FLOURESCENT LAMP WITH INTEGRAL PROXIMITY SENSOR FOR BUILDING ENERGY MANAGEMENT

• US 20080309243A1
• Filed: 06/16/2008
• Published: 12/18/2008
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Cooley, John J., Avestruz, Al-Thaddeus, Leeb, Steven B., Norford, Leslie K.
• Granted Patent: US 7,923,936 B2
• Time in Patent Office: Days
• US Class Current: 315/158
• CPC Class Codes: H05B 47/115 by determining the presence or movement of objects or living beings
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A fluorescent lamp sensor system is provided. The fluorescent lamp sensor system includes a plurality of bulbs and a plurality of electrodes coupled to the bulbs. A balanced differential circuit measures changes in electric fields produced by the bulbs in front of the electrodes. The balanced differential circuit includes a symmetric current source associated with alternating the surface potential of the bulbs. A current mode detection circuit detects the current associated with the capacitive effects of the balanced differential circuit. A synchronous detection circuit isolates the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase.

Claims

1. A fluorescent lamp sensor system comprising:

a plurality of bulbs;

a plurality of electrodes coupled to said bulbs;

a balanced differential circuit for measuring changes in electric fields produced by said bulbs in front of said electrodes, said balanced differential circuit includes a symmetric current source associated with alternating the surface potential of said bulbs;

a current mode detection circuit for detecting the current associated with the capacitive effects of the balanced differential circuit; and

a synchronous detection circuit for isolating the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase.

2. The fluorescent lamp sensor system of claim 1, wherein said balanced differential circuit comprises a capacitive bridge circuit.

3. The fluorescent lamp sensor system of claim 1, wherein said balanced differential circuit comprises a capacitive bridge circuit.

4. The fluorescent lamp sensor system of claim 1, wherein said symmetric current source is symmetrically centered about said fluorescent lamp sensor system by reversing the ballast connection to one of said bulbs.

5. The fluorescent lamp sensor system of claim 1, wherein said current mode detection circuit comprises a fully differential front-end amplifier.

6. The fluorescent lamp sensor system of claim 5, wherein said electrodes are directly coupled to said differential front-end amplifier.

7. A method of implementing a fluorescent lamp sensor system comprising:

providing a plurality of bulbs;

providing a plurality of electrodes coupled to said bulbs;

providing a balanced differential circuit for measuring changes in electric fields produced by said bulbs in front of said electrodes, said balanced differential circuit includes a symmetric current source associated with alternating the surface potential of said bulbs;

providing a current mode detection circuit for detecting the current associated with the capacitive effects of the balanced differential circuit; and

providing a synchronous detection circuit for isolating the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase.

8. The method of claim 7, wherein said balanced differential circuit comprises a capacitive bridge circuit.

9. The method of claim 7, wherein said balanced differential circuit comprises a capacitive bridge circuit.

10. The method of claim 7, wherein said symmetric current source is symmetrically centered about said fluorescent lamp sensor system by reversing the ballast connection to one of said bulbs.

11. The method of claim 7, wherein said current mode detection circuit comprises a fully differential front-end amplifier.

12. The method of claim 11, wherein said electrodes are directly connected to said differential front-end amplifier.

13. A method of performing the operations of a fluorescent lamp sensor system comprising:

providing a plurality of bulbs;

providing a plurality of electrodes coupled to said bulbs;

measuring changes in electric fields produced by said bulbs in front of said electrodes using a symmetric current source associated with alternating the surface potential of said bulbs;

detecting the current associated with the capacitive effects of the balanced differential circuit; and

isolating the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase.

14. The method of claim 13, wherein said symmetric current source is symmetrically centered about said fluorescent lamp sensor system by reversing the ballast connection to one of said bulbs.

15. The method of claim 13, wherein said electrodes are directly connected to a fully differential front-end amplifier.

16. A lighting system comprising:

a plurality of fluorescent lamp structures being positioned to provide lightening in an enclosed space; and

a plurality of detection structures comprising a selective number of said fluorescent lamp structures to detect whether an occupant is within said enclosed space, each of he detection structures comprising;

a balanced differential circuit for measuring changes in electric fields produced by said occupant, said balanced differential circuit includes a symmetric current source associated with alternating the surface potential of bulbs associated with each of said detection structures;

a current mode detection circuit for detecting the current associated with the capacitive effects of the balanced differential circuit; and

a synchronous detection circuit for isolating the capacitive effects of the symmetrical current source from stray signals that differ in either frequency or phase;

wherein

the intensity of the fluorescent lamp structures are increased from its initial point of intensity when an occupant has been detected by said detection structures.

17. The lighting system of claim 16, wherein the initial point of intensity of the fluorescent lamp structures is set at dim.

18. The lighting system of claim 16, wherein a selective number of said fluorescent lamp structures are turned off and a selective number of said detection structures are turned on.