Capacitive position encoder
In one embodiment, a method comprises driving one or more drive electrodes formed on a substrate with one or more drive signals. A wiper comprising at least one arm is driven to a predetermined voltage. The wiper is electrically insulated from a plurality of sense electrodes formed on the substrate. For each sense electrode of the plurality of sense electrodes, a charge stored by the sense electrode is detected. A processor determines a position of the wiper based on the detected charges stored by the plurality of sense electrodes.
1. A device comprising:
a substrate;
a drive electrode disposed on a first side of the substrate;
a plurality of sense electrodes disposed on a second side of the substrate;
a wiper comprising at least one arm, the wiper electrically insulated from the plurality of sense electrodes, the wiper coupled to a ground of the device; and
a controller coupled to the drive electrode and the plurality of sense electrodes, the controller comprising:
a drive unit configured to generate at least one drive signal and drive the drive electrode with the at least one drive signal;
a sense unit configured to detect, for each sense electrode of the plurality of sense electrodes, a charge stored by the sense electrode; and
a processor unit operable to determine a position of the wiper relative to the plurality of sense electrodes, the determination based on the plurality of charges detected by the sense unit.
2. The device of claim 1 , wherein the wiper further comprises a rotary shaft coupled to the at least one arm of the wiper.
3. The device of claim 1 , wherein the wiper comprises a plurality of arms that extend in a radial direction from a rotary shaft of the wiper.
4. The device of claim 1 , wherein at least one radial angle formed between a first pair of adjacent arms of the wiper is different from at least one other radial angle formed between a second pair of adjacent arms of the wiper.
5. The device of claim 1 , the drive electrode having an annular shape.
6. The device of claim 1 , wherein the wiper further comprises a shaft that extends in a first direction and each of the at least one arm of the wiper extends in a second direction from the shaft, the first direction being perpendicular to the second direction.
7. The device of claim 1 , wherein the wiper is configured to change position relative to the plurality of sense electrodes in response to a user action.
8. A method comprising:
driving one or more drive electrodes former on a substrate with one or more drive signals;
driving a wiper comprising at least one arm to a predetermined voltage, the wiper electrically insulated from a plurality of sense electrodes formed on the substrate;
detecting, for each sense electrode of the plurality of sense electrodes, a charge stored by the sense electrode; and
determining, by a processor, a position of the wiper based on the detected charges stored by the plurality of sense electrodes.
9. The method of claim 8 , further comprising changing the position of the wiper in response to a user action.
10. The method of claim 8 , wherein the one or more drive electrodes are formed on a first side of the substrate and the plurality of sense electrodes are formed on a second side of the substrate.
11. The method of claim 8 , wherein the wiper further comprises a rotary shaft coupled to the at least one arm.
12. The method of claim 8 , wherein the wiper comprises a plurality of arms that extend in a radial direction.
13. The method of claim 8 , wherein at least one radial angle formed between a first pair of adjacent arms of the wiper is different from at least one other radial angle formed between a second pair of adjacent arms of the wiper.
14. The method of claim 8 , wherein the at least one arm of the wiper extends in a first direction from a shaft of the wiper that extends in a second direction, the first direction being perpendicular to the second direction.
15. An apparatus comprising:
at least one drive electrode disposed on a substrate;
a plurality of sense electrodes disposed on the substrate;
a wiper comprising at least one arm, the wiper electrically insulated from the plurality of sense electrodes; and
a controller operable to:
drive the at least one drive electrode;
detect a plurality of charges stored by the plurality of sense electrodes; and
determine a position of the wiper based on the plurality of charges detected by the sense unit.
16. The apparatus of claim 15 , wherein the wiper further comprises a rotary shaft coupled to the at least one arm of the wiper.
17. The apparatus of claim 15 , wherein the wiper comprises a plurality of arms that extend in a radial direction from a rotary shaft of the wiper.
18. The apparatus of claim 15 , wherein at least one radial angle formed between a first pair of adjacent arms of the wiper is different from at least one other radial angle formed between a second pair of adjacent arms of the wiper.
19. The apparatus of claim 15 , the drive electrode having an annular shape.
20. The apparatus of claim 15 , wherein the wiper further comprises a shaft that extends in a first direction and each of the at least one arm of the wiper extends in a second direction from the shaft, the first direction being perpendicular to the second direction.