The first part of the paper treats the general problems concerning the shape memory alloy actuators and their operation principle. Then, our work referring to the developing a modular family of linear and rotational actuators, realized in many typo dimensions, in a compact design, with facile connection with the actuated mechanisms and supplying module is presented. The active elements of these actuators are shape memory alloy wires, ribbons and helical springs. The influence of the geometry of the active elements on the time response is studied. The most important solutions to reduce the resistive heating time of active elements and to improve the time response on cooling are identified.