Electronic device including a capacitive sensor in a housing
Disclosed are electronic devices for detecting contact or close proximity to an object to be detected. An electronic device includes a capacitive sensor enclosed by a housing and a controller coupled to the capacitive sensor, where the controller is configured to detect contact or close proximity to an object to be detected, and where the capacitive sensor includes a capacitor with a sensor electrode. The sensor electrode is separated from an outer surface of the housing by the housing. At least a portion of the housing includes a partially conductive material and the sensor electrode is in conductive contact with the partially conductive material, or the sensor electrode is in conductive contact with an electrically conductive element on an inner surface of the housing or at least partially embedded in the housing.
1. An electronic device comprising:
a capacitive sensor including a capacitor having at least one sensor electrode;
a housing that encloses the capacitive sensor and having an inner surface and an outer surface opposite the inner surface, wherein at least a first portion of the housing includes an electrically insulating material and at least a second portion of the housing includes a partially conductive material, wherein the at least one sensor electrode is in conductive contact with the second portion of the housing and separated from the outer surface by the housing; and
a controller coupled to the capacitive sensor, wherein:
the controller is configured to determine whether the electronic device is in contact or in close proximity to an object based at least in part on a rate of capacitance charge of the capacitor when the capacitive sensor is energized,
when the controller determines the electronic device is in contact or in close proximity to an object, the controller activates an active power mode of the electronic device, and
when the controller determines the electronic device is not in contact or in close proximity to an object, the controller activates a low-power mode of the electronic device.
2. The electronic device of claim 1 , wherein the at least one sensor electrode is disposed on the inner surface of the housing.
3. The electronic device of claim 1 , wherein the capacitive sensor further includes:
a resistor electrically connected in series with the capacitor, wherein the controller is configured apply a signal to the resistor to energize the capacitive sensor.
4. The electronic device of claim 3 , wherein an electrical resistance of the resistor is at least five times greater than an electrical resistance of the partially conductive material of the second portion of the housing.
5. The electronic device of claim 3 , wherein the partially conductive material of the second portion of the housing has an electrical resistance equal to or less than 1×10 5 Ω and the resistor has an electrical resistance equal to or greater than 5×10 5 Ω.
6. The electronic device of claim 3 , wherein the controller is further configured to:
receive a signal from the capacitive sensor after energizing the capacitive sensor; and
determine whether the electronic device is in contact or in close proximity to the object based at least in part on the received signal.
7. The electronic device of claim 1 , wherein the controller includes a processor having a clock rate that is less than about 100 Megahertz.
8. The electronic device of claim 1 , wherein the electrically insulating material of the first portion of the housing includes non-conductive plastic.
9. The electronic device of claim 1 , wherein the partially conductive material of the second portion of the housing includes carbon-impregnated plastic.
10. The electronic device of claim 1 , wherein the at least one sensor electrode is separated from the outer surface of the housing by a separation distance, the separation distance being between about 0.5 millimeters and about five millimeters.
11. The electronic device of claim 1 , wherein the at least one sensor electrode has a surface area of between about nine square millimeters and about 225 square millimeters.
12. The electronic device of claim 1 , wherein the at least one sensor electrode is separated from the outer surface of the housing by at least a thickness at the second portion of the housing.
13. An electronic device comprising:
a capacitive sensor including a capacitor having at least one sensor electrode;
a housing that encloses the capacitive sensor and having an inner surface and an outer surface opposite the inner surface, wherein the housing includes an electrically insulating material, wherein the at least one sensor electrode is separated from the outer surface by the housing;
an electrically conductive element disposed on the inner surface of the housing and in conductive contact with the at least one sensor electrode; and
a controller coupled to the capacitive sensor, wherein:
the controller is configured to determine whether the electronic device is in contact or in close proximity to an object based at least in part on a rate of capacitance charge of the capacitor when the capacitive sensor is energized,
when the controller determines the electronic device is in contact or in close proximity to an object, the controller activates an active power mode of the electronic device, and
when the controller determines the electronic device is not in contact or in close proximity to an object, the controller activates a low-power mode of the electronic device.
14. The electronic device of claim 13 , where the electrically conductive element has a surface area greater than a surface area of the at least one sensor electrode.
15. The electronic device of claim 13 , wherein the electrically conductive element is an electrically conductive paint coated on the inner surface of the housing.
16. The electronic device of claim 13 , wherein the capacitive sensor further includes:
a resistor electrically connected in series with the capacitor, wherein the controller is configured apply a signal to the resistor to energize the capacitive sensor.
17. The electronic device of claim 13 , wherein the at least one sensor electrode has a surface area between about nine square millimeters and about 225 square millimeters, and wherein the at least one sensor electrode is separated from the outer surface by a distance that is between about 0.5 millimeters and about five millimeters.
18. An electronic device comprising:
a capacitive sensor including a capacitor having at least one sensor electrode;
a housing that encloses the capacitive sensor and having an inner surface and an outer surface opposite the inner surface, wherein the housing includes an electrically insulating material, wherein the at least one sensor electrode is separated from the outer surface by the housing;
an electrically conductive element at least partially embedded in the housing and electrically connected to the at least one sensor electrode; and
a controller coupled to the capacitive sensor, wherein:
the controller is configured to determine whether the electronic device is in contact or in close proximity to an object based at least in part on a rate of capacitance charge of the capacitor when the capacitive sensor is energized,
when the controller determines the electronic device is in contact or in close proximity to an object, the controller activates an active power mode of the electronic device, and
when the controller determines the electronic device is not in contact or in close proximity to an object, the controller activates a low-power mode of the electronic device.
19. The electronic device of claim 18 , wherein the electrically conductive element has a surface area greater than a surface area of the at least one sensor electrode.
20. The electronic device of claim 18 , wherein the electrically conductive element is closer to the outer surface of the housing than the at least one sensor electrode.
21. The electronic device of claim 18 , wherein the capacitive sensor further includes:
a resistor electrically connected in series with the capacitor, wherein the controller is configured apply a signal to the resistor to energize the capacitive sensor.
22. The electronic device of claim 18 , wherein the at least one sensor electrode has a surface area of between about nine square millimeters and about 225 square millimeters, and wherein the at least one sensor electrode is separated from the outer surface by a distance that is between about 0.5 millimeters and about five millimeters.