Pseudo zero power position indication
A method and device detect the position of a device utilizing electronic sensors in applications with negligible power resources. The method utilizes an indicator circuit for monitoring a position of a device, the indicator circuit including a position sensor configured to detect a position of the device, a first position indicator operatively coupled to the position sensor and configured to provide a position output corresponding to the position of the device based on the position of the device as detected by the position sensor, a first sense line for receiving a sense voltage from a second position indicator different from the first position indicator; and an energy harvesting device operatively coupled to the first sense line, the position sensor and the first position indicator. The energy harvesting device is configured to harvest electric energy from the sense voltage, wherein the position sensor and the first position indicator obtain electric power from the harvested electric energy.
1. An indicator circuit for monitoring a position of a device, the indicator circuit comprising:
a position sensor configured to detect a position of the device;
a first position indicator operatively coupled to the position sensor and configured to provide a position output corresponding to the position of the device based on the position of the device as detected by the position sensor;
a first sense line for receiving a sense voltage from a second position indicator different from the first position indicator; and
an energy harvesting device operatively coupled to the first sense line, the position sensor and the first position indicator, the energy harvesting device configured to harvest electric energy from the sense voltage of the first sense line wherein the harvested electric energy is stored in a capacitor of the energy harvesting device, and wherein the capacitor supplies the harvested electric energy to power the position sensor and the first position indicator.
2. The indicator circuit according to claim 1 , further comprising the second position indicator, wherein the second position indicator is complementary to the first position indicator.
3. The indicator circuit according to claim 2 , wherein the first sense line corresponds to the second position indicator, further comprising at least one other sense line that corresponds to the first position indicator.
4. The indicator circuit according to claim 3 , further comprising a plurality of other position indicators, wherein at the least one other sense line comprises a plurality of other sense lines, respective ones of the plurality of other sense lines corresponding to respective ones of the plurality of other position indicators.
5. The indicator circuit according to claim 1 , further comprising an operating power input for receiving operating power to operate the indicator circuit, wherein the first position indicator obtains electric power from the operating power input when operating power is present.
6. The indicator circuit according to claim 1 , wherein the position sensor comprises an electronic sensor.
7. The indicator circuit according to claim 6 , wherein the position sensor comprises at least one of a hall-effect device or an optical sensor.
8. The indicator circuit according to claim 1 , wherein the first position indicator comprises a semiconductor device.
9. The indicator circuit according to claim 1 , further comprising a timing and driver module operatively coupled to the energy harvesting device and the first position indicator, the timing and driver module configured to provide power to the first position indicator upon an energy level harvested by the energy harvesting device exceeding a prescribed threshold level.
10. The indicator circuit according to claim 9 , wherein the timing and driver module comprises an RC timing circuit.
11. The indicator circuit according to claim 1 , wherein the first position indicator is configured to hold the position output over a duty cycle of the energy harvesting device.
12. A method for monitoring a position of a device via a circuit powered by a primary power source, the method comprising:
when the primary power source is inoperative, harvesting energy from a position indicator of a first sensor corresponding to the device being monitored and storing the harvested energy in a capacitor of an energy harvesting device, the position indicator connected to a secondary power source different from the primary power source;
supplying the harvested energy from the capacitor of the energy harvesting device over a duty cycle to intermittently power the circuitry; and
using the circuitry to detect a position of the device when the intermittent power is present.
13. The method according to claim 12 , wherein the position indicator comprises a first position indicator, and harvesting comprises using a sense voltage from a second position indicator that is complementary to the first position indicator.
14. The method according to claim 12 , further comprising outputting and holding the detected position over the duty cycle when the primary power is inoperative.
15. The method according to claim 12 , wherein harvesting comprises storing energy until a stored energy exceeds a predetermined threshold level, and outputting the stored energy upon reaching or exceeding the predetermined threshold level.
16. The method according to claim 12 , wherein the duty cycle comprises storing energy from an empty energy state to a full energy storage state and discharging the stored energy to the empty state.