Capacitive detection, energy transfer, and/or data transfer system

1. A system comprising a base and at least a first moveable entity, the first moveable entity being separate and freely moveable with respect to the base and positionable in at least a first position with respect to the base,

the base comprising at least a first base electrode, and the first moveable entity comprising at least a first moveable entity electrode, and

the first base electrode and the first moveable entity electrode being arranged to couple to form a first capacitor when the first moveable entity is in said first position,

the base further comprising signal supply means, arranged to supply a first time-varying electrical signal to the first base electrode, and

the first moveable entity further comprising first circuitry connected to the first moveable entity electrode,

wherein said base is arranged to power said first circuitry via said first time-varying electrical signal and the coupling between the first base electrode and the first moveable entity electrode when the first moveable entity is in the first position, and

wherein said first circuitry includes a virtual ground.

2. A system in accordance with claim 1 , wherein said first circuitry is arranged to create a local electrical return.

3. A system in accordance with claim 1 , wherein said first circuitry comprises:

a first node, connected to the first moveable entity electrode, a second node, and a third node;

a first diode connected between the first node and the second node to allow current flow from the first node to the second node and block current flow from the second node to the first node; and

a second diode connected between the third node and the first node to allow current flow from the third node to the first node and block current flow from the first node to the third node.

4. A system in accordance with claim 1 , wherein the base further comprises signal detection means arranged to detect an electrical signal from the first base electrode.

5. A system in accordance with claim 4 , wherein the signal detection means is adapted to determine whether the first moveable entity is in said first position from the electrical signal from the first base electrode.

6. A system in accordance with claim 4 , wherein the signal detection means is adapted to determine an identity of the first moveable entity when the first moveable entity is in said first position from the electrical signal from the first base electrode.

7. A system in accordance with claim 4 , wherein said first circuitry is arranged to provide a second time-varying electrical signal to the first moveable entity electrode, the second time-varying electrical signal carrying data, and the signal detection means is adapted to detect said second time-varying signal when the first moveable entity is in said first position.

8. A system in accordance with claim 7 , wherein the first moveable entity includes data transmission means configured to generate at least part of the second time-varying electrical signal.

9. A system in accordance with claim 3 , wherein said first circuitry further comprises a second capacitor connected between the second node and the third node.

10. A system in accordance with claim 9 , wherein a first voltage is developed across the second capacitor (i.e. between the second and third nodes) in response to the first time-varying electrical signal being applied to the first base electrode when the first moveable entity is in said first position.

11. A system in accordance with claim 9 , wherein said first circuitry further comprises a first resistor connected between the second node and the third node.

12. A system in accordance with claim 11 , wherein an electrical current is driven through said first resistor in response to the first time-varying electrical signal being applied to the first base electrode when the first moveable entity is in said first position.

13. A system in accordance with claim 9 , wherein said first moveable entity further comprises data transmission means connected to the second and third nodes and adapted to supply a second time-varying electrical signal carrying second data to the first moveable entity electrode.

14. A system in accordance with claim 13 , wherein said first moveable entity further comprises power supply circuitry connected to the second and third nodes, adapted to receive power via the second and third nodes when the first moveable entity is in said first position, and adapted to power the data transmission means using said received power.

15. A system in accordance with claim 1 , wherein the base comprises only a single electrode (i.e. the first base electrode), and the first moveable entity comprises only a single electrode (i.e. the first moveable entity electrode).

16. A system in accordance with claim 1 , wherein the base comprises a second base electrode coupled to the first base electrode and the first moveable entity comprises a second moveable entity electrode, and the second base electrode and second moveable entity electrode are arranged to couple to form a third capacitor when the first moveable entity is in said first position.

17. A system in accordance with claim 16 , wherein the first moveable entity comprises second circuitry connected to the second movable entity electrode, and the second circuitry is connected to the virtual ground.

18. A system in accordance with claim 17 , wherein said second circuitry comprises:

a fourth node, connected to the second moveable entity electrode, a fifth node, and a sixth node;

a third diode connected between the fourth node and the firth node to allow current flow from the fourth node to the fifth node and block current flow from the fifth node to the fourth node; and

a fourth diode connected between the sixth node and the fourth node to allow current flow from the sixth node to the fourth node and block current flow from the fourth node to the sixth node.

19. A system in accordance with claim 18 , wherein said second circuitry further comprises a fourth capacitor connected between the fifth node and the sixth node.

20. A system in accordance with claim 19 , wherein a second voltage is developed across the fourth capacitor (i.e. between the fifth and sixth nodes) in response to the first time-varying electrical signal being applied to the second base electrode when the first moveable entity is in said first position.