Ambient light responsive illumination brightness control circuit

• US 3,962,600 A
• Filed: 02/14/1975
• Issued: 06/08/1976
• Est. Priority Date: 02/14/1975
• Status: Expired due to Term

• Current Assignee: Arvin Hong Kong Limited
• Original Assignee: Arvin Hong Kong Limited
• Inventors: Pittman, Carl R.
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US05/549,913
• Time in Patent Office: 480 Days
• Field of Search: 315/149-159, 250/214 R, 250/214 D, 250/206, 250/214 AL, 58/50 R, 307/311
• US Class Current: 315/158
• CPC Class Codes: H05B 39/081 by measuring the incident light H05B39/083 takes precedence

Abstract

A circuit for automatically changing the amount of light provided by an illuminating source which contains a light sensitive device for monitoring the ambient light level. The light sensitive device controls current flow through a first path which includes the illumination source. A second path also provides current flow through the illumination source. When current is flowing through both paths, the source emits a predetermined amount of light. When only the second path conducts, the light provided by the illuminating source is substantially decreased.

Claims

1. A controllable illuminating system comprising a power supply, a pair of terminals adapted to be coupled to said power supply, illuminating means coupled to one of said terminals, and control means coupled to said illuminating means and to the other of said pair of terminals, said control means having a diode coupled for inducing current flow of a first polarity from one of said terminals through said illuminating means and light sensitive circuit means coupled for controllably inducing current flow of opposite polarity from one of said terminals through said illuminating means in response to the ambient light level where said control means is located for varying the power supplied to said illuminating means thereby varying the intensity of illumination emitted from said illuminating means in response to said ambient light level.

2. A controllable illuminating system according to claim 1 wherein said illuminating means and said control means are coupled in series between said pair of terminals.

3. A system according to claim 1 wherein said light sensitive circuit means includes a light sensitive transistor.

4. A system according to claim 1 wherein said light sensitive circuit means includes a light activated silicon controlled rectifier.

5. A controllable illuminating system according to claim 1 wherein said light sensitive circuit means comprises a silicon controlled rectifier coupled for inducing current flow of opposite polarity from one of said terminals through said illuminating means when said silicon controlled rectifier is placed in condition for conduction, and a light sensitive transistor coupled in the gate electrode circuit of said silicon controlled rectifier for controlling the conduction of said silicon controlled rectifier in response to said ambient light level.

6. A controllable illuminating system according to claim 1 wherein said light sensitive circuit means comprises a light activated silicon controlled rectifier for inducing current flow of opposite polarity from one of said terminals through said illuminating means when said light activated silicon controlled rectifier is placed in condition for conduction in response to ambient light levels in excess of a predetermined ambient light level.

7. A controllable illuminating system comprising a power supply;

a pair of terminals adapted to be coupled to said power supply;

illuminating means coupled to one of said terminals; and

control means coupled to said illuminating means and to the other of said pair of terminals, said control means having a diode coupled for inducing current flow of a first polarity from one of said terminals through said illuminating means, a silicon controlled rectifier coupled for inducing current flow of opposite polarity from one of said terminals through said illuminating means when said silicon controlled rectifier is placed in condition for conduction, and a light sensitive transistor coupled in the gate electrode circuit of said silicon controlled rectifier for controlling the conduction of said silicon controlled rectifier in response to ambient light level thereby varying the intensity of illumination emitted from said illuminating means in response to ambient light level.

8. A controllable illuminating system comprising a power supply;

a pair of terminals adapted to be coupled to said power supply;

illuminating means coupled to one of said terminals; and

control means coupled to said illuminating means and to the other of said pair of terminals, said control means having a diode coupled for inducing current flow of a first polarity from one of said terminals through said illuminating means, and a light activated silicon controlled rectifier for inducing current flow of opposite polarity from one of said terminals through said illuminating means when said light activated silicon controlled rectifier is placed in condition for conduction in response to ambient light levels in excess of a predetermined ambient light level to thereby vary the intensity of illumination emitted from said illuminating means in response to ambient light level.

9. A controllable illuminating system comprising a power supply;

a pair of terminals adapted to be coupled to said power supply;

illuminating means coupled to one of said terminals; and

control means coupled to said illuminating means and to the other of said pair of terminals, said control means having a series resistance and capacitance so that current flow of a first polarity charges said capacitance through said resistance to illuminate said illuminating means, a silicon controlled rectifier connected in parallel with said resistance and capacitance for inducing current flow of an opposite polarity when placed in condition for conduction, and a light sensitive transistor coupled in the gate electrode circuit of said silicon controlled rectifier and in parallel with said resistance so that current flow of an opposite polarity charges said capacitance through said resistance to control the conduction of said silicon controlled rectifier, said light sensitive transistor being responsive to ambient light levels to cause said capacitance to charge through said resistance and said transistor when said ambient light exceeds a predetermined level to further control the conduction of said silicon controlled rectifier, and thereby vary the intensity of illumination of said illuminating means in response to ambient light level.