• Status: Expired due to Term

• Current Assignee: Michael A. Potopinski
• Original Assignee: Michael A. Potopinski
• Inventors: Potopinski, Michael A.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nelms, D. C.
• Application Number:
  US05/488,114
• Time in Patent Office: 410 Days
• Field of Search: 250/208,209,214,206 307/311 317/124 315/154,155,156,158
• US Class Current: 250/208.4
• CPC Class Codes: H03K 17/795 controlling bipolar transistors

Abstract

A light responsive switching circuit especially adapted for use in warning light apparatus such as highway markers. The circuitry includes first and second photosensors, one responsive to ambient light and one responsive to a headlight or other signal light source. A solid state switching circuit is enabled when ambient light is below a predetermined level and becomes disabled when the ambient light is at or above such level. In the enabled condition the circuit is switched in response to a signal light received by the second photosensor causing operation of an associated electronic flash circuit.

Claims

1. A LIGHT RESPONSIVE SWITCHING CIRCUIT COMPRISING:

FIRST AND SECOND PHOTOSENORS CONNECTED IN SERIES AND EACH DISPOSED TO RECEIVE LIGHT FROM A RESPECTIVE SOURCE, SAID FIRST PHOTOSENSOR BEING OPERATIVE TO PROVIDE A SWITCHING SIGNAL IN RESPONSE TO RECEIVED LIGHT HAVING AN INTENSITY ABOVE A PREDETERMINED LEVEL, SAID SECOND PHOTOSENSOR BEING OPERATIVE TO PROVIDE AN ENABLE SIGNAL IN RESPONSE TO RECEIVED LIGHT HAVING AN INTENSITY BELOW A PRETERMINED LEVEL A FIRST TRANSISTOR SWITCH COUPLED TO SAID FIRST AND SECOND PHOTOSENSORS AND BEING SWITCHABLE TO A CONDUCTING STATE IN RESPONSE TO SAID ENABLE SIGNAL FROM SAID SECOND PHOTOSENSOR AND SAID SWITCHING SIGNAL FROM FIRST PHOTOSENSOR, SWITCH MEANS OPERATIVE WHEN SAID FIRST TRANSISTOR SWITCH IS IN A CONDUCTING STATE TO PROVIDE A CONDUCTION PATH, A SECOND TRANSISTOR SWITCH CONDUCTIVE DURING CONDUCTIVVE OPERATION OF SAID SWITCH MEANS AND PROVIDING A CHANGING SURRENT,

2. The circuit according to claim 1 wherein said firsT and second photosensors are disposed on the opposite side of a translucent shield from the side upon which light is received, said shield transmitting diffused light to said photosensors.

3. The circuit according to claim 1 including a translucent shield disposed between said first and second photosensors and said source of light and operative to transmit a portion of light from said second source to said first photosensor for biasing thereof.

4. The circuit according to claim 1 wherein said switch means includes a relay switch having a relay coil and a pair of switch contacts.

5. The circuit according to claim 4 wherein said first transistor switch includes a base electrode coupled to the junction between said first and second photosensors, a collector electrode coupled to said first photosensor and an emitter electrode coupled via said relay means to a source of reference potential;

and wherein said second transistor switch includes a base electrode coupled to said relay switch and a collector electrode coupled to a source of operating potential.

6. The circuit according to claim 4 further including a third transistor switch conductive at a predetermined voltage level of said charge storage means and operative to cause turnoff of said pulse generating means.

7. The circuit according to claim 6 wherein said output means includes:

a zener diode operative to trigger at a predetermined voltage level of said charge storage means;

a controlled rectifier triggerable in response to triggering of said zener diode;

a transformer having its input winding coupled to said controlled rectifier and its output winding coupled to said flash tube and operative in response to triggering of said controlled rectifier to provide a high voltage pulse to said flash tube for the triggering thereof.

8. The circuit according to claim 7 wherein said charge storage means includes:

first storage capacitor means operative to charge to a predetermined level for biasing of said flash tube; and

second storage capacitor means operative to charge to a predetermined level for triggering of said zener diode.

9. The circuit according to claim 8 further including timer means operative in response to triggering of said zener diode to provide a timing interval at the end of which charging of said charge storage means is discontinued.