SUPERVISION FOR A LIGHT DISPLAY DEVICE

• US 20140062491A1
• Filed: 11/08/2013
• Published: 03/06/2014
• Est. Priority Date: 09/17/2010
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Simplexgrinnell LP (Johnson Controls International plc)
• Inventors: Farley, Joseph D.
• Granted Patent: US 9,642,210 B2
• Time in Patent Office: Days
• US Class Current: 324/414
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/37 Converter circuits

Abstract

A device and method may include, in a display device, emitting visible light in a humanly imperceptible manner and sensing said light to verify operation of the display device.

Claims

1. A method for determining operability of a LED in a light display device, comprising:

initiating a reduced current test by activating the LED with a reduced drive current relative to a normal drive current to emit light with an intensity that is imperceptible to a human;

sensing an intensity of light emitted from the LED; and

determining whether the LED is operational by comparing said sensed intensity with a predetermined intensity value.

2. The method of claim 1, wherein determining whether the LED is operational comprises determining whether an electrical signal associated with an intensity of the light emitted by the LED is greater than a minimum signal.

3. The method of claim 1, wherein the step of activating the LED further comprises activating the LED in a dome lamp.

4. The method of claim 1, wherein the step of activating the LED further comprises activating the LED in an emergency notification strobe.

5. The method of claim 1, wherein the step of activating the LED further comprises automatically activating the LED after a predetermined period.

6. The method of claim 1, wherein activating the LED comprises activating a plurality of LEDs simultaneously, and wherein obtaining results of the activation comprises measuring an output of the plurality of LEDs collectively.

7. The method of claim 1, wherein activating the LED comprises activating a plurality of LEDs simultaneously, and wherein obtaining results of the activation comprises measuring a collective output of less than all of the plurality of LEDs.

8. The method of claim 1, wherein activating the LED with a reduced drive current comprises reducing a pulse-width modulation duty cycle of the LED.

9. The method of claim 1, wherein activating the LED further comprises turning the LED on for a time period of less than 20 microseconds.

10. The method of claim 1, wherein activating the LED further comprises activating the LED for a pulse width which is imperceptible to a human.

11. The method of claim 1, wherein activating the LED further comprises activating the LED for an amount of time that is imperceptible to a human.

12. A device comprising:

a LED;

a driver circuit connected to the LED; and

a microcontroller connected to said driver circuit and the LED, said microcontroller configured to initiate a reduced current test to determine the operability of the LED, wherein during the reduced current test the microcontroller is configured to;

activate the LED via the driver circuit with a reduced drive current relative to a normal drive current to emit light with an intensity that is unable to be detected by a human;

receive an indication when the LED is activated;

obtain results of the activation; and

determine whether the LED is operational.

13. The device of claim 12, further comprising a photodetector disposed adjacent the LED, the photodetector configured to detect an intensity of light emitted from the LED and to send an electrical signal indicative of the intensity to the microcontroller.

14. The device of claim 12, wherein determining whether the LED is operational comprises determining whether the electrical signal is greater than a minimum signal.

15. The device of claim 12, wherein activating the LED comprises turning on the LED for less than 20 microseconds.

16. The device of claim 12, wherein the device includes a plurality of said LEDs, and the microcontroller is configured to simultaneously activate the plurality of LEDs using a reduced duty cycle.

17. The device of claim 12, wherein the device includes a plurality of said LEDs, and the microcontroller is configured to simultaneously activate the plurality of LEDs and to obtain results of the activation by measuring an output of the plurality of LEDs collectively.

18. The device of claim 12, wherein the device includes a plurality of said LEDs, and the microcontroller is configured to simultaneously activate the plurality of LEDs to obtain results of the activation by measuring a collective output of less than all of the plurality of LEDs.

19. The device of claim 12, wherein the reduced drive current is 5% of the normal drive current.

20. The device of claim 12, wherein the microcontroller is configured to initiate the reduced current test automatically on a periodic basis.

21. A method for determining operability of a LED in a light display device, comprising:

initiating a reduced current test by activating the LED with a reduced drive current relative to a normal drive current to emit light with a reduced intensity as compared to a normal operating intensity;

sensing an intensity of light emitted from the LED; and

determining whether the LED is operational by comparing said sensed intensity with a predetermined intensity value.

22. The method of claim 21, wherein the reduced drive current is less than or equal to 5% of the normal drive current.

23. The method of claim 21, wherein the reduced drive current is less than or equal to 10% of the normal drive current.

24. The method of claim 21, wherein the reduced intensity light is imperceptible to a human.

25. A method comprising:

initiating a flash test to determine the operability of a LED in a light display device, wherein the flash test comprises one of activating the LED for a time period of less than about 15 microseconds and activating the LED for a pulse width of 20 microseconds or less; and

determining whether the LED failed to operate based on the intensity of light emitted by the LED.

26. The method of claim 25, wherein determining whether the LED failed to operate comprises determining, by a control circuit, whether an electrical signal associated with the intensity of light of the LED is greater than a minimum signal.

27. The method of claim 25, wherein light emitted by the LED during the flash test is imperceptible to a human.