Touch sensor and control with random pulse spacing

• US 20060221061A1
• Filed: 03/31/2005
• Published: 10/05/2006
• Est. Priority Date: 03/31/2005
• Status: Abandoned Application

• Current Assignee: Tyco Electronics Corporation (TE Connectivity Limited)
• Original Assignee: Tyco Electronics Corporation (TE Connectivity Limited)
• Inventors: Fry, Charles David
• Application Number:
  US11/095,987
• Publication Number:
  US 20060221061A1
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A control system for controlling a device includes a touch sensitive interface. The control system also includes a controller configured to communicate with the touch sensitive interface and to detect user manipulation of the touch sensitive interface with a series of non-periodic test pulses and monitored responses thereto, thereby avoiding inaccurate touch detection attributable to synchronous noise in an ambient environment of the control system.

Claims

1. A control system for controlling a device, said control system comprising:

a touch sensitive interface; and

a controller configured to communicate with said touch sensitive interface and to detect user manipulation of said touch sensitive interface with a series of non-periodic test pulses and monitored responses thereto, thereby avoiding inaccurate touch detection attributable to synchronous noise in an ambient environment of said control system.

2. A control system in accordance with claim 1 wherein said controller is configured, for each test pulse, to:

obtain a pre-test pulse baseline signal level from said touch sensitive interface;

obtain a post-test pulse signal level from said touch sensitive interface;

compare the post-test pulse signal level to the pre-test pulse baseline signal level; and

if a difference between the post-test pulse signal level and the pre-test pulse baseline signal level exceeds a current detect threshold, to respond to said touch sensitive interface and to operate the device accordingly.

3. A control system in accordance with claim 2 wherein said controller is further configured to ignore said touch sensitive interface and fail to operate the device when the difference between the post-test pulse signal level and the pre-test pulse baseline signal level is less than the current detect threshold.

4. A control system in accordance with claim 1, wherein said controller is further configured to determine a moving average of pre-test pulse baseline signal levels over time, and for each test pulse, said controller is further configured to compare a current pre-test pulse baseline signal level to the moving average of baseline signals, and to ignore the monitored response to the current test pulse when a difference between said current pre-test pulse baseline signal level and the moving average of baseline signals exceeds a predetermined blanking threshold.

5. A control system in accordance with claim 2, wherein said controller is further configured to, for each test pulse, compare a current pre-test pulse baseline signal level to a predetermined baseline reference value, and if said current pre-test pulse baseline signal level exceeds said predetermined baseline reference value, to set said predetermined baseline reference value at least equal to the current pre-test pulse baseline signal level.

6. A control system in accordance with claim 5, wherein said controller is further configured to decay the predetermined baseline reference value before the comparing of the current pre-test pulse baseline signal level to the predetermined baseline reference value.

7. A control system in accordance with claim 6, wherein said controller is further configured to use for the current detect threshold, a temporary value instead of a predetermined detect threshold when said temporary value is greater than the predetermined detect threshold, said temporary value being equal to a constant added to an absolute value of a difference between the predetermined baseline reference value and the current pre-test pulse baseline signal level.

8. A control system in accordance with claim 1 wherein said series of non-periodic test pulses are generated by the controller with a pseudo random or random jitter to periodic pulses.

9. A control system in accordance with claim 1, wherein said touch sensitive interface includes a capacitive touch sensor.

10. A control system for controlling a device, said control system comprising:

a touch sensitive interface; and

a controller configured to pulse said touch sensitive interface at randomized pulse spacing and conduct a touch detection sequence responsive to said pulses, thereby avoiding inaccurate touch detection attributable to synchronous noise in an ambient environment of said control system.

11. A control system in accordance with claim 10 wherein, at each touch detection sequence, said controller is further configured to:

obtain a pre-test pulse baseline signal level from said touch sensitive interface;

send a test pulse signal to said touch sensitive interface;

sense a post-test pulse signal level from said touch sensitive interface;

compare the post-test pulse signal level to the pre-test pulse baseline signal level; and

if a difference between the post-test pulse signal level and the pre-test pulse baseline signal level exceeds a current detect threshold, to respond to said touch sensitive interface and to operate the device accordingly.

12. A control system in accordance with claim 11 wherein the controller is further configured to ignore said touch sensitive interface and fail to operate the device when the difference between the post-test pulse signal level and the pre-test pulse baseline signal level is less than the current detect threshold.

13. A control system in accordance with claim 11, wherein said controller is further configured to determine a moving average of pre-test pulse baseline signal levels over time, and at each touch detection sequence, said controller is further configured to compare a current pre-test pulse baseline signal level to the moving average of baseline signal levels, and if the difference between said current pre-test pulse baseline signal level and said moving average of baseline signals exceeds a predetermined blanking threshold, to ignore a touch detect for the current touch detection sequence and begin another touch detection sequence.

14. A control system in accordance with claim 11, wherein said controller is further configured, at each touch detection sequence, to compare a current pre-test pulse baseline signal level to a predetermined baseline reference value, and if said current pre-test pulse baseline signal level exceeds said predetermined baseline reference value, to set the predetermined baseline reference value at least equal to the current pre-test pulse baseline signal level.

15. A control system in accordance with claim 14, wherein said controller is further configured to reduce the predetermined baseline reference value before the comparing of the current pre-test pulse baseline signal level to the predetermined baseline reference value.

16. A control system in accordance with claim 15, wherein said controller is further configured to use for the current detect threshold for the current touch detection sequence, a temporary value instead of a predetermined detect threshold when said temporary value is greater than the predetermined detect threshold, said temporary value being equal to a constant added to an absolute value of a difference between the predetermined baseline reference value and the current pre-test pulse baseline signal level.

17. A control system in accordance with claim 10 wherein said randomized pulses are generated by the controller with a pseudo random or random jitter to periodic pulses.

18. A control system in accordance with claim 10, wherein said touch sensitive interface includes a capacitive touch sensor.

19. A control system in accordance with claim 10, wherein said controller comprises a microprocessor and a memory, said controller further configured to record touch detection sequence information in said memory for diagnostic purposes.

20. A control system for controlling a device, said control system comprising:

a touch sensitive interface including at least one capacitive touch sensor configured to complete a circuit through earth ground when touched by a user; and

a controller configured to pulse said touch sensitive interface and conduct a touch detection sequence responsive to said pulses, said pulses being randomized to avoid inaccurate touch detection attributable to synchronous noise in an ambient environment of said control system, and said controller further configured to compare a pre-test pulse baseline signal level to a post-test pulse signal level at each touch detection sequence to validate or invalidate a detected touch based upon a difference between pre and post-test pulse signal levels and a current detect threshold.