US Patent No. 9,870,887

DRIVE CIRCUIT FOR DC LATCHING DEVICES


Patent No. 9,870,887
Issue Date January 16, 2018
Title Drive Circuit For Dc Latching Devices
Inventorship Peter John Woytowitz, San Diego, CA (US)
Lucian Scripca, San Marcos, CA (US)
Assignee Hunter Industries, Inc., San Marcos, CA (US)

Claim of US Patent No. 9,870,887

1. A drive circuit for a DC latching device, the drive circuit comprising:
a battery;
a plurality of switches for momentarily energizing a coil of a DC latching device from the battery;
a microcontroller in communication with the plurality of switches and configured to establish a first inductance associated
with the DC latching device being in an open state, to establish a second inductance associated with the DC latching device
being in a closed state, and to establish an inductance threshold that is between the first and second inductances;

a sensing resistor configured in series with the coil to form a sensing circuit;
circuitry configured to measure voltage and current across the sensing resistor while applying an AC signal to the sensing
circuit, the AC signal having insufficient energy to change the state of the DC latching device;

the microcontroller further configured to calculate an inductive reactance of the DC latching device based on the measured
voltage and current, to calculate an inductance of the DC latching device based on the inductive reactance and a frequency
of the AC signal, and to compare the calculated inductance of the DC latching device with the threshold inductance to determine
a state of the DC latching device; and

circuitry responsive to the determined state of the DC latching device.