Monitoring the characteristics of a load driver controlled by a microcontroller

• US 5,497,322 A
• Filed: 03/20/1995
• Issued: 03/05/1996
• Est. Priority Date: 10/26/1992
• Status: Expired due to Fees

• Current Assignee: Lear Corporation Eeds & Interiors (Rtx Corporation)
• Original Assignee: United Technologies Automotive, Inc. (Lear Corporation)
• Inventors: Barrs, John A., Kolomyski, Darrell J.
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): Peeso, Thomas
• Application Number:
  US08/407,562
• Time in Patent Office: 351 Days
• Field of Search: 324/522, 324/523, 340/825.06, 340/825.16, 340/825.18, 364/424.03, 364/483
• US Class Current: 701/29
• CPC Class Codes: G01R 31/007 using microprocessors or computers

Abstract

Loads, such as power relays controlling wipers, windows and lights are connected to an automobile battery through individual transistor drives that are controlled by a microcontroller. A switch, connected to the microcontroller, is operated to activate each drive. The microcontroller checks the load characteristic when each drive is activated and inactivated. When the load is inactivated, it is part of a resistance network producing a test voltage that is digitally converted and supplied to the microcontroller, which compares the test voltage to a stored voltage to determine if the load is correct. An analog multiplexer is controlled by the microcontroller to select the voltage produced for each load.

Claims

1. A control system comprising a DC power source, a load, a drive, and a control for activating the drive to provide power to the load, characterized in that:

the drive comprises means in connection with said load and the power source for producing a load test signal with a magnitude that is a function of load resistance;

means for converting said load test voltage into a digital signal equivalent supplied to the control; and

said control comprises signal processing means for receiving said digital signal before said drive is activated, for comparing said digital signal to a stored signal for said load and for preventing activation of said drive if the difference between said digital signal and said stored signal exceeds a stored magnitude.

2. A control system according to claim 1, characterized in that said means in connection with said load comprises a first resistor in parallel with said load and in series with a second resistor in series with a third resistor, said first second and third resistors carrying current from the power source.

3. A control system according to claim 2, characterized in that the drive comprises a transistor supplied with power from the source through said first resistor.

4. A control system according to claim 1 or 3, characterized in that said signal processor comprises means for inactivating a drive if the difference between said load signal and a stored value exceeds a stored level and disabling subsequent activation of said drive.

5. A control system according to claim 4, characterized in that said means in connection with a load comprises a first resistor in parallel with said load and in series with a second resistor in series with a third resistor, said first second and third resistors carrying current from the power source.

6. A control system according to claims 4 or 5, characterized in that said signal processor comprises means for inactivating a drive if the difference between said load signal and a stored value exceeds a stored level and for disabling subsequent activation of said drive.

7. A control system comprising a DC power source, first and second loads, a drive for each load, and a control for activating a drive to provide power to the load, characterized in that:

said first and second drives each comprise means in connection with a load connected to the drive and connected to the power source for producing a load test signal with a magnitude that is a function of load resistance;

means for converting said load test voltage into a digital signal equivalent supplied to the control;

means for selecting one load test signal from load test signals produced for each of the drives and supplying said one signal to said means for converting in response to a drive select command; and

said control comprises signal processing means for providing said drive select command;

for receiving said digital signal when said drive is inactivated, for comparing said digital signal to a stored signal for said load and for preventing activation of said drive if the difference between said digital signal and said stored signal exceeds a stored magnitude.

8. A control system according to claim 7, characterized in that the drive comprises a transistor supplied with power from the source through said first resistor.

9. A control system for controlling a load, the load having an impedance, an operating minimum and an operating maximum, said control system comprising:

a driver for driving the load in response to a control signal, and for generating a driver test signal in response to a monitor signal, said driver test signal having a magnitude corresponding with the impedance, said monitor signal being below said operating minimum; and

a controller for generating said monitor signal before generating said control signal, and for inactivating said driver when said driver test signal is greater than the operating maximum.

