Patent ID: 6969920

Claim:
A shape memory alloy device in which a shape memory alloy actuating element is operated for a single cycle periodically at a low voltage by power derived from charge accumulated from a source current which is too low to heat the actuating element for effective operation, comprising a capacitor of low resistance and high capacity operably connected to receive a low current source for continuous charging thereby; switching means operably connected between the capacitor and the shape memory alloy device and monitoring means operably connected between the capacitor and the switching means for monitoring discharge of the capacitor by sensing a voltage of the capacitor and operating the switching means to partially discharge the capacitor periodically through the shape memory alloy actuating element, commencing discharge in response to a sensed voltage corresponding to an upper threshold amount of charge stored by the capacitor and ceasing discharge in response to a sensed voltage corresponding to a lower threshold amount of charge remaining in the capacitor thereby to periodically supply the shape memory alloy actuating element with a transient current level sufficiently high for effective operation for a single cycle.