Light monitor

• US 6,788,195 B1
• Filed: 08/09/2002
• Issued: 09/07/2004
• Est. Priority Date: 08/09/2002
• Status: Active Grant

• Current Assignee: The Osborne Coinage Co.
• Original Assignee: The Osborne Coinage Co.
• Inventors: Leonard, Matt Michael, Stegman, Todd Robert
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Vu, Jimmy T.
• Application Number:
  US10/216,370
• Time in Patent Office: 760 Days
• Field of Search: 340/80, 340/458, 340/641, 340/642, 340/510, 340/652, 340/653, 340/693.1, 702/63, 702/82, 702/183, 315/86, 363/101
• US Class Current: 340/458
• CPC Class Codes: B60Q 11/005 for lighting devices, e.g. indicating if lamps are burning or not

Abstract

A monitor for a light circuit comprising a power source, a light being monitored, and a sense resistor. A first voltage amplifier circuit connected to the light circuit has a first output signal representing the voltage across the sense resistor. A second voltage amplifier circuit connected to the circuit has a second output signal representing the voltage across the sense resistor. A microprocessor is configured to receive the output signals from the first and second voltage measuring circuit and is programmed to calculate the current to the light based on the first and second digital output signals, compare the calculated current against a threshold current, and initiate a failure signal if the calculated current is less than the threshold current. A visual indicator activates if the microprocessor initiates a failure signal, whereby the activated indicator notifies that the light is not operating correctly. The calculated current is based on the first output signal if the light is a low current light, and the current is calculated is based on the second output signal if the light is a high current light. The calculated current can be a function of the measured voltage of the power source. The threshold current can be a percentage of a calibrated current, which is based on a measured voltage across the sense resistor when the light is operating correctly.

Claims

1. A monitor for a light circuit comprising a power source, a light being monitored, and a sense resistor, the monitor comprising:

a) a first voltage amplifier circuit connected to the light circuit having a first output signal representing the voltage across the sense resistor;

b) a second voltage amplifier circuit connected to the circuit having a second output signal representing the voltage across the sense resistor;

c) a microprocessor configured to receive the output signals from the first and second voltage measuring circuits, said microprocessor being programmed to;

(i) calculate the current to the light based on the first and second digital output signals;

(ii) compare the calculated current against a threshold current;

(iii) initiate a failure signal if the calculated current is less than the threshold current; and

d) an indicator that activates if the microprocessor initiates a failure signal, whereby the activated indicator notifies that the light circuit is not operating correctly.

2. The light monitor of claim 1, wherein the light is an exterior light on a vehicle comprising one or more incandescent lights.

3. The light monitor of claim 1, wherein the light is an exterior light on a vehicle comprising one or more LEDs.

4. The light monitor of claim 3, wherein the first and second digital output signals each have a maximum value.

5. The light monitor of claim 1, wherein the calculated current is based on the first output signal if the light is a low current light, and the calculated current is based on the second output signal if the light is a high current light.

6. The light monitor of claim 5, wherein low current is greater than about 0 amps and less than about 1 amp.

7. The light monitor of claim 5, wherein high current is greater than about 1 amp and less than about 10 amps.

8. The light monitor of claim 5, wherein the calculated current is based on the second output signal if the second output signal is greater than a threshold value, and the current is calculated is based on the first output signal if the second output signal is less than the threshold value.

9. The light monitor of claim 1, wherein the first and second voltage amplifier circuits each comprise an operational amplifier.

10. The light monitor of claim 9, wherein the gain ratio between the first and second operational amplifier is about 1:

10.

11. The light monitor of claim 1, wherein the calculated current is a function of the measured voltage of the power source.

12. The light monitor of claim 1, wherein the threshold current is a percentage of a calibrated current, said calibrated current being based on a measured voltage across the sense resistor when the light is operating correctly.

13. The light monitor of claim 2, wherein the indicator is an LED visible to the vehicle operator.

14. The light monitor of claim 1, wherein the sense resistor is connected in series with the light.

15. A system for monitoring the operability of exterior lights on a vehicle, the system comprising:

a) a plurality of light circuits each comprising a light positioned on the exterior of the vehicle;

b) a plurality of sense resistors each connected to a light circuit in series with the corresponding exterior light;

c) a plurality of first operational amplifiers each connected in parallel with a sense resistor, each first operational amplifier amplifying the voltage across the corresponding sense resistor to generate a first amplified signal;

d) one or more multiplexers connected to the operational amplifiers to select a first amplified signal;

e) at least one second operational amplifier connected to the one or more multiplexers, said at least one second operational amplifier amplifying the selected first amplified signal to generate a second amplified signal;

f) an analog to digital converter converting the second amplified signal into a digital value;

g) an indicator to notify the vehicle operator if an exterior light is inoperable; and

h) a microprocessor being programmed to;

(i) control the one or more multiplexers to select a first amplified signal corresponding to an exterior light;

(ii) calculate the current through the sense resistor based on the digital value corresponding to the selected first amplified signal;

(iii) compare the calculated current against a threshold current;

(iv) if the calculated current is less than the threshold current active the indicator corresponding to the exterior light.

16. The system of claim 15, further comprising a low impedance buffer for buffering the first amplified signal.

17. The system of claim 15, wherein the at least one second operational amplifier comprises a low current operational amplifier and a high current operational amplifier.

18. The system of claim 17, wherein the calculated current is based on the second amplified signal from the low amperage operational amplifier if the light is a low current light, and the calculated current is based on the second amplified signal from the high current operational amplifier if the light is a high current light.

19. The light monitor of claim 18, wherein a low current light is less greater than about 0 amps and less than about 1 amp.

20. The light monitor of claim 18, wherein a high current light is greater than about 1 amp and less than about 10 amps.

21. The light monitor of claim 18, wherein the calculated current is based on the digital value corresponding to the high current operational amplifier if such digital value is greater than a threshold value, and if such digital value is less than the threshold value then the current is calculated is based on the digital value corresponding to the low current operational amplifier.

22. The system of claim 15, further comprising a battery powering the light circuits and a voltage measurement circuit, wherein the calculated current is normalized based on the voltage measured by the voltage measurement circuit.

23. A vehicle light monitor, comprising:

a) a plurality of exterior lights on the vehicle, each of said lights having a corresponding light circuit and power source;

b) means for determining a calibrated current for each of said lights;

c) means for measuring a voltage in each light circuit, said measured voltage being proportional to the current to the corresponding light;

d) means for calculating the current to a selected light based on the corresponding measured voltage;

e) means for normalizing the calculated current based on the voltage of the power source;

f) means for determining if a light is inoperable based on the corresponding normalized calculated current and the corresponding calibrated current; and

g) means for signaling the vehicle operator if light is determined to be inoperable.