10. The control system of claim 9, further comprising:

an analog to digital converter for converting said driver test signal into a digitized driver test signal.

11. The control system of claim 10, wherein the operating maximum is digitally stored in a memory such that said digitized driver test signal is compared with said digitally stored operating maximum.

12. The control system of claim 9, wherein said driver is coupled with the load by a resistor in parallel with the load, and said resistor is coupled with said controller by a transistor.

13. The control system of claim 9, wherein said controller further generates a diagnostic signal when said driver test signal is less than the operating minimum.

14. The control system of claim 9, wherein said controller further inactivates said driver when said driver test signal is less than the operating minimum.

15. A control system for controlling a first and a second load, each of the first and second loads having an impedance, an operating minimum and an operating maximum, said control system comprising:

a first driver for driving the first load in response to a first control signal, and for generating a first driver test signal in response to a first monitor signal, said first driver test signal having a magnitude corresponding with the impedance of the first load, said first monitor signal being below said operating minimum of the first load;

a second driver for driving the second load in response to a second control signal, and for generating a second driver test signal in response to a second monitor signal, said second driver test signal having a magnitude corresponding with the impedance of the second load, said second monitor signal being below said operating minimum of the second load;

a multiplexer for receiving said first and said second driver test signals, and for generating a selected driver test signal in response to a select signal, said selected signal corresponding with a selected driver of said first and second drivers, said selected driver corresponding with a selected load of the first and second loads; and

a controller for generating said first monitor signal before generating said first control signal, for generating said second monitor signal before generating said second control signal, for generating said select signal, and for inactivating said selected driver when said selected driver test signal is greater than the operating maximum of the selected load.

16. The control system of claim 15, further comprising:

an analog to digital converter for converting said selected driver test signal into a selected digitized driver test signal.

17. The control system of claim 16, wherein the operating maximum of the selected load is digitally stored in a memory such that said selected digitized driver test signal is compared with said digitally stored operating maximum of the selected load.

18. The control system of claim 15, further comprising:

an analog to digital converter for digitizing said first and said second driver test signals.

19. The control system of claim 18, wherein the operating maximum of the selected load is digitally stored in a memory such that said selected driver test signal is compared with said digitally stored operating maximum of the selected load.

20. The control system of claim 15, wherein said selected driver is coupled with the selected load by a resistor in parallel with the selected load, and said resistor is coupled with said microcontroller by a transistor.

21. The control system of claim 15, wherein said controller inactivates said driver by failing to generate said control signal.

22. The control system of claim 15, wherein at least one of the first and second loads comprises at least one of a wiper motor, a headlight, and a power window motor.

23. The control system of claim 15, further comprising a first and a second switch for transmitting a first and a second enabling signal to said controller, said first enabling signal corresponding with said first control signal and said second enabling signal corresponding with said second control signal.

24. The control system of claim 15, wherein said controller further generates a diagnostic signal when said selected driver test signal is less than the operating minimum of the selected load.

25. The control system of claim 15, wherein said controller further inactivates said selected driver when said selected driver test signal is less than the operating minimum of the selected load.

26. A control system for controlling a load, the load having an impedance, an operating minimum and an operating maximum, said control system comprising:

a driver for driving the load in response to a control signal, and for generating a driver test signal in response to a monitor signal, said driver test signal having a magnitude corresponding with the impedance, said monitor signal being below the operating minimum; and

a controller for generating said monitor signal before generating said control signal, for generating a diagnostic signal when said driver test signal is less than the operating minimum, and for inactivating said driver when said driver test signal is greater than the operating maximum.

27. The control system of claim 26, further comprising:

an analog to digital converter for converting said driver test signal into a digitized driver test signal.

28. The control system of claim 27, wherein the operating minimum and the operating maximum are digitally stored in a memory such that said digitized driver test signal is compared with both said digitally stored operating minimum and said digitally stored operating maximum.